基于PDA测量技术的螺旋翅片管外热态气固两相流动的特性研究

【作者】 韩志航；

【导师】 孙奉仲；

【作者基本信息】 山东大学 ， 热能工程， 2006， 硕士

【摘要】 在火力发电厂中，煤燃烧后形成的烟气中含有大量飞灰，灰粒通常保持固体状态，对于锅炉尾部烟道中的受热面带来了很严重的磨损，从而造成了大量的安全问题和经济损失。工程实践中发现，用螺旋翅片管受热面代替光管受热面是一种有效解决磨损问题的方法。山东大学能源与动力工程学院做过一些相关的研究工作，主要是单管翅片间浓度场和速度场的研究。本论文就是基于前面所做的工作，进一步研究热态条件下，不同翅片几何尺寸气固两相流在螺旋翅片管翅片间的流场特性，以摸清含灰气流在管束间的速度、浓度和粒径的分布规律。 要研究含灰烟气的流动特性，就必须掌握气固两相流的有关知识。本文从气固两相流的基本理论入手，分析了气固两相流中单个固相颗粒的受力与运动情况。在翅片间的流道里，对于质量微小的灰粒而言，只考虑重力，阻力，Magnus力和Saffman力的影响，其中当颗粒进入边界层后，Saffman力增大，托住颗粒使它不易沉到管壁；而当颗粒转速较大时，Magnus力可保证颗粒不向壁面沉降，这些力都减小了颗粒与壁面接触的机会，从而为减轻磨损提供了理论基础。 对换热元件磨损起主要作用的几个参数主要是固相颗粒的速度、浓度和粒径以及撞击角度。因此，除了理论研究以外，此次研究还在实验室建立了热态的烟气循环PDA实验台，对气固两相流流动特性进行了实验测量。为了与工程实际紧密结合，利用三维粒子动态分析仪(PDA)这种先进的激光测量仪器，首次测量了热态条件下翅片间5个有代表性的平面上的固相颗粒的速度、浓度和粒径分布，并分别对比测量了不同翅片高度和不同翅片间距的速度、浓度和粒径分布。 实验结果表明，螺旋翅片管翅间固相颗粒的速度、浓度、粒径都存在着比较规律的分布，在不同温度下、不同翅片间距和翅片高度均对上述几个参数的分布规律产生一定的影响。这些研究为今后进一步优化螺旋翅片管结构，提高其在工程实践中的应用价值提供了一定的借鉴意义。更多还原

【Abstract】 The coal is the mainly fuel of boiler in the power plant. There is a large amount of ash after coal’s combustion, which results that the heat-exchanger is abraded in the tail flue of the boilers in the power plant, further more, results in a great deal of the safety problems and the economy loss. Engineering practice witnesses that the heat-exchangers used of spiral finned tubes instead of that used of smooth tubes is an effective method lightening abrasion. Some research about the concentration and velocity between two adjacent fins has been observed by researchers of Energy Source and Power Engeering School of Shandong University. On the basis of the former research, this research’ purpose is observing the flow characteristic between two adjacent fins under the hot conditions and that of spiral finned tubes with different structures to find out the distribution of velocity, concentration and diameter of two-phase smoke.In order to find out the flow characteristics, gas-solid two-phase flow is a subject that should be studied. A single microcosmic granule’s flow state is studied in this research. Between the fins a small ash gets gravitation, resistance Magnus force and Saffman force. Magnus force and Saffman force result that the granule kept away from the pins, which can reduce the opportunity of the granule and fins contact and is theory base of lightening abrasion.The most important parameters that influence the abration are the paticle velocity, concentration and diameter. Besides the theory study, experimental study under the hot condition is necessary, so there is the cold smoke circulating test unit with PDA system set up in the laboratory. With the particle dynamic analyzer (PDA), which is advanced laser instrument made of Dantec Company in Danmark, the paticle velocity, concentration and diameter are measured on 5 representational planes between the pins under the hot condition for the fist time.Experiment research shows that there are disciplinarian distributions about the paticle velocity, concentration, diameter and velocity vector, which are influenced by the temperature,更多还原