汽车尾气余热回收热电发电

发布时间：2018-01-26 00:01

本文关键词： 热电发电器汤姆逊效应附加热阻锯齿错列肋片净输出功率泡沫金属　出处：《天津大学》2014年硕士论文　论文类型：学位论文

【摘要】：随着经济的快速发展,中国的汽车数量平均以每年超过1100万辆的速度快速增加。然而,当前的汽车燃料燃烧所释放出的热量中只有25%左右能被有效利用,超过30%的热量均以废热的形式随汽车尾气直接排放到环境中。因此,若能回收和再利用这一部分能量,将对提高汽车发动机效率,减少环境污染具有非常重要的意义。热电发电是一种可以将热能直接转化为电能进行发电的全固态绿色环保的能量转换方式,具有性能稳定、无噪声、使用寿命长等优点,在汽车尾气余热回收利用方面具有其独特的优势和良好的应用前景。针对汤姆逊效应及陶瓷板、金属导流片、接触表面产生的附加热阻等影响热电模块性能的因素,本文通过数值模拟计算的方法,对比研究了考虑与不考虑汤姆逊效应及附加热阻时热电模块的性能。结果表明:相比不考虑汤姆逊效应和附加热阻,当热电模块的工作电流比较大时,考虑汤姆逊效应和附加热阻,热电模块的输出功率、热电转化效率及?效率均显著减小。且随着热端温度的增加,考虑和不考虑汤姆逊效应及附加热阻两者的最大输出功率差不断增大;最大热电转化效率差先增大后减小;最大?效率差不断减小。此外,强化热端换热是提高热电发电器性能的主要手段之一。针对强化热端换热带来汽车尾气压降增加这一问题,本文提出了采用热电发电器的总输出功率减去为维持尾气压降不增加所需的泵功后的净输出功率为优化标准,通过数值模拟的方法,分别研究了保持热端换热器外部尺寸不变的情况下,热端采用锯齿错列肋片及泡沫金属强化换热时,热电发电器的性能变化。结果表明:采用锯齿错列肋片增强热端换热效果时,存在最佳的肋片间距和肋片厚度使得热电发电器的净输出功率达到最大值。采用泡沫金属增强热端换热时,同一种泡沫金属材料,孔隙率越低,孔密度越小,热电发电器的净输出功率越大。相比于锯齿错列肋片,采用多孔介质材料增强热端换热时,热电发电器虽可获得更大的总输出功率和热电转化效率,但由于汽车尾气流过热端换热器时的压降过大,净输出功率甚至为负值。为此,作为后续工作,本文提出具有热电发电和催化转化两个功能的新型热电发电器,以期避免汽车尾气流过整个排气系统时产生过大压降。
[Abstract]:With the rapid development of the economy, the number of cars in China is increasing rapidly at an average rate of more than 11 million vehicles a year. At present, only about 25% of the heat released from automotive fuel combustion can be effectively utilized, and more than 30% of the heat is discharged directly into the environment with the automobile exhaust gas in the form of waste heat. If this part of energy can be recovered and reused, it will improve the efficiency of automobile engine. It is very important to reduce environmental pollution. Thermoelectric power generation is a kind of all-solid-state green energy conversion mode which can directly convert heat energy into electric energy for power generation. It has stable performance and no noise. With the advantages of long service life and so on, it has its unique advantages and good application prospects in the recovery and utilization of automobile exhaust waste heat, aiming at Thomson effect, ceramic plate and metal diversion sheet. The additional thermal resistance produced by the contact surface affects the performance of the thermoelectric module. In this paper, the method of numerical simulation is used to calculate the performance of the thermoelectric module. The performance of the thermoelectric module considering and without Thomson effect and additional thermal resistance is studied. The results show that compared with not considering the Thomson effect and the additional thermal resistance, when the working current ratio of the thermoelectric module is larger. Considering Thomson effect and additional thermal resistance, thermoelectric module output power, thermoelectric conversion efficiency and? With the increase of the temperature at the hot end, the maximum output power difference between considering and not considering the Thomson effect and the additional thermal resistance increases, the difference of the maximum thermoelectric conversion efficiency increases first and then decreases, and the maximum power difference decreases with the increase of the temperature at the hot end. In addition, the enhancement of heat transfer at the hot end is one of the main means to improve the performance of the thermoelectric generator. In this paper, the optimization standard of the total output power of the thermoelectric generator minus the pump power needed to maintain the pressure drop of the tail gas is proposed as the optimization standard, and the method of numerical simulation is used. Under the condition of keeping the external dimension of the hot end heat exchanger unchanged, the heat transfer strengthened by the saw teeth staggered rib and foam metal was studied respectively at the hot end. The performance of thermoelectric generator is changed. The results show that the effect of heat transfer at the hot end is enhanced by using the jagged staggered ribbed blade. The optimum rib spacing and thickness make the net output power of the thermoelectric generator reach the maximum. The lower the porosity, the smaller the pore density of the same metal foam material when the hot end heat transfer is enhanced by foam metal. The larger the net output power of the thermoelectric generator is, the greater the total output power and the efficiency of thermoelectric conversion can be obtained when the heat transfer at the hot end is enhanced by using porous dielectric material, compared with the jagged staggered fin. However, the pressure drop of the heat exchanger at the overheated end of the automobile exhaust flow is too large, and the net output power is even negative. Therefore, as a follow-up work, a new type of thermoelectric generator with the functions of thermoelectric power generation and catalytic conversion is proposed in this paper. In order to avoid excessive pressure drop when the exhaust gas flows through the whole exhaust system.
【学位授予单位】：天津大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：U463.6;TM617

【参考文献】