Browse Topic: Dimethyl ether (DME)

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Methanol Mixing Controlled Combustion Process Enabled by Methanol Dehydration to Dimethyl Ether2026-01-03224/7/2026
This work demonstrates an initial proof-of-concept approach for operating a compression ignition off-road and marine relevant engine using neat methanol. The approach utilizes mixing controlled compression ignition (MCCI) of methanol that is enabled by a homogeneous charge compression ignition (HCCI) pre-burn of premixed dimethyl ether (DME). Although two fuels are used, this work explores and evaluates the opportunity and performance to generate the premixed fuel via methanol catalytic dehydration over an alumina catalyst at engine relevant temperatures, pressures, and space velocities. Conversion purity and species output results from catalytic dehydration bench flow reactor studies were coupled with single-cylinder experiments of the characterized output species for pre-burn HCCI performance. Subsequently, methanol MCCI performance is also evaluated and compared to conventional diesel combustion. The detailed flow reactor results show that the catalytic dehydration conversion efficiency of methanol to DME is a function of system pressure, temperature, and space velocity. The engine results demonstrate that a 100% conversion of methanol to DME is not required for successful pre-burn HCCI, and the water formed during the dehydration process does not need to be removed to achieve the desired HCCI event from this pre-burn mixture. Subsequent methanol MCCI combustion results show that the level of methanol slip in the dehydration process affects the pre-burn HCCI phasing, low temperature heat release process, and magnitude of energy release, all of which can dictate the available window for direct-injection of methanol for MCCI combustion. 1
Jatana, Gurneesh, Splitter, Derek, Park, Yeonshil, Szybist, James, Svensson, Kenth, Montgomery, David
Effect of Liquidized-Gas Fluid Properties in a High-Pressure Fuel Pump2026-01-02734/7/2026
Paper considers the effects of fluid properties from liquified gases during high pressure pumping, at ranges from 200 to 1500 bar, and at speeds of 500 to 1500 rpm. Tests represent highest to date pressure ranges attained with liquified fluids such as DME. The paper examines the effects of compressibility on the pumping and resulting loading torque characteristics described over the pumping cycle as resolved by a high-fidelity sensor. Experimental tests and simulated performance based on a 1-D model are compared for Diesel and DME for a high-pressure fuel pump, piston style, featuring two plunger-barrels. Each of the pump’s plunger-barrel is inlet metered electronically, allowing the pump to run at a variable displacement and with the flexibility to deactivate one or both plungers fully. The model captures the response of the inlet metering valve and output valve lifts across speed and loads. The output check valve is subject to pressure pulsations and shows the importance to optimize its time response to stabilize it and thus provide optimal pumping. The model also captures the torque response, with contributions arising from the pressure loading, spring return force, and acceleration. Torque depends on the volume pumped, which conversely is dependent on pressure and compressibility. The volumetric efficiency is reduced as pressure increases, but the mechanical efficiency of output pressure-work over input torque remains high, between 80-90% in most of the pump operating conditions. Experimental torque measurements show close alignment with the simulations at elevated pump speeds and pressures but differences are noted at lower speeds. The deviations appear to arise from the outlet check valve stability and from the flow dynamics experienced at the pump inlet. These inlet dynamics were not properly captured in the model, but they are notable in the experimental results. Tests show significant variability in the pump pressure feed owing to the flow dynamics. Test results show this variability is reduced when the pump operates with two plunger-barrels rather than one. With one plunger-barrel the torque profile is notably cyclical, a high torque from one plunger is succeeded by a lower toque on the following plunger, while with the two plunger-barrels configuration the torque profile becomes more uniform from one plunger to the next.
de Ojeda, William, Wu, Simon (Haibao)
Investigation of Transient High Current Ignition for Lean Mixture in Spark Assisted Compression Ignition2025-01-039010/7/2025
Lean burn combustion is an effective strategy to reduce the in-cylinder temperature. Hence reduce NOx emissions and increase the thermal efficiency of the system. One essential aspect of successful combustion is the flame kernel initiation and development. However, as the fuel-air mixture becomes leaner, challenges arise in achieving a stable flame kernel initiation and a moderate speed of flame propagation. This empirical research aims to investigate the impact of the transient high current ignition strategy on flame kernel development, flame propagation and auto-ignition timing of lean Dimethyl Ether (DME). In this work, a rapid compression machine is employed at engine-relevant conditions, a pressure of ~15 bar and temperature of ~650K. Spark-assistance is applied at the end of compression to enable a spark-assisted compression ignition combustion mode. The spark event is initiated by a transient high current ignition system, which includes a traditional transistorized coil ignition and an in-parallel high-voltage capacitor for boosting the transient current, enabling high discharge energy (up to 11.3J). The combustion process is qualitatively assessed with high-precision pressure data acquisition along with high-speed images and quantitatively processed through image processing. Test results indicate that as spark energy increases, faster flame propagation is observed resulting in a shorter time requirement for reaching the auto-ignition in lean DME along with a shorter combustion duration.
Asma, Sabrina, Yu, Xiao, Jin, Long, Tjong, Jimi, Zheng, Ming
Optimization of CI Engine Operation with DME on an FTP Cycle2025-01-039410/7/2025
Fuels that can be produced in a sustainable manner are of high interest because they can provide an essential step toward net zero emissions vehicles. This study examines the combustion of one such fuel, Dimethyl Ether (DME), in a compression ignition, 4-cylinder, 2.2L engine. Testing was conducted using the Federal Test Procedure (FTP) certification cycle from the US Environmental Protection Agency (EPA). Different sets of calibration maps were designed to target low-NOx (30-50ppm) by using high EGR and intake throttle and high-NOx (approximately 1000ppm) using no EGR. An intermediate, mid-NOx calibration was also evaluated. Varying calibration approaches yielded total integrated engine out emissions ranging from 118 to 145gCO2/km, all below the 191gCO2/km from the baseline diesel. The corresponding NOx+UHC and CO emissions were also evaluated. The mid-NOx calibration was overall more favorable, as it met TIER 3-Bin 20 emissions requirements with the current efficiencies of the base engine diesel aftertreatment system. This paper reviews the transient behavior with three different calibrations, noting the effect of air-to-fuel ratios where the engine combustion efficiency deteriorates. It also highlights the impact of improved air and fuel controls, and the application of real time combustion feedback to enhance the combustion stability of the engine and the reduction of CO2 emissions. The paper explores the impact of renewable DME, and its carbon index, on the CO2 emissions for the low-NOx calibration. While a 5% renewable DME content can reduce the CO2 to the target level, the fuel consumption remains high due to the poor combustion efficiency and corresponding high HC and CO during transient operation.
De Ojeda, William, Wu, Simon (Haibao), Harrison, Christopher, Hall, Carrie, Arslan, Elaheh, Pulpeiro Gonzalez, Jorge
Model-Based Optimization of Diesel/OMEx Fuelled CI Engine under Multiple Blending Conditions2025-24-00389/7/2025
The search for alternative solutions for vehicle electrification, while reducing the carbon footprint during the transition to green mobility, leads to the investigation of electro-fuels (e-fuels) in conventional internal combustion engines. Leveraging previous research, the present study focuses on the optimisation of a Compression Ignition (CI) engine combustion control in response to the use of the Oxymethylene Dimethyl Ethers (OMEx) blended with conventional diesel. The selected e-fuel is the OME3, which is expected to be used as a drop-in solution and to easily achieve a reduction in soot emissions due to both its high oxygen content and lack of direct carbon bonds in its molecular structure. To verify its potential, a 1D single-cylinder CI multi-zone engine model has been exploited to simulate various diesel/OME3 blends in a wide engine operating range. The first step deals with the evaluation of performance and emissions to demonstrate the differences, particularly in terms of emissions reduction compared to the baseline standard configuration. Each operating condition is then optimized to minimize the energy losses associated with fuel substitution while maintaining the beneficial emission reductions. The model parameters identification and the optimisation of the different blends for each engine operating point are carried out using the software GT-Suite. This approach aims to provide an assessment of the methodology to design new control strategies along with the analysis of the potential impact of using such blends. On the basis of these results, a further optimization was carried out to assess, for each optimized operating point, which blending ratio guarantees the best performance both in terms of emissions and fuel consumption.
Foglia, Antonio, Cervone, Davide, Frasci, Emmanuele, Arsie, Ivan, Polverino, Pierpaolo, Pianese, Cesare
Assessing the Performance of a Modified Fuel Injection System–Equipped Dimethyl Ether-Fueled Genset/Tractor Engine04-18-03-00145/21/2025
Ethers are emerging as suitable mineral diesel replacements. A customized mechanical fuel injection system was used to investigate the dimethyl ether–fueled genset/tractor, and ~75% rated engine load was achieved over diesel. The in-cylinder pressure rise rate was about half for the dimethyl ether engine. However, the lower pressure generated in the high-pressure dimethyl ether line reduced brake thermal efficiency for the dimethyl ether engine. Dimethyl ether engines emitted lower nitrogen oxide emissions than baseline diesel except at higher loads and reduced nozzle opening pressure. Carbon monoxide emissions increased due to prolonged and incomplete combustion at higher loads with reduced nozzle opening pressure. Blowby gas leakage was lower for dimethyl ether than for baseline diesel engines. Overall, the genset/tractor engine could perform satisfactorily using a customized fuel injection system and will help achieve carbon neutrality from the various sectors using this technology.
