Simulation Study On Catalytic Regeneration Characteristics Of Platelet Diesel Particulate

In the face of the increasingly serious environmental pollution and rising national emission regulations, catalytic particulate filter (CPF) instrument has two big functions of capture and regeneration. It plays an important role in reducing the particles to meet the emission regulation of Euro six. Plateau area in our country is wide, and this will bring more challenges for the modern and efficient low-emission diesel engine and its post-processing development.In this paper, firstly, the YN38CRD1 common rail diesel engine which installed CPF as the research model. In view of the external characteristic, ESC and ETC bench test research shows that:after installing the CPF, with the speed increasing, the engine power decrease and power loss is larger. When the speed is 3000r/min, the power loss and fuel consumption is the largest. ESC test shows that:equipped with CPF, the exhaust back pressure increase greatly, and it increase with the increasing of engine speed and load. When the diesel engine equipped with CPF, the NOx emissions increase at light load, but it has little effect on NOx emission at heavy load. In the ESC test, the efficiency of particles conversion is up to 90% when adding CPF, and the efficiency is up to 99% in the ETC test. Thus, the results showed that, the efficiency of CPF is high, adding CPF can control particle emissions effectively.In this paper, with D19 high pressure common rail diesel engine as the research model, use AVL Boost, GT-Power and AVL Fire to build one-dimensional thermodynamic simulation model and the three-dimensional CFD simulation model of CPF which coupling with carbon smoke regeneration mechanism. Research the impact of inlet and exhaust characteristic parameters and fuel injection control strategy coupling with EGR on CPF regeneration process by numerical simulation.In the view of the exhaust characteristic parameters, the research shows that, compare with DPF, CPF lower the regeneration temperature by 150℃ and its regeneration efficiency is higher, but the NO2 emission increase. When the exhaust temperature is 450℃, the improvement of CPF regeneration performance is the biggest. When the exhaust temperature is 350℃, the NO2 in CPF outlet is the highest. When the exhaust temperature beyond 400℃, increasing the O2 concentration in exhaust can efficiently improve the regeneration efficiency of CPF, and the enhancing effect increase with the exhaust temperature rise. When the exhaust temperature between 250℃～450℃, increasing the CO2 concentration in exhaust can efficiently improve the regeneration efficiency of CPF. When the exhaust temperature is 400℃, the effect of increasing NO2 concentration on CPF regeneration performance is the largest. However, when the exhaust temperature beyond 500℃, the effect weaken.In view of the intake characteristic parameters, the research shows that, with decreased atmosphere oxygen concentration, both the oxidation rate of soot and the reducing rate of pressure drop for CPF slow down obviously, meanwhile, the emission of NOx and NO2 in the inlet and outlet of CPF reduce simultaneously. It is bad for CPF regeneration with the increase of altitude, while the pressure drop and the highest temperature of CPF regeneration process decrease simultaneously, also it is effective way to reduce the emission of NO2. The effects of altitude on CPF regeneration process is a combined effect of atmosphere oxygen concentration and atmosphere pressure, while the intake oxygen concentration plays a dominant role. For 2km plateau environment, CPF regeneration performance has weakened dramatically. Using EGR will significantly aggravate the difficulty of CPF regeneration in plateau environment. EGR rate play a greater role on the reduction of NO2 than NO.The research on the influence of injection parameters coupling with EGR on engine working process and CPF regeneration performance shows that, with the main injection timing delay, torque increase then decrease. With EGR ratio rising, engine torque decrease, and with the main injection timing delay the disadvantageous effect on torque is larger. The main injection timing delay from -22.6℃A ATDC to -10.6℃A ATDC, CPF regeneration rate and residual particles changes smaller. When the main injection timing delay from -10.6℃A ATDC to 1.4℃A ATDC, CPF residual particles, pressure drop and NO2 falling rapidly. With EGR ratio increasing, CPF regeneration performance becomes poor. When EGR ratio increase to 35%, adverse impact on the engine performance and post-processing system is larger. With the injection pressure increasing, the main injection time corresponding to peak of torque delay, in-cylinder NOx increase. When the main injection timing is early, improve the injection pressure will lower torque, and cause the NOx in cylinder increase rapidly, but it’s advantageous to the CPF regeneration. When the main injection timing is late, improve the injection pressure will increase torque, but it can lead to CPF regeneration performance variation, NOx emissions and NO2/NOx mass ratio increase at the same time.The research on the influence of post injection strategy coupling with EGR on engine working process and CPF regeneration performance shows that, when using post injection, with the post injection time delay, the engine fuel consumption, NOx and exhaust flow increase gradually, CPF residual particles and the pressure drop presents the trend of increasing with decreasing first. When post injection is 18℃A ATDC, CPF regeneration performance is the best, at the same time, NO2 mass fraction and NO2/NOx mass ratio is the lowest. With post injection fuel quantity increase, fuel consumption and exhaust temperature rise, NOx emission reduce. Increase the post injection fuel is advantageous to the CPF regeneration. When post injection time is 18℃A ATDC and fuel injection quantity is 15 mg, CPF regeneration performance is the best. It indicates that, considering the fuel economy and CPF regeneration efficiency, we should choose reasonable post injection time and fuel quantity. Besides, for single injection, the adverse effect of improving EGR ratio on CPF regeneration is less, but it can reduce the CPF pressure drop and NO2 significantly. Using post injection and the injection time is late, increase EGR ratio will reduce the CPF regeneration rate significantly, and the reducing effect on pressure drop and NO2 weaken. The post injection time correspond to best CPF regeneration efficiency move forward with the increase of EGR ratio.