直喷式柴油机瞬态工况燃烧噪声机理

Combustion Noise Mechanism Under Transient Conditions of DI Diesel Engine

通过测量瞬态工况与稳态工况燃烧噪声的各种影响参数,研究气体动力载荷及燃烧压力高频振荡对燃烧噪声的影响机理.瞬态工况的壁面温度、喷油压力、针阀升程最大值和针阀开启持续时间均高于同负荷、同转速的稳态工况,导致瞬态工况滞燃期、燃烧始点和喷油量与稳态工况相比产生差异,引起燃烧压力、压力升高率及高频压力振荡频率和幅值发生变化.结果表明,瞬态工况与同负荷、同转速的稳态工况相比,着火延迟期缩短,但每循环喷油量增大,燃烧噪声增大.

By measuring parameters under transient conditions and steady conditions, the stimulation of combustion noise mechanism by dynamic load and high-frequency pressure oscillation under transient conditions of DI diesel engine was studied in detail. Because the temperature of combustion chamber wall, fuel injection pressure, maximum of needle lift and unseal standing time of needle lift under transient conditions were higher than those under steady conditions, the ignition delay, start point of combustion, and fuel injection quantity under transient conditions were different from those under steady conditions. It also caused the difference in combustion pressure, pressure accelerating rate, oscillation frequency and amplitude of high-frequency oscillation of combustion pressure between transient and steady conditions. The results show that the ignition delay is shortened, while fuel injection quantity and combustion noise are increased under transient conditions compared with the steady conditions in the same load and rotation speed.