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Technical Paper

Modeling Alternative Prechamber Fuels in Jet Assisted Ignition of Gasoline and LPG

2009-04-20
2009-01-0721
Gas assisted jet ignition is a prechamber combustion initiation system for conventional spark ignition engines. With the system, a chemically active turbulent jet is used to initiate combustion in lean fuel mixtures enabling reliable combustion over a much broader range of air-fuel ratios. The extended range is due to the distributed ignition source provided by the jet, which can overcome the problems of poorly mixed main chamber charges and slower burning fuels. In addition, the ability to reliably ignite lean mixtures improves the thermal efficiency and enables ultra low emission levels. Experiments together with flame propagation modeling completed using STAR-CD with CHEMKIN Kinetics were done in order to examine the effects of numerous prechamber fuels on the ignition of the main fuel, which consisted of either liquefied petroleum gas (LPG) or gasoline.
Journal Article

4 L Light Duty LPG Engine Evaluated for Heavy Duty Application

2010-05-05
2010-01-1463
Many applications of liquefied petroleum gas (LPG) to commercial vehicles have used their corresponding diesel engine counterparts for their basic architecture. Here a review is made of the application to commercial vehicle operation of a robust 4 L, light-duty, 6-cylinder in-line engine produced by Ford Australia on a unique long-term production line. Since 2000 it has had a dedicated LPG pick-up truck and cab-chassis variant. A sequence of research programs has focused on optimizing this engine for low carbon dioxide (CO₂) emissions. Best results (from steady state engine maps) suggest reductions in CO₂ emissions of over 30% are possible in New European Drive Cycle (NEDC) light-duty tests compared with the base gasoline engine counterpart. This has been achieved through increasing compression ratio to 12, running lean burn (to λ = 1.6) and careful study (through CFD and bench tests) of the injected LPG-air mixing system.
Technical Paper

HAJI Operation in a Hydrogen-Only Mode for Emission Control at Cold Start

1995-02-01
950412
The HAJI (Hydrogen Assisted Jet Ignition) system for S.I. engines utilises direct injection of small amounts of hydrogen to enhance the combustion of a variety of automotive fuels. Although not the primary purpose of HAJI, the hardware, once in place, also lends itself to the possibility of hydrogen-only running during a cold start. Cold-start simulations have been performed using a single cylinder engine. Results are presented, comparing hydrogen-only tests with standard HAJI operation and normal spark-ignition operation. HAJI and spark ignition tests were carried out with gasoline as the main-chamber fuel. Emission levels and combustion stability characteristics were recorded as the engine warmed up. The differences between the various fueling/ignition scenarios are presented and the implications for possible automotive applications are discussed in light of current and proposed emissions legislation.
Technical Paper

Development of a 430cc Constant Power Engine for FSAE Competition

2006-04-03
2006-01-0745
This paper describes the design and development of an engine with constant power for SAE's student Formula race-car competition, allowing the avoidance of gear shifting for much of the Autocross event. To achieve constant power for over 50% of the speed range, turbocharging was adopted with a boost pressure ratio of 2.8 at mid-range speeds and applied to an engine capacity of 430 cc. This engine was specifically designed and configured for the purpose, being a twin cylinder in-line arrangement with double overhead camshafts. Most of the engine components were specially cast or machined from billets. The capacity was selected to minimise frictional losses and thus increase delivered power along with dry sump lubrication and a three speed gear box. The engine manifolds and plenums were designed using a CAE application and proved to be well suited to the task resulting in excellent agreement between predicted and actual performance.
Technical Paper

Why Liquid Phase LPG Port Injection has Superior Power and Efficiency to Gas Phase Port Injection

2007-08-05
2007-01-3552
This paper reports comparative results for liquid phase versus gaseous phase port injection in a single cylinder engine. It follows previous research in a multi-cylinder engine where liquid phase was found to have advantages over gas phase at most operating conditions. Significant variations in cylinder to cylinder mixture distribution were found for both phases and leading to uncertainty in the findings. The uncertainty was avoided in this paper as in the engine used, a high speed Waukesha ASTM CFR, identical manifold conditions could be assured and MBT spark found for each fuel supply system over a wide range of mixtures. These were extended to lean burn conditions where gaseous fuelling in the multi-cylinder engine had been reported to be at least an equal performer to liquid phase. The experimental data confirm the power and efficiency advantages of liquid phase injection over gas phase injection and carburetion in multi-cylinder engine tests.
Technical Paper

