摘要
基于热电效应和多孔介质的特性,研制成的多孔介质热电材料温差发电器件,可以安装在汽车排气管内部,通过对流传热将汽车高温尾气的一部分能量转化为电能。多孔介质温差发电器件具有无运动部件、无噪声、容易微型化、易于控制等优点,由于多孔介质的特性以及排气管设计等原因,可以在排气管内建立起比较大的温度梯度,提高温差发电器的发电功率。为了更好了解温度梯度的分布、发电功率的大小,可以更好利用尾气的热能,需要对排气管的流场和温度场进行数值模拟。
本文首先建立四个不同的汽车排气管物理模型。然后针对不同的排气管建立不同的三维单温度数学模型,区分为无旋和有旋数学模型。利用数值热传学原理,采用SIMPLE算法,对排气管的流场进行数值模拟,在有旋模型中使用带旋流修正的数学模型。接下来对流场、温度场的模拟结果进行比较分析,并发现带旋流修正的数学模型,其出口温度更加趋近于真实情况。最后由温度梯度的特点,确定多孔介质热电材料安插方式,计算排气管内多孔介质热电材料的发电功率,并对不同区域内发电功率进行比较,发现带旋流修正的数学模型在发电功率上更加科学合理。
借助仿真程序可以对不同工况下或者安装不同参数的多孔介质温差发电器的情形进行模拟,可对排气管内传热情况进行分析,其结论对多孔介质温差发电器件的研发与安装具有借鉴意义。
A new system for converting heat which came from car exhausts into electric power was proposed on basis of convection heat transfer in a thermoelectric porous medium. The elements are thermoelectric effect and character of porous medium. The thermoelectric generator by the steep temperature gradient in porous-medium exhaust pipe has several advantages: there are no moving parts and there is no noise, it can be made into micro size and it can be control easily. In exhaust pipe, a trapezoidal temperature distribution was established along y axis because of porous element and the exhaust pipe. The thermoelectric generator increased power generation as a result of this temperature gradient. In order to better research the distribution of the temperature gradient and the power generation, the flow field and temperature field in the exhaust pipe must be numerical simulated carefully.
Above all, four different physical models of a car exhaust pipe were established. Second, two different three-dimensional mathematical models of a single temperature were established for two different exhaust pipes. One mathematical model is non-rotational flow model, the other one is rotational flow model. The gas flow filed of exhaust pipe has been simulated numerically with SIMPLE method. A mathematical model Updating by rotational flow used in rotational flow model. Afterwards, the velocities and temperature are compared. It is found that temperature on outlet is closer to the real situation by mathematical model updating by rotational flow. Finally, the placement of thermoelectric materials in porous medium was determined by the character of the temperature gradient. The power generation was computed. Different power generation in different area compared with each other. It is found that power generating is more appropriate by mathematical model updating by rotational flow.
By the simulating method, we can simulate the heat transfer by different intake flows and the different thermoelectric generator by porous medium with different parameters. The simulate results are very helpful for optimizing the thermoelectric generator.
引文
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