【作者】 陈后涛；

【导师】 侯献军； 雷本刚； 袁晓红；

【作者基本信息】 武汉理工大学 ， 车辆工程， 2012， 硕士

【摘要】 自汽车诞生至今,汽乍技术经历了一个世纪的发展,汽车新技术正在向节能环保方向快速发展。当前研发汽车新技术都要在车辆的经济环保方面予以考虑,汽车燃油消耗和排放性能是国际汽车市场竞争的重要指标。在车用发动机节能环保技术登峰造极的背景下,研发新型车载节能技术可进一步提高车辆节能性能。汽车尾气温差发电技术是一项新型车载能量回收技术,该技术通过温差发电装置将尾气中的部分废热转换为电能。国内相应的研究刚刚起步,本文通过对温差发电装置构造和工作环境的研究,提出了对该装置进行热应力分析的课题。本文主要研究温差发电装置的热应力分布,研究方法是对温差发电装置的有限元模型进行CAE分析。先使用Hypermesh对装置的几何模型进行前处理,完成几何模型离散之后,使用Fluent计算出的气箱壁面温度和恒定的水箱壁面温度作为边界条件计算出离散模型的温度场。再将计算出的温度场和装置的约束作为边界条件施加到热应力计算模型上,使用ANSYS计算出离散模型的热应力分布。计算结果表明,在施加约束处有较为明显的应力集中点,最大应力值达到320MPa。其中X方向的分应力最小,但水箱应力值较大；Y向分应力值很均匀；Z向分应力有明显的应力集中,且应力梯度很大。固定横梁的位置影响了水箱表面的应力分布,固定横梁在安装螺栓处有应力集中点。热电模块阵列边缘有明显的应力集中点。针对装置的热应力分布提出消除气箱应力集中区域的优化目标。分析了约束对温差发电装置热应力的影响,约束模型中部一个节点的六个自由度,在相同的边界条件下计算出了模型的热应力分布。计算表明约束优化明显的消除了应力集中,模型综合应力和各向压应力值都有显著下降,拉应力只在X向有较小增加。为消除气箱棱边的应力集中区域将气箱的原棱边结构改为圆角过渡,在相同的壁面温度和约束下计算应力场。分析结果表明,优化后气箱的综合应力值、X向分应力和Y向分应力的最大值减小都较小,但Z向分应力减小了36.1MPa,基本消除了气箱的应力集中区域。另外,合理的选择箱体材料也可以减小装置的热应力。本文采用温差发电装置能承受的最高温度作为应力计算的温度载荷,得出装置的最大稳态热应力分布,提出的热应力优化方案优化效果显著。研究表明装置不合理的安装固定会带来严重的热应力集中问题。更多还原

【Abstract】 The vehicle industry has already developed for a century since the first car of the world has been made, and the new vehicle technology keep developing and promoting in the environmental and economical field. Now, the new technology applying to vehicles must consider the fuel consumption and air pollution. The most important norms in the international automobile market will be the energy saving and environment protecting. Therefore, in the era of the vehicle engine has the best perfonnance in energy saving, studying new board methods to make full use of the burning chemical energy could further improve vehicle energy-saving performance. Thermoelectric generator (TEG) is a new method which could turn west heat into electric power based on the material property. Domestic research on TEG technology just staring while overseas has been studied for years. After a study of the TEG device operation environment and the structure, I have put forward the analysis the thermal stress distribution on the TEG device.This paper mainly studies the thermal stress on the TEG set. The main content is calculating the stress field with the CAE software. The preliminary CAE treatment is handled by hyermesh, a very useful engineering software, extract the middle plane and discrete the model with finite elements, use the cooling water tank and air channel’s wall temperature provide by Fluent computed result as the boundary condition to compute the temperature distribution of the finite element model. Then set the temperature computed result and constraint conduction to the finite element model, analysis the thermal stress distribution by ANSYS. The thermal stress distribution result indicates a few stress concentration areas on the of the air channel, where the constraints have been set, and the X direction stress sharing has a uniform distribution with a smaller value, but the air channel get a bigger sharing. Y direction stress sharing has a smaller stress, obvious stress concentration areas with grate gradient in Z stress sharing. The fixing beams changed the stress distribute of the water tank surface, and several stress concentration points in the bolt position of the beam surface. Many stress concentration points on the boundary of thermoelectric module array.Through rationalization analysis, put forward an optimization objective decreasing the max stress on the air channel surface. In order to achieve the target, limit the nodes’s six degrees of freedom which locate on the middle of air channel. Keep other boundary all the s(?)me as the original model and calculate the thermal stress field. The stress concentration area show up around those limit nodes in the original model all has gone, the max stresses value have been decreased, as well as sharing of Y direction and Z direction. Only X direction sharing have increased a several MPa. In order to eliminating the stress concentration areas on the air channel surface, change the sharp edge to a round transition structure, calculate the thermal stress distribute with the same temperature and constraint condition. Max value of thermal stress and X direction share and Y direction share did not have changed much, but Z direction stress share decreased36.1MPa, therefore the optimization right on their target. In addition, reasonable selection of material also can reduce the thermal stress of the device.Applying the maximum temperature which the device could bearing as boundary condition, and obtain the extreme stress value on steady state. Geometry optimization got remarkable result. Research shows that devices unreasonable installation can bring serious thermal stress concentration problems.更多还原