Agarwal, Avinash Kumar, Pal, Manojit, Valera, Hardikk
Experimental Quantitative Analysis of Spray Velocity Field Characteristics of Four Compression-Ignition Engine Oxygenated Alternative Fuels03-18-03-00215/10/2025
As the suitable substitutes for diesel in compression-ignition (CI) piston engines, hydrotreated vegetable oil (HVO), polyoxymethylene dimethyl ethers (PODEs), and bio-aviation fuel (BAF), among other oxygenated alternative fuels have been widely recognized due to higher cetane values. To explore the in-cylinder fuel spray dynamics and subsequent fuel–air entrainment of these fuels, experimental studies on near-field and full-field spray characteristics were carried out by the diffuser back-illumination imaging (DBI) method within a constant-volume chamber. The local velocity was inferred by momentum flux conservation and Gaussian radial profile assumption, and the dimensionless Jet number was introduced to qualify the strength of interaction within two-phase flow. It was found that the initial spray transitions from a “needle” to a larger spray head structure as injection pressure rises, especially with PODE3-5 exhibiting a stable “mushroom” structure due to its higher surface tension. Superior axial penetration and velocity are achieved by PODE3-5 due to higher density (ρ = 1), resulting in the smallest spray cone angle. The largest Jet numbers for PODE3-5 at the center axis signify stronger friction between the fuel and gas, while the weaker droplet fragmentation and atomization were indicated by the lower Jet numbers at the spray periphery. BAF was characterized by the maximum cone angles and highest radial spray velocities near the nozzle due to the cavitation effect caused by the maximum saturated vapor pressure (ρ = 1), which promoted radial spray development. HVO exhibited smaller near-nozzle cone angles resulting from its higher viscosity (ρ = −0.6), though comparable cone angles to BAF were achieved in downstream regions owing to the second-highest saturated vapor pressure. Finally, a more accurate modified empirical spray penetration model is derived by incorporating fuel density.
Chen, Houchang, Jiang, Junxin, Hu, Yong, Yu, Wenbin, Zhao, Feiyang
Optimization of the Numerical Spray Modeling for Polyoxymethylene Dimethyl Ethers for Combustion Prediction in CONVERGE2025-01-50264/3/2025
Different approaches are undertaken to mitigate the impact of the transport sector on climate change. Alongside electrifying powertrains, sustainable e-fuels such as polyoxymethylene dimethyl ethers (OME) are considered a promising bridging technology for different applications. However, this requires that the engines are optimized for the new fuels. Accordingly, this study aims to optimize the numerical spray modeling of OME in CONVERGE. Based on the KH–RT break-up model, the spray simulations of three different commercial injectors for heavy-duty applications are analyzed regarding the predictability of the liquid and gaseous penetration lengths and the total simulation time. A sensitivity analysis is conducted for the turbulence model, mesh size, and spray parameters prior to optimizing the spray model and validating it with experimental results. While each parameter individually influences the different phases of the injection event, the sensitivity analysis reveals that the break-up time constant B1 has overall the most significant impact on the penetration length. Additionally, the standard k-ε model demonstrated the best alignment for turbulence modeling. The computational time was reduced by optimizing the parcel count and grid size while achieving a further optimized grid size with finer maximum size and coarser minimum size for use in the full-engine combustion model. The optimization reduced the RMSE for the liquid penetration length (LPL) and gaseous penetration length (GPL) by 75% to 1.01 mm and 1.26 mm, respectively. The validation with experimental data shows that the resulting model can be used in qualitative design optimization regarding injection pressure, counter pressure, and nozzle hole diameter with an overall RMSE for the penetration length around 2 mm.
Zepf, Andreas, Härtl, Martin, Jaensch, Malte
Investigation of Dimethyl Ether Injection Profiles in High-Pressure Direct Injection System2025-01-84644/1/2025
The majority of transportation systems continue to rely on internal combustion engines powered by fossil fuels. Heavy-duty applications, in particular, depend on diesel engines due to their high brake efficiency, power density, and robustness. Despite significant advancements in diesel engine technology that have reduced emissions and improved efficiency, complex and costly after-treatment systems remain necessary to meet the stringent emission regulations. Dimethyl ether (DME), which can be produced from various renewable feedstocks and possesses high chemical reactivity, is a promising alternative for heavy-duty applications, particularly in compression ignition direct injection engines. Its high reactivity, volatility, and oxygenated composition offer significant potential to address emission challenges while reducing reliance on after-treatment systems. However, DME’s lower energy density requires adjustments in injection parameters (such as injection pressure and duration) or modifications to the injector geometry to match the energy levels of diesel fuels. Although previous studies have explored adjustments like increasing injection pressure and duration to compensate for DME’s lower energy density, the impact of nozzle diameter on the rate of injection profile and spray morphology remains unclear. This study investigated the injection characteristics of DME in a high-pressure direct injection system. The rate of injection profile was measured using a custom-designed long tube platform based on the Bosch method. The results from the Bosch method showed strong consistency with those obtained from a commercial injection test bench based on Zeuch method. Additionally, the rate of injection profiles for two different nozzle diameters were measured to assess the impact of nozzle size on the rate of injection profiles. The effects of increased nozzle diameter on spray morphology were examined using high-speed photography.
Cong, Binghao, Leblanc, Simon, Tjong, Jimi, Ting, David, Yu, Xiao, Zheng, Ming
Design of a High-Pressure Fuel System for Use with Dimethyl Ether2025-01-84414/1/2025
The paper documents the modeling and experimental work on a common rail fuel injection system for Dimethyl Ether, a potential diesel substitute with a low carbon intensity signature. The DME fuel system is deployed on a light duty 2.2L compression ignition engine. The paper describes the injector optimization to shift to higher flows to account for the lower heating value and density of the DME when compared to diesel. The type of the injection system used for the DME application is an advanced rendering of the Common rail noted for a one-piece piston-needle injector construction and a solenoid driven spill valve featuring a pressure balanced poppet. A dedicated high-pressure fuel pump designed to pressurize DME is used. The design results in a fast acting open and close injection event, reduced leakage, with reduced cavitation in the fuel injector volume. Design parameters for system optimization included fill and spill orifices, needle lift, bias spring, and injector hole size. The design model provides good correlation of the instantaneous rates of injection with experiments across a wide range of pressure and injection timings. Proposed performance milestones for the design included similar DME injection duration to the diesel counterpart for same fuel energy injected into the cylinder to retain high engine cycle efficiency. The dedicated DME design provided reduced hydraulic delays of 50%. Tests demonstrated sustained operation at pressures of 1000 bar, with capability to reach 1500bar. Durability tests showed no cavitation-deterioration over a 200-hour test cycle by means of spray imaging and hardware inspection.
De Ojeda, William, Wu, Simon (Haibao)
Energy Conversion Efficacy of Neat Dimethyl Ether Combustion with Heat Release Characterization and Emission Analysis2025-01-84174/1/2025
Dimethyl ether (DME) is widely regarded as a suitable energy source for compression ignition power systems because of its high reactivity. It has been widely reported that DME possesses a significantly low propensity to form soot, hindering the innate NOx-soot trade-off encountered with diesel fuel operation. Beyond the fuel-borne oxygen content of DME, its unique physical properties present a contrasting combustion behavior which may be advantageous to direct injection systems, especially concerning the mixing-controlled combustion mode. This work aims to detail the energy conversion efficacy of DME through heat release characterization and exhaust emission speciation. The tests were controlled within a single-cylinder research engine with an off-board high-pressure injection system to handle liquified DME up to 1000bar. To mitigate interference in fuel additives over the combustion behavior, the high-pressure fuel system specifically managed neat DME. The in-cylinder pressure was the indicator for combustion behavior, whereas exhaust emissions were sampled with infrared and mass spectroscopy for exhaust speciation. The in-cylinder combustion profile was aligned with the actual rate of injection to designate the characteristics between the injection and combustion events. Overall, the fuel-to-heat conversion efficiency is comparable, while the combustion efficiency is slightly greater owing to lower carbon monoxide emissions. Without injection-combustion overlap, i.e. low load and primarily premixed combustion, the heat release pattern of DME was like diesel. Under extended injection-combustion overlap, diesel finished injection up to CA50% of cumulative heat release whereas DME injection often finished up to ~CA80%. The end of the injection was followed by a fast and abrupt drop in heat release, e.g. the end of combustion. The application of exhaust gas dilution, however, altered the end of the combustion pattern and promote carbon monoxide emissions.
Leblanc, Simon, Cong, Binghao, Leach, Jace, Yu, Xiao, Reader, Graham, Zheng, Ming
Characterization of Dimethyl Ether (DME) Spray Using ECN Spray D Under Engine-Relevant Conditions2025-01-84574/1/2025
This research experimentally investigates the spray vaporization of high-pressure dimethyl ether (DME) using a single-hole research injector focusing on nominal operating conditions from the Engine Combustion Network (ECN). DME is a synthetic alternative to diesel fuel, offering both high reactivity and potential reductions in particulate emissions. Because DME only features half of the energy density of diesel fuel, a specifically designed fuel system with a high mass flow rate to meet the energy delivery requirements is needed. The unique physical properties of DME, including higher vapor pressure and lower viscosity, introduce challenges like cavitation and unique evaporation characteristics that deviate from typical diesel fuel. These features are likely to lead to differences in fuel mixing and combustion. This study aims to provide detailed experimental data on DME spray characteristics under engine-like conditions, helping the development of predictive CFD models for optimal injector and combustion chamber design. High-pressure sprays injected via an ECN Spray D injector are analyzed using high-speed diffuse-back illumination extinction imaging (DBI-EI) to measure the liquid phase of the sprays and shadowgraphy imaging to measure the vapor penetration. DME injections show slower penetration when compared to more conventional liquid fuels, namely n-dodecane. This delayed injection might indicate cavitation and the role of an evacuated injector tip prior to injection. To confirm this aspect of the empty sac, the injection rate profile was investigated using the Musculus and Kattke jet model. Subsequently, the vapor-liquid equilibrium at the liquid length was analyzed, revealing the distinct mixing nature of DME. The measured DME liquid length on average extends 56% beyond the predicted vapor-liquid equilibrium distance. This research will provide comprehensive datasets on liquid/vapor mixing, which are crucial for developing reliable spray and combustion modeling tools.
