소형 리니어 엔진에서 LPG와 수소 연료에 따른 운전 특성 비교

A prototype of small-sized, spark ignition free piston engine combined with a linear alternator was designed and built, which is used to produce electric power for portable usage. Engine performance including indicated mean effective pressure and piston velocity were compared for hydrogen and liquefied petroleum gas. The total lower heating value of two fuels per unit time was maintained equal to compare the combustion and operation characteristics of each fuel. Effects of alternator load to the engine performance were observed. The combustion characteristics such as heat release rate, cycle-tocycle variation and the power output of two fuels were studied. Hydrogen resulted in stable operation due to its faster flame speed and wider flammability range, while LPG showed higher cycle-to-cycle variation and misfire in some cycles. Under the same alternator load, hydrogen resulted in better power output than LPG, because hydrogen had more energy released from the fuel than LPG, which is modified from the accumulated heat release analysis. As the load increased, operation with LPG showed higher possibility of engine operation failure due to misfire, which is mainly caused by the inappropriate combustion condition accompanied by the piston motion. Meanwhile, hydrogen showed a large operation range with various load conditions.