Effect of calorific value of fuel gas on performance of a stirling engine

Abstract

The effective utilization of low calorific gas produced from solid fuels such as biomass with the gasification technology needs an engine generator with minimum allowable fuel gas requirements. Stirling engines have great advantages for the fuel gas diversity because they are external combustion engines. But there are few experimental reports on the utilization of low calorific gases in Stirling engines. In this research, we conducted two types of unit tests to clarify the effect of the heating value of a gas fuel on the engine performance. One is the non-premix test in which the fuel gas with the rated gas heating value of 13.8-25.6MJ/Nm3 is supplied only into the fuel gas supply port. And the other is the premix test in which the fuel gas with the gas heating value of 6.3-13.8 MJ/Nm3 is supplied both into the fuel gas supply port and the combustion air supply port to expand the required gas heating value range. In the premix test, we demonstrated that we could decrease the lowest gas heating value down to 6.0 MJ/Nm3. As the results, we could expand the gas heating value range and demonstrated that the rated power output can be obtained within the heating value range of 6.0-25.6 MJ/Nm 3 with the elecrical efficiency of about 30%. And we measured the exhaust gas content and observed both NOx and CO emissions being below about 30 ppm (corrected to 14 vol% O:) in the same gas heating value range.