Browse Topic: HCCI engines

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Experimental Investigation of Fuel Cutout Strategies in a Heavy-Duty Gasoline Compression Ignition Engine03-19-03-00156/26/2026
This study investigates Gasoline Compression Ignition (GCI), a family of advanced combustion strategies that can be used to achieve low engine-out criteria pollutant emissions in the heavy-duty transportation sector. In particular, high fuel stratification GCI (HFS-GCI) has been shown to have high thermal efficiencies while maintaining a highly controllable and responsive mixing-controlled combustion event. However, stable combustion at low loads has been shown to be the principal challenge to the implementation of HFS-GCI in production applications. It has also been observed that several strategies that achieve stable combustion at low loads result either in increased emissions or efficiency penalties. While the achievement and maintenance of high enough exhaust temperatures for efficient aftertreatment operation is a significant challenge at low loads even for traditional diesel engine operation, this challenge is exacerbated by the low reactivity and colder flame temperature of gasoline. In recent single-cylinder and 1D simulation studies, fuel cutout strategies have been proposed as an enabling strategy to simultaneously improve combustion stability at low loads and increase exhaust temperatures. In this study, fuel cutout strategies are studied in a prototype multicylinder heavy-duty GCI engine based on a Cummins ISX15 diesel engine. Steady-state engine studies are conducted at warm and cold idle conditions to identify combinations of cylinders that provide the most benefit. NOx and soot limits are set and the performance of cutout strategies are compared to a pre-optimized baseline. The most optimal strategies from steady-state testing are then implemented under transient test cycle conditions similar to those required under United States regulatory testing. The strategies were found to offer simultaneous improvements in stability, fuel consumption, criteria pollutants, and turbine outlet temperature. The choice of cylinders whose fuel supply was cut was seen to be important in realizing the observed benefits. The use of fuel cutout strategies offered optimal performance at all the conditions considered, offering an additional lever to improve the performance of HFS-GCI and highlighting a promising pathway to the use of gasoline-like fuels as alternatives to diesel in heavy-duty engines.
Viswanathan, Aravindh Babu, Zhang, Yu, Merritt, Brock
Impact of High Compression Ratios on Ethanol Homogeneous Charge Compression Ignition2026-01-50386/10/2026
Ethanol requires elevated intake temperatures to initiate autoignition in Homogeneous Charge Compression Ignition (HCCI) as a high-octane single-stage fuel. To leverage the high thermal efficiency, low engine-out NOx, and near-zero soot inherent to HCCI with ethanol, a custom piston design was developed to enable high compression ratios (CR) up to 22.5:1. This study investigates HCCI combustion with ethanol at three CRs of 17.5, 20.0, and 22.5 through equivalence ratio and boost sweeps performed to assess the reduction in the intake temperature requirement at high CRs and the emissions and efficiency trade-offs. Results indicate a clear benefit with reduced intake temperature requirements with increasing CR. However, a combustion efficiency penalty was observed at high CRs. Three-dimensional Computational Fluid Dynamics (CFD) simulations were performed using Large Eddy Simulation (LES) coupled with a detailed chemistry model to investigate the underlying mechanisms of the combustion efficiency penalty. CFD results reveal that the combustion efficiency penalty at high CR is primarily due to increased crevice mass trapping unburned or partially oxidized species and a rapid expansion effect inhibiting complete carbon monoxide (CO) oxidation.
Vedpathak, Kunal, Kumar, Mohit, Motwani, Rahul, Datar, Aditya, Gainey, Brian, Lawler, Benjamin
Methane Emission Mitigation in Large-Bore Dual-Fuel Engines via Negative Valve Overlap Diesel Injection: Thermochemical Pathways and Reactivity Control2026-37-00456/9/2026
Low-load natural gas–diesel reactivity controlled compression ignition (RCCI) in medium-speed marine engines is constrained by an insufficient charge thermal state. This limitation leads to partial fuel oxidation, producing high methane emissions. This work evaluates the use of negative valve overlap (NVO) combined with NVO diesel injection as an in-cylinder reactivity enhancement strategy. The simulation study was performed using the University of Vaasa’s advanced thermo-kinetic multi-zone model (UVATZ), extended for reactive simulations during NVO. The extended framework was validated against test-bench data from a prototype Wärtsilä 6L20 dual-fuel engine operating in RCCI mode. The baseline low-load operating point for reforming simulations was defined by reducing the intake manifold temperature to replicate conditions close to partial misfire with 52% combustion efficiency. The parametric sweeps of NVO injection timing and ratio showed that the strategy can be used for in-cycle fast thermal management, effectively restoring complete combustion on an individual cycle basis. In simulated conditions, the best performance was obtained with an NVO injection ratio of 0.3, with the injection scheduled before top dead center. In contrast, increasing the NVO fraction beyond ~0.3 provided no benefit and led to complete misfire due to excessive reduction of main-event high-reactivity fuel. The simulations revealed a coupled thermal–chemical control mechanism. Early NVO injections stabilize combustion through recompression heat release and an increased next-cycle intake valve closing temperature. Sufficiently late injections stabilize combustion by carrying unreacted diesel into the subsequent cycle. Injections near NVO TDC primarily undergo fuel conversion to CO, H2O, and unsaturated light/mid-range hydrocarbons with negligible thermal boost, yielding an overall reactivity deficit.
Soleimani, Amir, Nurmi, Mikael, Hunicz, Jacek, Kim, Jeyoung, Hyvonen, Jari, Mikulski, Maciej
Rapid Fuel Distribution Prediction in RCCI Marine Engines Using CFD-Informed, Active Learning Framework2026-37-00176/9/2026
Accurate prediction of in-cylinder fuel distribution (FD) is fundamental to reduced-order combustion modeling and emissions prediction yet remains computationally prohibitive with high-fidelity CFD alone. This work develops a CFD-informed machine-learning surrogate for spatial FD in a large-bore diesel engine, based on a Wärtsilä W20 injector and representative engine conditions. A fully coupled injector–spray–engine CFD framework under engine-like RCCI inert conditions determines the needle-lift profile and resolves the combined effects of injector geometry, needle dynamics, and operating conditions on in-cylinder flow, capturing physical phenomena not reproducible by isolated free-spray simulations. A high-fidelity database is generated using Latin Hypercube Sampling, from which FD is extracted at 15 CAD before top dead center within an annular multi-zone (MZ) representation consistent with reduced-order combustion models. A multi-output Random Forest (RF) surrogate, augmented with uncertainty-driven active learning, is trained to predict the complete spatial FD vector. Prediction errors are higher near the combustion chamber core than in liner-adjacent zones, reflecting stronger nonlinear coupling and localized data sparsity. To address this, four additional CFD samples are selected from regions of maximum predictive uncertainty and incorporated into the training dataset. This targeted enrichment markedly improves surrogate performance, reducing mean absolute error (MAE) under worst-case input conditions. Although localized error amplification persists in a few zones, these regions are systematically identified and can be mitigated through further adaptive sampling using candidates proposed by the updated surrogate. Convergence of the active-learning framework is assessed using mean MAE, worst-zone MAE, global L1 error, and ensemble-based predictive uncertainty, ensuring robust and consistent accuracy across the design space. The framework integrates CFD-resolved physics, machine-learning surrogates, uncertainty quantification, and adaptive sampling, providing a scalable and physically consistent approach for efficient FD prediction in advanced engines.
Moradi, Jamshid, Salahi, Mahdi, Heidarabadi, Shadab, Andwari, Amin, Konno, Juho, Wik, Christer, Mikulski, Maciej
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
Reactivity Controlled Compression Ignition (RCCI) Combustion Engine Characteristics Fuelled with Diesel/Compressed Natural Gas (CNG) and Diesel/Methanol Fuel Pairs2026-01-03194/7/2026
Ultra-low oxides of nitrogen (NOx) and particulate matter (PM) from reactivity-controlled compression ignition (RCCI) combustion have motivated researchers to explore more about low temperature combustion (LTC) engines. In this study, a comparative analysis of combustion, performance, and emission characteristics of RCCI combustion fuelled with diesel/compressed natural gas (CNG) and methanol/diesel fuel pairs has been carried out with respect to baseline compression ignition (CI) combustion. All experiments were performed in a constant speed engine at four different engine loads. For RCCI combustion experiments, a constant premixed ratio (rp= 0.50) and 15% exhaust gas recirculation (EGR) were used. The results exhibited a significant reduction in NOx emissions and relatively smoother RCCI combustion compared to baseline CI combustion. RCCI mode combustion resulted in relatively superior engine performance compared to baseline CI combustion, especially at higher engine loads. A comparison between the RCCI combustion fuelled with gaseous fuel (CNG) as a low reactivity fuel (LRF) and a liquid fuel (methanol) showed a slightly lower brake thermal efficiency (BTE) of CNG/diesel fuelled RCCI combustion compared to methanol/diesel fuelled RCCI combustion at low loads. As the load increased, the trend of BTE was reversed. The combustion characteristics of CNG/diesel fuelled RCCI combustion were found to be more stable compared to methanol/diesel fuelled RCCI combustion. The NOx emissions were lowest in methanol/diesel fuelled RCCI irrespective of engine load. At low load, methanol/diesel fuelled RCCI suffered from higher hydrocarbon (HC) and carbon monoxide (CO) emissions, while CNG/diesel fuelled RCCI maintained relatively lower HC and CO emissions.