Yi, Junghwa, Wan, Kevin, Pickett, Lyle, Manin, Julien
Diesel Engine Performance and Combustion Imaging Analysis of Gas-to-Liquid and Polyoxymethylene Dimethyl Ether Blended Fuels04-18-02-00102/12/2025
To reduce carbon dioxide emissions from automobiles, the introduction of electric vehicles to the market is important; however, it is challenging to replace all existing IC engine vehicles with electric ones. Consequently, there is increasing anticipation for the use of carbon-neutral fuels, such as e-fuels. This study investigates the effects of GTL (gas-to-liquid), as a substitute for e-fuel, produced from natural gas via the Fischer–Tropsch synthesis method and polyoxymethylene dimethyl ether (OMEmix) produced from methanol, on engine performance. Additionally, combustion image analysis was conducted using a rapid compression and expansion machine (RCEM). GTL fuel combusts similarly to conventional diesel fuel but has slightly lower smoke emissions because it does not contain aromatic hydrocarbons. Further, its high cetane number results in better ignition properties. During the combustion, unburnt hydrocarbons and smoke are generated in the spray flame interference region near the cylinder wall due to insufficient oxygen, and as it moves from the cylinder wall toward the center of the cylinder, the re-oxidation is observed, which is reflected in the heat release rate as the after-burning duration. When the OMEmix is mixed with hydrocarbon fuels such as GTL, combustion continues even in the spray flame interference region, leading to a reduction in the after-burning duration and significantly lower smoke emissions. Further, the GTL was divided into four distillation regions, that are GTL Light, GTL Light Middle, GTL Middle Heavy, and GTL Heavy, and the effects of low and high-boiling fractions in GTL on diesel combustion were investigated. Heavy fractions have excellent ignition properties, resulting in shorter lift-off (set-off) length during combustion. However, due to the poor evaporation characteristics, they have longer high-temperature residence time, leading to greater cooling losses and reduced thermal efficiency. On the other hand, light fractions have longer lift-off lengths, mix well with air before combustion, and have shorter combustion durations compared to heavy fractions. Finally, an engine performance was evaluated using a fuel mixture of the fuel with the heavy fractions removed from GTL (heavy-cut GTL) and OMEmix in a 1:1 ratio.
Shibata, Gen, Yuan, Haoyu, Yamamoto, Hiroya, Tanaka, Shusuke, Ogawa, Hideyuki
Experimental Study on Combustion and Emission Characteristics of a Two-Stroke Engine applying PODE/Methanol Blends Direct Injection2025-01-71121/31/2025
In order to realize the Paris Agreement, which aims to strengthen the global response to climate change, conventional internal combustion engines (ICE) need to contribute to reducing carbon emissions and improving thermal efficiency. More importantly, in the face of energy shortages, it is urgent to search for sustainable fuels. Poly-oxymethylene dimethyl ethers (PODE) and methanol are both regard as important low-carbon, alternative fuels due to their high oxygen content. Using PODE can overcome the characteristics of methanol as a low-reactivity fuel with a low cetane number and poor ignition properties. In this study, the combustion and emission characteristics of PODE/methanol blends were investigated in a two-stroke direct injection engine. Firstly, the performance of the engine under pure PODE (P100) and PODE/methanol blends (P50) was compared. The results show that at BMEP of 0.31 MPa and injection timing of -8°CA ATDE, P50 blends have lower CO2, CO, NOX and THC emissions than P100 fuel. However, the start of combustion of P50 is delayed slightly and ITE is lower than that of P100. Then, the effect of injection timing on the performance of the P50 engine was investigated. With the delay of fuel injection timing, NOX emissions decrease, but CO2, CO, and THC emissions increase. Moreover, as the injection timing is delayed, the engine COVIMEP was reduced and combustion stability was improved. The engine indicated mean effective pressure (IMEP) reaches its maximum value of 0.441MPa at -8°CA ATDC and decreases as injection timing is delayed. However, the indicated thermal efficiency (ITE) decreases with the delay of injection timing, reaching a maximum of 41.8% at -8°CA ATDC. This study provides a theoretical foundation for adopting PODE/methanol blends in diesel engines, highlighting their potential to reduce conventional emissions while maintaining operational feasibility. Further research on varying methanol ratios and load conditions is recommended.
Dong, Pengbo, Sun, Zhuohan, Wang, Qingyang, Wang, Yang, Cui, Jingchen, Zhang, Zhenxian, Long, Wuqiang
Emission and Economic Characteristics of Diesel/PODE Blended Fuel in Actual Road Driving2025-01-71151/31/2025
Diesel/Polymethoxy Dimethyl Ether (PODE) blend fuel can significantly reduce emissions from diesel engines. However, emission levels often vary due to high transients during real-world driving conditions. To evaluate the emission and economic performance of diesel/PODE blend fuel, this study analyzed the real-world driving behavior of heavy tractors using different blend ratios (0%, 20%, 30%) across urban, suburban, and expressway road sections, in compliance with the national VI emission standard. Based on Vehicle Specific Power (VSP) bins, the study compared carbon monoxide, carbon dioxide, nitrogen oxide, particulate matter, and fuel consumption rates between pure diesel and blended fuels, providing insights into their performance under varying driving conditions. In addition, specific emissions of pollutants, effective fuel consumption, and effective thermal efficiency for urban, suburban, and expressway sections, as well as for the entire test process, are analyzed to quantify the impact of PODE. The results show that adding PODE reduces CO and PN emissions while increasing NOx emissions, with the most significant reductions in CO and PN occurring under high power output conditions. In actual road driving, CO and PN emissions are highest in urban sections, while NOx specific emissions peak in expressway sections. Adding PODE increases the effective fuel consumption rate. At a 30% blending ratio, the average effective thermal efficiency is approximately 2% higher than that of pure diesel, with varying effects observed at a 20% blending ratio across different sections. These findings provide valuable insights for the further development of diesel/PODE blends and their application in heavy-duty engines by manufacturers.
Liu, He, Yang, Yajing, Farooq, Muhammad Shahid, Liu, Shenghua, Wei, Yanju
Emission Characteristics of TCR Diesel Fuels in Comparison to Diesel Fuels Derived from other Sources2024-01-428911/5/2024
In this work we demonstrate the influence of different refined TCR refining diesel fuels on emission, power and efficiency in comparison to reference Diesel fuel (homologation fuel for Euro 6 emission testing), hydrotreated vegetable oil (HVO) and a blend of poly(oxymethylene)dimethyl ether (OME3) with reference Diesel. The emission characteristics of such TCR fuels used in a production type Diesel engine with modern common rail system has up to now not been tested. The comparison was performed at an engine test bench equipped with a Hatz 4H50 TIC direct injection common rail Diesel engine. For different engine operation points exhaust gas emissions and particulate matters were measured and the results analyzed.
Seeger, Jan, Taschek, Marco
Combustion and Emissions Comparison between a Diesel and a Dimethyl Ether (DME) Off-Highway Compression Ignition Engine2024-01-270011/5/2024
Dimethyl ether (DME) is a promising substitute for diesel as a fuel in heavy-duty engines. This article presents the comparison between a diesel- and a DME-powered compression ignition engine. The diesel-powered version was initially characterised at a range of operating points before being converted to operate on DME. This was achieved by replacing fuel system components with bespoke DME-compatible engine parts. An off-board fuel pressurisation and conditioning system was designed to replace the existing high-pressure fuel pump, while maintaining all other engine hardware and components. Engine behaviour, in terms of combustion and emissions on both fuels was examined. Firstly, the effect of varying recirculated exhaust gas (EGR) concentration at constant excess air ratio, combustion phasing (CA50) and equal fuel delivery rate (by energy input) was interrogated. DME combustion was significantly faster, as combustion duration was reduced by around 30%, in some cases, when comparing to diesel. The DME-powered version of the engine was also found to produce lower carbon monoxide (CO) and unburned hydrocarbon (uHC) emissions. Up to a threefold reduction was measured, depending on engine load. NOx emissions worsened, when transitioning to DME, for the medium load case. The low-load EGR sweep showed minimal changes in NOx emissions. High-pressure EGR can significantly lower DME NOx emissions to below the diesel baseline levels, depending on engine load and speed, as demonstrated by the results of the 8-mode test runs. Given the extremely low particulate emissions, higher EGR concentrations can be utilised by engines operating on DME. Despite resorting to the use of bespoke equipment in this study, the challenges faced during the engine conversion were deemed manageable with the currently available technology.
Apostolou, Christos, Elliott, Thomas, Rutledge, John, Butcher, Daniel, Long, Edward, Spencer, Adrian
Comparison of Different Injector Nozzles for the Utilization of Polyoxymethylene Dimethyl Ethers2024-01-429711/5/2024
Oxygenated substances are a promising approach in the field of alternative fuels. A current example of such a fuel are Polyoxymethylene Dimethyl Ethers (OME). With their physical and chemical properties, alternative fuels like OME pose new challenges for diesel engine injection systems. As the heating value is low compared to conventional Diesel fuel, measures must be taken to increase the amount of fuel injected. Possible solutions include increasing the nozzle hole diameter, the injection pressure, and the number of nozzle holes. All mentioned adaptions have an influence on the mixture formation and make it necessary to examine the injection process in detail also with regard to phenomena such as cavitation. In this study, three passenger car Diesel injector nozzles are compared, two of which are adapted in terms of nozzle hole diameter (increase by 20%) and number of nozzle holes (increase from 8 to 12) in order to increase the mass flow rate of fuel to the required elevated level. The injectors are examined under various operating conditions using the optical measurement methods of Mie scattering and Schlieren photography in a constantly purged high-temperature and -pressure injection chamber. Mixture formation is analyzed on basis of the measurement results for different fuels and blends. Results show that adaptions such as increasing the nozzle hole diameter or the number of nozzle holes are unavoidable, as increasing the injection pressure alone cannot realistically compensate for the lower calorific value of OME. In addition, strong cavitation can be observed without adjustments to the nozzle holes. With the adapted nozzles, increasing the nozzle hole diameter leads to an increase in the local fuel/air ratio, while increasing the number of nozzle holes leads to a decrease.
