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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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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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