Abstract: This paper introduces the compressed natural gas (CNG) gas supply system of a dual-fuel engine and the structural principle of the pilot solenoid valve integrated on the pressure reducer assembly. Pressure sensors are added for monitoring, and INCA software is adopted to investigate the fault of low gas rail pressure after cold start of the CNG gas supply system for a vehicle engine. Monitoring data indicate that the closing of the solenoid valve is the direct cause of low gas rail pressure. By checking the rail pressure before engine start, micro-leakage in the system is confirmed. Analysis based on the pressure-building principle of the pilot solenoid valve shows that the root cause of the fault is system-which prevents rail pressure establishment prior to engine start. After engine start, vehicle load rises, stable pressure build-up fails beneath the solenoid valve, and the valve core closes under the action of gas force. Eliminating the leakage resolves the low gas rail pressure issue during cold start of the vehicle.

Key words: gasoline/CNG dual-fuel engine; gas supply system; pilot solenoid valve; low rail pressure

摘要： 文章介绍一种双燃料发动机压缩天然气（CNG）供气系统，以及集成于减压阀总成上的 先导电磁阀的结构原理。通过增加压力传感器监测，借助 INCA 软件排查某车辆发动机 CNG 供气系统冷机启动后气轨压力低故障。监测数据表明，电磁阀关闭是造成气轨压力低的直接 原因，通过核查发动机启动前轨压，确认系统存在微泄漏。基于先导电磁阀建压原理分析， 故障根源为系统微泄漏致使启动前轨压无法建立，发动机启动后负载升高，电磁阀下方未能 稳定建压，阀芯受气动力作用发生关闭。消除泄漏后，该车辆冷机启动气轨压力低问题得以 解决。

关键词: 汽油/CNG 双燃料发动机；供气系统；先导电磁阀；气轨压力低