Exergic Comparison of SI Engines Performance for Gasoline, Methane and Hydrogen Fuels

Exergy analysis is a method for evaluating the contribution of each process on transmission of initial availability of the system and determining the positions of useful energy losses. In this research a comparison of the performance of a SI engine for gasoline, methane and hydrogen in the exergic point of view has been done respectively. Initially,-the performance of the engine by a multi-zones model based on flame propagation with uniform fluid properties in each zone is simulated. by defining exergy terms and using related exergy equilibrium equations for open and close systems a necessary conceptual basis for exergy analysis is made. The results show that the combustion process produces the most proportion of the system irreversibility. Furthermore, for stoichiometric condition the proportion of exergy transmission in the form of work is almost the samefor the mentioned fuels. In addition gasoline has the most proportion of irreversibilityin exergy transmission and hydrogen has the lowest one. Examination of exergy analysis results at different operating conditions reveals that the increase of engine speed will increase exergy transmission in the form of work and decrease it in the form of heat. By the way, an increase in equivalence ratio, will increase cylinder mixture exergy proportion and decrease irreversibility proportion.