| Diesel is more and more popular with the market for its fuel economy. But the emission pollution possess so many characteristics,so the traditional methods are not meeting the stringent emission law. Aftertreatment plays an important role on the arena of the future emission technology. Diesel Particulate Filter (DPF) is a widely used emission aftertreatment technology, has a good performance in trapping of the particulate emission from the diesel.DPF manage the deposit principle for trapping the PM emission from the diesel. The power and economy of the diesel would have a reduce while the PM trapping to a degree in the filter, so it is necessary to process a regeneration of DPF.The article studied several characteristics of wall-flow DPF during its regeneration time with AVL FIRE. Divided the serial time into three different parts, such as warm-up with controlled regeneration; uncontrolled, accelerated regeneration; controlled, homogeneous regeneration. Demonstrate and analyse some factors which affect the regeneration, such as the initial soot loading at the beginning of the regeneration, the oxidation constant in the diesel emission, the massflow at the inlet of the DPF, peak temperature of the assistant thermal source, the assistant thermal rate, the continuance time of the peak temperature of the assistant thermal source.The main work includes,1. Established the regeneration model of DPF in AVL FIRE, set the simulation parameters, and validated the model with the experiment.2. Divided the regeneration time into three steps, demonstrated the temperature distribution, the PM reminder, oxidation distribution in the filter. Analysed the characters of every step.3. Do some research for the initial soot loading of regeneration, the oxidation of exhaust, the massflow of DPF inlet, the peak temperature of assistant thermal resource, the rate of assistant thermal, the continuance time of the peak temperature of the assistant thermal source, in order to find how do they affect the regeneration of DPF.The conclusion are drawn via the simulation, 1. During the warm-up with controlled regeneration, it is in a temporary and spatially controlled manner, with a relatively smooth distribution of temperature, heat release and soot combustion in the filter. The elevated inlet temperature results in a warm-up of the filter material from front to rear, with the highest temperature corresponding to the core of the incident exhaust gas flow. The volume flow change, associated with the temperature increase, results in a correspondingly higher pressure drop across the filter. The oxidate of soot combustion have a increase.2. During the uncontrolled, accelerated regeneration, it is characterized by a distinctive, rapid, localized regeneration in the rear third of the DPF. The extreme local heat release spreads radially and uncontrolled until this portion is burned free of soot, with the very high local temperatures that appear, strong temporal and spatial temperature gradients arise, make the filter in a critical situation. It should pay much attention to the temperature of the DPF for fear it is too high to the filter could afford. The soot is still in the region which nearby the inlet and the outerboard axial direction of the outlet. It is caused by the effect of cold shock on the inlet and environment cooling to the outlet.3. During the controlled, homogeneous regeneration, the regeneration is nearly to an end. On the step, the mean filter temperature remains elevated and the temperature distribution is characteristically homogeneous within the entire DPF. The rear and inlet of DPF begin to regenerate. Because the flow which input to the filter should reduce the temperature of filter and control the regeneration process. But the filter is still in a controlled, homogeneous regeneration.4. To regenerate DPF in the condition of different initial soot loading. While the soot loading is higher, the average temperature and maximum temperature of filter are both lower than the condition which is on the lower initial soot loading. At the lower soot loading, regenerate process is rapider than higher soot loading. Regenerate the DPF while the initial soot loading is at 10g/L, 7g/L, 5g/L, 3g/L on the same work condition and assistant thermal way. The max temperature of the filter is 1287.03K, 1248.24K, 1208.77K, 1128.02K.5. To regenerate DPF in the condition of different exhaust oxidation constant. While the oxidation constant is higher, the soot reaction rate is higher than the condition which contains lower oxidation constant. The continuance time of uncontrolled, accelerated regeneration during the higher exhaust oxidation constant is much shorter than lower exhaust oxidation constant. Regenerate the DPF while the mass fraction of oxygen in the exhaust gas is at 7% and 17% on the same work condition and assistant thermal way. While the mass fraction of oxygen in the exhaust gas is at 17%, the max temperature of the filter is 1578.48K, appears at 114s; While the mass fraction of oxygen in the exhaust gas is at 7%, the max temperature of the filter is 1287.03K, appears at 124s.6. To regenerate DPF in the condition of different inlet massflow. While the inlet massflow is higher, regeneration process is rapider than the inlet massflow is lower. At different massflow, the peak temperatures of the filter have not obvious differences. But in the condition of higher massflow, the filter peak temperature appeared earlier than lower massflow condition.7. To regenerate DPF in the condition of different assistant thermal peak temperature. With the increase of assistant thermal peak temperature, the rate of regeneration is increasing, the average and maximum temperature of DPF are also increasing. Regenerate the DPF while the peak temperature of the assist thermal is different, on the same work condition and assistant thermal way. While the peak temperature is 750K, the max temperature of the filter appears at 140s, 941.35K; While the peak temperature is 850K, the max temperature of the filter appears at 124s, 1287.03K; While the peak temperature is 950K, the max temperature of the filter appears at 116s, 1320.96K. On the condition of the assistant thermal peak temperature is at 850K or 950K, it could regenerate completely, on the condition of the assistant thermal peak temperature is at 750K, the regeneration is not completely.8. To regenerate DPF in the condition of different assistant thermal rate. At the higher assistant thermal rate, the magnitude of average and maximum peak temperature of DPF are not much different, but appeared in different time. The appearing time of the average and maximum peak temperature of DPF in the condition of higher assistant thermal rate are earlier than the lower assistant thermal rate. While get the higher assist thermal rate regeneration, the soot density has an obvious decrease at 64 s. While get the lower assist thermal rate regeneration, the soot density hasn't an obvious decrease until 82 s.9. To regenerate DPF in the condition of different continuance time of the peak temperature of the assistant thermal source. Compared the transitory and successive thermal conditions. On different thermal ways, the temperature of flow and soot combustion should affect the reminder soot in the filter, especially on the condition of the temperature decrease to the light-off temperature of soot. While get the successive thermal rate regeneration, the efficiency of the soot obliteration could reach to 97.9%. While get the transitory thermal rate regeneration, the efficiency of the soot obliteration could reach to 92.5%.So that is need to give a suitable continuous thermal time, in order to reduce the consume of the regeneration, to ensure the economy of regeneration.
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