Numerical Study of a Turbocharged, Jet Ignited, Cryogenic, Port Injected, Hydrogen Engine

2009-04-20
2009-01-1425
Favorable and unfavorable properties of hydrogen as a combustion engine fuel have been accommodated in a design of a fuel efficient and clean engine providing similar to gasoline maximum torque and power. The advanced H2ICE being developed is a turbocharged engine fitted with cryogenic port hydrogen fuel injection and the hydrogen assisted jet ignition (HAJI). The combustion chamber is designed to produce a high compression ratio and therefore high thermal efficiency. A waste gated turbocharger provides pressure boosting for an increased power density running ultra lean for SULEV operation without after treatment. Thanks to the combustion properties of hydrogen further enhanced by the HAJI system, the engine load is mainly controlled throttle-less decreasing the fuel-to-air equivalence ratio from ultra lean ϕ=0.43 to ultra-ultra lean ϕ=0.18. The computational model developed for addressing the major design issues and the predicted engine performance and efficiency maps are included.
Technical Paper

The Lean Limit and Emissions at Near-Idle for a Gasoline HAJI System with Alternative Pre-Chamber Fuels

2007-09-16
2007-24-0120
Hydrogen assisted jet ignition (HAJI) is a pre-chamber ignition system for otherwise standard gasoline fueled spark ignition engines that involves the use of a chemically active turbulent jet to initiate combustion in lean fuel mixtures. HAJI burns the lean main charge rapidly and with almost no combustion variability, which allows for low hydrocarbon emissions and almost zero NOx, due to lower peak temperatures. This paper focuses on the effects of different pre-chamber fuels on combustion stability, lean limit and emissions in a single cylinder, HAJI equipped, CFR engine under a worst case, light load condition. Results indicate that the choice of pre-chamber fuel affects the main chamber lean limit but that emissions are not largely affected before this lean limit is reached. The lean limit was extended furthest, to λ = 2.5 with hydrogen, followed by λ = 2.35 with LPG, λ = 2.25 with CNG and λ = 2.15 with carbon monoxide.
Technical Paper

Direct Injection Compressed Natural Gas Combustion and Visualisation

2000-06-19
2000-01-1838
This paper details the development of a compressed natural gas (CNG) engine with ultra lean burn low emissions potential. Hydrogen assisted jet ignition (HAJI) is used to achieve reliable combustion and low NOx emissions, whilst direct injection is used to improve thermal efficiency and decrease hydrocarbon (HC) emissions. It is found that port inducted propane, port inducted CNG and directly injected CNG all produce negligible levels of CO and NOx when operating at air/fuel ratios higher than λ = 1.8. Furthermore, direct injection of CNG produced approximately 100 ppm C6 less HC emissions than port induction of CNG, and port induction of CNG decreased the HC emissions by around a factor of a third to a half in comparison with port induction of propane.
Technical Paper

The Systematic Evaluation of Twelve LP Gas Fuels for Emissions and Fuel Consumption

2000-06-19
2000-01-1867
The effects on bi-fuel car exhaust emissions, fuel consumption and acceleration performance of a range of LPG fuels has been determined. The LPGs tested included those representing natural gas condensate and oil refineries' products to include a spectrum of C3:C4 and paraffiinic:olefinic mixtures. The overall conclusions are that exhaust emissions from the gaseous fuels for the three-way catalyst equipped cars tested were lower than for gasoline. For all the LPGs, CO2 equivalent emissions are reduced by 7% to 10% or more compared with gasoline. The cars' acceleration performance indicates that there was no sacrifice in acceleration times to various speeds, with any gaseous fuel in these OEM developed cars.
Technical Paper