Saikia, Bhargav, Kant, Akshay, Gupta, Abhishek, Singh, Akhilendra Pratap
Effect of Key Operating Parameters on Homogenous Reactivity-Controlled Compression Ignition Concept with Renewable Fuels03-19-02-00094/1/2026
As part of the dTEC MORE project, sustainable powertrain technologies are being explored, including an alternative combustion concept tailored for engines in serial hybrid powertrains. Among the low-temperature combustion strategies, Reactivity-Controlled Compression Ignition (RCCI) is a prominent approach, offering significant reductions in NOx and soot emissions while enhancing combustion efficiency. The dual-fuel nature of RCCI enables improved control over combustion by utilizing fuels of differing reactivities. In this study, a premixed RCCI strategy was implemented using ethanol as a port-injected low-reactivity fuel and octanol as a directly injected high-reactivity fuel. The experimental work was conducted on a single-cylinder research engine with design features that are found in a gasoline passenger car application. Key combustion parameters such as the start of injection (SOI) of the high-reactivity fuel, injection pressure, intake temperature, lambda, premixed fuel ratio, and valve overlap were varied and evaluated on the engine test bench. The impact of these parameters on performance, combustion stability, and emissions was systematically analyzed. The results were benchmarked against a baseline direct-injected gasoline combustion cycle with a higher compression ratio. The comparison highlights the advantages of the premixed RCCI strategy, particularly in reducing NOx and soot emissions. Additionally, the test results also support in the future steps to model and validate the simulation models, to achieve higher efficiency and lower emissions.
Sundaram, Pravin Kumar, Grundl, Larissa Michaela, Trapp, Christian Thorsten, Tinschmann, Georg
A Comprehensive Study on the Effect of Compression Ratio and Pilot Injection Strategy on Alcohol Compression Ignition03-18-07-004411/13/2025
Achieving compression ignition (CI) with ethanol, a renewable fuel, comes with challenges because of its much lower cetane number compared to diesel. Additionally, ethanol’s high cooling potential and high volatility compared to diesel also offer challenges and opportunities to achieving robust, high-efficiency CI. Increasing the compression ratio (CR) and expanding the injection strategy beyond a conventional close-coupled pilot-main diesel injection strategy can help overcome these challenges. This work experimentally tested ethanol CI with several different injection strategies with CRs ranging from 16.3 to 22.3. The results showed that in homogeneous charge CI (HCCI), increasing the CR improved thermal efficiency but incurred a combustion efficiency penalty. In any CI concept, increasing the CR lowered the required intake temperature to achieve ignition. Using close-coupled pilot injections is an effective way to achieve ethanol CI, but it was also shown that HCCI-like intake stroke “pilot” injections offer a new avenue of ethanol CI. With a 25% pilot injection during the intake stroke, stable ethanol CI was achieved at 6 bar IMEPg with an intake temperature of 330 K using a CR of 20.0. There was a ~1 percentage point thermal efficiency benefit and ~50% reduction in NOx, though there was also a 1 percentage point combustion efficiency penalty. At lower loads, it was more beneficial to run with more fuel in the intake stroke pilot. Finally, experiments showed that the NOx emissions decreased from 5.75 g/kWh to 3.43 g/kWh at 6 bar IMEPg by increasing the CR from 16.3 to 20.0 and reducing the intake temperature by 60 K. Even with matched intake temperature, the engine-out NOx was 4.57 g/kWh with a CR of 20.0. CFD simulations showed that this was due to the higher CR having a more rapid expansion process, cooling the diffusion flames more rapidly.
Gainey, Brian, Vedpathak, Kunal, Kumar, Mohit, Lawler, Benjamin
Effect of Plasma-Assisted Ignition on Combustion and Emission Characteristics of Two Stroke Engines with Different Fuels2025-32-003011/3/2025
This study explores the effect of plasma-assisted ignition (PAI) on combustion stability and emissions in two-stroke spark-ignition engines. Two engine platforms were evaluated: a conventional single-cylinder two-stroke engine and a thermodynamically advanced opposed-piston two-stroke (OP2S) engine. The OP2S engine configuration offers reduced heat loss and higher power density due to its uniflow scavenging and favorable geometry, but suffers from high residual gas fraction, which increases ignition difficulty and combustion instability. To address this, nanosecond-pulsed PAI was applied in various spatial arrangements and discharge voltages, using both gasoline and a low-reactivity gasoline/DMC blend fuel. Spark ignition timing was held constant at the minimum advance for best torque across all tests. Combustion stability was assessed via indicated mean effective pressure (IMEP) and its coefficient of variation, while CO and HC emissions were measured as environmental indicators. Results show that PAI significantly enhanced ignition stability, reducing COVIMEP by up to 84% and HC emissions by up to 24%, depending on fuel and engine type. The OP2S engine showed greater responsiveness to ignition configuration and plasma positioning due to its uniflow scavenging method. These findings confirm that PAI is a promising strategy for improving ignition robustness and emission performance in both conventional and advanced two-stroke engine architectures.
Liu, Jinru, Yamazaki, Yoshiaki, Otaki, Yusuke, Kato, Hayato, Kobayashi, Daichi, Umegaki, Tetsuo, Asai, Tomohiko, Iijima, Akira
Effects of Intake-Air Heating on a Light-Duty CNG-Diesel Reactivity-Controlled Compression Ignition Engine2025-32-000311/3/2025
Reactivity controlled compression ignition (RCCI) is a promising low-temperature combustion strategy that offers high thermal efficiency with reduced nitrogen oxides (NOx) and soot emissions. However, at low loads, RCCI operation often suffers from incomplete combustion, leading to elevated partial combustion products, such as, unburned total hydrocarbons (THC) and carbon monoxide (CO) emissions. Intake-air heating is a potential strategy to address these issues by enhancing fuel reactivity and promoting more complete combustion. In this study, the effects of intake-air heating (from ambient to ~95°C) on performance, combustion, and emissions were experimentally investigated in a light-duty diesel engine operated in compressed natural gas (CNG)-diesel RCCI mode. Experiments were conducted at low and intermediate loads at various engine speeds. A single injection strategy was employed for low-load, while a double-injection strategy was used at intermediate-load operating condition s. CO and THC emissions were significantly reduced at low loads with intake-air heating, but at intermediate-loads no significant reductions in CO and THC emissions were observed. However, NOx emissions increased and combustion stability improved with intake-air heating at all the investigated operating conditions. Furthermore, increased intake-air temperature at low-load high-speed operation with single injection strategy resulted in significant combustion oscillations due to end-gas auto-ignition. The presence of oscillations was confirmed by a fast Fourier transform (FFT) analysis of the in-cylinder pressure that revealed significant resonance in the first circumferential mode at higher intake temperatures. Furthermore, with intake-air heating, an increase in the energy substitution by CNG from 50% to 70%, and a marginal increase in EGR from 45 to 55%, improved the THC-NOx trade-off in RCCI operation.
Navaneethakrishnan, P., Sarangi, Asish K, Suman, Abhishek, Sreedhara, Seshadri, Singh, Arvind Kumar
Analysis of Combustion Characteristics and Performance of a Multi-Cylinder Engine Operating on Syngas/Diesel in Dual-Fuel Mode2025-24-00429/7/2025
Despite improvements in internal combustion engine efficiency, fossil fuel reliance remains a challenge for sustainable energy. Syngas, a hydrogen-carbon monoxide mixture produced from gasification, typically of carbon-based feedstocks, offers a viable transitional fuel due to its compatibility with existing combustion technologies and reduced emissions. However, its low ignition propensity elevated intake temperatures or pressures, a limitation that can be overcome through diesel pilot injection in dual-fuel engine configurations. This study extends prior single-cylinder research to a 1.6 L four-cylinder HCCI engine operating in dual-fuel mode, resembling a Reactivity Controlled Compression Ignition (RCCI) engine. The analysis focuses on cylinder-to-cylinder combustion variation, thermal efficiency, and pollutant emissions, with particular emphasis on the influence of diesel pilot injection timing. Experimental evaluations are conducted across a range of injection timing and Syngas flow rates (100 to 160 L/min). Key metrics include ignition delay, heat release rate, maximum pressure rise rate, coefficient of variation of indicated mean effective pressure, and pollutant emissions. Results indicate that diesel pilot injection timing significantly affects combustion phasing, heat release dynamics, and overall engine efficiency. Advancing or retarding the injection timing alters ignition delay and heat release characteristics, with optimal settings improving Syngas utilization and reducing particulate emissions. These findings highlight the importance of injection strategy optimization for realizing the full potential of Syngas in multi-cylinder engines, supporting their integration into cleaner and more efficient propulsion systems.
