内燃机余热回收温差发电器多参数数值模型及优化设计

发布时间：2018-06-13 16:30

本文选题：温差发电器 + 数值模型　；参考：《天津大学》2016年硕士论文

【摘要】：能源与环境是人类面临的重大课题,开发新能源和充分利用低品位能源、废热能源具有重大意义。内燃机所产生的能量中,大约有30%的能量以废热形式由尾气排出,温差发电技术可以利用半导体热电转换材料直接将热能转换为电能,容易在汽车发动机上进行布置且环境友好,可以有效回收内燃机排气中的余热。鉴于国内、外在温差发电器建模方面存在的缺陷,本文基于热力学定律和FLUENT UDF基本理论,建立多参数三维温差发电器数值模型。论文主要工作如下:首先建立多参数三维温差发电单偶数值模型,此模型所考虑参数包括变物性参数、几何参数、维度、陶瓷片、外部温度和流动参数、可逆参数和不可逆参数。其中,可逆参数主要包括塞贝克效应和帕尔贴效应,不可逆参数包括傅立叶效应、焦耳效应、汤姆逊效应、空气间隙热损失、接触热阻和接触电阻。其次,验证了本文所建数值模型正确性。分析不同热端温度和不同对流换热系数条件下,温差发电单偶性能随电流的变化趋势;重点分析变物性参数、汤姆逊效应、空气间隙热损失对模型的影响。结果显示:输出功率和转化效率的变化趋势与之前的数学模型模拟结果相一致,但是,最大效率电阻并不符合之前的数学模型所得出最大效率电阻与内阻相等的结论,而是有一定的漂移;物性参数对数值模型的影响最大,不可忽略;考虑汤姆逊效应可以提高模型的精度;空气间隙热损失仅影响温差发电器的转化效率,而对输出功率的影响可以忽略。然后,基于所建模型,从温差发电单元的长度、截面面积影响两个方面,对温差发电单偶结构做出优化设计。结果显示:存在最优长度使得输出功率和转化效率均得到最优值;最大输出功率随横截面积的增大而增大,但转化效率随横截面积的增大而减小。最后,将温差发电单偶数值模型扩展到温差发电模块层面,利用该数值模型对温差发电模块与热交换器进行了模拟分析和优化设计,为温差发电技术回收发动机排气余热提供依据。结果显示:根据换热器表面温度合理的布置不同材料的温差发电模块,可以提高输出功率。
[Abstract]:Energy and environment are important tasks for human being. It is of great significance to develop new energy sources and make full use of low grade energy and waste heat energy. About 30% of the energy generated by internal combustion engines is discharged by exhaust gas in the form of waste heat. Thermoelectric power generation technology can directly convert heat energy into electric energy by using semiconductor thermoelectric conversion materials. Easy to arrange on the automobile engine and environment friendly, can effectively recover the waste heat in the exhaust gas of the internal combustion engine. In view of the defects in the modeling of the external thermoelectric generator in China, based on the laws of thermodynamics and the basic theory of fluent UDF, the numerical model of the multi-parameter three-dimensional thermoelectric generator is established in this paper. The main work of this paper is as follows: firstly, a multi-parameter three-dimensional thermoelectric single-couple numerical model is established. The parameters of the model include variable physical parameters, geometric parameters, dimensions, ceramic chips, external temperature and flow parameters. Reversible and irreversible parameters. Among them, reversible parameters mainly include Sebek effect and Partier effect, irreversible parameters include Fourier effect, Joule effect, Thomson effect, air gap heat loss, contact thermal resistance and contact resistance. Secondly, the correctness of the numerical model is verified. The variation trend of single couple performance with current under different hot end temperature and different convection heat transfer coefficient is analyzed, and the effects of variable physical parameters, Thomson effect and air gap heat loss on the model are analyzed. The results show that the variation trend of output power and conversion efficiency is consistent with the simulation results of previous mathematical models, but the maximum efficiency resistance does not accord with the conclusion that the maximum efficiency resistance and the internal resistance obtained from the previous mathematical model are equal. But there is a certain drift; physical parameters have the greatest influence on the numerical model, can not be ignored; considering the Thomson effect can improve the accuracy of the model; air gap heat loss only affects the conversion efficiency of thermogenerators, The effect on output power can be neglected. Then, based on the model, the structure of thermoelectric unit is optimized from two aspects: the length of thermoelectric unit and the influence of cross-section area. The results show that the maximum output power increases with the increase of cross-sectional area, but the conversion efficiency decreases with the increase of cross-sectional area. Finally, the single and even numerical model of thermoelectricity generation is extended to the thermoelectricity generation module, and the simulation analysis and optimization design of the thermoelectricity generation module and heat exchanger are carried out by using the numerical model. It provides the basis for the recovery of engine exhaust heat by thermoelectric technology. The results show that according to the surface temperature of heat exchanger, the output power can be increased if different materials are reasonably arranged.
【学位授予单位】：天津大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TM913;TK403

【参考文献】