EFFECT OF HYDROCARBON CONCENTRATION ON PARTICULATE DEPOSITION AND MICROSTRUCTURE OF THE DEPOSIT IN EXHAUST GAS RECIRCULATION COOLER

摘要

The effect of hydrocarbon (HC) concentration on particulate deposition and the microstructure of the deposit in exhaust gas recirculation (EGR) cooler was investigated. The EGR cooler inlet gas temperature was 300 degrees C and the coolant temperature was 85 degrees C throughout the test, and the HC concentration was fixed at 200 ppm, 450 ppm, and 850 ppm respectively. The results indicated that there is a HC concentration region in which the effect of HC condensation on particle deposition in EGR cooler was enhanced. The HC concentration is not only affecting the particulate regeneration and deposition but also affecting the deposit microstructure. The deposit that built up under low HC concentration has two layers, of which the top layer is a thinner loose flocculent dendrite layer and the bottom layer is a thicker dense layer. The deposit in the EGR cooler that built up under high HC concentration conditions is mainly a dense layer, and with clusters of flocculent particles scattered on the surface of it. Due to the large amount of HC volatilized in the deposit layer, the structure of deposit in the EGR cooler that built up under extreme high HC concentration finally becomes coarser and the density decreases.