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K Ando or aL/Fjwv 30 aws)2206-2218 2217 believed that the reason of increase of CO at fuel-lean side(greats than A iS)is due to a reduction of combustion speed.Gas 1 does not have HC carnpouenta originally, so emission of HC is low. For Gas 2,large amounts of HC and CO are discharged as unburned species due to poor combustion %aracteristics.High HC emission is caused by the undesirable methane Combustion:Especially outside Of the stable engine oparatluS range.exhaust emissions are so poor that operation state is execrable.As described above,in Rc nal gasification system,it will be necessaryto control the air—fuel ratio c order er to deal with the fluctuations is fuel composition.For control of air-fucl ratio,feodback from exhaust gas components is thought to be appropriate. But for methane-rich Iow-BTU gas such as Gas 2,it is very difficult to control optimum air—fitel ratio by the way of such feedbaclk.Because one cannot proper air excess ratio from value of CO or HC emission.that has stee V-shaped fY the in Figs. 15 and 16 P Profiles such as shown From above results, it was shown that engine performance depends more on the combustion characteristics than heating value of the gaseous fuel,and increasing combustion efficiency is the goal for development of actual engines. Regarding to the fluctuation of fuelas corn gasification sY described above, g position in actual spark ignition engines are not desirable. In order to solve these problems,this research aims at development of the diesel engine fueled with both gasification gas and gas oil.Thereby,we can expect that startability problem will be solved and engine will be adaptable to fluctuation of gas compositions. From now on, it is necessary to grasp characteristics of dual fueled engine by experimental investigation.Moreover,it is also necessary to pursue the gasification conditions that can generate the gaseous fuel with high hydrogen concentration. 4.Conclusions In this research,we obtained following results by testing a small-scale spark ignition engine fueled with a simulated low-BTU gas produced from the one-step high temperature gasification process (hydrogen rich). The engine operating on this low-BTU gas showed similar thermal efficiency as for natural gas,about 23%,although output was lower. It also showed wide air excess ratio range up to A-2 for stable engine operation. NO,and HC emissions were quite low. Compared with stoichiometric mixture, changes in ignition delay and combustion speed were minimum for fuel-rich or fuel-lean operations. We obtained following results by testing a small-scale spark ignition engine fueled with a simulated low-BTU gas produced from the two-steep pyrolysialrd0 mng gasification process (methane rich). The engine operating on this fuel gas showed similar thermal efficiency and output as that forth hydrogen rich low-BTU gas, at suitable air—fuol ratio and Iowa engine speed. Owing to further increase of ignition delay in crank angle base and decrease of air—fuel ratio range, operation in higher rotation range was difficult. Stable air—fuel ratio was very narrow,and ig set to slightly lean side. NO,emission was quite low. HC and CO emission were high outside of stable engine operating range.