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Effects of Prechamber on Efficiency Improvement and Emissions Reduction of a SI Engine Fuelled with Gasoline and CNG

Istituto Motori CNR-Paolo Sementa, Francesco Catapano, SILVANA Di Iorio, Bianca Maria Vaglieco
  • Technical Paper
  • 2019-24-0236
To be published on 2019-10-07 by SAE International in United States
The permanent aim of the automotive industry is the further improvement of the engine efficiency and the simultaneous pollutant emissions reduction. The aim of the study was the optimization of the gasoline and compressed natural gas (CNG) combustion by means of a passive prechamber. This analysis allowed the improvement of the engine efficiency in lean-burn operation condition too. The investigation was carried out in an real small Spark Ignition (SI) engine fueled with Gasoline and CNG and equipped with a proper designed passive prechamber. In particular, Gasoline and CNG were used to analyze the effects of the prechamber on engine performance and associated pollutant emissions. Indicated Mean Effective Pressure, Heat Release Rate and Mass Burned Fraction were used to evaluate the effects on engine performance. Gaseous emissions were measured as well. Particulate Mass, Number and Size Distributions were analyzed. Emissions samples were taken from the exhaust flow, just downstream of the valves. Opacity was measured downstream the Three-Way Catalyst. Three different engine speeds were investigated, namely 2000, 3000 and 4000 rpm. Stoichiometric and lean condition…

Ultra-Lean Pre-Chamber Gasoline Engine for Future Hybrid Powertrains

FEV Europe GmbH-Knut Habermann
IFP Energies Nouvelles, Institut Carnot IFPEN TE-David Serrano, Jean-Marc Zaccardi
  • Technical Paper
  • 2019-24-0104
To be published on 2019-09-09 by SAE International in United States
Lean burn gasoline spark-ignition engines can support the reduction of CO2 emissions for future hybrid passenger cars. Very high efficiencies and very low NOx raw emissions can be achieved, if relative air/fuel ratios (lambda) of 2 and above can be reached. The biggest challenge here is to assure a reliable ignition process and to enhance the fuel oxidation in order to achieve a short burn duration and a good stability for the combustion. This article aims at introducing an innovative combustion system fully optimized for ultra-lean operation and very high efficiency. Thereto, a new cylinder head concept has been realized with high peak firing pressure capability and with a low surface-to-volume ratio at high compression ratios. 1D and 3D simulations have been performed to optimize the compression ratio, charge motion and intake valve lift. Numerical calculations also supported the development of the ignition system. Stable ignition and fast flame propagation were achieved thanks to a centrally located active pre-chamber which allows to control the air/fuel ratio independently of the air/fuel ratio in the main combustion…

Experimental Studies of Gasoline Auxiliary Fuelled Turbulent Jet Igniter at Different Speeds in Single Cylinder Engine

Brunel University-Khalifa Isa Bureshaid, Hua Zhao
Mahle Powertrain Ltd-Michael Bunce
  • Technical Paper
  • 2019-24-0105
To be published on 2019-09-09 by SAE International in United States
Turbulent Jet Ignition (TJI) is a pre-chamber ignition system for an otherwise standard gasoline spark ignition engine. TJI works by injecting chemical active turbulent jets to initiate combustion in a premixed fuel/air mixture. The main advantage of TJI is its ability to ignite and burn completely very lean fuel/air mixtures in the main chamber charge. This occurs with a very fast burn rate due to the widely distributed ignition sites that consume the main charge rapidly. Rapid combustion of lean mixtures leads to lower exhaust emissions due to more complete combustion at lower combustion temperature. This research investigates the effectiveness of the TJI system on combustion stability, lean limit and emissions in a single cylinder spark engine fuelled with gasoline at different speeds. The combustion and heat release process was analysed and exhaust emissions measured. Results show that the effect of TJI system on the lean-burn limit and exhaust emissions varied with engine speeds. The lean limit was extended by increasing engine speed, to λ = 1.71 with 1200 rpm, followed by λ = 1.69…

