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Effect of Prechamber on Exhaust Emission and Efficiency of a SI Small Engine Fuelled with Gaseous and Liquid Fuels

Istituto Motori CNR-Paolo Sementa
  • Technical Paper
  • 2020-37-0035
To be published on 2020-06-23 by SAE International in United States
The aim of the study was the optimization of the gasoline combustion process by means of a passive/active prechamber. The improvement of the engine efficiency in lean-burn operation condition is an opportunity to give further use of Spark Ignition (SI) engine. A commercial small Spark Ignition (SI) engine was modified with a proper designed prechamber fuelled with methane. Engine performance in terms of indicated Mean effective pressure, heat release rate and fuel Consumption were evaluated as well as gaseous emissions. Particulate Mass, Number and Size Distributions were measured. Several engine operative conditions were investigated at full load varying the engine speeds for stoichiometric and lean conditions and with different prechamber types. The results were compared with those obtained with the engine equipped with the standard spark plug. The results indicated that both performance and emissions were strongly influenced by the prechamber.
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A Numerical Investigation on VVA Influence on the Combustion Phase for Premixed Combustion Engine Under Partial Load Conditions

DMMM - Politecnico di Bari-Sergio Camporeale
DMMM - Politecnico di Bari, GNFM INDAM-Francesco Fornarelli
  • Technical Paper
  • 2020-37-0005
To be published on 2020-06-23 by SAE International in United States
Nowadays, the vehicle hybridization and the use of more clean fuel in heavy-duty applications brings to a new beginning in the use of spark ignition engine. In standard intake system, the pre-mixed fuel air mixture is controlled by the injection of fuel after the throttle valve. Then, intake system, consisting in intake duct, valve number and geometry and cylinder head shape influence the characteristics of the intake flow within the cylinder up to the ignition of the combustion by the spark plug. The technology advancement in fluid-power and electrical actuation gives the opportunity to decouple the intake and exhaust valve actuation with respect to the standard cam shaft distribution. The Variable Valve Actuation (VVA) concepts is not new, but its application is now affordable and flexible enough to be applied in partial load conditions. Here, by means of three-dimensional numerical simulations the intake and combustion process is studied with a finite volume approach to solve the mass, momentum and energy equations together with an Extended Coherent Flamelet Model (ECFM). Two different approaches in driving the…
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Assessing the Engine-Out Pollutant Emissions of a S.I. Engine for Hybrid Powertrain Applications

Université de Bourgogne Franche-Comté-Jérémy Pelluet, Alan Keromnes, Luis Le Moyne
Université de Lyon - IFSTTAR AME ECO7-Alice Guille des buttes, Bruno Jeanneret
  • Technical Paper
  • 2020-37-0016
To be published on 2020-06-23 by SAE International in United States
Car manufacturers are introducing more and more hybrid powertrains in order to reach CO2 emissions targets and answer increasingly stringent pollutant emission regulations such as unburned hydrocarbons (HC), nitrogen oxides (NOx), carbon monoxide (CO) and particulate matter. The addition of an electric engine to a thermal engine introduces an additional degree of freedom in the energy management of the powertrain since two energy sources are available. Thus, the energy management system must also account for regulated pollutant emissions when devising an optimal energy management strategy to avoid a pollutant emission increase due to CO2 only driven optimisation. It is therefore necessary to model the influence of thermal engine operating conditions such as load and speed on these emissions to evaluate their concentration in the exhaust gases. This study presents an empiric modelling approach based on an extensive parametric study using a spark-ignition port-injection four-cylinder engine. Such a model intend to be used in the context of hybrid powertrain optimization. In order to reduce the computing costs required by ECU (Engine Control Unit), the number of…
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Influence of Port Water Injection on the Combustion Characteristics and Exhaust Emissions in a Spark-Ignition Direct-Injection Engine

