| With the increase of inventory of diesel vehicles in our country, the pollutants ofdiesel exhaust particulate emission has seriously harmed the environment and humanhealth. Purification technics against it has already become a principal subject atpresent on controlling vehicular pollutants discharge. Nowadays, diesel particulatefilter (DPF) is universally accepted by scholars both home and abroad as the mosteffective post-processing device in controlling the particulate discharge from dieselengines. The key technologies to it are filter materials and filter regeneration. Atpresent, the research on filter materials has achieved greater breakthrough, whereasthe research on filter regeneration technology has long been one of the importantsubjects explored by researchers on vehicular emission control both home and abroad.Due to the many defects with the single regenerative way of DPF filter, thecombination of single regeneration techniques has become an effective method to fixthe regenerative problem of DPF. The regeneration technique of catalyst combustion-supporting with microwave heating is a new-type composite regeneration technique,which employs chemical catalysts to reduce the initiation temperature of particulateso that the particulate can be ignited under the condition of lower temperature. Thistechnique can be adopted to effectively lessen the thermal load of the filter, reduce themicrowave energy consumption during the composite regeneration process and extendthe service life of DPF. However, how to effectively and correctively judge thecombustion characteristics of composite regeneration of DPF under differentconditions with different influencing factors and how to analyze regeneration timeand the synergy of intensified heat transfer have become an important problem to besolved to realize real-time adjustment and control during the composite regenerativeprocess of DPF.Based on fields synergy theory, this thesis, by adopting the method of combiningof numerical simulating and experiment, makes an analysis on the compositeregenerative performance and multi-fields synergetic performance of DPF filter underthe composite regenerative mode of microwave heating MnOx-CeO2catalysts on thebasis of research into the law of effect of appropriate MnOx-CeO2catalysts upon theinitiation temperature of the particulate inside the filter. The temperature field and thevelocity field are ensured consistent with the composite regenerative process, the heatand mass transfer during the composite regenerative process of DPF filter as well as the effect of particulate combustion are enhanced in the hope of fulfilling reducing theinitiation temperature of particulate and electric energy consumption, boosting the useratio and regeneration efficiency of microwave energy, expanding its regenerationwindow and extending its service life. This research attaches not only importanttheoretical and applicative value to emission control of diesel engines, but significantreferential value to treating mobile pollutants sources and protecting the environment.Therefore, the research is supported by the project of China Scholarship Council(CSC)“Research on the Strengthening Mechanism and Application of MicroscaleCombustion in the Porous Medium Filter (201306130031)”，the project of NationalNatural Science Foundation of China (NSFC)“Study on Composite Regeneration andMulti-fields Synergic Mechanism of the Filtering Body on Diesel Particulate Filterand Its Optimization (51176045)” and “Analysis on Failure of Porous Medium Filterof Diesel Particulate Filter and its Failure Mechanism (51276056)”, and thesubproject of National “863” Program “Manufacture of High Efficiency&LowEmission Diesel (2008AA11A116)”. The mechanisms of field synergy and compositeregeneration, and its optimal control of DPF have been studied using numericalsimulation and experiment. The main innovative points are expressed as follows:(1) Aimed at the regenerative property of DPF filter containing MnOx-CeO2catalysts, physical and mathematical calculation models were built based on DPF withthe catalysts. In combination with bench tests, a research was conducted on theignition temperature of5different concentrations of MnOx-CeO2catalysts;meanwhile, an activity evaluation was made on these catalysts of differentconcentrations.(2) Based on the mechanism of transient composite regeneration for DPF, athree-dimensional simulation model of DPF was established. The change pattern andproperty of temperature gradients and seepage velocity vectors at different timesduring the ignition process of DPF were studied. In pertinence to the simulation resultof the ignition process, a synergy analysis of the composite regenerative performanceof DPF was conducted using multi-field synergy principle, obtaining the regeneratingtime and the optimal areas of regenerative ignition in correspondence to the bestsynergy between velocity field and temperature field throughout the ignition processof DPF.(3) The cosine value of fuzzy membership and Euclidean distance formula wereadopted to build a fuzzy grey correlation analysis model based on factors influencingcomposite regeneration of DPF. Based on a3D simulation experiment of DPF, the fuzzy grey correlation analysis was conducted on the importance degree of thecharacteristic indices affecting the composite regenerative performance of DPF.Meanwhile, on the basis of computation of the fuzzy grey correlation analysis, theeffectiveness index of the overall performance of composite regeneration of DPF wasanalyzed, reaching the conclusion that the dose of MnOx-CeO2catalysts, among theindicators of characteristic performance of composite regeneration of DPF, have thegreatest influence on regenerating time, whereas oxygen concentration in exhaust gasand discharge temperature has the greatest influences on the peak temperature ofregeneration and regeneration efficiency, respectively. Moreover, the greatest effecton overall performance of composite regeneration of DPF comes from regeneratingtime, followed by regeneration efficiency, and peak temperature of regeneration hasthe smallest effect on efficacy.(4) A single predictive value of different predictive models was taken as the primitiveinput value of the function link neural network. After the fuzzy function link neuralnetwork fit necessary-and-sufficient condition was determined to meet necessaryrequirements, a regenerating time forecasting model of DPF filter based on fuzzyself-adaptive weight-variable function link neural network was built. The result ofapplication suggested that this forecasting model was highly precise and fewer inerrors. Meanwhile, the factors influencing composite regenerating time of DPF wereanalyzed and verified.(5) Taking fields synergic DPF as a research object, a genuine target function wasfigured out about microwave energy consumption during the composite regenerativeprocess of DPF. The calculus of variations in functional theories was adopted to solvethe genuine target function during the regenerative process, obtaining the optimal pathof heating rate of exhaust gas as well as the optimal control over microwave energyconsumption rate during the regenerative process. The results of simulation andapplication consistently demonstrated that the terminal point of compositeregeneration was accurately forecasted and that the DPF had high compositeregeneration efficiency with a significant decline of microwave energy consumption. |
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