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Investigation of Diesel/Natural Gas RCCI Combustion Using Multiple Reaction Mechanisms at Various Engine Operating Conditions

FEV North America Inc.-Mufaddel Dahodwala, Satyum Joshi, Erik Koehler, Michael Franke, Dean Tomazic
Michigan Technological Univ-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 /natural gas Reactivity Controlled Compression Ignition (RCCI) combustion targeting low NOx emissions becomes progressively difficult to control as the engine load is increased due to difficulty in controlling reactivity levels at higher loads. For the current study, CFD investigations were conducted using the SAGE combustion solver in Converge with the application of Rahimi mechanism. Studies were conducted at a load of 5 bar BMEP to validate the simulation results against RCCI test 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 30bTDC. This behavior 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 found to accurately predict the ignition delay and combustion behavior with early…
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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…
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Combustion and Emission Characteristics of SI and HCCI Combustion Fueled with DME and OME

Ford Motor Company-Jimi Tjong
Univ of Windsor-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, OME 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 OME 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. The high reactivity of DME suits the capability to be used in compression ignition combustion whereas OME 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 DME…
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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
Deposit formation on components in the exhaust aftertreatment system is critical since RDE limits must be observed at any time. Besides, uncontrolled oxidation of carbonaceous deposits might damage the affected exhaust gas component. To comply with current and future emission standards diesel engines are usually operated with high EGR rates which leads to increased soot and hydrocarbon emissions what makes formation of carbonaceous deposits on EAT components more likely. With this background, a research project was carried out that investigates influencing parameters and mechanisms of deposit formation on DOCs. Within the project a reference driving cycle was developed in order to create deposits within short time. In further endurance runs the driving cycle was modified and the changes of the deposits’ properties were analyzed. Furthermore, the engine was operated using different fuels, monoliths and engine operation modes. The thermal stability of the deposits is highly affected be the engine operation mode and the engine load within the driving cycle. On the other hand the thermal stability of the deposits does not change in a single…
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Simulation of SACI Autoignition Phasing Sensitivity for Production Controls Strategies

Clemson University-Dennis Robertson, Robert Prucka
  • Technical Paper
  • 2020-01-1145
To be published on 2020-04-14 by SAE International in United States
Spark-assisted compression ignition (SACI) is a combustion strategy that leverages flame propagation to trigger autoignition. The autoignition event is highly sensitive to several parameters, and thus, achieving SACI in production demands a robust response to variations in conditions. However, limited research is available to quantify the combustion response of SACI to these variations. A simulation study is performed to identify the sensitivity in autoignition timing as ethanol content, fuel RON, air-fuel ratio, EGR level, and the phasing of flame propagation are swept. An experimentally-validated one-dimensional simulation model provides the composition, state, and flow metrics at BDC. The results are applied to the Leeds diagram to ensure the conditions are viable for flame propagation. The conditions at BDC are then transferred to a chemical kinetics solver, where autoignition is modeled using a detailed chemical kinetics mechanism. These results are used to explore the SACI combustion controls space. The range of CA50 control authority is particularly important as combustion phasing is used to perform rapid torque changes. The steady-state combustion control authority is evaluated, and potential controls…
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The effect of an active thermal coating on efficiency and emissions from a high speed direct injection diesel engine

Thistle Dubh Ltd-Robert Gilchrist
University of Oxford-Nick Papaioannou, Felix Leach, Martin Davy
  • Technical Paper
  • 2020-01-0807
To be published on 2020-04-14 by SAE International in United States
This study looked into the application of active thermal coatings on the surfaces of the combustion chamber as a method of improving the thermal efficiency of internal combustion engines. The combination of low thermal conductivity and low heat capacity that these coatings are offering, reduces the temperature gradient between the hot combustion gases and the cooler surroundings during the engine cycle thus leading to lower heat transfer losses and increased piston work. The use of such coatings also results in increased exhaust temperatures which has the potential to improve the cold start performance of after-treatment systems. The active thermal coating was applied to a production aluminium piston and its performance was compared against a reference aluminium piston on a single-cylinder diesel engine. The two pistons were tested over a wide range of speed/load conditions and the effects of EGR and combustion phasing on engine performance and tailpipe emissions were also investigated. A detailed energy balance approach was also employed to study the thermal behaviour of the active thermal coating. In general, improvements in indicated specific…
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Impact of plasma length on flame kernel development under flow condition