El Younsi, Laila, Nelson-Gruel, Dominique
The Effect of Nitric Oxide (NO) on the Reactivity of Ethanol and Gasoline: An Experimental Study2025-01-84134/1/2025
Achieving stable HCCI combustion requires specific in-cylinder boundary conditions. Trace residual species, such as nitric oxide (NO), can have an impact on the reactivity, and thus the combustion stability, of different fuels in HCCI. This study investigates the effects of nitric oxide (NO) on the reactivity and combustion stability of ethanol and gasoline in a single-cylinder HCCI engine. The promoting and inhibiting impact of NO on iso-octane’s ignition delay time are available in the literature; nevertheless, as a baseline study, these effects on the autoignition of gasoline were documented in this work. For ethanol, the NOx concentration seeded in the intake air varied from 0-1000 ppm while maintaining a constant combustion phasing (CA50 at 7.5 CAD) and a global equivalence ratio of 0.34. Ethanol exhibited a linear reduction in intake temperature, decreasing by 47 K with 927 ppm NO. For gasoline, a 225-ppm increase in NO reduced the intake temperature required for HCCI by 40 K. However, gasoline showed a non-linear response, attributed to different autoignition characteristics of the fuels. Ethanol's reactivity enhancement is linked to NO's role in converting less reactive HȮ2 radicals into more reactive OḢ radicals in a chain propagation step. Therefore, NO significantly influences combustion stability, introducing a potential “runaway” effect on combustion phasing in advanced combustion modes. In traditional mixing-controlled combustion, NO affects the kinetically controlled pilot heat release, altering the premixed heat release spike. However, the ignition delay correlation for ethanol widely used in the literature failed to capture these reactivity enhancement effects, as the Livengood Wu integral predicted the same autoignition threshold for ethanol with varying NO concentration.
Bhatt, Ankur, Gandolfo, John, Vedpathak, Kunal, Lawler, Benjamin, Gainey, Brian
Assessment of Performance and Emissions from a Hybrid Vehicle Integrated with a Low Temperature Combustion Engine Undergoing a Drive Cycle2024-28-014012/5/2024
In the last decade, the increased global temperature, stringent regulations, and customer demand for high fuel economy have led to the accelerated development of alternative propulsion solutions, with particular focus on electrified vehicles. Hybrid electric vehicles (HEVs), the combination of electric machinery with conventional powertrains, allows diversifications of powertrain architectures. In addition, it has been demonstrated that engines employing advanced low temperature combustion concepts, such as dual fuel reactivity controlled compression ignition (RCCI), and able to operate on both renewable and conventional fuels, produce ultra-low nitrogen oxides (NOx) and particulate matter (PM) emissions while maintaining thermal efficiency similar to conventional diesel operation at part load operating conditions. This study aims to investigate the potential of integrating a gasoline-diesel RCCI engine in an HEV in achieving reduced fuel consumption and lower NOx and PM emissions compared to a conventional diesel powertrain. In this work a combination of engine experimental data and a vehicle powertrain simulation tool (AVL CRUISE) is employed to determine the vehicle level emissions and performance of a commercial vehicle on the worldwide harmonised light-duty vehicles test cycle (WLTC). In order to assess the emissions, the powertrains are simulated utilising both conventional diesel combustion (CDC) and RCCI-CDC dual combustion mode engines as the primary power sources. For a series hybrid vehicle, NOx emissions decreased by 67% and soot emissions decreased by 70% compared to a CDC vehicle. However, the combustion efficiency decreased in the RCCI mode, resulting in a significant increase in total hydrocarbon (THC) and carbon monoxide (CO) emissions. Moreover, the implementation of the HEV technology results in decreased fuel consumption, leading to a 40% reduction in carbon dioxide (CO2) emissions compared to the CDC vehicle. These results indicate the potential of HEVs, particularly when equipped with RCCI-CDC dual combustion mode engines, to achieve reduced fuel consumption and emissions, thereby offering a promising solution for sustainable transportation.
Marwaha, Tejasva, Khedkar, Nikhil Dilip, Sarangi, Asish Kumar
Effect of Water Injection Parameters on Upper Load Limit and Nitrogen Oxides Emissions of a Homogeneous Charge Compression Ignition Engine—A Computational Fluid Dynamics Study03-18-01-000611/22/2024
Direct water injection inside the cylinder is a promising technique to enhance the upper load limit and reduce nitrogen oxides emissions. The advantage of water injection depends on the percentage of water evaporated inside the cylinder. The percentage of water evaporation depends upon the water injection parameters. Hence, a computational fluid dynamics analysis is done to determine the effect of water injection temperature, water spray cone angle, nozzle hole diameter, and number of nozzle holes on in-cylinder distribution and percentage of water evaporation, engine performance, and emissions of a homogeneous charge compression ignition engine. This analysis considers water injection temperature from 295 K to 385 K, water spray cone angle from 8° to 24°, nozzle hole diameter from 0.14 mm to 0.205 mm, and number of nozzle holes from 4 to 7. The computational fluid dynamics models used are validated from the available experimental data in the literature for the engine considered. Here, the water injector parameters are optimized based on the nitrogen oxides emissions, maximum rate of pressure rise, heat release rate, and distribution of water vapors. This study found that the case of a water injector with a nozzle hole diameter of 0.205 mm, six nozzle holes, 12° spray cone angle, and a water injection temperature of 295 K gave better results than the other cases considered. With the optimum water injection parameters, the indicated mean effective pressure increased from 3.23 bar to 4.39 bar, which is about 35.9% more than the without water injection case, and nitrogen oxides emissions are reduced by about 64.7% compared to without water injection case.
Naik, Bharat, Mallikarjuna, J. M.
Investigation of Combustion Stability in an RCCI Engine Using Recurrence Analysis of Cylinder Pressure Data2024-01-428711/5/2024
The Reactivity Control Compression Ignition (RCCI) engine, with its dual fuel system and coordinated injection strategy, offers superior emission control and fuel efficiency compared to conventional diesel engines. However, cyclic variations leading to engine combustion instability poses a significant challenge to their development and commercialization. In this study, statistical (COV and Histogram) and nonlinear dynamic (Recurrence Plot and its Quantification) analysis techniques are applied on the time-series data obtained from a single-cylinder diesel engine modified to operate in CNG-Diesel RCCI mode. The engine, while advancing the main injection timing (SOI-2), is tested under various operating conditions, including different engine loads, direct injection mass ratios (DIMR) and port fuel injection (PFI) masses, to help identify the configurations with better temporal correlations and deterministic traits. Such configurations hold potential for control strategy implementation. Through this study it is found that the engine operates in RCCI mode primarily at intermediate to advanced SOI-2 timings. After comparing RQA results of IMEP, Pmax, and CA50; IMEP is determined to be ideal for recurrence analysis. Ultimately, the configuration with a 70-30 DIMR at higher load and higher PFI mass demonstrates superior deterministic traits compared to the other test cases.
Prashar, Rajat, Kumar, Kamal S., Yadav, Ratnesh Kumar, Maurya, Rakesh Kumar
Quantifying Environmental and Health Impacts of Conventional Diesel and Methane Diesel RCCI Engine Emissions: A Numerical Analysis2024-01-430711/5/2024
A reactivity-controlled compression ignition (RCCI) engine offers ultralow soot and nitrogen oxide (NOx) emission in addition to higher thermal efficiency than diesel or compression ignition (CI) engines. However, the higher emissions of unburned hydrocarbons (HC) and carbon monoxide (CO) from RCCI engines pose a significant challenge that hinders their adoption in the future automotive sector. Additionally, HC includes several hydrocarbons that harm human health and the environment. This study aims to minimize HC and CO formation and emissions by implementing different injection strategies, including adjustments to spray angle configuration, injection timing, and fuel premixing ratio. Additionally, the study examines how different injection strategies affect the spatial and temporal distribution of HC and CO inside the combustion chamber. To achieve this objective, a numerical investigation is conducted on a single-cylinder diesel engine modified to operate in RCCI mode, utilizing a detailed reaction mechanism with ANSYS FORTE. The reaction mechanism comprises 137 species and 1,022 reactions, using n-heptane and CH4 as fuel surrogates. Initially, the computational model is developed using engine geometry and validated against experimental results for conventional diesel and RCCI modes, after which a parametric investigation is conducted. The results demonstrate that, among injection strategies, the spray configuration has the greatest impact on HC and CO emissions. Narrow spray configuration in RCCI combustion leads to a significant decrease in HC and CO emissions. HC and CO emissions increase with advanced injection timing and a higher fuel premixing ratio. RCCI engines exhibit lower acidification potential and eutrophication potential equivalent emissions compared to conventional diesel engines.