Riess, Sebastian, Fuchs, Thorsten, Strauß, Lukas, Günthner, Michael, Wensing, Michael
Letter from the Focus Issue Editors03-17-07-004910/12/2024
Letter from the Focus Issue Editors
Lakhlani, Hardik, Kumar, Vivek, Wenbin, Yu, Bagga, Kalyan, Gundlapally, Santhosh, Di Blasio, Gabriele, Splitter, Derek, Rajendran, Silambarasan
TOC99-06-05-0TOC10/10/2024
TOC
Tobolski, Sue
Effects of Dimethyl Ether and Propane Blends on Knocking Behavior in a Boosted SI Engine03-17-07-00566/12/2024
Dimethyl ether (DME) is an alternative fuel that, blended with propane, could be an excellent alternative for exploring the use of fuels from renewable sources. DME–propane blends are feasible for their comparable physicochemical properties; these fuels may be pressured as liquids using moderate pressure at ambient temperature. Adding a proportion of DME with a low octane number to a less reactive fuel like propane can improve the combustion process. However, the increased reactivity of the mixture induced by the DME could lead to the early appearance of knocking, and this tendency may even be pronounced in boosted SI engines. Hence, this study experimentally analyzes the effect of E10 gasoline (baseline) and DME–propane blends, with varying proportions of DME in propane ranging from 0% to 30% by weight, in increments of 5% on knocking tendency, combustion characteristics, gaseous emissions, and particle number concentration, under different intake pressure conditions (0.8, 0.9, 1.0, and 1.1 bar) in an SI engine. The results show that as the proportion of DME in the propane blend rises, the knocking tendency becomes more pronounced. That behavior intensifies with increasing intake pressure, but with 20% DME in the propane blend, reaching the maximum brake torque (MBT) without knocking in the four boosted conditions is feasible. The presence of knock limited the advance of combustion phasing and decreased the gross indicated thermal efficiency (ITEg) with E10 gasoline and 25% and 30% DME in propane blends under 1.0 and 1.1 bar boosted conditions. In these knock-limited circumstances, the NOx emissions decreased due to the retarded phasing, and THC and PN emissions increased due to the lower combustion stability, considerably raising the concentration of accumulation mode particles in the particle size distribution (PSD) compared to the other fuel blends tested.
Soto, Lian, Han, Taehoon, Boehman, Andre L.
Dimethyl Ether Biogas Reactivity-Controlled Compression Ignition for Sustainable Power Generation with Low Nitrogen Oxide Emissions03-17-07-00544/22/2024
Biogas (60% methane–40% CO2 approximately) can be used in the reactivity-controlled compression ignition (RCCI) mode along with a high-reactivity fuel (HRF). In this work dimethyl ether (DME) that can also be produced from renewable sources was used as the HRF as a move toward sustainable power generation. The two-cylinder turbocharged diesel engine modified to work in the DME–biogas RCCI (DMB-RCCI) mode was studied under different proportions of methane (45–95%) in biogas since the quality of this fuel can vary depending on the feedstock and production method. Only a narrow range of biogas to DME ratios could be tolerated in this mode at each output without misfire or knock. Detailed experiments were conducted at brake mean effective pressures (BMEPs) of 3 and 5 bar at a speed of 1500 rpm and comparisons were made with the diesel–biogas dual-fuel and diesel–biogas RCCI modes under similar methane flow rates while the proportion of CO2 was varied. The DMB-RCCI mode exhibited superior brake thermal efficiency (25.3% as against 22% and 31.5% as against 29% at the BMEPs of 3 and 5 bar) as compared to the other modes and was not sensitive to the concentration of methane. The NOx and soot emissions were also negligible and the lowest CH4 emission levels were also attained. The cyclic fluctuations in IMEP were lower than 5% in this mode. Thus, DME can be used along with biogas to enhance its reactivity for sustainable power generation in the RCCI mode.
Gopa Kumar, S., Mohan, Aneesh, Ramesh, A.
Potential Analysis of Defossilized Operation of a Heavy-Duty Dual-Fuel Engine Utilizing Dimethyl Carbonate/Methyl Formate as Primary and Poly Oxymethylene Dimethyl Ether as Pilot Fuel03-17-07-00534/18/2024
This study demonstrates the defossilized operation of a heavy-duty port-fuel-injected dual-fuel engine and highlights its potential benefits with minimal retrofitting effort. The investigation focuses on the optical characterization of the in-cylinder processes, ranging from mixture formation, ignition, and combustion, on a fully optically accessible single-cylinder research engine. The article revisits selected operating conditions in a thermodynamic configuration combined with Fourier transform infrared spectroscopy. One approach is to quickly diminish fossil fuel use by retrofitting present engines with decarbonized or defossilized alternatives. As both fuels are oxygenated, a considerable change in the overall ignition limits, air–fuel equivalence ratio, burning rate, and resistance against undesired pre-ignition or knocking is expected, with dire need of characterization. Two simultaneous high-speed recording channels granted cycle-resolved access to the natural flame luminosity, which was recorded in red/green/blue and OH chemiluminescence. Selected conditions were investigated in more detail with the simultaneous application of planar laser-induced fluorescence of OH and HCHO and recording natural flame luminescence in a cycle-averaged manner. Poly oxymethylene dimethyl ether was used as pilot fuel, building on prior investigations. The mixture of 65 vol% Dimethyl Carbonate and 35 vol% Methyl Formate with prior verification on a passenger-car-sized engine substitutes synthetic natural gas in this study. Thermodynamically, the increased compression ratio up to 17.6 resulted in feasible operation and increased indicated efficiency. On the lower compression ratio of 15.48, a more comprehensive range of applicable air–fuel equivalence ratios and increased degrees of freedom regarding the pilot’s total energy share are observed compared to the base configuration with natural gas and EN590 as pilot fuel. The air–fuel equivalence ratio sweep from λ = 1.0–2.0 revealed predominantly premixed and high-temperature heat release via OH*. The temporal and spatial evolution shifts while leaning out the mixture with increasing gradients on the radial distribution and decouples for lean mixtures from the initial spray trajectory.
Mühlthaler, Markus Sebastian, Härtl, Martin, Jaensch, Malte
Experimental Investigation of Internal and External EGR Effects on a CNG-OME Dual-Fuel Engine2024-01-23614/9/2024
Dual-fuel engines powered by renewable fuels provide a potential solution for reducing the carbon footprint and emissions of transportation, contributing to the goal of achieving sustainable mobility. The investigation presented in the following uses a dual-fuel engine concept running on biogas (referred to as CNG in this paper) and the e-fuel polyoxymethylene dimethyl ether (OME). The current study focuses on the effects of exhaust gas rebreathing and external exhaust gas recirculation (EGR) on emissions and brake thermal efficiency (BTE). A four-cylinder heavy-duty engine converted to dual-fuel operation was used to conduct the engine tests at a load point of 1600 min-1 and 9.8 bar brake mean effective pressure (BMEP). The respective shares of high reactivity fuel (HRF, here: OME) and low reactivity fuel (LRF, here: CNG) were varied, as were the external and internal EGR rates and their combinations. CNG was injected into the intake manifold to create a homogeneous air-fuel mixture, while OME was introduced as a pilot injection directly into the combustion chamber. Results showed an increase in total hydrocarbons (THC) and carbon monoxide (CO) emissions, while nitric oxide (NOx) emissions were significantly reduced compared to diesel operation. Soot emissions were completely mitigated due to the absence of direct carbon bonds in both CNG and OME. For the initial stage of the study, exhaust gas rebreathing was implemented on only one exhaust valve through a second event lift. For the second part of the study, the second event lift was also installed on the other exhaust valve. At a substitution rate of 50 % CNG, THC emissions could be lowered by up to 35 %, CO emissions by up to 50 % and NOx emissions by up to 18 % with the use of internal EGR. The combination of internal and external EGR reduced emissions even further.
Jost, Ann-Kathrin, Guenthner, Michael, Weigel, Alexander
Effect of Spark Assisted Compression Ignition on the End-Gas Autoignition with DME-air Mixtures in a Rapid Compression Machine2024-01-28224/9/2024
Substantial effort has been devoted to utilizing homogeneous charge compression ignition (HCCI) to improve thermal efficiency and reduce emission pollutants in internal combustion engines. However, the uncertainty of ignition timing and limited operational range restrict further adoption for the industry. Using the spark-assisted compression ignition (SACI) technique has the advantage of using a spark event to control the combustion process. This study employs a rapid compression machine to characterize the ignition and combustion process of Dimethyl ether (DME) under engine-like background temperature and pressures and combustion regimes, including HCCI, SACI, and knocking onsite. The spark ignition timing was swept to ignite the mixture under various thermodynamic conditions. This investigation demonstrates the presence of four distinct combustion regimes, including detonation, strong end-gas autoignition, mild end-gas autoignition, and HCCI. The observation indicates that HCCI exhibits a relatively low-pressure rise rate and a prolonged combustion duration. On the other hand, the detonation case can achieve a fast flame propagation velocity of up to 2.4 km/s, generating high-frequency pressure oscillation. Pressure traces were processed using the Fast Fourier Transform (FFT) method to characterize the different end gas autoignition regimes under various spark timing. Moreover, hydrogen fuel blends with DME to reduce the auto-ignition tendency of DME fuel but increase the flame propagation speed. The combustion characteristics of the autoignition-initiated flames are compared with that of using neat DME fuel via pressure measurement and high-speed images. The results demonstrated that deploying hydrogen into the fuel exhibits enhanced knock resistance and reductions in pressure oscillations.
Jin, Long, Yu, Xiao, Wang, Meiping, Reader, Graham, Zheng, Ming
Light Duty Engine Performance Characteristics with Dimethyl Ether and Propane2024-01-21264/9/2024
The paper explores the performance characteristics of a compression ignition HYUNDAI 2.2L engine operating with Dimethyl Ether (DME). Test are carried out at three operating conditions that weigh heavily in the FTP75 certification cycle (1000rpm-12Nm, 1500rpm-50Nm, 2000rpm-100Nm). The engine features a high-pressure common rail fuel injection system designed to operate with liquified gases. The main component of the fuel system is a high-pressure pump that incorporates an electronic inlet metering valve commanded on a crank-angle base to control the rail pressure. The pump, which requires no pressure regulator, provides the flow needed to the injectors without flow returning to the inlet. This novel fueling system is leveraged in tests that are conducted to examine the impact of EGR, combustion phasing, injection pressure on efficiency and emissions. In addition, the impact of introducing 15% Propane by mass is examined. During the tests, the engine ECU is aided by an Engine Controller High Speed Oversight unit (ECHO) to provide combustion phasing control, improved cylinder-to-cylinder uniformity, and an effective optimization over the testing effort. The use of DME and Propane allowed for peak thermal efficiency of nearly 43%. These fuels enable significant carbon index (CI) reductions over the baseline Diesel fuel, with indications that 50% reduction in CO2 over the Diesel engine are possible.
