Abstract:

A mathematical model of the engine supplementary brake was set up through discussing the working processes of engine supplementary brake. According to reference parameters of the supplementary brake (including the exhaust valve lash, engine speed, exhaust back pressure, etc.), the engine supplementary brake was analyzed with univariate and multivariate conditions by the method of numerical simulations and experimental tests. The results show that the cylinder pressure increases with speed and the peak pressure phase is more near the top dead center(TDC) under the higher speed conditions. The brake torque increases with the engine speed increase. The de-compressure brake has a maximum brake torque while the engine brake has the minimum brake torque. When the engine speed is constant, the bleeding brake and the de-compressure brake have a corresponding optimal exhaust valve lash, respectively. The higher the speed is, the bigger the exhaust valve lash is. The higher the exhaust back pressure is, the more the brake torque is.

Key words: engine, supplementary brake, brake torque, exhaust back pressure

摘要：

通过对发动机辅助制动工作过程进行理论分析,建立了发动机辅助制动计算模型,根据辅助制动相关参数（包括排气门开度、发动机转速和排气背压等）,对发动机辅助制动进行了单因素和多因素条件下的仿真研究及试验验证。结果表明：随着发动机转速的升高,缸内压力增大,且压力峰值更靠近上止点;制动扭矩随转速的升高而增大,减压制动时制动扭矩最大,发动机制动时制动扭矩最小;发动机转速一定时,泄漏制动和减压制动分别有一对应的最佳排气门开度值,并且转速越高,排气门开度最佳值越大,排气背压越高,制动扭矩越大。

关键词: 发动机, 辅助制动, 制动扭矩, 排气背压