柴油机颗粒捕集器捕集效率的数值模拟及试验验证

Numerical simulation and experiment verification of trap capture efficiency for diesel particulate filters

为研发高过滤效率的颗粒捕集器,通过填充床捕集理论建立其综合捕集效率的数学模型,并利用Matlab和试验对所建立的数学模型进行验证.结果表明：在整个微粒捕集过程中,布朗扩散起主导作用,减小排气流量和提高排气温度均能提高布朗扩散捕集系数和综合捕集系数,而排气流量和排气温度对直接拦截捕集机理的影响不大;当微粒粒径小于100 nm时,布朗扩散捕集机理起主导作用,综合捕集系数随微粒粒径的减小而迅速增加,数值与布朗扩散捕集系数相差不大;当微粒粒径大于100 nm时,直接拦截捕集机理作用增强,综合捕集系数随微粒粒径的增大而减小缓慢,数值大于布朗扩散捕集系数,但仍较小;当微粒粒径为100~500 nm时,由于各种捕集机理相互竞争,综合捕集系数出现最小值.

To develop particulate filter with high filtering efficiency, a comprehensive mathematical model of trap capture efficiency was established based on the capture theory of packed bed, and the established model was validated by Matlab. The results show that in the whole process of particulate trapping, Brownian diffusion plays a dominant role. The reduced exhaust flow rate and the improved exhaust temperature can improve the diffusion coefficient and the capture Brownian integrated capture eoefficiency, while the exhaust flow rate and the exhaust temperature have slight effect on the straight intercept capture mechanism. When the particle size is less than 100 nm, the integrated capture coefficient increases rapidly with the decreasing of particle size, and the number has little difference with the Brownian diffusion coefficient. When particle size is greater than 100 nm, the straight intercept capture mechanism is enhanced, and the comprehensive capture coefficient decreases slowly with the increasing of particle size. When the particle size is from 100 nm to 500 nm, the capture mechanisms compete each other to obtain the minimum value of comprehensive capture coefficient.