De Ojeda, William, Wu, Simon (Haibao), Ankobea-Ansah, King, Hassan, Hafiz Ahmad, Hall, Carrie
Oxygenated Fuels as Reductants for Lean NOx Trap Regeneration2024-01-21324/9/2024
The push for environmental protection and sustainability has led to strict emission regulations for automotive manufacturers as evident in EURO VII and 2026 EPA requirements. The challenge lies in maintaining fuel efficiency and simultaneously reducing the carbon footprint while meeting future emission regulations. Alcohol (primarily methanol, ethanol, and butanol) and ether (dimethyl ether) fuels, owing to their comparable energy density to existing fuels, the comparative ease of handling, renewable production, and suitable emission characteristics may present an attractive drop-in replacement, fully or in part as an additive, to the gasoline/diesel fuels, without extensive modifications to the engine geometry. Additionally, lean and diluted combustion are well-researched pathways for efficiency improvement and reduction of engine-out emissions of modern engines. Modern internal combustion engines typically employ various in-cylinder emission reduction techniques along with a multi-stage exhaust after-treatment system to comply with emission standards. Lean NOx trap (LNT) is one such aftertreatment system that can reduce the tailpipe NOx under lean conditions at a cost of fuel efficiency penalty due to regeneration. This penalty can be partially mitigated by using in-cylinder NOx reduction methodologies. In the present study, the impact of oxygenated fuels (ethanol and dimethyl Ether) on the regeneration of LNT catalyst under various lean burn exhaust conditions is investigated. The regeneration characteristics of the oxygenated fuels are compared to those of conventional gasoline fuels. Relevant engine-out exhaust conditions from SI and CI engines, including flow, temperature, and exhaust species, operating at different dilution conditions were replicated on a heated aftertreatment flow bench. A comprehensive analysis of species before and after the catalyst sections was performed using Fourier-transformed infrared (FTIR) and mass spectrometers to study and quantify the conversion and formation of species, including ammonia, methane, and hydrogen, under different catalyst conditions. The conversion selectivity of different species is also investigated. The results show that gasoline, ethanol and DME can act as effective reductants for LNT regeneration. LNT catalyst achieves the maximum storage efficiency at 350°C regardless of the reductant used. The NOx conversion efficiency of LNT increases unidirectionally with temperature.
Sandhu, Navjot Singh, Yu, Xiao, Ting, David, Zheng, Ming
Study of Dimethyl Ether Fuel Spray Characteristics and Injection Profile2024-01-27024/9/2024
The majority of transportation systems have continued to be powered by the internal combustion engine and fossil fuels. Heavy-duty applications especially are reliant on diesel engines for their high brake efficiency, power density, and robustness. Although engineering developments have advanced engines towards significantly fewer emissions and higher efficiency, the use of fossil-derived diesel as fuel sets a fundamental threshold in the achievable total net carbon reduction. Dimethyl ether can be produced from various renewable feedstocks and has a high chemical reactivity making it suitable for heavy-duty applications, namely compression ignition direct injection engines. Literature shows the successful use of DME fuels in diesel engines without significant hardware modifications. The lower energy density of DME calls for adjustments in injection parameters (such as injection pressure and duration) or modifications to the injector geometry to align with the energy levels found in diesel fuels. However, detailed direct comparisons between diesel and DME fuel injection characteristics over a wide testing range is lacking. This study investigates the injection characteristics of DME and diesel fuels in a common rail fuel injection system using the Bosch tube method. It is demonstrated that this method can be effectively applied to measure DME fuel injection characteristics, albeit with some limitations in predicting injector closing delay. The research emphasizes the presence of hydraulic delay, resulting in a ratio of actual to commanded injection duration for DME between 1.5 to 2 under the testing conditions. The study finds that mass-based injection quantities for diesel and DME fuels are quite similar at matching conditions, although the lower heating value of DME results in lower energy-based injection quantities and thus fuel injection scheduling need to be adapted to compensate that. Furthermore, the paper offers valuable insights and suggestions for those considering the modification of diesel-operated engines into DME-operated engines.
Cong, Binghao, Leblanc, Simon, Yu, Xiao, Zheng, Ming
A Novel Approach to Constructing Reactivity-Based Simplified Combustion Model for Dual Fuel Engine2023-01-162710/31/2023
To achieve higher efficiencies and lower emissions, dual-fuel strategies have arisen as advanced engine technologies. In order to fully utilize engine fuels, understanding the combustion chemistry is urgently required. However, due to computation limitations, detailed kinetic models cannot be used in numerical engine simulations. As an alternative, approaches for developing reduced reaction mechanisms have been proposed. Nevertheless, existing simplified methods neglecting the real engine combustion processes, which is the ultimate goal of reduced mechanism. In this study, we propose a novel simplified approach based on fuel reactivity. The high-reactivity fuel undergoes pyrolysis first, followed by the pyrolysis and oxidation of the low-reactivity fuel. Therefore, the simplified mechanism consists of highly lumped reactions of high-reactivity fuel, radical reactions of low-reactivity fuel and C0-C2 core mechanisms. We have applied this methodology to a dual-fuel engine fueled with poly(oxymethylene) dimethyl ether 3 (PODE3) and ammonia. Species concentrations and ignition delay times have been used to validate our reaction mechanism. In conclusion, combustion chemistry simplification can be formulated by a reactivity-based approach. In the future, numerical simulations will be used to investigate the combustion characteristics of a PODE3/ammonia dual-fuel engine based on this method to optimize the combustion strategy.
Li, Ang, Zhang, Zhenyingnan, Li, Zhuohang, Zhu, Lei, Huang, Zhen
Characterization of an Integrated Three-Way Catalyst/Lean NOx Trap System for Lean Burn SI Engines2023-01-165810/31/2023
The push for environmental protection and sustainability has led to strict emission regulations for automotive manufacturers as evident in EURO VII and 2026 EPA requirements. The challenge lies in maintaining fuel efficiency and simultaneously reducing the carbon footprint while meeting future emission regulations. Alcohol (primarily methanol, ethanol, and butanol) and ether (dimethyl ether) fuels, owing to their comparable energy density to existing fuels, the comparative ease of handling, renewable production, and suitable emission characteristics may present an attractive drop-in replacement, fully or in part as an additive, to the gasoline/diesel fuels, without extensive modifications to the engine geometry. Additionally, lean and diluted combustion are well-researched pathways for efficiency improvement and reduction of engine-out emissions of modern engines. Modern spark ignition (SI) engines typically employ various in-cylinder emission reduction techniques along with a three-way catalyst (TWC) based exhaust after-treatment system to comply with emission standards. However, the periodic lean-rich oscillations for this TWC system necessitate the SI engine to operate at near stoichiometric mixture conditions, which limits the viability of lean burn for SI engines. Lean NOx trap (LNT) system can reduce the engine out NOx under lean conditions at a cost of fuel efficiency penalty due to regeneration. In the present study, the feasibility of using a coupled TWC-LNT system with extensive dilution to achieve ultra-low tailpipe emissions is investigated. Relevant engine-out exhaust conditions from an SI engine, including flow, temperature, and exhaust species, operating at different dilution conditions were replicated on a heated aftertreatment flow bench. A comprehensive analysis of species before and after the catalyst sections was performed using Fourier-transformed infrared (FTIR) and mass spectrometers to study and quantify the conversion and formation of species, including ammonia, methane, and hydrogen, under different engine-out conditions. The results the integration of LNT to a TWC catalyst improves the conversion efficiency of reducing species during the lean operation period. TWC and LNT catalyst simultaneously achieve high conversion efficiency at ~350°C. The LNT regeneration behavior is noticeably affected by the presence of preceding TWC catalyst. The temperature rise because of the oxidation reactions on TWC can deteriorate the LNT regeneration efficiency beyond 400°C.
Sandhu, Navjot Singh, Leblanc, Simon, Yu, Xiao, Reader, Graham, Zheng, Ming
Investigation of Fuel Injection Pressure Impact on Dimethyl Ether Combustion2023-01-164410/31/2023
Compression ignition engines used in heavy-duty applications are typically powered by diesel fuel. The high energy density and feedstock abundance provide a continuing source for the immense energy demand. However, the heavy-duty transportation sector is challenged with lowering greenhouse gas and combustion by-product emissions, including carbon dioxide, nitrogen oxides, and particulate matter. The continuing development of engine management and combustion strategies has proven the ability to meet current regulations, particularly with higher fuel injection pressure. Nonetheless, a transition from diesel to a renewable alternative fuel source will play a significant role in reducing greenhouse gases while maintaining the convenience and energy density inherent in liquid fuels. Dimethyl ether is a versatile fuel that possesses combustion properties suitable for compression ignition engines and physical properties helpful for clean combustion. The higher volatility of DME may permit lower injection pressure than diesel fueling systems to achieve adequate atomization and mixing. In this work, an empirical study of the DME fuel injection pressure was conducted based on combustion and emission characteristics. The DME injection pressure was tested from 200bar to 770bar. A plunger-type injection system with an enlarged high-pressure reservoir was adopted to manage steady fuel injection pressures at 1200rpm. Each injection pressure condition was subject to a full-range exhaust gas dilution sweep into low-temperature combustion. The low sooting propensity of DME was apparent as engine-out soot emissions were below 2mg/kWh under all conditions. A higher injection pressure showed higher NOx emissions up to 70% EGR, thereafter NOx emissions persisted similarly low. A prominent improvement in combustion efficiency was observed from 325bar to 500bar followed by a minor improvement to 660bar. Correspondingly, exhaust gas speciation showed a similar trend in hydrogen, methane, and unburned DME emissions.