Shanghai Jiao Tong University-Yadong Fan, Tianbao Wu, Xuesong Li, Min Xu, David Hung
  • Technical Paper
  • 2020-01-0294
To be published on 2020-04-14 by SAE International in United States
It is well known that engine downsizing is still the main energy-saving technology for spark-ignition direct-injection (SIDI) engine. However, with the continuous increase of the boosting ratio, the gasoline engine is often accompanied by the occurrence of knocking, which has the drawback to run the engine at retarded combustion phasing. Besides, in order to protect the turbine blades from being sintered by high exhaust temperature, the strategies of fuel enrichment are often taken to reduce the combustion temperature, which ultimately leads to a high level of particulate number emission. Therefore, to address the issues discussed above, the port water injection (PWI) techniques on a 1.2-L turbocharged, three-cylinder, SIDI engine were investigated.Measurements indicate that the optimization of spark timing has a significant impact on its performance. The two factors of the water substance itself and spark advance caused by the knock mitigation are trade-offs, which eventually affect the combustion performance. Under knock limited spark advance (KLSA) condition, we find that the application of port water injection could effectively advance the combustion phasing and reduce exhaust gas…
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Downsized-Boosted Gasoline Engine with Exhaust Compound and Dilute Advanced Combustion

General Motors LLC-Jeremie Dernotte, Paul M. Najt, Russell P. Durrett
  • Technical Paper
  • 2020-01-0795
To be published on 2020-04-14 by SAE International in United States
This article presents experimental results obtained with a disruptive engine platform, designed to maximize the engine efficiency through a synergetic implementation of downsizing, high compression-ratio, and importantly exhaust-heat energy recovery in conjunction with advanced lean/dilute low-temperature type combustion. The engine architecture is a supercharged high-power output, 1.1-liter engine with two-firing cylinders and a high compression ratio of 13.5: 1. The integrated exhaust heat recovery system is an additional, larger displacement, non-fueled cylinder into which the exhaust gas from the two firing cylinders is alternately transferred to be further expanded.The main goal of this work is to implement in this engine, advanced lean/dilute low-temperature combustion for low-NOx and high efficiency operation, and to address the transition between the different operating modes. Those include well-mixed charge compression-ignition at low-load, and a mixed-mode combustion at higher loads, before transitioning to boosted homogenous and stochiometric spark-ignited combustion. Here, the mixed-mode combustion strategy is composed of a deflagration of a stratified mixture created by a late direct injection, then triggering a controlled autoignition of the surrounding gas, improving the robustness…
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Effects of Direct Injection Timing and Air Dilution on the Combustion and Emissions Characteristics of Stratified Flame Ignited (SFI) Hybrid Combustion in a 4-Stroke PFI/DI Gasoline Engine

Brunel University London-Hua Zhao
CATARC-Jian-Jun Yang, Shuang-Xi Liu, Haiyang Gao
  • Technical Paper
  • 2020-01-1139
To be published on 2020-04-14 by SAE International in United States
Controlled Auto-Ignition (CAI) combustion can effectively improve the thermal efficiency of conventional spark ignition (SI) gasoline engines, due to shortened combustion processes caused by multi-point auto-ignition. However, its commercial application is limited by the difficulties in controlling ignition timing and violent heat release process at high loads. Stratified flame ignited (SFI) hybrid combustion, a concept in which rich mixture around spark plug is consumed by flame propagation after spark ignition and the unburned lean mixture closing to cylinder wall auto-ignites in the increasing in-cylinder temperature during flame propagation, was proposed to overcome these challenges. The combustion and emissions characteristics in the SFI hybrid combustion were experimentally investigated in a single-cylinder 4-stroke gasoline engine operating at medium to high loads when direct injection timing was retarded from -100 °CA to -40 °CA after top dead center (ATDC) and excess air coefficient was increased from 1.0 to 1.2 at the direct injection ratio of 30%. The experimental results show that direct injection timing and excess air coefficient control the ignition timing and combustion duration. Ignition timing advances…
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A path towards high efficiency SI combustion in a CFR engine: Cooling the intake to sub-zero temperatures

