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Investigation of Diesel-CNG RCCI Combustion at Multiple Engine Operating Conditions

FEV North America Inc.-Mufaddel Dahodwala, Satyum Joshi, Erik Koehler, Michael Franke, Dean Tomazic
Michigan Technological University-Jeffrey Naber
  • Technical Paper
  • 2020-01-0801
To be published on 2020-04-14 by SAE International in United States
Past experimental studies conducted by the current authors on a 13 liter 16.7:1 compression ratio heavy-duty diesel engine have shown that diesel-Compressed Natural Gas (CNG) Reactivity Controlled Compression Ignition (RCCI) combustion targeting low NOx emissions becomes progressively difficult to control as the engine load is increased. This is mainly due to difficulty in controlling reactivity levels at higher loads. For the current study, CFD investigations were conducted in CONVERGE using the SAGE combustion solver with the application of the Rahimi mechanism. Studies were conducted at a load of 5 bar BMEP to validate the simulation results against RCCI experimental data. In the low load study, it was found that the Rahimi mechanism was not able to predict the RCCI combustion behavior for diesel injection timings advanced beyond 30 degCA bTDC. This poor prediction was found at multiple engine speed and load points. To resolve this, multiple reaction mechanisms were evaluated and a new reaction mechanism, that combines the GRI Mech 3.0 mechanism with the Chalmers mechanism, was proposed. This mechanism was shown to accurately predict…
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Extend Syngas Yield through Increasing Rich Limit by Stratified Air Injection in a Single Cylinder Engine

Southwest Research Institute-Yanyu Wang, Graham Conway, D. Ryan Williams, Christopher Chadwell
  • Technical Paper
  • 2020-01-0958
To be published on 2020-04-14 by SAE International in United States
Dedicated exhaust gas recirculation (D-EGR®) concept developed by Southwest Research Institute (SwRI) has demonstrated a thermal efficiency increase on many spark-ignited engines at both low and high load conditions. The syngas (H2+CO) produced in the dedicated cylinder (D-cyl) by rich combustion helps to stabilize combustion at highly dilute conditions at low loads and mitigate knock at high loads. The dedicated cylinder with 25% EGR can typically run up to equivalence ratio of 1.4, beyond which the combustion becomes unstable. By injecting fresh air near the spark plug gap at globally rich conditions, a locally lean or near-stoichiometric mixture can be achieved, thus facilitating the ignitability of the mixture and increasing combustion stability. With more stable combustion a richer global mixture can be introduced into the D-cyl to generate higher concentrations of syngas. This in turn can further improve the engine thermal efficiency.This study investigated the possibility of extending the rich limit by stratified air injection in a single cylinder engine. A custom modified spark plug with air passage was used to realize stratified air injection.…
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Combustion and Emission Characteristics of SI and HCCI Combustion Fueled with DME and OME

Ford Motor Company-Jimi Tjong
University of Windsor-Simon Leblanc, Xiao Yu, Navjot Singh Sandhu, Meiping Wang, Ming Zheng
  • Technical Paper
  • 2020-01-1355
To be published on 2020-04-14 by SAE International in United States
DME has been considered an alternative fuel to diesel fuel with promising benefits because of its high reactivity and volatility. Research shows that an engine fueled with DME will produce zero smoke emissions. However, the storage and the handling of the fuel are underlying difficulties owing to its high vapour pressure (530 kPa @ 20 °C). In lieu, OME1 fuel, a derivate of DME, offers advantages exhibited with DME fuel, all the while being a liquid fuel for engine application. In this work, engine tests are performed to realize the combustion behaviour of DME and OME1 fuel on a single-cylinder research engine with a compression ratio of 9.2:1. The dilution ratio of the mixture is progressively increased in two manners, allowing more air in the cylinder and applying exhaust gas recirculation (EGR). The high reactivity of DME suits the capability to be used in compression ignition combustion whereas OME1 must be supplied with a supplemental spark to initiate the combustion. The results indicate that a low-temperature heat release (LTHR) is present during the combustion of…
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Model Predictive Control of an Air Path System for Multi-Mode Operation in a Diesel Engine

