Study On Exhaust Gas Recirculation Cooler Fouling In Diesel

Cooled Exhaust Gas Recirculation(EGR)technology is one of the technologies to significantly reduce diesel engine nitrogen oxides(NOx)emissions while taking into account diesel engine particulate emissions.However,it is inevitable to face the problem of EGR cooler fouling when using cooled EGR technology.The fouling of EGR cooler will not only reduce the heat exchange efficiency of the EGR cooler,but also increase the pressure drop of the EGR cooler and increase the flow resistance of the EGR gas,which in turn leads to a decrease in engine performance.In this paper,the total EGR gas flow rate,inlet EGR gas temperature and coolant temperature of the EGR cooler were kept constant.The effects of EGR gas flow rate and EGR gas velocity on the deposition mass and deposition process of the EGR cooler were studied by changing the number of heat exchange pipes of EGR cooler to change the EGR gas flow rate through the EGR cooler heat exchange pipe.The HC concentration in the EGR gas was changed by additional injection of gasoline fuel to study the effect of HC concentration on the deposition mass,microstructure and heat transfer efficiency of EGR cooler.Based on the self-designed EGR square cooler,the effect of gravity on the deposition mass of the EGR cooler was studied,and the deposition on the surface of the EGR square cooler affected by gravity deposition was analyzed by thermogravimetric analysis under the conditions of EGR gas flow rate,inlet gas temperature and constant ambient temperature.The test results show that:(1)Under the same heat transfer tube length,the main mechanism of EGR gas flow rate on particulate deposition of EGR cooler is the effect of EGR gas flow velocity on particulate deposition.As the flow rate increases,the effect of gas flow velocity on the deposition mass of EGR cooler particulate gradually decreases.(2)HC concentrations have a concentration range for the promotion of EGR coolers,and in the concentration range increases with the HC concentration,the deposition mass of EGR coolers increases,and the deposition layer has more density;the HC concentration exceeds the concentration range,a sporadic particulate cluster is formed on the surface of the deposit layer,and the deposit layer structure becomes rough,and the EGR cooler heat transfer efficiency is significantly deteriorated.(3)The effect of gravity on the deposition quality of EGR square cooler is obvious,but this phenomenon gradually decreases with the increase of time.The content of HC is low in the deposit near the inlet at the lower surface of the EGR cooler affected by ravity,and the content of HC in the deposit near the outlet is larger than the deposits t the outlet and the HC is mixed with the particulate.