Leblanc, Simon, Wang, Linyan, Sandhu, Navjot Singh, Yu, Xiao, Zheng, Ming
Effects of Hydrocarbon with Different Ignition Properties and Hydrogen Blended Fuels on Autoignition and Combustion in an IC Engine2023-01-180210/24/2023
Hydrogen has attracted attention as one of the key fuels for making internal combustion engines carbon neutral. However, the combustion characteristics of hydrogen differ greatly from those of conventionally used hydrocarbons. Therefore, in order to develop next-generation internal combustion engines that operate on hydrogen, it is first necessary to have a thorough understanding of the combustion characteristics of hydrogen. Engines that can take maximum advantage of those characteristics should be developed on the basis of that knowledge. Toward that end, the purpose of this study was to investigate the fundamental combustion characteristics of hydrogen in a test engine. This paper presents the results of an investigation of the effects on low-temperature oxidation reactions and autoignition when hydrogen was blended into dimethyl ether (DME) [1, 2], a gaseous hydrocarbon fuel. Combustion experiments were conducted using a single-cylinder engine, and chemical kinetic simulations were performed. The experiments and simulations were carried out under homogeneous charge compression ignition (HCCI) conditions in order to investigate the fundamental reaction characteristics of DME and hydrogen. In the experiments, the input heat energy of hydrogen was increased while keeping that of DME constant so as to examine how blending with hydrogen would affect the reaction and combustion characteristics of DME. Chemical kinetic simulations were performed with Chemkin-Pro software to investigate the reaction kinetics of the experimental results. The results revealed that the ignition and combustion characteristics of the blended fuels used in the test engine were markedly different from those of hydrocarbon fuels because the reaction temperature region of hydrogen differed greatly from that of the latter fuels.
Kuwabara, Kenta, MANABE, YUSUKE, Mito, Shinji, YAMAGIWA, REO, Yamaguchi, Takahiro, Yoshihara, Shintaro, MIYAMOTO, Sekai, Iijima, Akira
Study on Combustion and Exhaust Emissions Characteristics of Oxymethylene Dimethyl Ether Blends with Fischer-Tropsch Fuels in Diesel Engines2023-32-01679/29/2023
Synthetic fuels (e-fuels) synthesized from H2 and CO by renewable electricity are expected as the next- generation diesel fuels and two types of e-fuels have received extensive attention: Fischer-Tropsch (FT) fuel and Oxymethylene dimethyl ether (OME). In this study the effects of OME blending ratios with 0 to 50 vol.% in FT fuels on combustion, emissions and spray characteristics in diesel engines are investigated. The results suggest that the OME blends to FT fuels suppressed the deterioration in combustion efficiency under low intake oxygen concentration conditions. The smoke emissions of FT fuels and OME blended fuels were both lower than those of diesel fuel and decreased with the increase in the OME blend ratio, and the soot-NOx trade-off relation in diesel engines can be improved.
Yuan, Haoyu, Tsukuda, Takuma, Nishino, Jumpei, Shibata, Gen, Ogawa, Hideyuki
The Effect of Methane Addition on the Low-Temperature Oxidation Preparation and the Thermal Ignition Preparation of Dimethyl Ether Under Representative Engine In-Cylinder Thermal Conditions2023-32-01509/29/2023
Dimethyl ether (DME) is a highly reactive diesel substitute that can be used as a pilot fuel to ignite low- reactivity methane (CH4) in heavy-duty engines. To optimize the efficiency and emissions of CH4/DME dual-fuel engines, it is crucial to study the fundamental combustion characteristics of DME mixed with methane. This study focuses on the influence of CH4 addition on the low-temperature oxidation (LTO) preparation stage and the thermal ignition (TI) preparation stage of DME in the two-stage ignition process, as these two stages respectively control the ignition delay of the first and second stages. The comparison is made between pure DME and a 50% CH4 and 50% DME blended fuel, operating under thermodynamic conditions representing the engine in- cylinder environment at 30 atm pressure, 650K temperature, and a stoichiometric equivalence ratio. The results show that the addition of methane hardly affects the control mechanism of the two-stage ignition of DME. Specifically, the LTO preparation stage is still promoted by the increase in OH radicals in the DME’s low-temperature oxygenation pathways to form KET, and the second stage is still controlled by the H2O2 loop mechanism. The kinetic analysis also reveals that methane addition can compete for some of the OH radicals in the LTO preparation stage, which has a suppressing effect on ignition. However, in the TI preparation stage, methane can promote the loop reaction of OH→HO2→H2O2→OH and promote ignition. For the operating conditions studied here, although methane consumes a total of 7.24% prior to thermal ignition, it only consumes 0.63% of the total amount in the LTO preparation stage and 1.81% of the total amount in the TI preparation stage. This indicates that methane is mainly consumed in the LTO stage, accounting for 65% of the total methane consumption amount. It can be concluded that the kinetic effect of methane has a relatively small impact on the ignition delay of the DME, at least for the conditions investigated here. In other words, the dilution and thermal effects caused by adding methane are the main reasons for the prolonged time of LTO/TI preparation. Overall, more fundamental research is warranted to understand the role of methane in the two-stage ignition process of DME, which could facilitate the development of CH4/DME dual-fuel engines.
Ou, Juan, Yang, Ruomiao, Yan, Yuchao, Liu, Zhentao, Liu, Jinlong
A Study of Autoignition and Combustion Characteristics in an HCCI Engine using a Blended Fuel of DME and City Gas2023-32-00179/29/2023
In recent years, there has been a need to reduce CO2 emissions from internal combustion engines in order to achieve an energy-saving and low-carbon society. Against this backdrop, the authors have focused attention on Homogeneous Charge Compression Ignition (HCCI) combustion that achieves both high efficiency and clean emissions. With HCCI combustion, a premixed mixture of fuel and air is supplied to the cylinder and autoignited by piston compression to drive the engine. Autoignition makes it possible to operate the engine at a high compression ratio, enabling the HCCI combustion system to attain high efficiency. However, HCCI combustion also has some major unresolved issues. Two principal issues that can be cited are ignition timing control for igniting the mixture at the proper time and assurance of suitable combustion conditions following ignition to prevent incomplete combustion and knocking. The combustion characteristics of a blended fuel of dimethyl ether (DME) as the ignition source and city gas as the main fuel, which have vastly different ignition characteristics, were investigated in experiments conducted with a test engine. The intermediate combustion products of the two fuel components were also investigated and analyzed by conducting chemical kinetic simulations. The results revealed that, combustion of a mixture of DME and city gas was strongly affected by methane, which was the main component of the mixture and slowed down the main combustion, while other alkanes showed a slowing effect on low-temperature oxidation reactions.
Yamagiwa, Reo, MANABE, Yusuke, MITO, Shinji, IIJIMA, Akira, YOSHIHARA, Shintaro, YAMAGUCHI, Takahiro, MIYAMOTO, Sekai
Investigation of Dimethyl Ether Dual-Fuel Combustion Using Propane and Ethanol as Premixed Fuel2023-32-00189/29/2023
The combustion and emission characteristics of dual-fuel combustion were investigated using dimethyl ether direct injection and premixed low-carbon fuels. Dimethyl ether was used as the direct injection fuel for its high reactivity and low propensity to form particulate matter. Ethanol and Propane, two fuels of low reactivity, were premixed in the intake port. An injection timing sweep of varying premixed energy shares and engine loads was tested. Combustion analysis was conducted based on in-cylinder pressure measurements while detailed speciation of engine-out emissions was performed via FTIR. The proper injection advance and premixed energy share can realize low NOx and high combustion efficiency. Ethanol showed stronger impact to DME ignition delay as compared with propane.
LeBlanc, Simon, Wang, Linyan, Yu, Xiao, Zheng, Ming
Insights into combustion and performance of HCCI engine fed with PODE 1 and H 2 -rich PODE 1 -reformate2023-32-00049/29/2023
A transition to sustainable energy sources, carbon- free/neutral energy carriers and efficient combustion technologies is intensively discussed as a key pathway in achieving a greener, more secure energy future. In particular, enhancement of internal combustion engine (ICE) performance using promising alternative carbon- neutral propellants, waste heat recovery (WHR) and state-of-the-art combustion methods has gained high research attention. Polyoxymethylene dimethyl ethers (PODEn, OMEn), well-suited for compression-ignition (CI) combustion, arouse strong interest as potentially sustainable and cleaner alternatives to diesel fuel. This study reports for the first-time numerically examined combustion performance characteristics of reforming- controlled compression ignition (RefCCI) ICE engine, managed by mixing of polyoxymethylene dimethyl ether 1 (PODE1) and its hydrogen-rich reforming products (PODE1-reformate) obtained through thermo- chemical recuperation. The results showed that the RefCCI combustion-control is possible by maintaining an appropriate H2/PODE1 ratio in the process of in- cylinder mixing of PODE1 and PODE1-reformate prior to auto-ignition. Beneficial high engine efficiencies of 40.6-48.4% and reduced NOx and CO emissions were achieved at the examined compression ratio of 16.
Buntin, Denis, Tartakovsky, Leonid
Electrofuel Concept of Diesel and Oxygenate Fuels Reduces Engine-Out Emissions2023-24-00908/28/2023
Electrofuels produced from renewable hydrogen (H2) and captured carbon dioxide (CO2) can be sustainable and carbon-neutral. Paraffinic electrodiesel (e-diesel) can be produced via Fischer-Tropsch synthesis with fuel properties resembling hydrotreated vegetable oils. Electrofuels can be also oxygenated compounds, such as oxymethylene dimethyl ethers (OMEn), having different chain lengths. We studied emissions using paraffinic diesel mimicking e-diesel and its blend with 10% of OME3-5, which has diesel-type fuel properties, in comparison with normal EN590 diesel fuel. An intensive measurement campaign was performed with a modern diesel engine without exhaust aftertreatment to study the effect of fuel on the engine-out emissions. Measurements with the RMC-C1 cycle included detailed characterization of gaseous, particle and polyaromatic hydrocarbon (PAH) emissions having adverse effects on health and the environment. In these tests without a diesel particulate filter, the fuel containing the OME3-5 component reduced the black carbon (BC) emissions substantially in comparison with EN590. PM and PAH emissions, as well as the number of non-volatile particle numbers (nvPN), were lower for paraffinic fuel than for the EN590 fuel, and particularly for the OME3-5 blend. As regards gaseous emissions, paraffinic fuel showed lower engine-out NOx emissions than the EN590 fuel, however, OME3-5 oxygenate did not further increase this NOx reduction. Higher formaldehyde concentration in the exhaust was found for OME3-5 containing fuel than for the hydrocarbon-only fuels, which can be tackled with an inexpensive oxidation catalyst. In summary, e-diesel type paraffinic fuel reduced the engine-out exhaust emissions from a modern diesel engine substantially, and OME3-5 addition further reduced the most harmful emission species even at a 10% blending level.