Yadav, Neeraj Kumar, Chandel, Amit Singh, Maurya, Rakesh Kumar, Padhee, Srikant Sekhar
Effect of Premixing Ratio on the Deterministic Characteristics of Combustion Dynamics Butanol-Diesel RCCI Engine2024-01-429211/5/2024
The rising demand for vehicles has increased CO and HC emissions, worsening air quality and contributing to climate change, key issues under the clean development mechanism and UN SDG 13: Climate Action. Reactivity-Controlled Compression Ignition (RCCI) offers a promising solution to reduce PM and NOx while maintaining fuel efficiency. However, the cyclic variation of the RCCI engine remains an underexplored area in control strategies, necessitating further research for optimization in line with sustainable development goals. This study explores the impact of premixing ratios on RCCI engines fueled with butanol and the nature of cyclic variation to know the controllability. Tests were conducted on a single-cylinder diesel engine at 1500 rpm and constant engine load. The experiments reveal that increasing the premixing ratio from 45% to 60% decreases the heat release rate by 15%, Pmax by 10%, and IMEP by 12%. Recurrence Quantitative Analysis (RQA) confirmed strong deterministic combustion patterns, with determinism exceeding 85%. Multifractal Detrended Fluctuation Analysis (MFDFA) indicated that the Total Heat Release (THR) time series exhibited the least multifractality (∆α = 0.15) compared to Pmax and IMEP. These findings provide essential insights for optimizing RCCI control systems, enabling improved performance across varying operating conditions.
Yadav, Ratnesh Kumar, Mohite, Avadhoot Abaso, Maurya, Rakesh Kumar
Numerical Investigations on Reducing Unburned Hydrocarbon and Carbon Monoxide Emissions in Reactivity-Controlled Compression Ignition Using Partial Reactivity Stratification with Alternative Fuels and Additive03-18-01-000510/4/2024
A numerical investigation has been performed in the current work on reactivity-controlled compression ignition (RCCI), a low-temperature combustion (LTC) strategy that is beneficial for achieving lower oxides of nitrogen (NOx) and soot emission. A light-duty diesel engine was modified to run in RCCI mode. Experimental data were acquired using diesel as HRF (high-reactivity fuel) and gasoline as LRF (low reactivity fuel) to check the accuracy and fidelity of predicted results. Blends of ethanol and gasoline with DTBP (di-tert-butyl peroxide) addition in a small fraction on an energy basis were used in numerical simulations to promote ignitability and reactivity enhancement of PFI charge. Achieving stable, smooth, and gradual combustion in RCCI is challenging at low loads, especially in light-duty engines, due to misfiring and poor combustion stability. DTBP is known for enhancing cetane number and accelerating combustion, and it is mixed in a PFI blend to avoid combustion deterioration. The factors governing reactivity stratification to achieve optimal combustion phasing were investigated in the present study. DTBP decomposition and its low-temperature oxidation chemistry were found to be responsible for affecting combustion phasing, heat release patterns, and emission trends. DTBP additive and different in-cylinder strategies were applied and studied to reduce unburned emissions. Adopting a multiple injection approach utilizing dual-pulse assisted in reducing HC and CO levels. It enhances combustion quality by providing adequate control over combustion phasing. Altering operating parameters like intake temperatures reduced HC, CO, and soot emissions by 97.6%, 57.6%, and 52.8%, respectively, compared to baseline gasoline/diesel RCCI data. Optimizing the injection timings of the first and second pulse helps achieve optimal combustion phasing and a 72.95% reduction in NOx emissions. The higher injection pressure of DI helped lower the CO and soot emissions by 53.33% and 51.84%, respectively.
Tripathi, Saurabh, Krishnasamy, Anand
Novel Chemical Kinetics Mechanism for Robust Simulation of Multi-Component Fuel Blends in Engine Conditions2024-24-00359/18/2024
Ammonia, with its significant hydrogen content, offers a practical alternative to pure hydrogen in marine applications and is easier to store due to its higher volumetric energy density. While Ammonia's resistance to auto-ignition makes it suitable for high-compression ratio engines using pre-mixed charge, its low flame speed poses challenges. Innovative combustion strategies, such as dual-fuel and reactivity-controlled compression ignition (RCCI), leverage secondary high-reactivity fuels like diesel to enhance Ammonia combustion. To address the challenges posed by Ammonia's low flame speed, blending with hydrogen or natural gas (NG) in the low reactivity portion of the fuel mixture is an effective approach. For combustion simulation in engines, it is crucial to develop a chemical kinetics mechanism that accommodates all participating fuels: diesel, Ammonia, hydrogen, and NG. This study aims to propose a kinetics mechanism applicable for the combustion of these fuels together. The mechanism is tailored for engine conditions, including high pressures and temperatures, and diverse chemical species concentrations. To render the mechanism suitable for computationally efficient 3-D Computational Fluid Dynamics (CFD) simulations, it is reduced and contains 82 species and 636 reactions, with N-heptane serving as the surrogate for diesel fuel. The mechanism is tuned using optimization methods to match available experimental data on ignition delay time (IDT) for N-heptane. The prediction of IDT and laminar burning velocity values by the mechanism is validated with available experimental data. Additionally, 3-D CFD and quasi-dimensional multi-zone engine simulations are conducted using the new mechanism to verify engine operating parameters against available experimental data.
Salahi, Mohammad Mahdi, Mahmoudzadeh Andwari, Amin, Kakoee, Alireza, Hyvonen, Jari, Gharehghani, Ayat, Mikulski, Maciej, Lendormy, Éric
Auto-Ignited Combustion Control in an Engine Equipped with Multiple Boosting Devices03-17-06-00436/3/2024
The combustion timing of auto-ignited combustion is determined by composition, temperature, and pressure of cylinder charge. Thus, for a successful auto-ignition, those key variables must be controlled within tight target ranges, which is challenging due to (i) nature of coupling between those variables, and (ii) complexity of managing multiple actuators in the engine. In this article, a control strategy that manages multiple actuators of a boosted homogeneous charge compression ignition (HCCI) engine is developed to maintain robust auto-ignited combustion. The HCCI engine being considered is equipped with multiple boosting devices including a supercharger and a turbocharger in addition to conventional actuators and sensors. Since each boosting device has its own pros and cons, harmonizing those boosting devices is crucial for successful transient operation. To address the multi-variable transient control problem, speed-gradient control methodology is applied to minimize coupling between boosting devices. Simulation results show that the control strategy overcomes turbo lag by utilizing the supercharger during transient. The controller developed is still appliable to manage multiple boosting devices with conventional engines as well as HCCI engine.
Kang, Jun-Mo
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.
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
Investigation on Combustion Stability, Unregulated and Particle Emissions in RCCI Engine2024-01-20884/9/2024
This study experimentally investigates the combustion stability in RCCI engines along with the gaseous (regulated and unregulated) and particle emissions. Multifractal analysis is used to characterize the cyclic combustion variations in the combustion parameters (such as IMEP, CA50, and THR). This analysis aims to investigate the multifractal characteristics of the RCCI combustion mode near the misfiring limit. The investigation is carried out on a modified single-cylinder diesel engine to operate in RCCI combustion mode.The RCCI combustion mode is tested for different diesel injection timing (SOI) at fixed engine speed (1500rpm) and load (1.5 bar BMEP). The particle number characteristics and gaseous emissions are measured using a differential mobility spectrometer (DMS500) and Fourier Transform Infrared Spectroscopy (FTIR) along with Flame Ionizing Detector (FID), respectively. The results indicate that the NOx emissions decrease with advanced SOI while the Total Hydro-Carbon (THC) emission increases. The result shows that advanced SOI decreases the formation of propylene (C3H6), ethylene (C2H4), 1-3 butadiene (C4H6), and methane (CH4). However, formaldehyde (HCHO) emission increased with advanced SOI. The emission of the total particle number (PN) and nucleation mode particles (NMPs) decreased with advanced diesel SOI. Multi-Fractal Detrended Fluctuation Analysis (MFDFA) demonstrated a positive correlation between diesel SOI and the level of multifractality. It is found that the time series of combustion parameters exhibits large fluctuations at smaller time scales, while small fluctuations are detected at higher time scales.
