Construction Of Evaluation System And Study On The Formation Mechanism Of Carbon Deposition Based On EGR Cooler Condensation And Gravity Effect

Exhaust gas recirculation(EGR)technology is an effective means to reduce NOx emissions.Cooled EGR Technology can further play its advantages,but the carbon deposition in EGR cooler will cause heat transfer performance degradation and increase exhaust back pressure.In this paper,according to the research status of carbon deposition in EGR cooler,based on the self-developed carbon deposition test platform and the established carbon deposition evaluation system,the typical characteristics of carbon deposition are characterized,and the effects of condensation and gravity on carbon deposition are studied.The experimental equipment for the generation of carbon deposition in EGR cooler is designed,and a test platform for the generation of carbon deposition of EGR cooler is built.The emission parameters of typical working conditions of HR186 FA diesel engine are collected and analyzed,and the test parameters are studied and selected;The typical carbon deposition samples were obtained and the evaluation system of carbon deposition was established.The results show that the carbon deposition can be characterized from macro,surface,spatial and physical characteristics respectively.The evaluation system of EGR cooler carbon deposition includes 7 primary and 20 secondary characterization parameters.Based on the evaluation system of carbon deposition,the experimental scheme of the effect of condensation on carbon deposition is designed according to the principle of condensation.The characteristic parameters of carbon deposition samples produced under different condensation degrees are extracted and compared by means of balance,color difference,contact angle test and microscope.The influence of condensation on carbon deposition is discussed.The results show that the condensation will increase the quality of carbon deposition;The color difference of carbon deposition will be increased by condensation;Condensation can enhance the hydrophilicity of carbon deposition;The condensation will make the morphology of carbon deposition more humid and compact;The temperature distribution of weak condensation is about 200 ℃.Based on the constructed carbon deposition evaluation system,the experimental scheme of the effect of gravity on carbon deposition is designed according to the principle of gravity action.The characteristic parameters of the carbon deposit samples produced by gravity are extracted and compared by the balance,microscope and software image J,and the influence of gravity on carbon deposition is discussed.The results show that gravity will increase the mass of carbon deposition,the number of carbon clusters will increase by gravity,and the proportion of carbon accumulating area will be increased by gravity.The closer the exhaust end,the larger the average equivalent diameter of the carbon cluster,the more prominent the gravity effect,the greater the difference between the carbon mass and the carbon area.The results show that condensation and gravity have an important influence on the weight,color,hydrophilicity and micro morphology of carbon deposition.The research work provides a reference for the prevention and control of EGR carbon deposition in diesel engine and the design of EGR cooler.