发动机泄漏辅助制动数值模拟

为了研究发动机泄漏辅助制动系统的工作过程, 应用计算流体力学软件Fluent建立了发动机泄漏辅助制动系统的数值模拟计算模型, 利用压力曲线对模型进行了验证, 计算了发动机泄漏制动时的缸内压力和流场分布情况。发现: 发动机泄漏辅助制动系统工作时, 排气门预开间隙大, 则缸内所能达到的压力峰值小, 得到的制动功率小。
在压缩过程开始阶段与膨胀过程中, 出现了气体由排气道倒流入气缸中的现象, 且转速低, 排气门开度大时, 倒流现象出现得早。分析结果表明: 适当选择排气门预开间隙, 可以提高发动机泄漏辅助制动系统的制动功率。

Numerical simulation of engine bleeding brake

In order to investigate the working process of engine bleeding brake, a numerical simulation model was built by computational fluid dynamics software Fluent. Its prescision was tested by using pressure curves. The pressure and flowfield of cylinder under bleeding brake were calculated. It is pointed that when exhaust valve lash is larger, the maximum pressure of cylinder and brake power are smaller in the working process of engine bleeding brake.
At the beginning of compress process and the expand process, gas flows into cylinder from exhaust pipe. When engine speed is higher and exhaust valve lash is larger, the starting of flow backwards is earlier. The result indicates that the brake power of engine bleeding brake will increase if the choice of exhaust valve lash is reasonable.