Object-oriented modeling and simulation of a natural gas-fuelled spark ignition engine with Modelica

A quasi dimensional model for a four-stroke spark ignition natural gas engine was developed using Modelica. Three different kinds of heat transfer models were evaluated and compared in Modelica in order to determine suitable heat transfer correlation for the natural gas engine simulation. Three important parameters of the natural gas engine, including compression ratio, spark timing and combustion duration, were investigated to optimize the design and work of the natural gas engine. The model was validated against measured data from a natural gas engine which was conversed from a gasoline engine by retrofitting fuel intake system. The results show: correlation proposed by Woshni led to a better matching with experimental data than those by Hohenberg and Eichelberg. Good agreement was observed between the simulated engine performance and measured data. Modelica, featured with “re-usable” and “object-oriented”, would be efficient for the theoretical design and the optimum work of natural gas engine.