Use of a thermodynamic cycle simulation to determine the difference between a propane-fuelled engine and an iso-octane-fuelled engine



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Texas A&M University


A thermodynamic cycle simulation of the four-stroke spark-ignition engine was used to determine the effects of variations in engine design and operating parameters on engine performance and emission characteristics. The overall objective was to use the engine cycle simulation to determine the difference between a propane-fuelled and an iso-octane-fuelled engine for the same operating conditions and engine specifications. A comprehensive parametric investigation was conducted to examine the effects of variations in load, speed, combustion duration, spark timing, equivalence ratio, exhaust gas recycle, and compression ratio for a 3.3 liter, Chrysler Minivan, V 6 engine operating on propane. Parameters were selected for the analysis. Variations in the brake specific fuel consumption, brake specific NOx emissions, and mean exhaust temperature were determined for both the propane-fuelled and the iso-octane-fuelled engines. Brake specific fuel consumption and mean exhaust temperature values for the propane-fuelled engine were consistently lower (3 to 5 %) than the corresponding values for the iso-octane-fuelled engine. Fuel structure did not have a significant effect on brake specific nitric oxide emissions. Predictions made from the simulation were compared with some of the available experimental results. Predicted brake torque and brake power showed acceptable quantitative agreement (less than 10 % variation) in the low engine speed range (1,000 to 3,000 rpm) and similar trends with the available experimental data.