Keywords: variable compression ratio, LPG engines, exergy analysis, second-law analysis, stroke length, compression ratio, spark ignition engines, SI engines, simulation, thermodynamics, fuel availability, LPG combustion, liquefied petroleum gas
Second-law analysis of an LPG-powered 4-stroke SI engine under variable stroke length and compression ratio
A second-law analysis of an LPG-powered, 4-stroke, single-cylinder, water-cooled, variable stroke length spark-ignition engine was carried out to assess the engine's energy efficiency. The engine was simulated at each stroke length/compression ratio combination. The second law of thermodynamics with the aid of the first law represents the results of entropy generation, reversible work output and exergy destruction of combustion processes of propane fuel. This work shows that, from the second-law analysis point of view, lowering the bore-to-stroke ratio increases the fuel availability and minimises the destruction of thermodynamic availability in LPG combustion. It also minimises the availability transfer due to heat and improves the availability transfer due to work.