高压直喷点燃式发动机燃用航空煤油掺混乙醇对燃烧性能优化的试验研究

Experimental Study on the Optimization of Combustion Performance of a High-Pressure Direct Injection SI Engine Fueled with Aviation Kerosene Blended with Ethanol

为提高航空煤油在点燃式发动机中的燃烧热效率,改善发动机爆震及拓宽发动机负荷范围,以3号航空煤油(RP3)为基础燃料,以乙醇为辅助燃料,基于一台单缸水冷、压缩比可调、四冲程点燃式发动机结合高压共轨缸内直喷技术,开展了不同负荷、不同乙醇和航空煤油掺混比、不同喷射压力、不同喷射时刻下航空煤油燃烧特性的试验研究。结果表明,在压缩比为7的条件下,由于爆震的限制,发动机负荷仅能达到原机的72.0%。而乙醇具有较强的抑制爆震的能力,随着乙醇在航空煤油中掺混比例的增加,发动机负荷区间不断拓展,当乙醇的掺混比为10%时发动机可实现全负荷工作。继续增大乙醇的掺混比例,可进一步提升功率并降低油耗。为探究喷油时刻对动力性、经济性的影响,试验测定了5种喷油时刻对燃烧性能的影响。当喷油时刻为压缩上止点前300°时,发动机具有较好的动力性;当喷油时刻为上止点前360°时,发动机具有较好的经济性。

In order to improve the thermal efficiency,detonation and operating range of spark ignition engines fueled with aviation kerosene,a single-cylinder,water-cooled,4 stroke,variable compression ratio engine with high pressure common rail and in-cylinder direct injection was used to test the combustion characteristics of using kerosene/ethanol blend fuel under different load,ethanol/kerosene blending ratio,injection pressure and injection timing conditions.Results show that under the condition of injection pressure of 7,the engine load can only reach 72% of the original engine load due to the limitation of detonation.Ethanol has a higher ability to suppress detonation.With the increase of ethanol content in the blend fuel,the engine operating range expands continuously.When the ethanol/kerosene blending ratio is 10%,the engine can be operated at full load.On this basis,continuing increase in ethanol content can further increase engine power,and reduce fuel consumption.In order to explore the influence of fuel injection timing on engine power and fuel economy,the effect of five injection timings on combustion performance was tested.As observed,the engine has better power with an injection timing of 300°before top dead center,and higher economy with an injection timing of 360°before top dead center.