Experimental Study On Spark Ignited Aviation Piston Engine Fueled With Kerosene And Alternative Fuel

To solve the problem that the aviation gasoline is highly volatile and to satisfy “Single Fuel on the Battlefield” goal in military,this paper proposed a solution that replace the aviation gasoline by gasoline alternative fuel and aviation kerosene in spark ignited aviation piston engines.There are many types of gasoline surrogate fuels.In this paper,n-butanol was selected as the research object because n-butanol has a wide range of preparation methods and it has many application researches findings in piston engines.Meanwhile,n-butanol has a high heat value and its octane number is closer to aviation gasoline.N-butanol is miscible with gasoline in any proportion,as a result it can be used in part in spark ignited engines or entirely replace gasoline.Aviation kerosene has problem in cold start and low knock limit when applied in spark ignited aviation piston engines because of its poor volatility and low octane number.By blending short-chain alcohols such as ethanol,n-propanol and n-butanol in aviation kerosene to simultaneously increase the volatility and octane number of aviation kerosene,it is possible to obtain a large load in spark-ignition piston engines.The experiment was carried out on a Rotax 914horizontally-opposed four-cylinder four-stroke engine.Firstly,the combustion and emission characteristics were studied about gasoline,n-butanol and their blend fuel under different loads and speeds.The volume fraction of gasoline and n-butanol in the blend fuel is 50%.The study found that n-butanol had a shorter flame development duration and rapid combustion duration than gasoline;n-butanol can achieve higher thermal efficiency.Under most load and speed conditions,the CO,NOx and HC emissions of n-butanol have significant advantages over gasoline.Comparing the characteristics of gasoline and n-butanol under various working conditions,it can be found that n-butanol can directly replace gasoline on an aviation piston engine without any engine modification,and it had better combustion and emission characteristics than gasoline.Secondly,in order to apply aviation kerosene to spark-ignition aviation piston engines,ethanol,n-propanol and n-butanol were blended with kerosene in volume ratios of 30%,50% and 70%.The combustion and emission characteristics were studied under different load.It has been found that the fewer the carbon numbers of the blended alcohol and the higher the alcohol blending ratio,the better the improvement the ultimate load of kerosene.Under their ultimate loads,with the decrease of the carbon numbers of alcohol and the increase of the alcohol blending ratio,the knock resistance of the kerosene was significantly enhanced,the overall combustion phase was advanced,and the pressure peak and the heat release rate peak increased.As the engine load increases,the combustion phase of kerosene was advanced,the flame development duration and rapid combustion duration were shortened,the in-cylinder temperature,in-cylinder pressure,the thermal efficiency,the NOx and HC emissions increased,and the fuel consumption and CO emissions were reduced.Finally,in order to investigate the influence of combustion controlling parameters(spark timing and excess air coefficient)on combustion and emission characteristics of kerosene blended with different proportions of ethanol.It was found that with the advance of the spark timing,the engine power first increased and then decreased,the combustion phase advanced,the in-cylinder maximum pressure,maximum temperature,maximum pressure rise rate and the NOx emission increased,and cycle variation of indicated mean effective pressure first decreased and then increased.As the excess air coefficient increased,the combustion phase postponed,the flame development duration and the rapid combustion duration were prolonged,and the in-cylinder maximum pressure,maximum temperature,maximum pressure rise rate,the CO emission and the HC emission are reduced,and the cycle variation is enhanced.