温差发电器的特性分析及其基于发动机排气余热能回收利用的研究

发布时间：2018-04-27 07:21

本文选题：温差发电器 + 内燃机排气　；参考：《天津大学》2014年博士论文

【摘要】：将内燃机的余热能回收再利用是提高总能效率、降低油耗和CO2排放的一个有效途径。温差发电器(Thermoelectric generator,TEG)利用了半导体热电材料将热能直接转化为电能的特性,具有无机械运动、运行安静、小型轻便和对环境无污染等优点,在内燃机排气的余热能回收利用领域具有重要的应用价值和前景。本文采用了模型研究和实验研究的方法,进行了温差发电器的特性分析,及其基于发动机排气余热能回收利用的研究。从单电偶臂对的分析,扩展到多个电偶臂对串联成的温差发电器,从稳态模型递进至瞬态模型,然后将模型进行横向扩展,与整车行驶工况相耦合,分析瞬态工况以及一些典型的车辆行驶工况下发电器的性能,并进行了基于发动机排气余热能利用的温差发电器的台架实验。论文主要工作如下:(1)利用CFD(Computational Fluid Dynamics)工具,基于不同的守恒方程表述和边界条件划分,对同一电偶臂对(即相同的计算域)建立了两种三维数值模型,并指出了前人文献中相关模型的不完善之处,对温差发电的深层现象进行研究,以理解热电转换过程。并对电偶臂的形状进行优化设计,采用新结构的电偶臂对,可以更好的将热电材料匹配工作温度区间,以提高材料的功率密度。CFD模型可以直观的展示不同工况下电偶臂对内部的温度分布和电势分布云图。(2)对于由多个电偶臂对组成的温差发电器,通过实验的方法,研究了冷却方式、冷热源温度、装配压力、组合方式和负载电阻等因素对发电性能的影响,为CFD模拟和仿真计算提供数据支撑和验证。重点研究了温差发电的瞬态行为,在温差发电器的启动过程中发现了过冲现象,该现象是由于冷、热端与环境的温度变化速率不一致造成的,定义过冲度这一概念对其进行表述。(3)将单电偶臂对的模型,扩展到多个电偶臂对串联成的温差发电器模型,建立了基于发动机排气余热能利用的温差发电器的瞬态模型,并对求解过程中模型的时间步长和空间步长中的变化给出了介绍。对于其内部不同区域的守恒方程和边界条件作了细致的分析,根据温度守恒和热流密度守恒,建立了四个界面的热学边界条件;给出了五种启动模式的电学边界条件,分别是恒流模式、恒压模式、最大功率模式、恒功率大电流和恒功率小电流启动模式,分别比较了这五种模式下发电器的稳态性能和瞬态行为,分析了启动过程中,电偶臂内部的温度、电势和热流变化,对发电性能达到额定功率的时间进行了研究。同时,考虑了车速和环境温度等外部因素对发电性能的影响。(4)将发电器的瞬态模型进行扩展,与整车的行驶工况模型相耦合,分析了加、减速工况、阶梯车速工况和往复车速工况中发电器的性能变化情况。选取了三种典型的车辆行驶工况进行分析,分别是10-15、NEDC(New European Driving Cycle)和UDDS(Urban Driving Dynamometer Schedule)工况,代表了日本、欧洲和美国的典型工况,比较了温差发电器在具体行驶工况中,对于车辆输出功率的提升。(5)进行了温差发电器的发动机台架实验。以某1.5 L汽油机的排气为热源,以恒温水箱供给的循环水为冷源,观察了不同工况下,发电器的稳态性能以及变工况阶段的瞬态行为。对变工况下,发电性能变化的时间量纲进行确定,为基于发动机排气余热能的温差发电器的瞬态模型的变工况数据提供了实验基础。
[Abstract]:The recovery and reuse of the afterheat energy of the internal combustion engine is an effective way to improve the total energy efficiency and reduce the fuel consumption and CO2 emission. The thermoelectric generator (Thermoelectric generator, TEG) uses the semiconductor thermoelectric materials to convert the heat energy into the electric energy directly, and has the advantages of no mechanical motion, quiet operation, small light and no pollution to the environment. It has important application value and prospect in the field of waste heat recovery and utilization in the exhaust gas of internal combustion engine. This paper adopts the method of model research and experiment research, and carries out the characteristics analysis of the thermoelectric generator and the research based on the recovery and utilization of the exhaust heat energy of the engine. From the analysis of the single couple arm pair, it extends to the series of couple arms to the series. The thermoelectric generator is passed from the steady state model to the transient model, then the model is extended horizontally and coupled with the driving condition of the whole vehicle. The transient condition and the performance of some typical electric appliances under the typical vehicle driving condition are analyzed. The paper has carried out the bench test of the thermoelectric generator based on the exhaust energy of the engine. The following work is as follows: (1) using the CFD (Computational Fluid Dynamics) tool, based on the different conservation equation expression and boundary condition division, two three dimensional numerical models are established for the same electric couple arm pair (i.e. the same computing domain), and the imperfections of the related models in the previous literature are pointed out, and the deep phenomenon of the thermoelectric power generation is studied. To understand the thermoelectric conversion process, and to optimize the shape of the electric couple arm, with the new structure of the couple arm pair, the thermoelectric material can be better matched to the working temperature