Particulate Emission Characteristics and GPF Performance of WLTC Cycle based on Exhaust Gas Simulator

Abstract

<div class="section abstract"><div class="htmlview paragraph">GDI engine has gained much popularity in vehicle market with its high thermal efficiency. However, because of higher particulate emissions, it becomes harder for GDI engines to fulfill the iteration of emission regulations in various countries. As a result, Gasoline Particulate Filter (GPF) has received more and more attention and applications. It is important to study the particulate emission and GPF performance especially for transient cycles. With a self-designed test bench with burner named Exhaust Gas Simulator, a transient control strategy to simulate the exhaust state of the WLTC cycle has been developed and achieved a fast and stable ash accumulation rate. Three levels of ash loading, in terms of 0g/L, 5g/L and 35g/L, were accumulated on respective GPF for different aging degrees with this test bench. The effect of ash loading on GPF performance was investigated. A Cambustion DMS500 was used to record the particulate emission before and after the GPFs, and then the particulate size distribution, collection efficiency of GPF were analyzed. The results show that with this test bench and control strategy, an ash accumulation rate of 5g/L can be achieved. In terms of particulate size distribution, particulate concentration before and after GPF mainly presents a bimodal distribution. The first peak is mainly composed of nucleation mode particles, and the second peak is mainly composed of accumulation mode particles. In terms of GPF collection efficiency, the average collection efficiency of GPF measured in the three groups is above 99% for particulates of various sizes ranging from 5 to 1000nm. In terms of average particulate size before and after GPF collection, the collection efficiency of fresh and slightly aged GPF for small-size particulates (5-20nm) is higher than that of large-size particulates (larger than 20nm). However, the GPF with higher aging degree has a higher collection efficiency for large -size particulates (larger than 20nm) than small-size particulates (5-20nm).</div></div>