Yadav, Ratnesh Kumar, Saxena, Mohit Raj, Maurya, Rakesh Kumar
Strategies to Reduce Higher Unburned Hydrocarbon and Carbon Monoxide Emissions in Reactivity Controlled Compression Ignition2024-01-23604/9/2024
Reactivity Controlled Compression Ignition (RCCI) is a promising, high-efficiency, clean combustion mode for diesel engines. One of the significant limitations of RCCI is its higher unburned hydrocarbon (HC) and carbon monoxide (CO) emissions compared to conventional diesel combustion. After-treatment control of HC and CO emissions is difficult to achieve in RCCI because of lower exhaust gas temperatures associated with the low-temperature combustion (LTC) mode of operation. The present study involves combined experimental and computational fluid dynamic (CFD) investigations to develop the most effective HC and CO control strategy for RCCI. A production light-duty diesel engine is modified to run in RCCI mode by introducing electronic port fuel injection with the replacement of mechanical injectors by the CRDI system. Experimental data were obtained using diesel as HRF (High reactive fuel) and gasoline as LRF (low reactive fuel). The combustion simulation was performed using the CONVERGE 3D CFD tool. A reduced PRF mechanism was used where iso-octane represents gasoline and n-heptane as diesel. After validation of engine combustion, performance, and emission parameters, parametric investigations were carried out to investigate the effects of HRF's start of injection timing, premixed energy share, and intake charge temperature on combustion and exhaust emissions. The results obtained from both CFD and experiment show that the start of injection and intake charge temperature significantly influence combustion phasing, while the premixed ratio controls mixture reactivity and combustion quality. The blending ratio of high HRF to LRF governs reactivity stratification, which controls the magnitude of low and high-temperature heat release, combustion phasing and combustion duration. Controlling the amount of LRF and HRF in direct injection (DI) allows for shifting the heat release rate, which modifies combustion phasing and rate of pressure rise. Multiple injection strategies using double pulse helped reduce CO formation and achieve better control over combustion parameters with improved efficiency. By varying IVC temperature, optimizing SOI timing using a double injection strategy up to 18.57%, 25.5% reduction in CO and 93.68% drop in HC emissions, 3.7% reduction in soot are obtained in RCCI compared to the baseline case.
Tripathi, Saurabh, Krishnasamy, Anand
Machine Learning-Based Modeling and Predictive Control of Combustion Phasing and Load in a Dual-Fuel Low-Temperature Combustion Engine03-17-04-00301/18/2024
Reactivity-controlled compression ignition (RCCI) engine is an innovative dual-fuel strategy, which uses two fuels with different reactivity and physical properties to achieve low-temperature combustion, resulting in reduced emissions of oxides of nitrogen (NOx), particulate matter, and improved fuel efficiency at part-load engine operating conditions compared to conventional diesel engines. However, RCCI operation at high loads poses challenges due to the premixed nature of RCCI combustion. Furthermore, precise controls of indicated mean effective pressure (IMEP) and CA50 combustion phasing (crank angle corresponding to 50% of cumulative heat release) are crucial for drivability, fuel conversion efficiency, and combustion stability of an RCCI engine. Real-time manipulation of fuel injection timing and premix ratio (PR) can maintain optimal combustion conditions to track the desired load and combustion phasing while keeping maximum pressure rise rate (MPRR) within acceptable limits. In this study, a model-based controller was developed to track CA50 and IMEP accurately while limiting MPRR below a specified threshold in an RCCI engine. The research workflow involved development of an imitative dynamic RCCI engine model using a data-driven approach, which provided reliable measured state feedback during closed-loop simulations. The model exhibited high prediction accuracy, with an R 2 score exceeding 0.91 for all the features of interest. A linear parameter-varying state space (LPV-SS) model based on least squares support vector machines (LS-SVM) was developed and integrated into the model predictive controller (MPC). The controller parameters were optimized using genetic algorithm and closed-loop simulations were performed to assess the MPC’s performance. The results demonstrated the controller’s effectiveness in tracking CA50 and IMEP, with mean average errors (MAE) of 0.89 crank angle degree (CAD) and 46 kPa and Mean absolute percentage error (MAPE) of 9.7% and 7.1%, respectively, while effectively limiting MPRR below of 10 bar/CAD. This comprehensive evaluation showcased the efficacy of the model-based control approach in tracking CA50 and IMEP while constraining MPRR in the dual-fuel engine.
Punasiya, Mohit, Sarangi, Asish Kumar
Environmental and Cancer Risk Potential Assessment of Unregulated Emissions from Methanol-Diesel Dual Fuel RCCI Engine2024-26-01521/16/2024
The influence of engine load and fuel premixing ratio (PMR) on unregulated emission from a methanol-diesel dual-fuel RCCI (MD-RCCI) engine is examined in this study. The study focuses on assessing the adverse effects of unregulated emissions (saturated HC, unsaturated HC, carbonyl compounds, aromatic hydrocarbon, NH3, and SO2) on the health of human beings and the environment. To quantify the effect on the environment, the greenhouse gas potential (GWPs), Eutrophication potential (EP), Acidification potential (AP), and Ozone forming potential (OFP) are calculated and presented. The cancer risk potential (CRP) of the carbonyl compounds (HCHO and CH3CHO) is calculated and presented to see the effect on human health. The results demonstrate that at lower engine load, with an increase in PMR, the OFP and CRP for MD-RCCI operation increase significantly, whereas AP, EP, and GWPs decrease. Additionally, with a rise in the load at a constant PMR, the AP, EP and OFP decrease significantly. The presence of low carbon content and inherent oxygen atom in methanol decreases the concentration of main GWPs species such as CO2. MD-RCCI operation emits significantly lower concentration of NOx, and hence AP, EP potential decreases.
Yadav, Neeraj Kumar, Saxena, Mohit Raj, Maurya, Rakesh Kumar
Experimental Study of Combustion Characteristics and Emissions of Pre-Chamber Induced HCCI Combustion2023-01-162310/31/2023
It is a well-known fact that HCCI combustion offers the possibility of achieving high efficiency with low emissions, but with the challenges in combustion control and ability to adjust to changing environmental conditions. To resolve the aforementioned challenges, a pre-chamber induced homogeneous charge compression ignition (PC-HCCI) combustion mode was experimentally tested with aim of providing initial operating boundaries in terms of combustion stability and obtaining initial performance results. The single cylinder engine equipped with active pre-chamber and compression ratio (CR) of 17.5 was fueled by gasoline. The initial experiments were performed at the engine speed of 1600 rpm with intake air temperatures varied from 33°C to 100°C to verify the possibility of achieving the PC-HCCI combustion mode and to compare the achieved engine performance and emission results with both PCSI and pure HCCI combustion modes used as reference cases. The results showed that PC-HCCI combustion mode ensures stable operation at low loads, extending the lean limit while maintaining higher efficiency compared to PCSI combustion mode. When compared to the pure HCCI combustion mode, lower efficiency is obtained, possibly only due to non-optimized operating parameters. The results however confirm that a significant reduction and narrowing of the required intake temperature range is feasible along with the direct control of ignition timing and thus much improved resilience to the changing of boundary conditions. The analysis further showed that pre-chamber fuel mass has a major impact not only on ignition and combustion stability but is also directly corelated with total emissions of NOX, confirming that at such diluted mixtures most of the engine-out emissions come from the pre-chamber.
Ugrinić, Sara, Krajnovic, Josip, Sjeric, Momir, Kozarac, Darko
TOC99-05-05-0TOC10/24/2023
TOC
Tobolski, Sue
Operation Range Extension of Homogeneous Charge Compression Ignited Small-Bore Off-Road Diesel Engine Using Acetone-Gasoline Blends2023-01-180010/24/2023
The Homogeneous Charge Compression Ignition (HCCI) combustion eliminates the issues of higher particulate matter and nitrogen oxides emissions that prevail in the traditional compression ignition (CI) combustion mode. The complete replacement of traditional fuels with renewable fuels for internal combustion engines is challenging because significant infrastructure changes in the production and delivery systems are required to ensure renewable fuel availability and economic feasibility. Thus, the use of renewable acetone blended with traditional gasoline has been proposed in the present study to smoothen the transition from the traditional CI to the HCCI engines. HCCI experiments were performed in a light-duty diesel engine at 1500 rpm rated speed. By varying the volumetric proportion of the acetone in the gasoline from 20% to 40%, the HCCI engine load range from 20%-60% was achieved, significantly higher than the limited diesel HCCI load range of 20%-38%. An ignition-quality enhancer, 2-Ethylhexyl nitrate, at 6 vol.%, was blended in the acetone-gasoline to prevent the higher cyclic IMEP fluctuations at the lower engine loads. The empirical correlation of the start of combustion (CA10) established on a rapid compression machine facility was validated for the HCCI engine. The combustion phasing (CA50) was predicted using CA10 and fresh air equivalence ratio. A double-Weibe function was developed to characterize specifically the high-temperature heat release rate during the HCCI combustion and determine the extent of its fast-burning core region. An in-depth energy balance study was conducted to elucidate the reason for the indicated thermal efficiency trends. The acetone-gasoline-fuelled HCCI engine generated smoke and nitrogen oxides emissions that were less than 0.0007 g/kW-h and 2.5 g/kW-h, respectively, at all the engine loads. This study concluded that lower exhaust emissions could be obtained without compromising engine performance when the acetone-gasoline blends are used as fuels for operating the HCCI engine.
