本文選題：直接甲醇液流燃料電池　切入點：二維模型　出處：《天津大學》2014年碩士論文　論文類型：學位論文

【摘要】：直接甲醇燃料電池（DMFC）的陰極水淹問題，甲醇滲透問題，以及貴金屬催化劑的成本問題，是DMFC商業(yè)化的主要障礙。直接甲醇液流燃料電池（DMRFC）是采用液流電池陰極替代傳統(tǒng)直接甲醇燃料電池（DMFC）陰極的一種新型燃料電池。由于DMRFC陰極使用Fe3+/Fe2+氧化還原電對，不使用貴金屬催化劑，降低了電池成本，陽極和陰極都為液體進料，避免了陰極水淹和甲醇滲透氧化等問題。 目前通過實驗手段來獲得DMRFC內(nèi)部的物理化學過程，如工作溫度分布、壓強分布、物質(zhì)濃度分布、電流密度分布等比較困難，，而且代價昂貴，實驗周期較長。采用模擬仿真方法成本低，時間短，可以依據(jù)不同的實際需要改變運行條件，來獲得完整的模擬數(shù)據(jù)。通過對DMRFC的模擬，可以加深對燃料電池內(nèi)部工作機理的認識，從而根據(jù)實際的需求來優(yōu)化電池的結(jié)構(gòu)和確定電池的最佳工作條件,具有重要的指導意義。 本文以DMRFC單電池為研究對象，依據(jù)有限元方法，使用COMSOL模擬仿真軟件，分別建立了DMRFC的二維單相模型和二維兩相模型。模型考慮了流體流動，物質(zhì)傳輸，電荷傳輸和電化學反應(yīng)等過程，模擬區(qū)域包括陽極流道，陽極擴散層，陽極催化層，質(zhì)子交換膜和陰極電極。 DMRFC二維單相模型中，忽略陽極產(chǎn)生二氧化碳氣體的影響，考慮甲醇和水通過質(zhì)子交換膜的滲透，通過耦合電荷守恒方程，質(zhì)量守恒方程，物種守恒方程和動量守恒方程，研究了不同操作條件和結(jié)構(gòu)參數(shù)對電池性能的影響。研究結(jié)果表明電池運行溫度，甲醇和Fe3+濃度，陰極電極厚度對電池性能影響很大。隨著陰極電極厚度的減小，電池運行溫度的升高，電池的性能將顯著增加；當甲醇濃度從2M升高到16.7M時，電池性能不斷提高，當甲醇濃度繼續(xù)提高時，電池性能開始降低；提高陽極流量不影響電池性能；提高陰極流量和Fe3+濃度將有利于提高電池性能。在DMRFC二維單相模型基礎(chǔ)上，通過考慮陽極產(chǎn)生二氧化碳氣體的影響，建立了DMRFC二維兩相模型，研究了二氧化碳氣體濃度和壓強在電池內(nèi)部的分布。研究結(jié)果表明二氧化碳濃度沿陽極流道方向不斷增加；二氧化碳氣體壓強沿陽極催化層到陽極流道方向不斷降低；減少陽極擴散層的厚度、增加陽極催化層的厚度，增大陽極擴散層和催化層的孔隙率，提高陽極和陰極流量，有利于提高電池的性能，當陰極Fe3+濃度低于1.41M時，提高Fe3+濃度能顯著提高電池性能，當陰極Fe3+濃度高于1.41M時，F(xiàn)e3+濃度對電池性能影響不大。
[Abstract]:The cathodic flooding, methanol permeation, and the cost of noble metal catalysts for DMFCs, Direct methanol liquid flow fuel cell is a new type of fuel cell which uses liquid flow cell cathode instead of traditional direct methanol fuel cell cathode. Because DMRFC cathode uses Fe3 / Fe 2 redox electric pair, direct methanol liquid flow fuel cell is a new type of fuel cell. Without noble metal catalyst, the cell cost is reduced, the anode and cathode are liquid feed, and the problems of cathodic flooding and methanol permeation oxidation are avoided. At present, it is difficult to obtain physical and chemical processes in DMRFC by experimental means, such as working temperature distribution, pressure distribution, material concentration distribution, current density distribution, and so on. The experiment period is long. The simulation method is of low cost and short time. The simulation data can be obtained by changing the operating conditions according to different actual needs. It can deepen the understanding of the internal working mechanism of the fuel cell, thus optimize the structure of the battery and determine the optimal working conditions of the battery according to the actual demand, which has important guiding significance. Based on the finite element method and COMSOL simulation software, the two-dimensional single-phase model and two-dimensional two-phase model of DMRFC single cell are established in this paper. The model takes into account the fluid flow and mass transfer. The simulated regions include anodic channel, anodic diffusion layer, anodic catalytic layer, proton exchange membrane and cathode electrode. In the DMRFC two-dimensional single-phase model, the influence of anode producing carbon dioxide gas is ignored, and the permeation of methanol and water through the proton exchange membrane is considered, and the coupling charge conservation equation, mass conservation equation, species conservation equation and momentum conservation equation are considered. The effects of different operating conditions and structure parameters on the performance of the battery are studied. The results show that the operating temperature, concentration of methanol and Fe3, and the thickness of cathode electrode have great influence on the performance of the battery. With the increase of the operating temperature of the battery, the performance of the battery will increase significantly, when the concentration of methanol increases from 2m to 16.7 M, the performance of the battery will continue to improve, and when the concentration of methanol continues to increase, the performance of the battery will begin to decrease, and the increase of the anode flow rate will not affect the performance of the battery. Increasing cathode flow rate and Fe3 concentration will help to improve the performance of the cell. Based on the DMRFC two-dimensional single-phase model, a two-dimensional DMRFC two-phase model is established by considering the effect of anode generation of carbon dioxide gas. The distribution of carbon dioxide concentration and pressure in the cell is studied. The results show that the concentration of carbon dioxide increases along the anodic channel direction, and the pressure of carbon dioxide gas decreases from the anode catalytic layer to the anode channel. Reducing the thickness of anode diffusion layer, increasing the thickness of anode catalytic layer, increasing the porosity of anode diffusion layer and catalytic layer, and increasing anode and cathode flow rate are beneficial to improve the performance of the battery. When the concentration of cathode Fe3 is lower than 1.41 M, Increasing the concentration of Fe3 can significantly improve the performance of the battery. When the concentration of cathode Fe3 is higher than 1.41m, the concentration of Fe3 has little effect on the performance of the battery.
【學位授予單位】：天津大學
【學位級別】：碩士
【學位授予年份】：2014
【分類號】：TM911.4

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