减少天然气发动机后燃的改进优化

李晓东，游凯，许晓颖，马俊方

潍柴动力股份有限公司，山东 潍坊   261061

摘要：为解决某天然气发动机后燃问题，进行台架试验，分析点火角域电压、空燃比、缸压及主从两侧电子控制单元（electronic control unit，ECU）实际燃气质量流量，确定后燃的主要原因为从侧ECU采用速度密度法计算混合气质量迟滞，使瞬态工况实际空燃比偏小，燃气体积分数偏大。采用调整从侧充气效率、提高最小节气门限值减缓瞬态过程、将从侧ECU燃气质量流量由速度密度法改为节气门计算方法3种措施进行改进并进行验证试验，结果表明：3种方法均能解决后燃问题；调整充气效率只适用于发动机卸去全部负荷，减缓瞬态过程导致转矩卸载时间增大，将从侧ECU燃气质量流量由速度密度法改为节气门计算方法效果最佳。

关键词：后燃；速度密度法；节气门计算；空燃比

Improvement and optimization for eliminating post-combustion of a natural gas engine

LI Xiaodong, YOU Kai, XU Xiaoying, MA Junfang

Weichai Power Co., Ltd., Weifang 261061, China

Abstract: In order to solve the post-combustion problem of a natural engine, the bench test is carried out to analyze the ignition angle domain voltage, air-fuel ratio, cylinder pressure and actual gas mass flow rate of the main side and slave side electronic control unit (ECU), it is determined that the reason for post-combustion is that the slave side ECU calculate the delay by using the speed density method, which makes the transient air-fuel ratio being too small and the gas volume fraction being too large under transient conditions. Three measures are taken to improve and verify: adjusting the slave side charging efficiency, increasing the minimum throttle threshold to slow down the transient process, changing the gas mass flow rate of the slave side ECU from the speed density method to the throttle calculation method. The results show that the three methods can solve the post-combustion, adjusting the charging efficiency is only suitable for unloading all loads, slowing down the transient process leads to an increase in the torque unloading time, and changing the gas flow rate of the slave side ECU from the speed density method to the throttle calculation method is the best.

Keywords: post-combustion; speed density method; throttle calculation; air-fuel ratio