| Diesel Particulate Filter (DPF) is a well-known device to decrease the particulate emission of diesel engine significantly. How to let the particulate be filtered effectively, and then be regenerated reliably, becomes to be the most important and difficult objectives during the development of DPF, respectively. At the present time, the microwave heating technology is the most popular approach to be adopted to regenerate the particulate trapped in the DPF, due to some particular advantages of microwave technique such as heating rapidly, high energy utilization ratio and excellent controllability. However, there are still several key problems need to be investigated further when the microwave regeneration technology is considered to be used in DPF. For instant, the particulate filtering process can not be integrated with the process of regenerating coordinately. Large numbers of power consumption will be occurred to create the microwave energy during regeneration process, however, the battery on-vehicle can not supplied so much consumption of electric energy completely.As mentioned above, several serious problems exist when the microwave regeneration technology is applied to the DPF of vehicle. Trying to resolve these problems becomes much of practical interest. An idea that "regenerates the particulates in DPF divisionally by microwave" was proposed in present dissertation. In order to assess the feasibility and reliability of this approach, a related structure model of the DPF regenerated divisionally by microwave was designed and studied. Particularly, some important control models during the particulate filtering and regenerating processes were modeled, and furthermore, these models were applied to investigate the effect of primary factors on DPF filtration and regeneration processes. Considering market practicability of the present DPF in the future time, a suite of regeneration control system for this DPF was also explored to be designed and developed in present dissertation. Note must be pointed out that the present dissertation is supported by the project of 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 the key project of the Natural Science Foundation of Hunan Province (06JJ20018)"Numerical Simulation of Gas-Particle Two-Phase Flow and Combustion Process in a Vehicle Diesel Particulate Filter Operating in a Mixed Regeneration Condition". Except the descriptions discussed above, other research results of this dissertation are summarized as follows:1. The effect of geometry parameters of DPF (i.e., divergence angle, diameter ratio, length of filtration unit) on the flow velocity distribution in DPF was investigated. Basing on the classic filtering theory of porous medium, a filtering efficiency model of filtration unit was suggested. The effect of the volume fraction of porosity, average diameter of filtration hole, length and thickness of filtration unit, and operation conditions of diesel exhaust flow on filtration efficiency of DPF were considered in present model.2. A pressure loss computation model of the DPF filtration unit was developed. In the current model, the model permeability and inertia coefficients were calculated using a new approach against the typical Forchheimer-Ward pressure loss model. In order to assess the new model, available pressure loss characteristic experiment of filtration units was utilized to compare. Results indicated that the new model gave much more accurate predictions and showed a more practical utility than the typical Forchheimer-Ward model.3. A multi-objective optimization mathematic model was established to reduce the pressure loss of filtration unit together with increasing filtration efficiency of DPF at the same time. In present modeling approach, the key dimension parameters (volume fraction of porosity, average diameter of filtration hole, length, number, and inner and external diameter of filtration unit) of filtration unit are treated as constraint conditions when the exhaust operating conditions of diesel engine are determined. In the meantime, the penalty function was introduced to treat the current model to be unconstrained optimization condition, and then the multi-objective optimization model was resolved using the micro-genetic algorithm. As the result, the local optimal dimensions of filtration unit were obtained under different filtration efficiency conditions of DPF. This modeling approach also indicated a collaborative optimization rule that much higher filtration efficiency will be received together with a relatively lower pressure loss optimization.4. Combining the microwave electric field distribution model in DPF regeneration cavity into the microwave regeneration control model. The effect of different factors on distribution homogeneity of microwave electric field was investigated, and the temperature distribution during microwave regeneration process of filtration unit was either studied. The research results provided not only important reference for the optimization design of DPF regeneration cavity and increasing the microwave energy utilization, but also significant foundation for developing the regeneration control system of DPF regenerated divisionally discussed in the following section.5. As one of key components of DPF regeneration control system, the Electronic Control Unit (ECU) hardware was also studied and analyzed in present dissertation. The ECU hardware system was designed by a suite of control circuits, which included the microcomputer system circuit, bus circuit, power source module circuit, signal inputting circuit, low side driving circuit, and Lambda sensor control circuit as well as bypass valve driving circuit.The research work in present dissertation provides a new strategy for studying and developing the DPF "basing on microwave regeneration technique". Research results in present thesis can be not only used as theoretical foundations and technical reference for the structural design, performance analysis, and regeneration process control of the DPF regenerated divisionally by microwave, but also an important foundation for its market practicability considered in the future. Some research methods and results of this dissertation can also be used as important reference for studying and developing the DPF regenerated by other approaches. |
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