浅析流量计扰流杆污染对机动车尾气测试结果的影响

Analysis on the Influence of Flow Meter Spoiler Pollution on Vehicle Exhaust Test Results

为掌握流量计扰流杆存在附着物时对机动车尾气测量结果的影响情况,首先通过仿真模型研究了扰流杆存在附着物污染时对流量测试结果的影响,并设置3种扰流杆表面附着物的情景对排气流量进行实测比较研究。结果表明由于扰流杆直径的增加,造成漩涡之间宽度减小即漩涡脱落频率下降,从而降低了超声波所测得的涡街频率,最终导致气体流量测量值下降,并且随扰流杆直径增大,误差值不断增加。实测的碳素墨水加粉笔灰、细线缠绕、油脂涂抹三种情景下,流量误差分别达到6.98%、11.8%和16.94%。在机动车尾气测试中,流量测定值的减少会直接影响污染物排放测定的真实结果,因此,有必要对检验机构使用的气体流量分析仪中的扰流杆进行定期清洁。

In order to master the influence of the presence of Spoiler lever on the measurement results of motor vehicle exhaust,the influence of the spoiler with attachment contamination on the flow test result was studied,and the exhaust flow was measured and compared under three scenarios of attachment on the spoiler surface.The results showed that due to the increase of the diameter of the spoiler lever,the width between the vortices decreases,that is,the vortex shedding frequency decreases,and the vortex street frequency measured by ultrasonic waves decreases,resulting in a decrease in the gas flow measurement value,and the error value increases as the diameter increases.In the three scenarios of carbon ink with chalk ash,thin line winding and grease washing,the flow errors reached 6.98%,11.8%and 16.94%respectively.In the vehicle exhaust test,the flow reduction will directly affect the real results of pollutants.Therefore,it is necessary to effectively clean the spoiler lever in the gas flow analyzer used by the inspection agency.