King Abdullah University of Science & Technology-Sufyan M. Jan, Abdulrahman Mohammed, Ali Elkhazraji, Jean-Baptiste Masurier
University of California-Robert Dibble
  • Technical Paper
  • 2020-01-0550
To be published on 2020-04-14 by SAE International in United States
Textbook engine thermodynamics predicts that SI (Spark Ignition) engine efficiency η is a function of both the compression ratio CR of the engine and the specific heat ratio γ of the working fluid. In practice the compression ratio of the SI engine is often limited due to “knock”. When this knock limit is reached, increase in heat transfer losses result in reduction in efficiency. One way to lower the end-gas temperature is to cool the intake gas before inducting it into the combustion chamber. With colder intake gases, higher CR can be deployed, resulting in higher efficiencies. In this regard, we investigated the indicated efficiency of the standard Waukesha CFR engine. The engine is operated in the SI engine mode. The engine was operated with three different mediums using the same fuel Methane (Gas). First is Air + Methane at room temperature, second was O2 + Argon + Methane gas mixture at room temperature, and lastly O2 + Argon +Methane at sub-zero conditions. We replace the Air by an Oxygen-Argon mixture to increase the specific…
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Combustion Characterization of Neat n-Butanol in an SI Engine

Shanghai Jiao Tong University-Tie Li
University of Windsor-Navjot Singh Sandhu, Xiao Yu, Simon Leblanc, Ming Zheng, David Ting
  • Technical Paper
  • 2020-01-0334
To be published on 2020-04-14 by SAE International in United States
Increasingly stringent emission standards have promoted the interest in alternate fuel sources. Because of the comparable energy density to the existing fossil fuels and renewable production, alcohol fuels may be a suitable replacement, or an additive to the gasoline/diesel fuels to meet the future emission standards with minimal modification to current engine geometry. In this research, the combustion characteristics of neat n-butanol are analyzed under spark ignition operation using a single cylinder SI engine. The fuel is injected into the intake manifold using a port-fuel injector. Two modes of charge dilution were used in this investigation to test the limits of stable engine operation, namely lean burn using excess fresh air and exhaust gas recirculation (EGR). The in-cylinder pressure measurement and subsequently, heat release analysis are used to investigate the combustion characteristics of the fuel under low load SI engine operation. Additionally, a comprehensive emission analysis is performed to study the combustion by-products. Furthermore, the combustion and emission characteristics of n-butanol fuel are compared to those of the gasoline fuel. Preliminary results highlight the effect…
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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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Determination of Octane Index and K in a 2.0L, 4-Cylinder Turbocharged SI Engine Using the Primary Reference Fuel (PRF) Method

Michigan Technological University-Siddharth Gopujkar, Jeremy Worm, Joel Duncan, William Hansley
  • Technical Paper
  • 2020-01-0552
To be published on 2020-04-14 by SAE International in United States
Research Octane Number (RON) and Motor Octane Number (MON) have traditionally been used to describe fuel anti-knock quality. The test conditions for MON are harsher than those for RON, causing the RON for a particular fuel to be higher than the MON. Previous researchers have proposed the anti-knock performance of a fuel can be described at other operating conditions using the Octane Index (OI), defined as OI=RON-K (RON-MON), where ‘K’ is a weighing factor between RON and MON, and is a function of engine operating condition. The K-factor indicates that at a particular operating condition, knock tolerance is better described by RON as K approaches a value of 0, and MON as K approaches a value of 1. Previous studies claim that K-factor is dependent only on the engine combustion system and the speed-load point, and that it is independent of fuel chemistry. In most of these studies, K was determined experimentally using linear regression. In this particular study, K was determined using the PRF method for two test fuels; EPA certification tier 2 and…