Performance Characteristics of a Spark Ignited Variable Compression Ratio Engine at Erratic Loads

Abstract

Never ending demand for efficient and less polluting engines have always inspired newer technologies. Extensive study has been done on variable compression ratio, a promising in-cylinder technology, in the recent past. The present work is an experimental investigation to examine the variation of different parameters such as brake thermal efficiency, exhaust gas temperature and emissions with respect to change in compression ratio in a single-cylinder carbureted SI engine at different loads with two different fuels. Experiments were conducted at three different compression ratios (CR = 7.6:1, 7.8:1 and 8:1). The fuels used in this study are pure gasoline. The results showed that brake thermal efficiency increases with CR at all loads. Further, the experimental results showed the scope of improving the part-load efficiency of SI engine by adopting the concept of variable compression ratio (VCR) technology, especially when fuels with better anti-knock characteristics are used. The uncertainty analysis of the experiments based on the specifications of the equipment used is also tabulated.