range and the power density.CFD model of the material can be used to display the temperature distribution and the potential distribution of the electric couple arm in different working conditions. (2) for the different working conditions, the temperature distribution and the potential distribution of the electric potential can be displayed. (2) The effects of cooling mode, cold and heat source temperature, assembly pressure, combination mode and load resistance on the power generation performance are studied by experiments, and the data support and verification are provided for CFD simulation and simulation calculation. The transient behavior of temperature difference generator is studied. The phenomenon of overshoot is found in the dynamic process, which is caused by the inconsistency of the temperature change rate of the cold, the hot end and the environment. The concept of overshoot is defined. (3) the model of the single couple arm pair is extended to the thermoelectric generator model in series with a number of galvanic arms, based on the use of the exhaust heat energy of the engine exhaust. The transient model of the thermoelectric generator is introduced and the changes in the time step and the spatial step of the model are introduced. The conservation and boundary conditions of the different regions are carefully analyzed. According to the conservation of the temperature and the heat flux, the thermal boundary conditions of the four interfaces are established, and five kinds of start-up are given. The electrical boundary conditions of the model are constant current mode, constant pressure mode, maximum power mode, constant power large current and constant power small current starting mode. The steady-state performance and transient behavior of the five modes are compared respectively. The temperature, potential and heat flux in the electric couple arm are analyzed in the starting process, and the power generation performance is reached. The time of rated power is studied. At the same time, the influence of external factors, such as speed and ambient temperature, on the performance of power generation is considered. (4) the transient model of the generator is expanded to be coupled with the driving condition model of the whole vehicle, and the performance changes of the generator are analyzed in addition, deceleration working conditions, staircase speed conditions and reciprocating speed conditions. Three typical vehicle driving conditions are analyzed, which are 10-15, NEDC (New European Driving Cycle) and UDDS (Urban Driving Dynamometer Schedule), representing the typical working conditions of Japan, Europe and the United States. Compared with the temperature difference generator in the specific driving conditions, the output power of the vehicle is raised. (5) the temperature is heated. The engine bench test of a differential generator, taking the exhaust of a 1.5 L gasoline engine as the heat source, taking the circulating water supplied by the constant temperature water tank as the cold source, observed the steady state performance of the generator and the transient behavior in the variable working condition under the different working conditions. The time interval of the change of the power generation performance under the variable condition was determined, based on the exhaust heat of the engine exhaust. The transient data of the thermoelectric generator can provide experimental basis for the off design data.

【学位授予单位】：天津大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TM913

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