Effect Of EGR On Working Process Of High Pressure Common Rail Diesel Engine Fueled With Oxygenated Fuel

With the energy security situation and the increasingly serious environmental pollution,the internal combustion engine is developing towards the direction of high efficiency and low pollution.The emissions of nitrogen oxide(NOx)and particulate matter(PM)is the difficulty of emission control of diesel engine because of the contradiction between the NOx and PM generation mechanism,which leads to the increase of the difficulty of the diesel engine emission control compared to the gasoline engine.Exhaust gas recirculation(EGR)technology is effective to reduce the NOx emission of the engine cleaning technology,diesel engine operating at different altitudes,due to different atmospheric pressure to bring changes in the intake of oxygen content,meantime,EGR technology will further deteriorate the performance of diesel engine in Plateau area,.Mixed burning biodiesel or bioethanol in diesel,it is helpful for the elevation of NOx and PM emissions performance and the contradiction with the EGR system of diesel engines.The mixed fuel is biodiesel and ethanol and diesel with a certain mixed solution(the oxygenated fuel for BED).It is researching on the installation of EGR system under different atmospheric pressure common rail diesel engine fueled with BED and the influence of BED oxygen fuel.It provides a theoretical basis for the research of high efficiency and low pollution diesel engines.It is study on the influence of EGR on the performance of diesel engines fueling with pure diesel,B15E5(15%biodiesel and 5%ethanol)and B25E5 three kinds of fuel,under atmospheric conditions in 81kPa and 100kPa using atmospheric simulation system on an engine bench.It is using test and combustion simulation methods to study the combined with EGR system research carried out in different atmospheric pressure,simulation the different fuels of high pressure common rail fuel economy,power performance,combustion characteristics and emission characteristics.And it is also studied in different atmospheric pressure EGR influence on the operation characteristic of BED oxygen fuel.The results are as follows:(1)The influence of the BED fuel technology and EGR technology on the performance of diesel engine under high altitude environment.The dynamic and economic performance of BED is lower than that of pure diesel fuel,under high altitude environment.With the increase of the EGR,the dynamic and economic performance of BED oxygenated fuel is decreased.BED oxygenated fuel economy and power were lower than the pure diesel under the three kinds of speed of load characteristics.Increasing the rate of EGR the power of the three fuels are reduced in different degrees.And in the whole range of engine load,BED oxygen fuel soot,HC and CO emissions are improved,the NOx the discharge increased slightly.With the increase of EGR rate,the maximum cylinder pressure,maximum combustion temperature of different fuel is reducing,the maximum heat release rate and pressure rise rate was reduced,but the corresponding crankshaft phase peak pressure in cylinder with the change rate of EGR is very small.When the injection timing is constant,the NOX emissions of pure diesel and B25E5 fuel at two speeds are reduced compared to no EGR,with an average decrease of 22.96%.(2)The performance of diesel engine at different altitudes affected on BED fuel technology and EGR technology.When the atmospheric pressure is increased from 81kPa to 100kPa,the power of pure diesel,B15E5 and B25E5 were increased,compared to the low speed region in high speed power increased greatly.Compared with pure diesel,BED multi-component fuel increases the engine power to a high-speed offset,with the increase of biodiesel and ethanol with the atmospheric pressure.With the increase of the proportion of BED in the fuel,with the influence of atmospheric pressure,it is gradually widening on the power.With the increasing of biodiesel and ethanol ratio,the influence of the atmospheric pressure on the economy is gradually decreased.The increase of atmospheric pressure influence on BED fuel economy is not obvious under low load,but under high load,it can effectively improve its economy.After the installation of EGR,both the power and economy of diesel engine have been reduced.The NOx emission is obviously decreased with the EGR system,and the amplitude is increased with the increase of the load.When EGR system shut down,the NOx 81kPa emissions slightly higher than 100kPa,when the rate of EGR on 16%,the NOx emissions 81kPa slightly lower than 100kPa.With the opening of EGR system diesel engine soot and CO emissions increased significantly,while the carbon smoke and CO emissions of B15E5 fuels was significantly lower than pure diesel.The soot has maximum increase,under the full load condition,and CO at 50%load.With EGR system working,the soot emission of pure diesel oil is higher than that of 100kPa under 81kPa,and the CO emission of 81kPa is higher than that of 100kPa.Under high load conditions,the emission of B15E5 fuel in 100kPa is lower than that of 81kPa With the increase of atmospheric pressure,the maximum pressure,cylinder three kinds of fuel within the maximum combustion temperature,the maximum heat release rate and pressure rise rate are increasing.(3)Study on the combustion mechanism of BED fuel technology and EGR Technology.The simulated respectively are based on 2200r/min,75%load conditions and AVL software in FIRE,to find the combustion process of the OEGR rate and 16%EGR rate fueled with B15E5.and it is finding cylinder pressure field,temperature field,velocity field,spray NOx emission concentration field,Soot emission concentration field.The simulation results show that:in different periods,compared with no EGR,the cylinder pressure,cylinder temperature and spray speed decreased,NOx production decreased and Soot production increased when EGR rate was 16%.(4)Prediction of emission characteristics of diesel engine model coupled with BED fuel technology and EGR Technology.The main factors influencing the local linear model trees with different fuels based on engine emissions were predicted,HC,CO and NOx prediction model has high accuracy,small error between the predicted value and the experimental value.The results showed that:for different fuels,engine speed,torque,fuel consumption and air flow influence on HC emission speed,fuel consumption,air flow and air temperature is larger,the influence on CO emission and rotational speed,torque,fuel consumption,air flow and vortex front temperature has a great influence on NOx emission.The emission model can provide exact simulation model for optimizing the emission characteristics of mechanical coupling BED technology and EGR technology of diesel fuel.