Active And Passive Regeneration Of DPF System For Heavy-duty Diesel Engines

Diesel Particulate Filter(DPF)is an effective technology to reduce the particulate emissions from diesel engines.The filtration efficiency of DPF is normally over 90%.With the continuous upgrading of emission regulations,DPF has become one of the key technologies for diesel vehicles to meet the requirements of China VI emission regulation.In China,research and application experience especially for the DPF regeneration technology of DPF is still insufficient.This paper deals with the problems of soot load,temperature field,safety and economy in the process of DPF active regeneration.Through some experiments,the method of reducing the rail pressure of the fuel injection was proposed.The regeneration characteristics of soot using new loading method were similar to that from the engine normal emission.The temperature field of DPF was tested,and the highest temperature and maximum temperature gradient were obtained.The paper carried out the optimization of DPF active regeneration safety and economy,and analyzed the influence of exhaust flow,soot load and regeneration temperature on the maximum temperature and regeneration fuel consumption in the DPF.The paper adopted a method of the highest temperature and regenerative fuel consumption compromise(trade-off)curve,and got the best regeneration temperature is 600°C.Drop to idle(DTI)test further determined the soot load of safety regeneration was 4 g/L.The optimal regeneration fuel consumption was obtained from the regeneration economic curve,and the optimal end-point of the regeneration was about 1g/L soot load.According to the average exhaust gas flow level of engine and the level of particle emission,It was estimated that the fuel consumption of regeneration was about 0.15~0.3% of the normal fuel consumption of the engine.This paper researched the influence of several factors such as DPF inlet temperature and soot load on the passive regeneration rate.The temperature and soot load of DPF have obvious influence on the passive regeneration rate.The influence of DPF inlet temperature is larger,at about 250°C,the passive regeneration rate is very slow,regeneration rate of less than 1 g/h,but the same soot load under 320°C in the regeneration rate can reach about 10 g/h.The influence of soot load on a certain range has a better linear relationship,and when the carbon load exceeds 5g/L,the influence of high soot load on the passive regeneration rate is not significant.In addition,the paper also discussed the possibility of realizing DPF continuous passive regeneration.This analysis method selected two representative cycles: one was World Harmonized Transient Cycle(WHTC)representing the running condition of the city road in the majority and the other one was European Transient Cycle(ETC)representing of the city road,rural road and highway combination.Because WHTC cycle average temperature was low,even with the advanced air control system,the average temperature of DPF inlet could reach only about 250°C when ambient temperature was 25°C.When PM emissions was lower than 0.022 g/kW·h,passive regeneration could be used.ETC in cyclic average exhaust temperature is higher,the average DPF inlet temperature of ETC cycle could reach 290°C or more.At 290°C passive regeneration could clean 0.03 g/kW·h of PM emission.However,passive regeneration has a great relationship with ambient temperature and needs to be used cautiously after real vehicle test in the cold weather and cold regions.