电控共轨柴油机燃用甲醇-柴油双燃料的燃烧循环变动
Combustion cyclical variation of electronically controlled common rail diesel fueled with methanol-diesel dual-fuel

摘 要：为了研究双燃料发动机燃烧的循环变动，在1台由电控共轨柴油机改装的甲醇？膊裼退？燃料发动机上进行4种工况的试验，发动机转速为1 400 r/min，负荷率为40%（51.6 kW），最佳引燃柴油喷油正时工况下改变掺烧比；转速为1 400 r/min，掺烧比为21.2%，最佳引燃柴油喷油正时工况下改变负荷率；转矩为220 N？m，掺烧比为39.6%，最佳引燃柴油喷油正时工况下改变发动机转速；转速为1 400 r/min，负荷率为25%（32.84 kW），掺烧比为37.2%的工况下改变喷油正时。研究了参数变化对双燃料发动机峰值压力pmax、峰值压力升高率(dp/dφ)max、峰值压力循环变动系数COVpmax和平均指示压力循环变动系数COVIMEP等参数的影响。研究结果表明：随着掺烧比增大，峰值压力有所减小，峰值压力升高率变大，在大掺烧比下，燃烧稳定性差，循环变动较大；随着负荷率增加，峰值压力增大，峰值压力升高率先增加后减小；随着转速升高，峰值压力变大，峰值压力升高率减小；负荷率增大或转速升高时，燃烧循环变动减小；随着引燃柴油喷油正时提前，峰值压力和峰值压力升高率均增加，小负荷、较大掺烧比工况下适当提前引燃柴油喷油正时可提高燃烧稳定性，但提前太多会引起爆震。
In order to investigate the combustion cyclical variation of dual-fuel engine, tests were conducted on a methanol-diesel dual-fuel engine modified by an electronically controlled common rail diesel engine. The tests were carried out under four operation conditions. The first was conducted by changing co-combustion ratio under engine speed of 1 400 r/min, load ratio of 40% (51.6 kW) and the optimum timing of pilot-diesel injection. The second was conducted by changing load ratio under engine speed of 1 400 r/min, co-combustion ratio of 21.2% and the optimum timing of pilot-diesel injection. The third was conducted by changing engine speed under the torque of 220 N？m, co-combustion ratio of 39.6% and the optimum timing of pilot-diesel injection. The fourth was conducted by changing pilot-diesel injection timing under engine speed of 1 400 r/min, load ratio of 25% (32.84 kW) and co-combustion ratio of 37.26%. Effects of parameter variations on the peak pressure (pmax), the peak pressure-rise rate ((dp/dφ)max), the coefficient of cyclical variation of peak pressure (COVpmax) and the coefficient of cyclical variation of mean indicated pressure (COVIMEP) of the dual-fuel engine were studied. The results show that with the increase of co-combustion ratio, the peak pressure reduces a little and the rising-rate of peak pressure becomes larger. Combustion stability is poor and there is a large cyclical variation under large co-combustion ratio. With the increase of load ratio, the peak pressure increases, and its rising rate increases first and then decreases. As engine speed increases, the peak pressure becomes bigger with low rising-rate. When the load ratio or the speed increases, the combustion cyclical variation becomes smaller. As the injection timing is advanced, the peak pressure and its rising-rate increase. Properly advancing the injection timing under small load and big co-combustion ratio can improve the stability of combustion, while excessively advancing the injection timing can bring knockings