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Brear, Michael J.
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An Integrated Model of Energy Transport in a Reciprocating, Lean Burn, Spark Ignition Engine

SAE International Journal of Engines

University of Melbourne-Peter A. Dennis, Michael J. Brear, Harry C. Watson, Pedro J. Orbaiz, Payman Abbasi Atibeh
  • Journal Article
  • 2015-01-1659
Published 2015-04-14 by SAE International in United States
This paper presents a combined experimental and numerical method for analysing energy flows within a spark ignition engine. Engine dynamometer data is combined with physical models of in-cylinder convection and the engine's thermal impedances, allowing closure of the First Law of Thermodynamics over the entire engine system. In contrast to almost all previous works, the coolant and metal temperatures are not assumed constant, but rather are outputs from this approach. This method is therefore expected to be most useful for lean burn engines, whose temperatures should depart most from normal experience.As an example of this method, the effects of normalised air-fuel ratio (λ), compression ratio and combustion chamber geometry are examined using a hydrogen-fueled engine operating from λ = 1.5 to λ = 6. This shows large variations in the in-cylinder wall temperatures and heat transfer with respect to λ. In keeping with our other works, thermal efficiency also appears to be limited by in-cylinder heat transfer on the rich side of optimum λ, and diminishing combustion quality on the lean side.By comparing different compression…
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The Effect of Charge Cooling on the RON of Ethanol/Gasoline Blends

SAE International Journal of Fuels and Lubricants

Princeton University-Frederick L. Dryer
The University of Melbourne-Tien Mun Foong, Kai J. Morganti, Michael J. Brear, Gabriel da Silva, Yi Yang
  • Journal Article
  • 2013-01-0886
Published 2013-04-08 by SAE International in United States
This paper examines the effect of charge cooling on the Research Octane Number (RON) of ethanol/gasoline blends. While gasoline is fully vaporized prior to entry into the engine in a standard RON test, significant charge cooling is observed for blends with high ethanol content, with the presence of a near-saturated and potentially two-phase air-fuel mixture during induction. Thus, the relative significance of the charge cooling and the autoignition chemistry cannot be determined from the standard RON test.In order to better delineate the effects of charge cooling and autoignition chemistry, a so-called ‘modified RON’ test is therefore devised in which the temperature of the air-fuel mixture entering the engine is fixed and representative of that observed for primary reference fuels (PRFs). Thermodynamic modeling of this modified RON test suggests the mixture is always fully vaporized prior to compression, and that the modified RON test maintains much more constant temperatures during compression, regardless of the enthalpy of vaporization. The modified RON test thus appears to be a more practical means of examining the significance of autoignition chemistry…
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A Comparative Study of a Spark Ignition Engine Running on Hydrogen, Synthesis Gas and Natural Gas

SAE International Journal of Engines

University of Melbourne-Pedro Orbaiz, Michael J. Brear, Payman Abbasi, Peter A. Dennis
  • Journal Article
  • 2013-01-0229
Published 2013-04-08 by SAE International in United States
This paper presents an experimental, numerical and theoretical study of the performance of the same spark ignition engine running on four different gaseous fuels: hydrogen, two synthesis gases and natural gas. Measurements of the brake thermal efficiency, the combustion variability, the engine out emissions and the indicated, pumping and friction mean effective pressures are first presented, with particular interest placed on the lean burn performance. Combustion analysis is then undertaken, with the crank angle resolved in-cylinder turbulence and the flame propagation plotted on the so-called ‘Bradley diagram’ for turbulent premixed combustion. The loci of the combustion events on the Bradley diagram are then used to explain the observed, relative performance of the engine running on these four fuels. In particular, turbulent flame stretch is argued to play a significant role in determining variations in engine performance on these four fuels, and also appears to explain the ability of hydrogen-rich fuels to perform well over a relatively wide range of lean engine operating conditions.
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Lean Burn Performance of a Natural Gas Fuelled, Port Injected, Spark Ignition Engine

University of Melbourne-Payman Abbasi Atibeh, Peter A. Dennis, Pedro J. Orbaiz, Michael J. Brear, Harry C. Watson
Published 2012-04-16 by SAE International in United States
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.
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Performance of a Port Fuel Injected, Spark Ignition Engine Optimised for Hydrogen Fuel

Ford Motor Company of Australia-Glen Voice
University of Melbourne-Peter A. Dennis, Robert J. Dingli, Payman Abbasi Atibeh, Harry C. Watson, Michael J. Brear
Published 2012-04-16 by SAE International in United States
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. Finally, first law analyses of energy losses for varying cam timings, varying manifold pressure and varying torque are presented and used to suggest reasons for values of λ for optimal BTE in each case.
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The Always Lean Burn Spark Ignition (ALSI) Engine – Its Performance and Emissions

University of Melbourne-Harry C. Watson, Pouria. Mehrani, Michael J. Brear
Published 2009-04-20 by SAE International in United States
This paper is based on extensive experimental research with lean burn, high compression ratio engines using LPG, CNG and gasoline fuels. It also builds on recent experience with highly boosted spark ignition gasoline and LPG engines and single cylinder engine research used for model calibration. The final experimental foundation is an evaluation of jet assisted ignition that generally allows a lean mixture shift of more than one unit in lambda with consequential benefits of improved thermal efficiency and close to zero NOx.The capability of an ultra lean burn spark ignition engine is described. The concept is operation at air-fuel ratios similar to the diesel engine but with essentially homogenous charge, although some stratification may be desirable. To achieve high thermal efficiency this engine has optimized compression ratio but with variable valve timing which enables reduction in the effective compression ratio when desirable. High specific power output is achieved by supercharging the engine and no NOx reduction is proposed with only an oxidation catalyst needed to meet Euro 6 standards.The 2.6L four-cylinder engine is optimized using…
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Low Temperature Starting on a Pure Ethanol Fuelled Direct Injection Engine

Orbital Corporation, Australia-Tyron Dean Utley, Simon Christopher Brewster, Andrew Tilmouth
University of Melbourne, Australia-Seong Ho Jin, Michael J. Brear
Published 2008-10-07 by SAE International in United States
In the current study cold start tests have been performed on a multi-cylinder, spray guided direct injection, spark ignition engine. The direct injection system was a centrally mounted dual fluid type injecting fuel and air simultaneously. The engine has been started on ethanol at soaked temperatures from +25°C through to -10°C. Development of engine hardware, software and calibration was undertaken to optimise cold start times, whilst quality metrics were used to evaluate the performance of the starts. Consideration has been taken to restrict hardware options to production viable components. Conclusions are drawn regarding the start performance of an E100 spray guide DI engine at low temperatures.
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