The effects of compression ratio and EGR on the performance and emission characteristics of diesel-biogas dual fuel engine

Abstract

In this study, an experimental investigation on diesel-biogas dual fuel (DF) engine is presented based on energy and exergy analyses. The effects of change in compression ratio (CR), exhaust gas recirculation (EGR) and EGR temperature on the performance and emission characteristics of DF engine have been studied. In the first stage, engine was studied with increasing CRs of 16.5, 17.5, 18.5 and 19.5 in stepwise manner. It was found that the higher CRs were not only advantageous to the engine performance from first and second-law point of view but also to the exhaust emissions. In the second stage, DF engine was studied at the highest CR (19.5) and the effects of EGR were analysed. The engine was studied with EGR percentages of 5%, 10% and 15%, which caused slight improvements in engine efficiency at low load and simultaneous decrease in oxides of nitrogen (NOx) emissions. However, high EGR percentages at high loads showed slight decrease in engine efficiency. In the third stage, hot EGR was employed and the results obtained were compared with the cold EGR case. The results showed that the highest efficiencies both at low and high loads were obtained with hot EGR cases and at the same time exhaust emissions could also be kept in check.