Gas Assisted Jet Ignition of Ultra-Lean LPG in a Spark Ignition Engine

2009-04-20
2009-01-0506
Gas assisted jet ignition is an advanced prechamber ignition process that allows ignition of ultra lean mixtures in an otherwise standard spark ignition engine. The results presented in this paper indicate that in a gas assisted jet ignition system fuelled with LPG in both the main chamber and prechamber, the lean limit can be extended to between λ = 2-2.35, depending on the load and speed. Although the fuel combinations that employ H2 as the prechamber fuel can extend the lean limit furthest (λ = 2.5-2.6), the extension enabled by the LPG-LPG prechamber-main chamber combination provides lower NOx emission levels at similar λ. In addition, when LPG is employed in place of gasoline as the main chamber fuel, hydrocarbon emissions are significantly reduced, however with a slight penalty in indicated mean effective pressure due to the gaseous state of the LPG.
Technical Paper

Joint Efficiency and NOx Optimization Using a PSO Algorithm

2006-04-03
2006-01-1109
The challenge of tough fuel consumption reduction targets and near zero NOx emission standards can be met by optimization of the full range of engine design variables. Here these are explored through an engine simulation model and the application of an optimizing algorithm that can work in discontinuous data space. The combustion model has main features that include flame propagation, the effects of turbulence, chamber shape interaction and NOx formation. Two engine configurations are used to illustrate the application of the model and optimizer. Both allow the adoption of extra lean burn possible with LPG as fuel and EGR through an external route or cam phasing. In the first the compression ratio and cam profiles are fixed, in the second study they are also optimized.
Technical Paper

Optimization of All SI Engine Combustion Control and Related Events for Efficiency

2006-04-03
2006-01-0045
There are two parts to achieving the optimization reported here. The development of an engine simulation model and an optimization algorithm. The engine performance is evaluated using a quasi-dimensional engine combustion model with sub models to incorporate friction, heat losses and abnormal combustion, that is knocking. After extensive search and development a new Particle Swarm Optimizer (PSO), has been developed. Optimization includes, for the first time, the search of discontinuous design variables. The input variables considered for this investigation are manifold air pressure, air-fuel ratio, spark timing, compression ratio, valve timing events including valve open duration, maximum valve lift and engine speed. This enables the identification of the maximum thermal efficiency at a given power output at any engine operating speed.
Technical Paper

Optimum Control of an S.I. Engine with a λ=5 Capability

1995-02-01
950689
HAJI (Hydrogen Assisted Jet Ignition) is an advanced combustion initiation system for otherwise standard S.I engines. It utilises the fluid mechanics of a turbulent, chemically active jet, combined with the reliability of spark igniting rich hydrogen mixtures. The result is an extremely robust ignition system, capable of developing power from an engine charged with air-fuel mixtures as lean as λ = 5. Experiments have been performed using a single cylinder engine operating on gasoline in the speed range of 600-1800 r/min. Data are presented in the form of maps which describe fuel efficiency, combustion stability and emissions with respect to load, speed, air-fuel ratio and throttle. The results are incorporated into a model of a known engine and vehicle and this is used to estimate performance over the Federal drive-cycle.
Technical Paper

Performance of a Port Fuel Injected, Spark Ignition Engine Optimised for Hydrogen Fuel

2012-04-16
2012-01-0654
This paper presents a study of the performance of a 6-cylinder, spark-ignited, port-fuel-injected, production engine modified for hydrogen fueling. The engine modifications include turbo-charging, multiple fuel injectors per port and charge-dilution control techniques. Pumping losses are reduced through ultra-lean burn and throttle-less operation alongside high charge dilution ratio control achieved by twin independent variable cam timing without external EGR. Lean-burn combustion, engine-out emissions and brake thermal efficiency results are examined in detail. In particular, low NO emissions and brake thermal efficiencies near 38% are observed experimentally at the same operating conditions. The former is explained in terms of the usual thermal NOx pathway. Usage of throttle position, injection timings and cam timings for avoiding preignition and knock over the entire engine map are also discussed.
Technical Paper

