不同海拔条件下喷油参数对柴油机性能的影响

通过内燃机高原环境模拟试验台,研究了不同海拔条件下高压共轨柴油机在最大转矩转速点(1500 r/min)全负荷(2300 N·m)和部分负荷(500 N·m)工况下喷油提前角、共轨压力及循环喷油量(全负荷)对柴油机燃烧特性与性能的影响规律.结果表明:全负荷工况下,随着喷油提前角增加,柴油机滞燃期增加,最高燃烧压力和最大压力升高率增大,增大趋势随海拔增加而降低,柴油机转矩在0 km和3 km海拔先增加后减小,在5 km海拔时逐步增加.随着共轨压力增加,柴油机燃烧相位提前,最高燃烧压力、最大压力升高率和转矩均增加,排温降低;部分负荷工况下,有效燃油消耗率随共轨压力增加而降低.随循环喷油量增加,转矩、排温和缸内压力均逐渐增大,最大压力升高率在3 km海拔范围内逐渐增加、在5 km海拔时逐渐减小.海拔每升高1 km,柴油机在全负荷工况下,最佳循环喷油量平均降低5.81%,最佳喷油提前角和共轨压力在全负荷和部分负荷工况下平均分别增加了1.2°,CA、0.8°,CA和4 MPa、3 MPa.

Effects of Injection Parameters on the Performance of a Diesel Engine at Different Altitudes

The influence of injection advance angle,injection pressure and cyclic fuel injection quantity on combustion and performance at different altitude conditions were experimentally studied on a plateau environment simulating test bed at full load(2300 N·m)and part load(500 N·m)of 1500 r/min.The results show that,with the fuel injection advance angle increasing under full load,the ignition delay period,maximum combustion pressure and pressure rise rate increase,but the rate decreases with the increase of the altitude.Meanwhile,with the injection advance angle increasing,the engine torque takes a change of first increase and then decrease at the altitude of 0 km and 3 km and monotonically increases at 5 km,while the exhaust temperature decreases steadily.As the injection pressure increases,the combustion phase is advanced,leading to increase in the maximum combustion pressure,the pressure rise rate and the torque output.At part load operations,the brake specific fuel consumption decreases steadily with the increase of injection pressure.Furthermore,with the increase of the cyclic fuel injection quantity,the torque,the exhaust temperature and the cylinder pressure increase,but the maximum pressure rise rate increases from 0 km to 3 km and decreases at 5 km.It is found that each increment of 1 km in altitude gives a reduction of the optimal cyclic fuel injection quantity by 5.81%at full load,the optimal injection advance angle increases by 1.2°,CA and 0.8°,CA and the optimal rail pressure increases by 4 MPa and 3 MPa,respectively at full load and part load conditions.