Garrett Advancing Motion-Paul Dickinson, Jaroslav Pekar, MinSeok Ko
Hyundai Motor Group-Buomsik Shin, Yohan Chi, Minsu Kim
  • Technical Paper
  • 2020-01-0269
To be published on 2020-04-14 by SAE International in United States
A supervisory Model Predictive Control (MPC) approach is developed for an air path system for multi-mode operation in a diesel engine. MPC is a control method based on a predictive dynamic model of system and determines actuator control positions through the optimization of various factors such as tracking performances of target setpoints, moving speed of actuators, limits, etc. Previously, linear MPC has been successfully applied on the air path control problem of a diesel engine, however, most of these applications were developed for a single operation mode which has only one set of control target setpoint values. In reality, a single operation mode cannot cover all requirements of current diesel engines and this complicates practical implementations of linear MPC. The high priority targets for the development of diesel engines are low emissions, high thermal efficiency and robustness. These objectives require multi-mode operations such as a HP EGR (High pressure exhaust gas recirculation) mode in cold coolant condition, a Double EGR mode for sufficient EGR rates, a Diesel Particulate Filter (DPF) regeneration mode for the heat-up…
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Instantaneous PLII and OH* Chemiluminescence Study on Wide Distillation Fuels, PODEn and Ethanol Blends in a Constant Volume Vessel

Birmingham University-Hongming Xu
CNPC Ji Chai Power Co., Ltd.-Dong Liu
  • Technical Paper
  • 2020-01-0340
To be published on 2020-04-14 by SAE International in United States
The combustion characteristics and soot emissions of three types of fuels were studied in a high pressure and temperature vessel. In order to achieve better volatility, proper cetane number and high oxygen content, the newly designed WDEP fuel was proposed and investigated. It is composed of wide distillation fuel (WD), PODE3-6 mixture (PODEn) and ethanol. For comparison, the test on WD and the mixture of PODEn-ethanol (EP) are also conducted. OH* chemiluminescence during the combustion was measured and instantaneous PLII was also applied to reveal the soot distribution. Abel transformation was adopted to calculate the total soot of axisymmetric flame. The results show that WDEP has similar ignition delays and flame lift-off lengths to those of WD at 870-920 K. But the initial ignition locations of WDEP flame in different cycles were more concentrated, particularly under the condition of low oxygen atmosphere. Comparing with WD, the soot amount of WDEP decreased for 55% and 27% at 870 K and 920 K. For the case of 920 K and 15.8% of ambient oxygen, the soot amount…
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Neat Oxymethylene Ethers: Combustion Performance and Emissions of OME2, OME3, OME4 and OME5 in a Single-Cylinder Diesel Engine

Technical University of Munich-Patrick Dworschak, Vinicius Berger, Martin Härtl, Georg Wachtmeister
  • Technical Paper
  • 2020-01-0805
To be published on 2020-04-14 by SAE International in United States
Diesel engines are arguably the superior device in the ground transportation sector in terms of efficiency and reliability, but suffer from inferior emission performance due to the diffusive nature of diesel combustion. Great research efforts gradually reduced nitrogen oxide (NOX) and particulate matter (PM) emissions, but the PM-NOX trade-off remained to be a problem of major concern and was believed to be inevitable for a long time. In the process of engine development, the modification of fuel properties has lately gained great attention. In particular, the oxygenate fuel oxymethylene ether (OME) has proven potential to not only drastically reduce emissions, but possibly resolve the formerly inevitable trade-off completely. Although intensified investigations with OME were conducted within the past decade, little is known about the specific influence of fuel properties inherent to unimolecular, high chain-length OME on combustion characteristics, emission performance and particle size. The latter is of special concern, as studies on oxygenate fuels reported increased formation of nanoparticles, which are known to have adverse effects on human health.In this paper, the authors present a…
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Investigations Regarding Deposit Formation on Diesel Oxidation Catalysts

FEV Europe GmbH-Bernhard Lüers
Technical University of Braunschweig-Kevin Friese, Peter Eilts
  • Technical Paper
  • 2020-01-1432
To be published on 2020-04-14 by SAE International in United States
Catalyst fouling by deposit formation on components in the exhaust aftertreatment system is critical since RDE limits must be obtained at any time. Besides, uncontrolled oxidation of carbonaceous deposits might damage the affected exhaust aftertreatment component. To comply with current and future emission standards, diesel engines are usually operated with high EGR rates leading to increased soot and hydrocarbon emissions, which increases the likeliness of the formation of carbonaceous deposits on EAT components. With this background, a research project investigating the influencing parameters and mechanisms of deposit formation on DOCs was carried out. In a follow-up project, the results will be used in order to compare different deposit removal strategies. Within the scope of the presented project, a reference driving cycle was developed in order to create deposits within a short time. The driving cycle was modified during further endurance runs and analyzed for changes in the deposit’s properties. Furthermore, the engine was operated using different fuels and under various operating modes. The stability of the deposits was highly affected by the engine operation mode…
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Impact of Spark Plasma Length on Flame Kernel Development under Flow Condition

