Predicting Optimum Spark Timing of a Biofuel Four Stroke Spark Ignition Combustion Engine

Abstract

There has been an increasing interest in the enhancement the efficiency and functionality of engines, particularly petrol ones, in recent years. In this paper, four stroke spark ignition internal combustion engine cycle has been simulated based on first law of thermodynamics. The second law analysis has also been conducted to analyse the effects of ignition timings, combustion duration as well as engine speed upon engine efficiency and performance. The availability (exergy) balance equations of the engine cylinder has been considered in detail. Moreover, total availability fractions and process irreversibilities have been evaluated. By considering the results for brake and indicated mean effective pressure, it is shown that they behave in an opposite way in terms of increasing engine speeds. After perusing the figures, a conclusion is made, revealing that exergetic efficiency rises by increasing engine speed, whereas the opposite is true for brake thermal efficiency. Furthermore, The optimum point in which total efficiency ( both thermal and exergetic) shows the highest possible level happens at the speed of 2500 rpm