整车排放试验污染物瞬态质量测量方法研究

Pollution real-time mass measurement method for vehicle emission test

针对整车排放开发试验中直采排放测量设备不能直接测量出污染物瞬态质量的问题,采用了在袋采排放测量系统中增加稀释空气流量计SAO或者示踪CO2分析仪的方法,将袋采和直采测量设备关联起来,实现了污染物的瞬态质量测量。采用SAO方法时,通过测量混合前稀释空气的瞬态流量,计算出汽车排气的瞬态体积,再用直采系统测出污染物的瞬态体积浓度值就可以换算成汽车排气污染物的瞬态质量值。采用Trace CO2方法时,通过比较稀释管道中混合气的CO2瞬态体积浓度值与稀释前尾气的CO2体积浓度,得出了动态稀释比,从而间接计算出了汽车排气的瞬态体积,进而计算出污染物瞬态质量值。试验结果证明,加装稀释空气流量计SAO和示踪CO2分析仪的排放测量系统,能够有效测量出汽车排气中污染物的瞬态质量值。

Aiming at exhaust pollution instantaneous mass not been directly measured by direct sampling measurement system in vehicle de- velopment emission test, SAO and trace CO2 analyzer were developed. SAO was used to real time measure dilution air flow rate. Through CVS flow rate subtracts dilution air flow rate, the vehicle exhaust gas flow rate can be calculated. Trace CO2 analyzer was used to real time measure CO2 concentration of diluted gas. Through computing the dynamic ratio of CO2 concentration of diluted gas with CO2 concentration of tailpipe exhaust gas, the vehicle exhaust gas flow rate also can be calculated. Then pollution instantaneous mass can be calculated through multiplying tailpipe pollution concentration with vehicle exhaust real time volume at the same time. The emission test results indicate that the emission measurement system which additional SAO or trace CO2 analyzer can efficiently measure vehicle pollution instantaneous mass.