A Study of Lean Burn Pre-chamber Concept in a Heavy Duty Engine

King Abdullah Univ of Science & Tech-Ponnya Hlaing, Manuel Echeverri Marquez, Vijai Shankar Bhavani Shankar, Moez Ben Houidi, Bengt Johansson
Saudi Aramco-Emre Cenker
  • Technical Paper
  • 2019-24-0107
To be published on 2019-09-09 by SAE International in United States
Due to stringent emission standards, the demand for higher efficiency engines has been unprecedentedly high in recent years. Among several existing combustion modes, pre-chamber initiated combustion emerges to be a potential candidate for high-efficiency engines. Research on the pre-chamber concept exhibit higher indicated efficiency through lean limit extension while maintaining the combustion stability. In this study, different pre-chamber geometries were tested in a single-cylinder heavy-duty engine at different loads. The geometries were prepared with three different pre-chamber volumes and with three varying nozzle area to pre-chamber volume ratios. The pre-chambers were fueled with methane while two sets of experiments were conducted, the first with ethanol as main chamber fuel and the second with methane. The `avalanche activated combustion' or L.A.G. process was explored which relies on enriched pre-chamber combustion to generate radicals which, upon being discharged into the main combustion chamber, will trigger ignition sites distributed in the combustion chamber, thus achieving volumetric heat release. Parametric studies were performed with different pre-chamber fueling rate. In addition, passive pre-chamber concept, where no additional fuel was injected…

A Fundamental Study on Combustion Characteristics in a Pre-Chamber Type Lean Burn Natural Gas Engine

Waseda University-Masashi Tanamura, Shintaro Nakai, Mahoko Nakatsuka, Shota Taki, Kohei Ozawa, Beini Zhou, Ratnak Sok, Yasuhiro Daisho, Jin Kusaka
  • Technical Paper
  • 2019-24-0123
To be published on 2019-09-09 by SAE International in United States
Pre-chamber spark ignition technology can stabilize combustion and improve thermal efficiency of lean burn natural gas engines. During compression stroke, a homogeneous lean mixture is introduced into pre-chamber, which separates spark plug electrodes from turbulent flow field. After the pre-chamber mixture is ignited, the burnt jet gas is discharged through multi-hole nozzles which promotes combustion of the lean mixture in the main chamber due to turbulence caused by high speed jet and multi-points ignition. However, details mechanism in the process has not been elucidated. To design the pre-chamber geometry and to achieve stable combustion under the lean condition for such engines, it is important to understand the fundamental aspects of the combustion process. In this study, a high-speed video camera with a 306 nm band-pass filer and an image intensifier is used to visualize OH* self-luminosity in rapid compression-expansion machine experiment. The results show that the OH* self-luminosity is observed in outer edge of the jet, while the luminosity in the jet temporarily weakens because the turbulent jet is exposed to low temperature surrounding in…

Experimental Studies of the Effect of Ethanol Auxiliary Fuelled Turbulent Jet Ignition in an Optical Engine

SAE International Journal of Engines

Brunel University, UK-Khalifa Bureshaid, Ray Shimura, Hua Zhao
MAHLE Powertrain, LLC, USA-Mike Bunce
  • Journal Article
  • 03-12-04-0026
Published 2019-07-26 by SAE International in United States
Internal combustion (IC) engines are widely used in automotive, marine, agricultural and industrial machineries because of their superior performance, high efficiency, power density, durability and versatility in size and power outputs. In response to the demand for improved engine efficiency and lower CO2 emissions, advanced combustion process control techniques and more renewable fuels should be adopted for IC engines. Lean-burn combustion is one of the technologies with the potential to improve thermal efficiencies due to reduced heat loss and higher ratio of the specific heats. In order to operate the IC engines with very lean air/fuel mixtures, multiple turbulent jet pre-chamber ignition has been researched and developed to extend the lean-burn limit. Turbulent Jet Ignition (TJI) offers very fast burn rates compared to spark plug ignition by producing multiple ignition sites that consume the main charge rapidly. In this research, studies were carried out on the ignition and combustion characteristics of pre-chamber ignition produced by a Mahle TJI unit installed in a single-cylinder engine with optical access. In particular, this article focuses on the spatial…
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High Power-Density, High Efficiency, Mechanically Assisted, Turbocharged Direct-Injection Jet-Ignition Engines for Unmanned Aerial Vehicles

