甲醇预混合气F-T柴油引燃模式下发动机燃烧特性研究

Study on Combustion Characteristics of Methanol/F-T Fuel Dual Fuel Engine with Pilot Injection

为了提高甲醇在能量转化效率方面的优势,在一台CY25TQ型柴油机上,利用F-T柴油和煤基甲醇研究了甲醇占能比、F-T柴油喷油时刻对甲醇预混合气F-T柴油引燃燃烧方式下发动机燃烧特性的影响。试验结果表明:甲醇占能比增加,此燃烧方式滞燃期、持续期波动较大。在平均有效压力为0.45MPa下,缸内最大压力、瞬时放热率峰值、最大压力升率明显降低,最大降幅分别为26.40%、59.25%和58.00%。高负荷时,不同甲醇占能比下F-T柴油喷射时刻调整,能促进压升率进一步降低。与原柴油机扩散燃烧方式相比,虽然采用引燃喷射的双燃料发动机在中低负荷时的有效热效率有所降低,但是随着负荷增加,高负荷下的热效率比原柴油机高,最大提高了17.14%。

In order to use the advantage of F-T fuel and methanol in improving the energy conversion efficiency of methanol, the effect of methanol/diesel energy ratio and F-T fuel injection timing on combustion characteristics was investigated on a CY25TQ diesel engine. The mixture of methanol and air was induced into cylinder from the intake port, and ignited by pilot F-T fuel. Experimental results show that the ignition delay and combustion duration would fluctuate greatly with the increase of methanol/diesel energy ratio. When the brake mean effective pressure is 0.45 MPa, the maximum cylinder pressure, the peak value of instantaneous heat release rate and the maximum pressure rise rate are significantly lower with a maximum drop of 26.40%, 59.25% and 58.00% respectively. At high load operation, the pilot fuel injection timing can promote the further reduction of pressure rise rate in different methanol/diesel energy ratio. Although the effective thermal efficiency of dual fuel engine with pilot injection than that of the original diesel engine with diffusion combustion mode at low and middle loads, however, with the increase in load, the thermal efficiency of the duel fuel engine is higher than that of the original diesel engine at high load, which leads to the increase in the maximum thermal efficiency of the engine by 17.14%.