Aakko-Saksa, Paivi, Järvinen, Anssi, Karppanen, Mikko, Koponen, Paivi, Piimäkorpi, Pekka, Lehtonen, Juha, Harni, Sami, Aurela, Minna, Timonen, Hilkka, Marjanen, Petteri, Markkula, Lassi, Rönkkö, Topi, Hoivala, Jussi
CFD Modeling of a DME CI Engine in Late-PCCI Operating Conditions2023-01-02034/11/2023
Predictive combustion models are useful tools towards the development of clean and efficient engines operating with alternative fuels. This work intends to validate two different combustion models on compression-ignition engines fueled with Dimethyl Ether. Both approaches give a detailed characterization of the combustion kinetics, but they substantially differ in how the interaction between fluid-dynamics and chemistry is treated. The first one is single-flamelet Representative Interactive Flamelet, which considers turbulence-kinetic interaction but cannot correctly describe the stabilization of the flame. The second, named Tabulated Well Mixed, correctly accounts for local flow and mixture conditions but does not consider interaction between turbulence and chemistry. An experimental campaign was carried out on a heavy-duty truck engine running on DME at a constant load considering trade-off of EGR and SOI. Simulations results of 10 operating conditions show that both models can be successfully employed to predict cylinder pressure, heat release rate and pollutant emissions.
Schirru, Andrea, Hardy, Gilles, Wright, Yuri M., Lucchini, Tommaso, D'Errico, Gianluca, Soltic, Patrik, Hilfiker, Thomas
DME-Propane Ignition Delay Time Measurements at Mixing Controlled Compression Ignition Engine-Relevant Conditions2023-01-03304/11/2023
The blend of dimethyl ether (DME, CH3OCH3) and propane (C3H8) is a potentially renewable fuel mixture that has the potential to replace diesel in compression ignition engines. The combination can potentially reduce particulate and greenhouse gas emissions compared to a conventional diesel engine operating under similar conditions. However, detailed conceptual and simulation studies must be conducted before adopting a new fuel on a compression ignition engine. For these simulations, accurate chemical kinetic models are necessary. However, the validity of chemical kinetic mechanisms in the literature is unknown for mixing controlled compression ignition (MCCI) engine operating conditions. Hence, in this work, we studied the ignition of dimethyl ether (DME) and propane blends in a shock tube at MCCI engine conditions. Ignition delay time (IDT) data was collected behind the reflected shock for DME-propane mixtures for heavy-duty compression ignition (CI) engine parameters. Undiluted experiments spanning temperatures of 700 to 1100 K and pressures of 55 to 84 bar for various blends (100% CH3OCH3/ 0% C3H8, 100% C3H8/ 0% CH3OCH3, 60% CH3OCH3/ 40% C3H8) of DME and propane were combusted in synthetic air (21% O2/ 79% N2). Some experiments were conducted at higher pressures (90-120 bar) to understand model performance at these conditions. Comparisons of IDT were made with the predictions of recent chemical kinetic mechanisms for DME-propane mixture, including the Aramco3.0, NUIG, and Dames et al. mechanisms. All mechanisms overpredicted IDT compared to experimental values. Sensitivity analysis was conducted with Dames et al. model, and critical reactions sensitive to IDT of DME-propane mixture near 100 bar are outlined.
Mohammed, Zuhayr Pasha, Khaleel Rahman, Ramees, Pierro, Michael, Urso, Justin, Vasu, Subith
Development of a High-Pressure Fuel Injection System for Use with Propane-DME2023-01-04034/11/2023
Paper details the design approach and performance of a high-pressure common rail fuel injection system used with Propane-DME mixtures targeting high injection pressures on a light duty 2.2L inline-4 compression ignition engine. The study estimates the bulk modulus of elasticity based on the hardware geometry and operating pressures to assess the compressibility of Propane and DME across a range of pressures typical of the LD engine application. The compressibility factor ranges from 500 to 3000 bar, significantly lower than the theoretical values for the conditions tested. The high-pressure pump performance is optimized via the implementation of an inlet metering valve operated on a crank-angle open/close sequence to control pressure at the common rail. The application of a model-based controller and the use of high-speed sampling of rail pressure indicate that pressure at the rail can be attained with the pump metering valve, and without use of the pressure relieve valve present in the rail. Results show a significant reduction on pumping work parasitics and of fuel heating, on the order of 40°C, at typical working conditions with the proposed approach. Injector rates of injection with Propane-DME are very similar to those of Diesel. Paper compares bench data of rates of injection versus simulation predictions across operating pressures of 200 to 1000bar and from injection commands spanning 0.20 to 2.0ms. The accuracy of the model predictions are attributed in part by to the updated fuel compressibility modulus descriptions attained during the testing.
De Ojeda, William, Wu, Simon (Haibao)
Extension and Validation of a Constant Equivalence Ratio Multi-Zone Approach to DME Combustion in Vessels and CI Engines2023-01-01934/11/2023
This work has the objective to present the extension of a novel quasi-dimensional model, developed to simulate the combustion process in diesel Compression Ignition (CI) engines, to describe this process when Dimethyl ether (DME) is used as fuel. DME is a promising fuel in heavy-duty CI engines application thanks to its high Cetane Number (CN), volatility, high reactivity, almost smokeless combustion, lower CO2 emission and the possibility to be produced with renewable energy sources. In this paper, a brief description of the thermodynamic model will be presented, with particular attention to the implementation of the Tabulated Kinetic Ignition (TKI) model, and how the various models interact to simulate the combustion process. The model has been validated against experimental data derived from constant-volume DME combustion, in this case the most important parameters analyzed and compared were the Ignition Delay (ID) and Flame Lift Off Length (FLOL). Following this first validation process, the model has been tested against experimental values obtained from a heavy-duty DME-fueled CI engine in different operating conditions, representative of real engine applications. In this second comparison, the focus shifted on Heat Release Rate (HRR) and in-cylinder pressure trends and NOx production during combustion. The results show good agreement between the experimental and computed values in all operating conditions, leading to the possibility of using the presented model to accurately predict the performance of engines with DME as fuel in a fast 1D- or quasi-dimensional simulation tool.
Ballerini, Alberto, D'Errico, Gianluca, Onorati, Angelo, Tamborski, Matteo
Performance and Emission Characteristics of Direct Injection DME Combustion under Low NOx Emissions2023-01-03274/11/2023
Compression ignition internal combustion engines provide unmatched power density levels, making them suitable for numerous applications including heavy-duty freight trucks, marine shipping, and off-road construction vehicles. Fossil-derived diesel fuel has dominated the energy source for CI engines over the last century. To mitigate the dependency on fossil fuels and lessen anthropogenic carbon released into the atmosphere within the transportation sector, it is critical to establish a fuel source which is produced from renewable energy sources, all the while matching the high-power density demands of various applications. Dimethyl ether (DME) has been used in non-combustion applications for several decades and is an attractive fuel for CI engines because of its high reactivity, superior volatility to diesel, and low soot tendency. A range of feedstock sources can produce DME via the catalysis of syngas. In this work, DME is applied in a direct injection compression ignition combustion application. A novel plunger-type injection system was used to pressurize DME to 415 bar. Each set of operating conditions was subject to exhaust gas dilution to lower NOx emissions below the current regulatory standards. The results focused on the combustion characteristics and exhaust emissions, with matching conditions under diesel-fueled operation as a baseline reference for proper comparison. Non-regulated exhaust species were compared, specifically hydrogen, methane, and formaldehyde. The ultra-low smoke characteristic of DME avoided the classical NOx-soot trade-off of diesel-fueled engines, allowing for combustion optimization through stronger exhaust gas dilution. DME showed improved combustion completeness likely owing to the self-containing oxygen and higher volatility minimizing the dependency on mixing with the in-cylinder surrounding compressed charge.
Leblanc, Simon, M, Murugesa Pandian, Han, Xiaoye, Tjong, Jimi, Zheng, Ming
Ignition and Combustion Characteristics of OME 3-5 and N-Dodecane: A Comparison Based on CFD Engine Simulations and Optical Experiments2023-01-03054/11/2023
Synthetic fuels derived from renewable power sources, so-called e-fuels, will play a crucial role in achieving climate-neutral future mobility because they can be used in the existing fleets and in hard-to-decarbonize applications. In particular e-fuels that contain oxygen in their chemical structure can also burn more cleanly in terms of soot formation. For compression-ignition engines, polyoxymethylene dimethyl ethers (PODEs or OMEs) are among the most promising candidates for such oxygenated e-fuels. Here, we investigated the characteristics of injection and combustion of OME3-5 mixture compared to n-dodecane, a reference diesel-like fuel. Both single and multi-injection, comprising a short pilot injection, is used. Experiments were performed in a single-cylinder optically accessible Bowditch-type engine, injecting with 1500 bar pressure with a 3-hole injector (Spray B of the Engine Combustion Network). Liquid and vapor penetration were measured by imaging the spray illuminated by a pulsed light-emitting diode (LED). Ignition delay, lift-off length and flame morphology were investigated based on multi-spectral high-speed imaging of chemiluminescence. For simulations, a 3D CFD engine model was developed. The combustion simulation was performed on a 120° sector mesh onto which flow and turbulence fields from a gas exchange simulation are mapped prior to fuel injection. The model accounts for piston-ring blow-by. For the combustion of both fuels, detailed reaction mechanisms were used. In general, quite good agreement between model predictions and experimental results was achieved. In particular the consideration of blow-by losses by the CFD model produced a realistic behavior during the high-pressure cycle. Both CFD simulation and optical experiments, reveal significant differences between the two fuels. For OME, the liquid phase penetrates further into the combustion chamber, the ignition delay is shorter compared to n-dodecane and the equivalence ratio of OME during combustion is significantly leaner.