Univ of Windsor-Qingyuan Tan, Xiao Yu, Zhenyi Yang, Li Liang, Ming Zheng, Graham Reader
Univ. of Windsor-Hua Zhu
  • 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 level have been extensively investigated in research, since they are highly regarded to have potentials to overcome challenges arisen when spark-ignition engines are running under lean or EGR diluted conditions. Local flow field is also of particularly importance to improve the ignitability of the ignition system as spark plasma channel is stretched under flow conditions, leading to more thermal spark energy distribution to the air-fuel mixture in the vicinity of the spark plug. Research results have shown that a constantly high discharge current is considered to be effective to maintain stable discharge with less restrikes and longer plasma holding period. However, with the further increase of the discharge current, plasma channel becomes thicker, and the stretched plasma length becomes shorter under certain flow speed, which may suppress the advantages of the presence of air flow. In this work, the interaction between discharge current level and plasma length under flow conditions is investigated. Whether a thick but short plasma or a thin but stretched long plasma are more effective…
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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-Chistou Panagiotis, Cedric Libert, Fano Rampanarivo, Maziar Dabiri
Universitat Politecnica de Valencia-Ricardo Novella, Josep Gomez-Soriano, Ibrahim Barbery, Jose Pastor
  • 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 pre-chamber 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 pre-chamber; therefore, it becomes a promising solution for passenger car applications as packaging and installation are simple and straightforward. Moreover, combining this concept with EGR dilution is an interesting alternative for both improving the engine efficiency maintaining low pollutant emissions as this approach is perfectly compatible with the three-way catalyst for NOX control. However, previous researches focused on developing the technology rather than understanding the governing physical phenomena. Consequently, the knowledge about the characteristics…
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Effect of Hydrous Ethanol Combined with EGR on Performance of GDI Engine

Tongji University-Yifei Duan, Xiuyong Shi, Yang Kang, Yansu Liao, Lishuang Duan
  • Technical Paper
  • 2020-01-0348
To be published on 2020-04-14 by SAE International in United States
In recent years, PM emission from GDI engines has been gradually paid attention to, while the hydrous ethanol has a high oxygen content and a fast burning rate, which can effectively improve the combustion environment. In addition, EGR can effectively reduce engine NOx emissions, and combining EGR technology with GDI engines is becoming a new research direction. In this paper, the effects of hydrous ethanol gasoline on the combustion and emission characteristics of direct injection engines are analyzed through direct injection engine bench test. The results show that the increase of the proportion of hydrous ethanol accelerates the combustion rate, shortens the combustion duration, and peaks the cylinder pressure and heat release rate. At the same time, the combustion efficiency is improved. The hydrous ethanol gasoline can effectively improve the gaseous and PM emissions of the direct injection engine. The concentration of CO, HC and the amount of PM is significantly reduced, and the particle size of the particles is transferred from the accumulation state to the nuclear state. Furthermore, a one-dimensional simulation model was…
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Experimental Study on EGR control strategy of Turbocharged Diesel Engine in transient conditions

CATARC-Le Liu
  • Technical Paper
  • 2020-01-0905
To be published on 2020-04-14 by SAE International in United States
For the deterioration of exhaust emissions in turbocharged diesel engine under transient conditions, a high pressure common rail turbocharged and Intercooled heavy duty diesel engine was used to study the influence of EGR closed-loop control method on the emission performance under typical transient conditions with constant speed and torque increasing in 5s. The results show: Using the air input, intake oxygen concentration, exhaust oxygen concentration as the feedback control parameter,the EGR overshoot characteristic still exists after PID setting, and the extinction smoke emission is worse than that of the original machine; The NOx emission can not be effectively reduced when the air input is used as feedback parameter; When the intake oxygen concentration is used as feedback parameter, smoke emission will increase sharply; When exhaust oxygen concentration is used as feedback parameter, the smoke deterioration is less, the peak smoke is 15.8%. It has a better compromise relationship with NOx and fuel consumption, and can be used as closed-loop control parameter for diesel engine transient performance optimization.