液化天然气（LNG）汽车冷能和尾气余热的温差发电系统研究

发布时间：2018-03-03 04:03

本文选题：LNG汽车　切入点：温差发电模块　出处：《太原理工大学》2015年硕士论文　论文类型：学位论文

【摘要】：近年来,我国汽车产业取得了飞速地发展，汽车已然成为人们日常生活必不可少的交通工具，随着汽车保有量的增加，导致燃料的需求不断增加，同时汽车排放对环境造成的污染也不容忽视。为应对这一系列问题,各国政府不断完善限制机动车对环境污染的法律法规,各种汽车先进技术的研究单位也投资大量资金和科研力量进行新型能量转换装置的开发。利用汽车废热进行温差发电的系统成为各大企业、高校及其研究机构的关注热点，该装置可以将汽车排放的尾气中的废热转换为电能,有效地解决了内燃机对燃料燃烧能量的利用率低的问题，从另一个角度可以视为提高了汽车的燃油利用率,而且进气温度的升高可以减少部分有害排气的排放量,具有很好的应用前景和重要的社会价值。本文在对国内外LNG汽车方面研究分析的基础上,发现液化天然气（LNG）汽车作为一种新能源汽车受到各国政府的大力推广，但目前利用汽车尾气废热的温差发电系统存在的输出功率小、转换效率低等缺点,而LNG汽车自身具备的低温冷源为提高温差发电装置的输出功率提供了良好的条件，但需要对温差发电装置在LNG汽车上的应用可靠性及性能进行分析，首先对装置中与废热回收利用率紧密相关的换热器进行流-固耦合分析,仿真能够通过多种方式来改善温差发电模块安装表面的温度分布情况，，分析其对传统排气系统的影响，为增大温差发电模块冷热端的温差提供有效途径。以对流体力学的学习为前提,利用UG建立了三种不同内部结构的尾气温差发电装置换热器三维模型,运用ANSYS Fluent有限元分析软件进行多物理场的耦合分析,据此分析汽车尾气温差发电装置换热器通道内的高温气体流动与传热过程。通过分析相关机构的研究方法，获得对应的有限元模型和边界条件,经过软件计算收敛后得到了三种换热器温度、压力和流场仿真结果,对比光滑表面、“一”字肋片和“人”字肋片三种换热器通道仿真结果，分析得到三者中最优的换热器结构，得到其温差发电模块安装表面的温度分布云图，确定合理的模块安装方式，为后续的仿真计算提供了基础条件，并考虑接触热阻对模块端面温度的影响，从接触热阻影响因素着手对接触传热进行优化。另外，本文对该汽车尾气温差发电装置进行热-固和热-电耦合分析,加载换热器热-流耦合分析得到的温度载荷,分析得到了汽车尾气温差发电器件的应力和应变云图，并与以冷却水为冷源的温差发电单元仿真结果进行对比，结果表明,本文所研究的汽车尾气温差发电装置满足使用要求,可以为今后的相关研究提供参考。
[Abstract]:In recent years, the automobile industry of our country has made the rapid development, the automobile has already become the essential vehicle of people's daily life, with the increase of the automobile quantity, the demand for fuel is increasing constantly. At the same time, the pollution caused by automobile emissions to the environment should not be ignored. In order to deal with this series of problems, the governments of various countries have constantly perfected the laws and regulations that limit the pollution caused by motor vehicles to the environment. All kinds of advanced automobile technology research units also invest a lot of funds and scientific research forces to develop new energy conversion devices. The system of thermoelectric power generation using automobile waste heat has become the focus of attention of enterprises, universities and their research institutions. The device can convert the waste heat from the exhaust gas of the automobile into electric energy. It effectively solves the problem of low utilization rate of fuel combustion energy in internal combustion engines. From another angle, it can be regarded as increasing the fuel efficiency of vehicles, and the increase of intake air temperature can reduce some harmful emissions. It has good application prospect and important social value. Based on the research and analysis of LNG vehicles at home and abroad, this paper finds that LNG vehicles as a new energy vehicle are popularized by the governments of various countries. However, the thermal power generation system using waste heat from automobile exhaust has some disadvantages, such as low output power, low conversion efficiency and so on. However, the low temperature cold source of LNG vehicle provides a good condition for improving the output power of thermoelectric device. However, it is necessary to analyze the reliability and performance of thermoelectric equipment in LNG vehicles. Firstly, the fluid-solid coupling analysis of heat exchangers which are closely related to the utilization ratio of waste heat recovery is carried out. The simulation can improve the temperature distribution on the installation surface of thermoelectric module in many ways, and analyze its influence on the traditional exhaust system. In order to increase the temperature difference between the cold and hot ends of the thermoelectricity generation module, a three-dimensional heat exchanger model of the tail gas thermoelectric unit with three different internal structures is established by using UG on the premise of the study of fluid mechanics. The coupling analysis of multiple physical fields is carried out by using ANSYS Fluent finite element analysis software, according to which the high temperature gas flow and heat transfer process in the heat exchanger channel of the automobile exhaust thermoelectric unit are analyzed. The corresponding finite element model and boundary conditions are obtained. The simulation results of temperature, pressure and flow field of three kinds of heat exchangers are obtained after the convergence of the software. The simulation results of three kinds of heat exchangers with smooth surface, "one" rib and "human" fin are compared. The optimal heat exchanger structure is obtained, the temperature distribution cloud diagram of the installation surface of the thermoelectricity generation module is obtained, and the reasonable installation mode of the module is determined, which provides the basic conditions for the subsequent simulation calculation. Considering the influence of contact thermal resistance on the end surface temperature of the module, the contact heat transfer is optimized from the contact thermal resistance factors. In addition, the thermo-solid and thermo-electric coupling analysis of the vehicle exhaust thermoelectricity generator is carried out, and the temperature load obtained from the thermal-flow coupling analysis of the heat exchanger is used to obtain the stress and strain cloud diagram of the thermoelectric device. The results are compared with the simulation results of thermoelectric units with cooling water as the cold source. The results show that the thermoelectric device of automobile exhaust gas in this paper can meet the requirements of application and can be used as a reference for the related research in the future.
【学位授予单位】：太原理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：U463.6;TM913

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