University of Windsor-Hua Zhu, Qingyuan Tan, Xiao Yu, Zhenyi Yang, Li Liang, Ming Zheng, Graham Reader
Zhuzhou Torch Spark Plug Co., Ltd.-Jin Qian
  • Technical Paper
  • 2020-01-1114
To be published on 2020-04-14 by SAE International in United States
Advanced ignition systems with enhanced discharge current have been extensively investigated in research, since they are highly regarded as having the potential to overcome challenges that arise when spark-ignition engines are running under lean or EGR diluted conditions. Local flow field is also of particular importance to improve the ignitability of the air-fuel mixture in SI engines as the spark plasma channel can be stretched by the flow across the spark gap, leading to longer plasma length, thus more thermal spark energy distributed to the air-fuel mixture in the vicinity of the spark plug. Research results have shown that a constantly high discharge current is effective to maintain a stable spark plasma channel with less restrikes and longer plasma holding period. However, with the further increase in discharge current, plasma channel becomes thicker, and the stretched plasma length becomes shorter under a constant flow speed, which may suppress the advantages of the enhanced discharge current.In this work, the interaction between discharge current level and plasma length under flow conditions is investigated. Whether a thick but…
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Experimental and Numerical Analysis of Passive Pre-Chamber Ignition with EGR and Air Dilution for Future Generation Passenger Car Engines

DEA-IRP Groupe Renault-Cedric Libert, Fano Rampanarivo, Chistou Panagiotis, Maziar Dabiri
Universitat Politecnica de Valencia-Ricardo Novella, Jose Pastor, Josep Gomez-Soriano, Ibrahim Barbery
  • Technical Paper
  • 2020-01-0238
To be published on 2020-04-14 by SAE International in United States
Nowadays the combination of strict regulations for pollutant and CO2 emissions, together with the irruption of electric vehicles in the automotive market, is arising many concerns for internal combustion engine community. For this purpose, many research efforts are being devoted to the development of a new generation of high-performance spark-ignition (SI) engines for passenger car applications. Particularly, the PC ignition concept, also known as Turbulent Jet Ignition (TJI), is the focus of several investigations for its benefits in terms of engine thermal efficiency. The passive or un-scavenged version of this ignition strategy does not require an auxiliary fuel supply inside the PC; therefore, it becomes a promising solution for passenger car applications as packaging and installation are simple and straightforward. Moreover, combining this concept with lean burn is an interesting alternative for both improving the engine efficiency and maintaining low pollutant emissions as it enables Low Temperature Combustion (LTC) which ultimately reduces NOX emissions. EGR dilution is also an attractive approach as it is compatible with the three-way catalyst for NOX control. However, previous researches…
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Assessment of the Ignition System Requirement on Diluted Mixture Spark Engines

Littelfuse-Jose Padilla
Universitat Politecnica de Valencia-Santiago Molina, Jaime Martin, Ricardo Novella, Josep Gomez-Soriano
  • Technical Paper
  • 2020-01-1116
To be published on 2020-04-14 by SAE International in United States
In order to face the new challenges, spark ignition engines are evolving by following some strategies and technologies. Among them, alternative combustion processes based on the dilution of the homogeneous mixture, either with fresh air or with Exhaust Gas Recirculation (EGR), are being explored. In a higher or lower extent, these changes modify in-cylinder thermodynamic conditions during the engine operation (pressure, temperature and gas composition) thus conditioning the spark ignition system requirements that will have to evolve to become more reliable and powerful.In this framework, an experimental study on the effect of the key in-cylinder conditions on the ignition system performance has been carried out in a single-cylinder spark-ignition (SI) research engine. The study includes EGR, lambda and energizing time sweeps to assess the behavior of the engine in different operating conditions. Furthermore, various Insulated-Gate Bipolar Transistors (IGBT) and spark plugs have been tested to assess the influence of these components on the ignition process at high diluted mixtures. Conclusions show that diluted mixtures (with EGR or lambda), even though they require more spark energy…