Kale, Aneesh Vijay, Krishnasamy, Anand
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
Prediction of the Spontaneous Ignition in a GCI Engine using an Extended Physical Model of the Ignition Delay2023-32-00199/29/2023
With the aim to further reduce and limit pollutant emissions and fuel consumption towards carbon neutrality, researchers and automotive manufacturers have been studying new combustion technologies, such as low temperature combustions, which provide an efficient combustion with low pollutant emissions. Despite innovative combustion techniques, such as Homogeneous charge compression ignition (HCCI) and Gasoline compression ignition (GCI), proved to reduce pollutant emissions and increase efficiency of internal combustion engines, their large-scale deployment has been limited by problems in combustion management and stability. In fact, the challenge related to these innovative combustion techniques consists in the development of new control strategies and new calibration methodologies, which allow to limit their combustion instability. By relying on the natural phenomenon of autoignition, researchers showed that, to optimize GCI combustion, it is necessary to adopt a multiple injections strategy. The rise in temperature and pressure produced by the premixed combustion of the first injections (long ignition delay) results in a controllable ignition of the main injection, responsible for torque delivery, which burns with an extremely short ignition delay. In the discussed process, the most critical aspect to be managed is the spontaneous ignition of the fuel introduced with the pre-injections, since its long ignition delay is affected by many engine control parameters, because it is very sensitive to the cylinder thermal conditions. As a result, the ignition delay might be strongly affected by a slight variation in the control parameters and, consequently, lead to misfire or knocking. The goal of this work was to develop an extended control-oriented ignition delay model, suitable to improve GCI combustion stability through the proper management of the pilot injections over the whole engine operating range.
Silvagni, Giacomo, Ravaglioli, Vittorio, Ponti, Fabrizio, Moro, Davide, Stola*, Federico, Cesare, Matteo De
Influence of Reforming by Non-Equilibrium Plasma on Spontaneous Ignition of n-Heptane/Ethanol/N2/02 Mixture2023-32-01489/29/2023
The influence of ethanol volume fraction on the spontaneous ignition of homogeneous premixed gas reformed by non-equilibrium plasma was investigated. The HCCI experiments of the gas was carried out using a Rapid Compression Machine (RCM). The spontaneous ignition process and reforming process were numerically investigated by reaction simulation in OD. A simplified model was proposed to explain the influence of the reforming of the gas with different ethanol volume fractions, and the model was validated. These results indicate that the influence of the reforming on ignition delay of cool flame is almost irrespective of the ethanol volume fractions.
Otani, Masaki, Takagi, Keigo, Gomi, Koichi, Sakurai, Eita, Sasaki, Yusuke, Saito, Masanori, Tanabe, Mitusuaki
Influence of Combustion Mode on Heat Loss Distribution in Gasoline Engines2023-32-00759/29/2023
As a technology to reduce the heat loss of engines, heat insulation coating to the surface of combustion chamber has been received a lot of attention. In order to maximize the thermal efficiency improvements by the technology, it is important to clarify the location where heat insulation coating can reduce heat loss more effectively, considering the impact on abnormal combustion etc. In this study, transient behavior of wall heat flux distribution on the piston was analyzed using 3D Computational Fluid Dynamics (CFD) for three combustion modes (spark ignition combustion (SI), homogenous charge compression Ignition (HCCI) and spark controlled compression ignition (SPCCI)).
Matsuda, Hirotsugu, Uchida, Kenji, Harada, Yuji, Yamashita, Hiroyuki
Residual Gas Fraction Measurement and Estimation of the CFR Octane Rating Engine Operating Under HCCI Conditions2023-32-00109/29/2023
The autoignition chemistry of fuels depends on the pressure, temperature, and time history that the fuel-air mixture experiences during the compression stroke. While piezoelectric pressure transducers offer excellent means of pressure measurement, temperature measurements are not commonly available and must be estimated. Even if the pressure and temperature at the intake and exhaust ports are measured, the residual gas fraction (RGF) within the combustion chamber requires estimation and greatly impacts the temperature of the fresh charge at intake valve closing. This work replaced the standard D1 Detonation Pickup of a CFR engine with a rapid sampling valve to allow for in-cylinder gas sampling at defined crank-angle times during the compression stroke. The extracted cylinder contents were captured in an emissions sample bag and its composition was subsequently analyzed in an AVL i60 emissions bench. Carbon dioxide levels beyond atmospheric concentration directly identified the existing RGF within the combustion chamber during the compression stroke. The CFR engine was operated under homogeneous charge compression ignition using iso-octane/n-heptane Primary Reference Fuels with seven blends of 0-100% iso-octane to measure the RGF as a function of compression ratio over a range from 6:1 to 17.5:1. Furthermore, a modified compressed air intake manifold enabled evaluation of intake pressure and intake temperature effects on the RGF. The measurements were shown to compare correctly with expected trends as a function of compression ratio and clearance volume. A model was developed to successfully estimate the RGF of a fresh charge based on intake and exhaust pressures and temperatures, as well as the compression ratio. This model showed significantly improved correlations over literature RGF models, such as simple geometric compression ratio models based on clearance volume and displacement.
Gonzalez, Jorge Pulpeiro, Hoth, Alexander, Kolodziej, Christopher P., Seong, Hee Je
Numerical Investigation of Multi-Stage HCCI Combustion with Small Chamber Inside Piston2023-32-00209/29/2023
Homogeneous charge compression ignition (HCCI) combustion is promising for not only high thermal efficiency but also reducing nitrogen oxides (NOx) and PM simultaneously. However, the operational range of the HCCI combustion is limited because of some issues, such as poor control of ignition timing and knocking by the excessive rate of pressure rise. In this study, a new combustion system based on the HCCI combustion process is proposed based on the authors' previous experimental work. This combustion system has a divided combustion chamber of two parts, one is small and the other is large. The most significant feature is the small chamber inside the piston. At first, combustion takes place in the small chamber, and then the burned gas is ejected into the large chamber to ignite the mixture in the large chamber. In this combustion system, the combustion in the large chamber takes the HCCI combustion process. 3D-CFD was conducted to predict HCCI combustion characteristics with small chamber inside the piston, varying the geometry of small chamber. Simulation results revealed that this combustion system can be achieve two-stage HCCI combustion with reduced pressure rise rate.
Nomura, Takuya, Moriyoshi, Yasuo, Morikawa, Koji, Kuboyama, Tatsuya
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
Charge Dilution Strategy to Extend the Stable Combustion Regime of a Homogenous Charge Compression Ignited Engine Operated With Biodiesel2023-32-01329/29/2023
The present research explores the application of biodiesel fuel in a stationary agricultural engine operated under the Homogenous charge compression ignition (HCCI) mode. To achieve HCCI combustion, a fuel vaporizer and a high-pressure port fuel injection system are employed to facilitate rapid evaporation of the biodiesel fuel. The low volatility of biodiesel is one of the significant shortcomings, which makes it inevitable to use a fuel vaporizer at 380oC. Consequently, the charge temperature is high enough to promote advanced auto-ignition. Further, the high reactivity of biodiesel favors early auto-ignition of the charge. Besides, biodiesel exhibits a faster burn rate due to its oxygenated nature. The combined effect of advanced auto-ignition and faster burn rate resulted in a steep rise in the in-cylinder pressures, leading to abnormal combustion above 20% load. Diluting the charge reduces reactivity and intake oxygen concentration, facilitating load extension. This study explores two charge diluents: recirculated exhaust gas (EGR) and water vapor induction into the intake manifold. With EGR, the maximum load is 40%, whereas 46% of the rated load could be achieved with water vapor induction. The maximum load could be extended up to 50% with the combined dilution using EGR and water vapor. The charge dilution required with water vapor is less than that of EGR. Additionally, charge dilution with water vapor results in better thermal efficiency, fuel economy, and lower emissions than EGR. Overall, the present study confirms the functionality and feasibility of biodiesel in HCCI engines, demonstrating the applicability of charge dilution to address its significant shortcoming of a narrow stable combustion regime.
