基于一台当量空燃比天然气发动机，研究了试验室全流测试设备运行状态对闭式曲轴箱通风系统曲轴箱压力的影响。CVS系统流量并不影响曲轴箱压力，而进气压力与曲轴箱压力呈正相关关系，在测量曲轴箱压力时应采取关闭进气空调或使用开式系统等措施避免干扰的引入。利用增压器入口前端的进气负压难以保证WHTC循环过程中曲轴箱一直保持负压状态，结合主动式油气分离器、节气门后端负压的引入可以优化曲轴箱通风系统。优化后的系统在WHTC过程中曲轴箱压力能够保持在－2.1~0 kPa，平均曲轴箱压力较改进前降低1 kPa，能够满足国六标准要求。

Based on an equivalent air-fuel ratio natural gas engine, the influence of full flow equipment operation state on crankcase pressure in closed crankcase ventilation system was studied. Flow of CVS system had no effect on crankcase pressure, but the intake pressure was positively correlated with the crankcase pressure. Therefore, measures such as turning off the intake air conditioning system or using an open system should be taken to avoid the introduction of interference for measuring the crankcase pressure. It's difficult to maintain negative pressure inside crankcase during WHTC cycle by using the negative pressure of supercharger inlet. Therefore the crankcase ventilation system could be optimized by combining the introduction of negative pressure at the back of throttle with the active oil-gas separator. With the optimized system, the crankcase pressure could be maintained between －2.1 kPa and 0 kPa and the average crankcase pressure was 1 kPa lower than the previous, which could meet the requirements of China Ⅵ legislation.