Numerical Simulation Research On Diesel Particulate Filter Of High Power Diesel Engine

With the implementation of increasingly stringent emission regulation, more and more attention has been paid to exhaust particles purification of diesel engines. Diesel Particulate Filter(DPF) with high capture efficiency has been widely used in automotive diesel engines. When it's working, the uneven distribution of flow field will reduce the capture efficiency; particles constantly accumulated in DPF channel and if don't clean up in time, it will lower the car's fuel economy and reduce the output power. So, it is particularly important to study the internal flow field distribution in DPF and regeneration process.Now, DPF is popular in vehicle diesel engine. But for high power Marine diesel engine, there is still lack of particles post-processing technology. Based on the MIIT and Ministry of Finance's high technology Marine scientific research project "Advanced research on Marine diesel engine particle emission control", used Weichai WP12 high power engine for the prototype and developed a set of large size particles trap.Used the three-dimensional modeling software ProE to model DPF, meshing software ICEM to generate hexahedral grid and computational fluid software Fluent to set boundary and solver conditions, the uniformity index has been introduced to analyze the flow field distribution in this paper. Through simulation analysis of the influence of the exhaust pipe inlet velocity, inlet expansion pipe cone angle, the porous media diameter and inlet pipe diameter ratio, the carrier aspect ratio and pre oxidation catalysts DOC on the velocity and pressure distribution, the study found that the greater inlet exhaust velocity is, the larger pressure drop of the porous media will be, but velocity and pressure uniformity index on carrier entrance surface hardly change with inlet velocity; the smaller the diameter ratio between porous media and inlet pipe is, the better the flow uniformity will be; the flow uniformity is best when carrier aspect ratio is 1.1; DOC can diffuse flow and velocity uniform index can be increased from 0.855 to 0.934.This paper also used AVL Fire ESE Aftertreatment software to analyze the pressure drop and regeneration characteristics of DPF, and found that the pressure drop is mainly composed of entrance pressure drop, inlet channel pressure drop, carbon cake pressure drop, wall pressure drop, outlet channel pressure drop and outlet pressure drop. When it is clean, its pressure drop is mainly caused by wall and it accounts for 64.4%, but the carbon cake pressure drop grows bigger with the accumulation of carbon and the proportion is as high as 82.6% when calculation time is 300s. The greater the wall thickness is, the larger pressure drop it will have; the smaller CPSI it has, the greater the pressure drop will be; the larger initial carbon loads are, the greater the pressure drop will be. It slowly starts from the entry point to the end of the tunnel along axial-direction when DPF regenerates, and carbon smoke density at the end of the tunnel will continue to increase during the regeneration process. Higher inlet temperature is good for carbon regeneration and the best inlet temperature should be about 850?900 K; the higher exhaust particle concentration is, the greater the carbon accumulation in DPF and the pressure drop will be, which will increase regeneration time, lay the DPF in high temperature for a longer time and increase the risk of heat damage.