Bukkarapu, Kiran Raj, Krishnasamy, Anand
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
Impact of Splitting n-Dodecane Pilot Injection on Ammonia RCCI Engine2023-24-00768/28/2023
The increased interest in ammonia as a hydrogen carrier and a carbon-free fuel for combustion applications continues to present several challenges to address. Moreover, the high auto-ignition temperature (925 K) for ammonia limits its use in compression ignition engines because excessively high compression ratio are required. One way to retrofit diesel engine is to help the ignition by injecting a pilot injection of reactive fuel, like diesel or biodiesel. In this study, the ammonia engine ignited by a dodecane pilot injection is investigated with a maximum ammonia energy share (until 98.5%). The effect of split diesel injection strategy in two-steps under medium load operating conditions is studied as a function of ammonia/air equivalence ratio. Splitting this injection reduces NOX, CO, UHC and unburnt NH3 emissions at the exhaust, even it remains above the recommended emissions limit, especially at stoichiometric or slightly rich ammonia/air mixture. Not evident tendencies can be drawn about the improvement of GHG reduction (i.e. N2O and CO2) by splitting the diesel pilot injection. However, a strategy when the pre and the main injections being set closer to TDC, proves to be the best configuration due to the improvement of the combustion process, with a minimum diesel energy amount.
Rousselle, Christine Mounaim, Brequigny, Pierre, Dupuy, Anthony
Experimental Investigation on the Combustion of Biogas Containing Hydrogen in a HCCI Engine2023-24-00568/28/2023
Biogas is a gas resulting from biomass, with a volumetric content of methane (CH4) usually ranging between 50% and 70%, and carbon dioxide (CO2) content between 30% and 50%; it can also contain hydrogen (H2) depending on the feedstock. Biogas is generally used to generate electricity or produce heat in cogeneration system. Due to its good efficiency through the rapid combustion and lean air-fuel mixture, Homogeneous Charge Compression Ignition (HCCI) engine is a good candidate for such application. However, the engine load must be kept low to contain the high-pressure gradients caused by the simultaneous premixed combustion of the entire in-cylinder charge. The homogenous charge promotes low particulate emissions, and the dilution helps in containing maximum in-cylinder temperature, hence reducing nitrogen oxide emissions. However, HC and CO levels are in general higher than in SI combustion. Moreover, HCCI engines usually require high intake temperature with values depending on compression ratio, fuel, equivalence ratio, and intake pressure. This paper presents the results of an experimental campaign on a diesel internal combustion engine for passenger cars, modified to operate in HCCI mode. The engine was fuelled by mixtures of methane, H2, and carbon dioxide, with the aim of reproducing the composition of innovative biogas naturally containing hydrogen. The equivalence ratio was kept constant at 0.4 and the intake charge temperature and pressure have been adjusted, depending on fuel composition, to control the combustion process. For each fuel, the intake charge conditions for an optimal combustion phasing have been determined, attaining a maximum indicated engine efficiency of 40% and specific NOx emissions down to 0.1 g/kWh.
Mariani, Antonio, Brequigny, Pierre, Masurier, Jean-Baptiste, Unich, Andrea, Minale, Mario, Foucher, Fabrice
Variable Compression Ratio Hydrogen-Fueled Homogeneous Charge Compression Ignition Engine2023-24-00678/28/2023
Hydrogen-fueled homogeneous charge compression ignition (HCCI) engines have shown the ability to provide a cleaner and more efficient alternative to conventional fossil fuels. The use of hydrogen as a fuel has the potential to reduce greenhouse gas and promote sustainability. In this study, a modified single-cylinder Cooperative Fuel Research (CFR) engine was utilised to operate on hydrogen in a HCCI combustion mode under various compression ratio (CR) conditions. In the experiments, the amount of hydrogen injected was adjusted at each CR to maintain the crank angle at 50% mass fraction burned (CA50) combustion phasing at 3±1 crank angle degrees after top dead center or as lean as possible. The engine speed was fixed at 600 rpm, and the impact of different intake air temperatures was also investigated. The results indicated that as the compression ratio increases, the air-fuel ratio needs to be increased to maintain the desired CA50 value, i.e., the engine needs to operate leaner. The net indicated mean effective pressure of the engine reached a value of 2.9 bar at a compression ratio of 14 and an intake air temperature of 150OC. The effects of CR and intake temperature on engine performance metrics, such as power output and the rate of heat release, were also investigated. The experimental data showed that the intake air temperature did not have a significant effect on engine performance and power output. At a compression ratio of 16:1 and 600 rpm, the engine's indicated thermal efficiency was found to be approximately 33% across the range of intake temperatures investigated. Furthermore, the fact that the engine effectively produced zero NOx emissions under the various CR conditions tested further highlights the potential for hydrogen HCCI engines to be adopted as a cleaner and more efficient alternative to internal combustion engines using conventional fuels, provided the available range of operation is acceptable and can be made large enough for practical applications.
Nguyen, Ducduy, Fernandes, Renston, Turner, James W.G.
Numerical Investigation of Ammonia-Diesel Fuelled Engine Operated in RCCI Mode2023-24-00578/28/2023
Ammonia, which is one of the most produced inorganic chemicals worldwide, has gained significant attention in recent years as a carbon-free fuel due to its significant energy density in maritime and power plant applications. This fuel offers several advantages including low production costs and being safe for storage and transport. Reactivity controlled compression ignition (RCCI) combustion mode is considered as a promising strategy reducing the level of nitrogen oxides (NOx) emissions and particulate matters (PM) in internal combustion engines (ICEs) due to the lower combustion temperatures and charge homogeneity. Ammonia-based RCCI combustion strategy can offer a simultaneous reduction of CO2 and NOx. In this study, a RCCI engine fuelled by ammonia and diesel is numerically simulated considering chemical reactions kinetics mechanism of the combustion. After validating the simulation results with literature experimental data, the effect of engine operational parameters such as the initial charge temperature together with injection timing on the engine operational characteristic including in-cylinder pressure, heat release rate (HRR), indicated mean effective pressure (IMEP) and emission levels are investigated and discussed accordingly. The results indicated that advancing the start of injection (SOI) timing from 20 to 100 CAD bTDC, increased the NOx emissions concentration at the initial intake charge temperatures of 460 and 480 K. Higher initial intake charge temperature increased the level of NOx emissions while advancing SOI timing from 20 to 100 CAD bTDC did not disturb the level of CO emission significantly.
Fakhari, Amir Hossein, Gharehghani, Ayat, Salahi, Mohammad Mahdi, Mahmoudzadeh Andwari, Amin, Mikulski, Maciej, Hunicz, Jacek, Könnö, Juho
Numerical Simulations of Pre-Chamber Induced HCCI Combustion (PC-HCCI)2023-01-02744/11/2023
Advanced combustion concepts that rely on the lean-burn approach are a proven solution for increasing the efficiency and reducing the harmful emissions of SI engines. The pre-chamber spark ignited (PCSI) engines utilize high ignition energy of the multiple jets penetrating from the pre-chamber, to enable fast and stable combustion of lean mixture in the main chamber. The combustion is still governed by the flame propagation, so the dilution level and efficiency benefits are highly restricted by strong decrease of laminar flame speeds. Homogeneous charge compression ignition (HCCI) combustion allows a higher dilution level due to rapid chemically driven combustion, however the inability to directly control the ignition timing has proven to be a major setback in HCCI deployment. The addition of the spark plug, to improve the controllability and widen the operating range, resulted in a combustion concept known as spark-assisted compression ignition (SACI), however spark ignition of lean mixtures is very difficult even at close to HCCI conditions. Since one of the features of active pre-chamber is the ability to control mixture dilution at the spark plug location, a combustion concept called pre-chamber induced HCCI combustion (PC-HCCI) that combines pre-chamber ignition and HCCI combustion is proposed. In this concept a near stoichiometric mixture in the pre-chamber is spark ignited and the combustion in pre-chamber triggers kinetically controlled combustion of lean main combustion chamber mixture. As a first step of the research, numerical modelling of the proposed combustion concept is made by employing 3D-CFD and 1D/0D simulation models. The main purpose of the modelling is to define main geometrical and operating parameters required for achieving a pre-chamber induced HCCI combustion and to predict possible benefits of employing such combustion concept.
