Study on Improvement of Natural Gas Fueled Spark Ignition Engines -Effect of EGR Utilization-

An experimental study was conducted to investigate the effect of EGR on combustion and exhaust emissions characteristics of a spark-ignited, super-charged, stoichiometric gas engine in order to achieve high BMEP equivalent to that of diesel engines. A four-stroke-cycle single-cylinder test engine was used. EGR was completely mixed with intake air before being introduced into the compressor. The results indicate that dry EGR utilizing drained exhaust gas improved the maximum mean effective pressure, as well as specific fuel consumption over the whole load due to improved knock characteristics of the unburnt mixture, increased specific heat ratio (κ), and reduced heat loss. Further experiments were conducted to identify the effect of humidity in the mixture on engine performance. The lean burn method was compared with the EGR method.