Thermodynamic Investigations On A Four Cylinder Four Stroke Cycle S.I. Engine Under Constant Speed And Variable Equivalence Ratio Operation In Hydrogen Direct Injection And GDI Modes

This paper presents the computational results of variable equivalence ratio on the performance and emissions characteristics of a 4-cylinder 4-stroke cycle spark ignition engine under constant speed operation The engine under consideration is modeled with hydrogen direct injection and gasoline direct injection modes. The term equivalence ratio has been used to represent the load or air fuel ratio for ease in the graphical comparison of the results of two different fuels hydrogen and gasoline in the direct injection modes.

The results were simulated in the professional internal combustion engine simulation software AVL BOOST. The software design is based on user friendly codes developed by using the thermodynamic and gas dynamic conservation laws of mass, energy and momentum. The differential equations involved with coding these laws are further solved by using the numerical finite volume method. In addition to this the software has provision for selecting various models for combustion, frictional power, heat transfer and other energy based components of the first law of thermodynamics. First the engine was modeled for gasoline direct injection concept with the help of the elements available in the software using its graphical user interface. The results for the performance and emissions characteristics were computed under constant speed and variable fuel-air equivalence ratio. Next the engine was modeled for the hydrogen direct injection version. The simulations were repeated for generating results for the performance and emission characteristics of the engine.

It was observed that the thermodynamic performance of the hydrogen direct injection engine was better than the thermodynamic performance of the gasoline direct injection engine. Further the emissions based computing shows that the hydrogen based engine does not produce any CO emissions. Also the hydrogen fueled engine produces least soot emissions from the hydrocarbons of the lubricating oil only. However the NOx emissions are higher in case of the hydrogen engine as compared to the gasoline engine.