Abstract
This study investigates the effects of various operating conditions in spark ignition engines via an exergy analysis. A thermodynamic cycle model including compression, combustion and expansion processes was used for investigation. Induction and exhaust processes were computed with a simple approximation method. The principles of the second law were applied to the cycle model to perform the exergy analysis. Exergetic variables, i.e., the exergy transfers with heat and work, irreversibilities, thermomechanical exergy, fuel chemical exergy and total exergy were calculated in the exergy analysis. Variation of the exergetic parameters and the distribution of them into the fuel exergy were determined for various operating conditions, i.e., engine speed and load. The first and second law efficiencies and specific fuel consumption were also computed to reveal the optimum operating conditions. The results show that the exergy transfer with heat decreases and the exergy transfer with exhaust gases increases with increasing engine speed. Engine speed of 3 000 rpm gives the maximum exergy transfer as work, the minimum irreversibility and the best efficiency and fuel consumption. Exergy transfers with heat, work and exhaust and irreversibilities increase with increasing engine load. Additionally, the first and second law efficiencies increase and fuel consumption decreases with increasing engine load, so a high engine load gives the best efficiency and fuel consumption.
Highlights
Complex physical and chemical events occur during Internal Combustion Engine (ICE) operation
The results show that the differences that cannot be ignored between energy and exergy analysis require the exergy analysis to improve the design and/or operation of the system by identifying the losses and irreversibilities in a realistic way
The effects of some operating parameters such as engine speed and load in Spark Ignition engines are investigated via exergy analysis by using a thermodynamic cycle model
Summary
Complex physical and chemical events occur during Internal Combustion Engine (ICE) operation. Engine cycle models are very suitable tools to investigate the effects of such parameters and to evaluate the engine performance [1, 2]. The use of the second law of thermodynamics has intensified in the studies devoted to ICEs in recent times. The effects of engine operating parameters such as engine speed and load are investigated via exergy analysis. To meet this goal, a thermodynamic cycle model originally developed by Ferguson [26] is adapted and used. The details of the cycle model and exergy analysis are given
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