Lean Mixture Ignition Systems for CNG in Diesel Applications

2004-01-16
2004-28-0017
A high compression ratio, single cylinder, open chamber diesel engine was converted to operate on homogenously charged compressed natural gas (CNG) with the aim of minimising pollutant emissions such as oxides of nitrogen, particulate matter and carbon dioxide. Three ignition systems were tested including spark ignition (SI), diesel pilot ignition (DPI) and hydrogen assisted jet ignition (HAJI). Irrespective of ignition system used, the efficiency of the engine operating on CNG was significantly reduced at part load compared to diesel. This was predominantly due to a greater amount of unburnt hydrocarbons, higher cycle-by-cycle variability, slow and partial burns and increased heat transfer to the walls. DPI and HAJI systems were able to extend the lean limit to lambda 2.7 and 3.3 respectively, however this did not result in efficiency gains.
Technical Paper

The Lean Burn Direct-Injection Jet-Ignition Flexi Gas Fuel LPG/CNG Engine

2009-11-02
2009-01-2790
This paper explores through engine simulations the use of LPG and CNG gas fuels in a 1.5 liter Spark Ignition (SI) four cylinder gasoline engine with double over head camshafts, four valves per cylinder equipped with a novel mixture preparation and ignition system comprising centrally located Direct Injection (DI) injector and Jet Ignition (JI) nozzles. With DI technology, the fuel may be introduced within the cylinder after completion of the valve events. DI of fuel reduces the embedded air displacement effects of gaseous fuels and lowers the charge temperature. DI also allows lean stratified bulk combustion with enhanced rate of combustion and reduced heat transfer to the cylinder walls creating a bulk lean stratified mixture.
Technical Paper

Lean Burn Performance of a Natural Gas Fuelled, Port Injected, Spark Ignition Engine

2012-04-16
2012-01-0822
This paper presents a study of the performance of a lean burn, natural gas-fuelled, naturally aspirated, spark ignition engine for an E class vehicle. Engine performance and exhaust emissions (NO, CO, and UHC) data are first discussed. An energy balance of the engine operating at different loads and air-fuel ratios is then presented, and used to explain why engine efficiency varies with air-fuel ratio. Finally, the hot start drive cycle CO2e (CO2 equivalent) emissions are estimated for a vehicle with this engine. This shows a potential for significant reduction in vehicle greenhouse gas emissions compared to an equivalent gasoline-fuelled vehicle.
Technical Paper

Exploring the Charge Composition of SI Engine Lean Limits

2009-04-20
2009-01-0929
In this paper the experimental performance of the lean limits is examined for two different types of engines the first a dedicated LPG high compression ratio 2-valve per cylinder engine (Ford of Australia MY 2001 AU Falcon) and the second a gasoline moderate compression 4-valve per cylinder variant of the same engine (Ford of Australia MY 2006 BF Falcon). The in-cylinder composition at the lean limit over a range of steady state operating conditions is estimated using a quasi-dimensional model. This makes it possible to take into account the effects of both residual fraction and fresh charge diluents (EGR and excess air) that allow the exploration of a modeled lean limit performance [1, 2]. The results are compared to the predictions from a model for combustion variability applied to the quasi-dimensional model operating in optimization mode.
Journal Article

Mixture Preparation Effects on Gaseous Fuel Combustion in SI Engines

2009-04-20
2009-01-0323
This paper presents a comparison of the influence of different mixture preparation strategies on gaseous fuel combustion in SI engines. Three mixture preparation strategies are presented for a dedicated LPG fuelled engine, showing varying results - gaseous phase port injection (PFI-G), liquid-phase port injection (PFI-L) and gaseous-phase throttle-body injection (TBI-G). Previous work by the authors has shown considerable differences in emissions and thermal efficiency between different fuelling strategies. This paper extends this work to the area of combustion characteristics and lean limit operation and closer analyses the differences between these systems. A dedicated LPG in-line six cylinder engine with compression ratio increased to 11.7:1 (up from the standard 9.65:1) was tested over a range of speed/torque conditions representing most of the steady-state parts of the Euro drive-cycle for light duty-vehicles. The air-fuel ratio was varied from lambda 1.0 to the lean limit.
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