Krajnovic, Josip, Dilber, Viktor, Tomic, Rudolf, Sjeric, Momir, Ilincic, Petar, Kozarac, Darko
Experimental Investigation of Cycle-to-Cycle Variations in Homogeneous Charge Compression Ignition Engine Fueled with Methanol Using Wavelets2023-01-02784/11/2023
The development of automotive engines continues to be determined by gradually more stringent emission norms including CO2 emissions and fuel consumption. To fulfill the simultaneous emission requirements for near-zero pollutants and low CO2 levels, several research studies are currently being carried out around the world on new engine combustion process, such as Homogeneous Charge Compression Ignition (HCCI). In HCCI engines, combustion rate, and ignition timing are dominated by physical and chemical properties of fuel/air/residual gas mixtures, boundary conditions including ambient temperature, pressure, and humidity, and engine operating conditions such as load, speed, etc. Higher cycle-to-cycle variations are observed in HCCI combustion engines due to the large variability of these factors. The cyclic variations in the HCCI engine are investigated on a modified four-stroke, four-cylinder engine. The HCCI combustion mode is tested with methanol fuel. This study presents the cyclic combustion analysis of the HCCI engine using statistical and Wavelet Transform techniques. The cyclic variations are characterized under different operating conditions such as relative air-fuel ratios (λ), intake air temperature (Ti), and engine speed (N). The wavelet analysis results indicate that cyclic variations in IMEP and combustion phasing (CA50) occur at different frequencies. Results indicate that with an increase in the Ti, the variations in IMEP are shifted from low periodicity to high periodicity. The high periodicity variations for higher Ti operation are found due to the too advanced CA50 position (before TDC position). Global wavelet spectrum results depict that peak power decreases with an increase in Ti and λ which implies the reduction in cyclic combustion variations.
Yadav, Ratnesh Kumar, Saxena, Mohit Raj, Maurya, Rakesh Kumar
Computational Investigation of Combustion Phasing and Emission of Ammonia and Hydrogen Blends under HCCI Conditions2023-01-01894/11/2023
There is a growing interest in ammonia as a potential carbon-free fuel due to the current trend of decarbonization in ground transportation. Benefits of ammonia as a fuel include its high volumetric energy density, ease of storage and transportation, and mature manufacturing infrastructure. On the other hand, ammonia suffers from a low flame speed, long ignition delay times and NOx formation. In this work, a computational investigation of ammonia and hydrogen blends in a 0-D homogeneous charge compression ignition reactor is conducted using different blends under a range of engine-relevant conditions. Iso-contours of the crank angle corresponding to 50% of total heat release (CA50) are developed to assess the reactivity of the different blends under different engine speeds and equivalence ratios. The results show that ammonia requires a high inlet temperature to achieve a CA50 close to top dead center (TDC). An increase in hydrogen concentration resulted in a lower inlet temperature required to achieve a CA50 close to TDC. The gradients of iso-contour can easily show the sensitivity of CA50, as well as NO and H2 formation, to operating temperature and pressure in a wide range of conditions. A sensitivity analysis of the ignition delay showed that combustion phasing is highly promoted through hydrogen oxidation and the chain-branching reactions of the intermediate species. In terms of emissions, H2 and NO possess the highest concentrations, which increase further with increasing hydrogen concentration in the fuel blend. A chemical flux analysis is conducted to understand the role of the reactions and species in H2 and NO formation and consumption. This work provides useful insights into the chemical and thermal role of hydrogen in promoting the combustion of ammonia for future engine applications.
Bakir, Ahmad, Ge, Haiwen, Zhao, Peng
Comparison of Combustion Parameters and Homogeneity of Full and Direct Injection Homogeneous Charge Compression Ignition Engine under Supercharger Conditions04-16-02-00101/9/2023
In this study, a numerical model validation of the supercharged homogeneous charge compression ignition (HCCI) engine, whose experimental studies at 100, 110, 120, 130, 140, 150, and 160 kPa pressures, was carried out using Converge CFD program. After validation, the in-cylinder pressure, heat release rate (HRR), and maximum pressure rise rate (PRRmax) of a fully HCCI engine and an early direct injection HCCI engine were compared numerically at different supercharger pressures. According to the comparison results, it was observed that the cylinder pressure increased and the maximum in-cylinder pressure point advanced with the increase of the supercharge pressure in the fully homogeneous and early direct injection mode. In the early direct injection system, it was observed that the maximum pressure was lower than the results obtained in fully homogeneous conditions, especially at high manifold absolute pressure (MAP) values. In both modes, it was determined that with increasing supercharger pressure, HRR increased and the maximum HRR point advanced. A wider HRR curve is obtained in the early direct injection mode. In both cases, PRRmax was found to increase with increasing supercharge pressure. It was determined that the PRRmax in the fully homogeneous mode was higher than in the early direct injection condition. At low MAP values, the difference in PRRmax value between a fully homogeneous mixture and early direct injection is low, but this difference gradually increased with the increase in MAP. As a result of the analysis, the heterogeneous air-fuel mixture is formed due to the fuel injected into the cylinder in the early direct injection HCCI mode. In early direct injection HCCI mode, the more heterogeneous filling is obtained by spraying the fuel into the air in the cylinder. It is seen that almost all of the mass fraction has the same equivalence ratio until the fuel injection starts and there is an inhomogeneous mixture after fuel injection in the early direct injection HCCI mode.
Polat, Seyfi, Bulut, Ahmet, Akbulut, Furkan, Eroğlu, Tuba Neslihan
Control-Oriented Data-Driven and Physics-Based Modeling of Maximum Pressure Rise Rate in Reactivity Controlled Compression Ignition Engines03-16-06-004012/8/2022
Reactivity controlled compression ignition (RCCI) is a viable low-temperature combustion (LTC) regime that can provide high indicated thermal efficiency and very low nitrogen oxides (NOx) and particulate matter (PM) emissions compared to the traditional diesel compression ignition (CI) mode [1]. The burn duration in RCCI engines is generally shorter compared to the burn duration for CI and spark-ignition (SI) combustion modes [2, 3]. This leads to a high pressure rise rate (PRR) and limits their operational range. It is important to predict the maximum pressure rise rate (MPRR) in RCCI engines and avoid excessive MPRRs to enable safe RCCI operation over a wide range of engine conditions. In this article, two control-oriented models are presented to predict the MPRR in an RCCI engine. The first approach includes a combined physical and empirical model that uses the first principle of thermodynamics to estimate the PRR inside the cylinder, and the second approach estimates MPRR through a machine learning method based on kernelized canonical correlation analysis (KCCA) and linear parameter-varying (LPV) methods. The KCCA-LPV approach proved to have higher prediction accuracy compared to physics-based modeling while requiring less amount of calibration. The KCCA-LPV approach could estimate MPRR with an average error of 47 kPa/CAD while the physics-based approach’s average estimation error was 87 kPa/CAD.
Irdmousa, Behrouz Khoshbakht, Basina, L. N. Aditya, Naber, Jeffrey, Mohammadpour Velni, Javad, Borhan, Hoseinali, Shahbakhti, Mahdi
Letter from the Special Issue Editors04-16-01-000112/7/2022
Letter from the Special Issue Editors
Solmaz, Hamit, Polat, Seyfi
Letter from the Special Issue Editors04-16-02-000712/7/2022
Letter from the Special Issue Editors
Solmaz, Hamit, Polat, Seyfi
Effectiveness of Exhaust Gas Recirculation on Low-Load Combustion Efficiency of a Reactivity Controlled Compression Ignition Engine04-16-02-000811/18/2022
Reactivity controlled compression ignition (RCCI) is a potential low-temperature combustion (LTC) technique for running intrinsically efficient compression ignition engines while reducing the oxides of nitrogen (NOx) and particulate matter (PM) emissions. However, poor low-load combustion efficiency is a major challenge in the RCCI strategy. In this work, a combination of injection strategy and cold and hot exhaust gas recirculation (EGR) strategies were investigated to improve the low-load combustion efficiency of a production light-duty compression ignition engine operating in the gasoline-diesel dual-fuel RCCI mode. The engine was operated at a low load of 3 bar gross indicated mean effective pressure and at an engine speed of 1500 rpm with wide ranges of single and multiple fuel injection strategies. Significant improvement in combustion efficiency was achieved by targeting the directly injected diesel fuel in the piston lip region. Multiple fuel injection strategy in which more than 50% of the diesel fuel was targeted in the squish region was beneficial in terms of NOx, total hydrocarbon (THC), and soot emissions. RCCI operation with cold EGR, at the optimum injection timing, resulted in more than 96% reduction in engine-out NOx emissions (<20 ppm, 0.4 g/kWh) with near-zero soot (0.001 g/kWh) emissions with indicated thermal efficiency (46%), similar to conventional diesel combustion (CDC). Increasing the reactivity of the gasoline-air mixture, with the optimum distribution of the diesel fuel between the piston bowl and squish regions, reduced THC emissions by 75% and carbon monoxide (CO) emissions by 30% and improved the combustion efficiency by ~25.3% points compared to the baseline dual-fuel operation.
Khedkar, Nikhil Dilip, Sarangi, Asish K.
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