Experimental Study On Emission Of Combined Injection Gasoline Engine Based On Auxiliary Heater During Start

In this study,we investigated the effects of different injection ratios and different injection times on the ignition characteristics of gasoline engine catalysts and the emission characteristics of warm-up process.The auxiliary heating technology is coupled on the combine injection technology in order to explore the effect of different auxiliary heating temperatures on the ignition characteristics of gasoline engine catalysts.Our study will provide theoretical support for the gasoline engine to meet the national VI emission regulations.Our study is divided into two parts.First,we investigate the effects of combined injection strategy on emission of gasoline engine during warm-up process.Our results show that combined injection effectively reduced the emission of HC and PN during the warm-up process.The optimal direct injection time was and the optimal injection ratio was.The detailed conclusions of the first part are as follows:(1)When the temperature of the coolant in the warm-up process rises from 30 °C to80 °C,the emission of HC decreases rapidly,however the emission of NOx increases gradually.With the increase of the ratio of direction injection,the emission of HC decreases firstly and then increases,however,the emission of NOx increases firstly and then falls.When the injection ratio is 80%-20%,the emission of HC is lowest and the emission of NOx is highest.With the delay of direct injection time,the emission of HC increases firstly and then falls.When the direct injection time is 60°CA BTDC,the emission of HC is lowest.While continue to delay the direct injection time(40°CA BTDC),the emission of HC increase.With the delay of direct injection time,the emission of NOx increases firstly and then decreases.When the direct injection time is 120°CA BTDC,the emission of HC is highest.(2)When the temperature of the coolant in the warm-up process rises from 30 °C to80 °C,the emission of PN decreases rapidly.With the increase of the ratio of direction injection,the emission of PN decreases firstly and then increases.When the injection ratiois 80%-20%,the emission of PN is lowest.With the delay of direct injection time,the emission of PN decreases.When the direct injection time is 60°CA BTDC,the emission of PN is lowest.While continue to delay the direct injection time(40°CA BTDC),the emission of PN increase.The effect of injection strategy on the particle size distribution during the warm-up process has a coupling effect with the water temperature.When the temperature of the coolant between 30? and 60?,the number of nucleation mode particle gradually increase with the delay of direct injection time,however the number of accumulation mode particle increases firstly and then falls.When the direct injection time is 100°CA BTDC,the number of accumulation mode particle is lowest.when the temperature of the coolant between 70? and 80?,the number of nucleation mode particle and accumulation mode particle decrease rapidly with the delay of direct injection time.With the increase of the ratio of direction injection,the number of nucleation mode particle and accumulation mode particle increases firstly and then falls when the coolant temperature between 30? and 60?,while the number of nucleation mode particle and accumulation mode particle increase gradually when the coolant temperature between 70?and 80??Second,we investigate the effects of combined injection strategy and auxiliary heater on the ignition of catalyst.Our results show that combined injection technology coupled with the auxiliary heating technology can effectively improve the characteristics of catalyst.The detailed conclusions of the first part are as follows:(1)With the ratio of direction injection increase,the inlet temperature of the catalyst increases firstly and then decreases,however the time of the ignition of catalytic reduces firstly and then increases.When the injection ratio is 50%-50%,the inlet temperature of the catalyst is the highest and the time of the ignition of catalytic the lowest.(2)With the delay of the direct injection time,the inlet temperature of the catalyst increases firstly and then decreases,while the time of the ignition of catalytic reduces firstly and then increases.When the direct injection time is 50°CA BTDC,the inlet temperature of the catalyst is the highest and the time of the ignition of catalytic the lowest.(3)Delaying of ignition can effectively improve the characteristics of catalyst.The inlet temperature of the catalyst rapidly increases and the time of the ignition of catalytic rapidly decreases with retarding ignition.However,excessive retarding ignition will make the combustion unstable and the power economy decrease.(4)The inlet temperature of the catalyst rapidly increases and the time of the ignition of catalytic rapidly decreases with the increase of excess air ratio.However,excessive increasing excess air ratio will make the maximum conversion efficiency of catalyst drop rapidly.(5)The auxiliary heating technology not only effectively reduces the HC emission but also dramatically reduces the time of the ignition of catalytic.The higher the preheating temperature,the higher the inlet temperature of catalyst and the shorter the time of the ignition of catalytic.When the preheating temperature is 60?,the time of the ignition of catalytic is 90 s,which is 33.3% lower than that without the auxiliary heater.