Rotary Continuous Microwave Regeneration Particulate Filter Regeneration Mechanism And Structural Optimization

With the rapidly increase of the total number of vehicles and enhance of people's concept for living environment, the control of vehicle emission was more and more taken into account. As the diesel emission standards become very strict now, the Diesel Particulate Filter (DPF) was considered to be one of the most effective and promising ways to reduce diesel particulate emission in the future. However, based on the current technology and methods, regeneration problem is the key factor to restrict the apply of DPF in wide range. In the current major regeneration methods, the microwave energy used for filter regeneration was regarded as valuable because of many peculiarity advantages, but this methods is limited by battery of the car which can not supply enough energy during the microwave generator at working statusThis paper is supported by National"863"Program(2008AA11A116)"Manufacture of High Efficiency & Low Emission Diesel", National Natural Science Foundation of China(50876027)"Research on Mixed Regeneration Mechanics of Diesel Particulate Trapped Porous Medium Based on Microwave and Ce-Mn Fuel Addition"and Hunan Natural Science Funding Key Program of China(06JJ20018)"Numerical Simulation of Gas-Particle Two-Phase Flow and Combustion During Complex Regeneration in Vehicle Diesel Particulate Filter". Aiming at the solving the current main problems on microwave regeneration of DPF, a new technique was provided. Based on the technical solution some in-depth research was done in this paper. The major jobs of this paper are as follows:(1) Analyzing the shortcomings of present axial-flow particulate filter regeneration technology, a new technical ideas and implementation of rotary continuous microwave regeneration DPF are proposed. Changing the direction of air flow from traditional axial to radial and from filtering the whole body recycling to area non-continuous rotation continuous regeneration are the main ideas. Then, the advantages of this technology, the key technologies of practical application and the difficulties to be overcomed and analyzed.(2) Calculating theoretical model on filtration unit of flow resistance characteristics was developed .In additional, pressure drop mechanism about the flow in porous media was revealed in this model. And the results are validated by experiment. Using this model, the permeability, inertia coefficient can be directly calculated, and the pressure drop of the flow in porous media can be accurately predicted based on the porosity and average pore diameter of the filter. The model can assess non-linear degree of flow in porous media, which also can be applied for low pressure drop filtration unit design.(3) A three-dimensional general mathematical model for the regenerating process of continuous microwave regeneration foam ceramic filtration unit was proposed. In this model, several major parameters, such as the particle non-uniform distribution in the filter, the convection heat transfer between the airflow and the filter and/or the carbon particles, airflow components etc. were considered. The methods for solving the model and processing approach for the airflow and solid coupling relationship in porous media were given. The results predicted by the model has good agreement with the experiment data, which indicates that the mathematical model can be used for simulation of the filtration unit regenerating process. Using this model, the effect of the flow characteristic parameters, PM content, microwave energy distribution on the regeneration filtration unit were studied, and the effect laws of major factors, such as the oxygen percentage and temperature of the flow, the porous velocity, PM total amount and its spatial distribution laws, microwave energy etc. on regeneration time, efficiency were obtained.(4) Based on the structure and air flow characteristics about rotating filtration unit, particulate trapping model which reveal the filtration unit static trapping mechanism was established. Using this model, not only the collection efficiency of specific filtration unit but also the spatial distribution of PM deposited in filtration unit can be predicted accurately. The model implied the effect laws on filter material microstructure, such as porosity, average pore diameter, and microstructure, such as flow distance on filtration unit, penetration speed on filtration efficiency and the distribution of PM. The results show that the porosity of filter material, the average pore diameter and filtration efficiency are inversely proportional relationship, and the distribution of PM along the flow direction in the filter obey exponential law approximately.(5) Based on the regeneration and filter trapping characteristic of the filtration unit, the relationship between regeneration process and filtering process was established. Based on it, the optimization model of the filtration unit structure, which due to reduce the loss of the flow. And at the same time, the special minimum filtration efficiency was considered as major constraint, and porosity, average pore diameter, filter diameter, ratio between outer diameter and the diameter ,ratio between length and diameter , the number of filtering units as variable parameters. Consequently, we can get the most optional structure to hold the minimum pressure drop at different efficiency.The research in this paper is expected to be a new idea and method for regeneration of DPF. Many conclusions of this paper are considered not only as the designing basis and theoretical guidance of rotary continuous microwave regeneration particulate filter, but also a valuable refer for other traditional DPF.