SAE International Journal of Aerospace

Ton Duc Thang University, Vietnam-Alberto Boretti
  • Journal Article
  • 01-12-01-0002
Published 2019-05-02 by SAE International in United States
More than a decade ago, we proposed combined use of direct injection (DI) and jet ignition (JI) to produce high efficiency, high power-density, positive-ignition (PI), lean burn stratified, internal combustion engines (ICEs). Adopting this concept, the latest FIA (Fédération Internationale de l’Automobile) F1 engines, which are electrically assisted, turbocharged, directly injected, jet ignited, gasoline engines and work lean stratified in a highly boosted environment, have delivered peak power fuel conversion efficiencies well above 46%, with specific power densities more than 340 kW/liter. The concept, further evolved, is here presented for unmanned aerial vehicle (UAV) applications. Results of simulations for a new DI JI ICE with rotary valve, being super-turbocharged and having gasoline or methanol as working fuel, show the opportunity to achieve even larger power densities, up to 430 kW/liter, while delivering a near-constant torque and, consequently, a nearly linear power curve over a wide range of speeds.
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Experimental Investigation of a Natural Gas Lean-Burn Spark Ignition Engine with Bowl-in-Piston Combustion Chamber

West Virginia University-Jinlong Liu, Cosmin Dumitrescu
Published 2019-04-02 by SAE International in United States
On- and off-road heavy-duty diesel engines modified to spark-ignition natural gas operation can reduce U.S. dependence on imported oil and enhance national energy security. Engine conversion can be achieved through the addition of a gas injector in the intake manifold and of a spark plug in place of the diesel injector. This paper investigated combustion characteristics and engine performance at several lean-burn operating conditions that changed spark timing, mixture equivalence ratio, and engine speed, using methane as NG surrogate. The results show that the bowl-in-piston geometry separated the combustion process into two distinct events: an inside-the-bowl burning (due to the squish effect) that had a short duration and consumed a high fraction of fuel, and a slower inside-the-squish burning process, most probably due to the large surface/volume ratio (that increased the heat transfer to the boundaries) and to the lower in-cylinder pressure and temperature during the expansion stroke. While the operating conditions affected the overlapping of these two combustion stages, conditions that increased their phasing separation produced a second peak in the rate of heat…
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An Investigation on the Regeneration of Lean NOx Trap Using Ethanol and n-Butanol

University of Windsor-Divyanshu Purohit, Shouvik Dev, Qingyuan Tan, Navjot Singh Sandhu, Linyan Wang, Graham Reader, Ming Zheng
Published 2019-04-02 by SAE International in United States
Reduction of nitrogen oxides (NOx) in lean burn and diesel fueled Compression Ignition (CI) engines is one of the major challenges faced by automotive manufacturers. Lean NOx Trap (LNT) and urea-based Selective Catalytic Reduction (SCR) exhaust after-treatment systems are well established technologies to reduce NOx emissions. However, each of these technologies has associated advantages and disadvantages for use over a wide range of engine operating conditions. In order to meet future ultra-low NOx emission norms, the use of both alternative fuels and advanced after-treatment technology may be required. The use of an alcohol fuel such as n-butanol or ethanol in a CI engine can reduce the engine-out NOx and soot emissions. In CI engines using LNTs for NOx reduction, the fuel such as diesel is utilized as a reductant for LNT regeneration. In the present work, a detailed evaluation of the performance of long breathing LNT (requiring fewer regenerations than conventional LNT) is carried out using ethanol and n-butanol as the reductants and are compared with diesel as the reductant. For this purpose, a long…
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Experimental and Numerical Analysis of Pre-Chamber Combustion Systems for Lean Burn Gas Engines

Ricardo UK Ltd-Evgeniy Shapiro, Nick Tiney
Swiss Federal Institute of Technology-Panagiotis Kyrtatos, Maria Kotzagianni, Michele Bolla, Konstantinos Boulouchos
Published 2019-04-02 by SAE International in United States
The current trend in automobiles is towards electrical vehicles, but for the most part these vehicles still require an internal combustion engine to provide additional range and flexibility. These engines are under stringent emissions regulations, in particular, for the reduction of CO2. Gas engines which run lean burn combustion systems provide a viable route to these emission reductions, however designing these engines to provide sustainable and controlled combustion under lean conditions at λ=2.0 is challenging. To address this challenge, it is possible to use a scavenged Pre-Chamber Ignition (PCI) system which can deliver favorable conditions for ignition close to the spark plug. The lean charge in the main combustion chamber is then ignited by flame jets emanating from the pre-chamber nozzles. Accurate prediction of flame kernel development and propagation is essential for the analysis of PCI systems. A modelling approach is proposed based on the Dynamic Discrete Particle Ignition Kernel model coupled with the G-equation combustion model. The model is validated for an air/methane academic benchmark. The approach is then applied to the investigation of…
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