柴油机怠速循环波动特性研究

Study on Cyclic Variation of Diesel Enginein Idle Condition

为探究不同运转参数对怠速燃烧过程的影响规律,在发动机试验台架上进行不同控制参数下的高压共轨柴油机怠速循环变动特性的实验,分析喷油提前角、冷却液温度和喷油压力对柴油机怠速燃烧循环变动的影响。结果表明:喷油定时从上止点前12°向上止点前2°变化时,缸内最大爆发压力的波动率和循环波动率在上止点前6°最低,表现为两边高中间低;冷却液温度由30℃增加至80℃时,缸内最大爆发压力的波动率和循环波动率分别由7.64%和1.61%下降到3.47%和0.67%,有效地降低了怠速循环波动;喷油压力从30 MPa增加到40 MPa,可以促进怠速时缸内燃料的雾化蒸发以及与空气的混合,而喷油压力过高时,燃烧重心向上止点平移,使缸内燃烧的可控性变差,各循环间的差异性增大;稳定怠速过程中,缸内最大爆发压力和平均指示压力之间表现出很强的相关性。

To explore the influence of different operating parameters on the combustion process of idling, the cyclic variation ofdiesel engine has been studied with different control parameters on the engine test bench, and the influences of different injection tim-ing ,coolant temperature and injection pressure on the combustion cycle fluctuations have been analyzed. The results showed that when the injection timing varied from 12 °CA BTDC to 2 °CA BTDC, minimum rate of maximum explosion pressure fluctuation and cycle - to - cycle variation were got at 6 °CA BTDC, which presented a high side but low middle figure. While coolant was varying from 30 ° C to 80 °C, the rate of maximal explosion pressure flucturation and cycle - to - cycle variation decreased from 7. 64% and 1.61% to 3.47% and 0.67% , respectively, and the cycle - to - cycle variation of idling condition could be sufficiently decreased. And the increase of injection pressure from 30 MPa to 40 MPa can promote the progress of fuel atomization, evaporation and mixed. While the pressure is too high, the burn center approach to the TDC, which leads to the result that the combustion got uncontrolled. The maximum explosion pressure in cylinder and the IMEP also show a strong correlation in the stable idle process.