Wiesmann, Frederik, Bauer, Esra, Kaiser, Sebastian A., Lauer, Thomas
Active Plasma Probing for Lean Burn Flame Detection2023-01-02934/11/2023
Combustion diagnostics of highly diluted mixtures are essential for the estimation of the combustion quality, and control of combustion timing in advanced combustion systems. In this paper, a novel fast response flame detection technique based on active plasma is introduced and investigated. Different from the conventional ion current sensing used in internal combustion engines, a separate electrode gap is used in the detecting probing. Further, the detecting voltage across the electrode gap is modulated actively using a multi-coil system to be slightly below the breakdown threshold before flame arrival. Once the flame front arrives at the probe, the ions on the flame front tend to decrease the breakdown voltage threshold and trigger a breakdown event. Simultaneous electrical and optical measurements are employed to investigate the flame detecting efficacy via active plasma probing under both quiescent and flow conditions. The RT-FPGA system provides flexible, prompt, and precise control for the detecting frequency to analyze the overall flame propagation process. Two types of fuels are used in the study, including methane, and DME, with an air-fuel ratio sweep from stoichiometric to extremely lean. Efforts are made to characterize the criteria of minimum, yet adequate voltage to succeed in the detection of the flame front arrival. For comparison, conventional ion current measurements are conducted under identical testing conditions. Results show that the active plasma probing has benefits in detecting the flame arrival robustly for lean combustion under both quiescent and turbulent flow conditions. Under lean combustion, the intensity of ion current signal is significantly suppressed and signal rise time is prolonged due to the lower flame temperature. The active plasma probing provides a detecting response approximately one hundred times faster compared with the conventional ion current sensing, which shows potential for more effective real-time combustion control.
Wang, Linyan, Yu, Xiao, Cong, Binghao, Li, Liguang, Chen, Guangyun, Zheng, Ming
Prediction of Spray Vapor Tip Penetration of Diesel, Biodiesel and Synthetic Fuels Using Artificial Neural Networks with Confidence Intervals2023-01-03154/11/2023
Fuel spray and atomization processes affect the combustion and emissions characteristics of fuels in internal combustion engines. Biodiesel and synthetic fuels such as oxymethylene dimethyl ethers (OME) show great promise as alternative fuels and are complementary in terms of reproducing the fluid properties of conventional diesel fuels through blending, for instance. Averaged experimental results, empirical correlations and Computational Fluid Dynamics (CFD) have typically been used to evaluate and predict fuel spray liquid and vapor penetration values so as to better design internal combustion engines. Lately, Machine Learning (ML) is being applied to these investigations. Typically, ML spray studies use averaged experimental data and then over-trained neural networks on the limited available data. By contrast, in this study we present spray vapor tip penetration predictions using artificial neural networks with systematic treatment of uncertainties arising from experimental variability and limitations in the neural network training process. This has not been presented previously, and it allows the calculation of confidence intervals on the spray penetration predictions produced by neural networks. Using the present method, we evaluate four different diesel, biodiesel and OME fuel blends under four fuel injection conditions each and predict spray vapor tip penetration values with a correlation coefficient of 0.999. Across all fuel variants and injection conditions, one standard deviation represented less than 1.5 mm spray tip penetration (circa 2% of spray tip penetration) 1 ms from the start of injection. Despite this precision, a 95% confidence interval on neural network predictions encompassed the experimental fuel penetration data across all fuel variants, injection conditions and time steps. By calculating the confidence intervals on neural network predictions, we enable internal combustion engine designers to better quantify the applicability of neural networks in predicting spray characteristics.
Richards, Bryn, Emekwuru, Nwabueze
PRODUCT BRIEFS23TOFHP04_164/1/2023
Strategies for Reduced Engine-Out HC, CO, and NOx Emissions in Diesel-Natural Gas and POMDME-Natural Gas Dual-Fuel Engine2022-01-04603/29/2022
Dual-fuel engines employ precisely metered amounts of a high reactivity fuel (HRF) such as diesel at high injection pressures to burn a low reactivity fuel (LRF) such as natural gas, which is typically fumigated into the intake manifold. Dual fuel engines have demonstrated the ability to achieve extremely low engine-out oxides of nitrogen (NOx) emissions compared to conventional diesel combustion at the expense of unburned hydrocarbon (HC) and carbon monoxide (CO) emissions. At low engine loads, due to low in-cylinder temperatures, oxidation of HC and CO is very challenging. This results in both compromised combustion and fuel conversion efficiencies. The experimental campaign discussed in this paper involved a set of six engine control parameters that were strategically varied to find the best possible efficiency-emissions trade-offs for both diesel- and poly-oxy methylene dimethyl ether (POMDME)-natural gas dual fuel combustion on the University of Alabama single-cylinder research engine (SCRE) based on a PACCAR MX-11 heavy-duty engine platform. The control parameters investigated include: ((1)) Start of Injection (SOI1) of HRF, ((2)) percentage energy substitution (PES) of LRF, ((3)) introduction of the second HRF injection (SOI2), ((4)) split ratio, i.e., ratio of the duration of the first injection to the duration of the second injection, ((5)) rail pressure, and (6) intake pressure. At a fixed gross indicated mean effective pressure (IMEPg) of 5 bar (representative of typical low load operation) and an engine speed of 1339 rpm (“B speed” of the SCRE), SOI1 was varied to determine the lowest engine-out NOx point. Using that SOI1 as baseline and not-to-exceed (NTE) limits of: ((1)) Indicated specific NOx < 1 g/kWh, ((2)) maximum pressure rise rate (MPRR) < 10 bar/deg, and ((3)) coefficient of variation (COV) of IMEPg < 10%, the rest of the five control parameters were systematically varied. Based on HC and CO vs NOx emissions trade-offs, the best PES, SOI2, and split ratio were determined to achieve the lowest possible HC emissions. Subsequently, rail pressure sweeps showed minimal impact on performance and emissions between 500 bar and 1500 bar. Finally, reducing the intake pressure significantly reduced CO emissions to achieve the best overall set of operating parameters. Compared to the baseline diesel-natural gas case, HC and CO were reduced by ~88% and ~82%, respectively, in addition to ~21% improvement in the indicated fuel conversion efficiency. Whereas for POMDME-natural gas dual fuel combustion, HC and CO were reduced by ~85% and ~92%, respectively, in addition to ~20% improvement in the indicated fuel conversion efficiency. Furthermore, due to the high oxygen content of POMDME (47% m/m), engine-out soot emissions were reduced to zero measurable filter smoke number (FSN) for all conditions investigated.
Hariharan, Deivanayagam, Partridge, Kendyl, Narayanan, Abhinandhan, Srinivasan, Kalyan, Krishnan, Sundar Rajan, Anandaraman, Nandagopalan
A Study of Combustion Inefficiencies in SI Engines Powered by Alcohol and Ether Fuels Using Detailed Emission Speciation2022-01-05203/29/2022
Advanced combustion engines, as power sources, dominate all aspects of the transportation sector. Stringent emission and fuel efficiency standards have promoted the research interest in advanced combustion strategies and alternative fuels. Owing to the comparable energy density to the existing fossil fuels and renewable production, alcohol and ether fuels may be a suitable replacement, or an additive to the gasoline/diesel fuels to meet the future emission standards with minimal modification to current engine geometry. Furthermore, lean and diluted combustion are well-researched pathways for efficiency improvement and reduction of engine-out emissions of modern engines. However, lean-burn or EGR dilution can introduce combustion inefficiencies in the form of excessive hydrocarbon, carbonyl species and carbon monoxide emissions. In this study, the total energy loss to the exhaust in the form of emission species due to incomplete/inefficient combustion of alcohol (butanol and ethanol) and ether (dimethyl ether) fuels in SI engine has been investigated. The impact of both dilution strategies, fresh air (lean) and EGR dilution on the exhaust gas components for different alternative fuels has been studied. A detailed analysis of the combustion products has been conducted to determine the contribution of different exhaust components to the fuel energy loss to the exhaust species. Additionally, the results have also been compared to gasoline combustion as a baseline. Preliminary test results indicate that as the charge is diluted (either lean or EGR dilution), the contribution of longer chain hydrocarbon species to the exhaust energy increases. DME, primarily following HCCI combustion, exhibits distinct emission speciation.
Sandhu, Navjot Singh, Leblanc, Simon, Yu, Xiao, Reader, Graham, Ting, David, Zheng, Ming
Laminar Flame Speed Measurements of Propane/Dimethyl-Ether/Air Mixtures2022-01-05103/29/2022
An experimental study on the laminar flame speeds (LFS) of premixed propane/dimethyl-ether (DME)/air flames was conducted inside a constant-volume chamber at UCF. Mixtures of propane and DME were selected for this study as they show promise as a fuel source that can be utilized in the automotive diesel industry as a low emission alternative fuel. The LFS of a fuel mixture is a crucial characteristic of combustion for its application in the design process of engines, as it can be used as a metric for fuel performance. Further underscoring the importance of gathering LFS data for these mixtures is its use in validating chemical kinetic mechanisms that can be utilized for further research in the field. LFS is dependent on fuel/oxidant mixture temperature, pressure, and equivalence ratio. While some studies exist examining other characteristics of combustion regarding propane/DME fuel mixtures, there is minimal information on the laminar flame speed of the mixtures. This study tested mixtures of propane and DME across a wide range of equivalence ratios from 0.8-1.5 to examine its effects on LFS. An elevated temperature of 373K under atmospheric pressure was selected for initial fuel conditions. In order to examine the variation of LFS with DME concentration, the composition of DME/propane mixtures varied from 0%, 25%, 50%, 75%, and 100% DME. Testing was conducted in a spherical constant volume combustion chamber, using schlieren imaging and high-speed photography to capture experimental data. Experimental data were also compared against available chemical kinetic mechanisms for further experimental validation. The tested fuel mixtures showed a maximum LFS value at around Φ = 1.1. The measured LFS values showed a general trend of increase with increased DME content in the fuel mixture, with pure propane mixtures exhibiting the lowest LFS, and pure DME mixtures exhibiting the highest values. The collected LFS data was in close agreement with simulations using the Aramco 3.0 chemical kinetic mechanism [1] , further validating its use for DME and propane combustion modeling.
Vasu, Subith, Weiner, Joshua, Kim, Gihun, Ghorpade, Ritesh
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