【作者】 刘颖；

【导师】 郑水英；

【作者基本信息】 浙江大学 ， 化工过程机械， 2013， 硕士

【摘要】 作为输送气体的设备,风机在国民经济的各个部门都有广泛地应用。从能量转换的角度来看,风机是一种把原动机的机械能转变为气体的动能和压力能的机械。根据行业的需求,风机有各种各样的形式。本文以船用轴流风机为研究对象,研究如何对轴流风机的实体模型进行数值模拟和性能改进。首先展开数值模拟计算的工作,研究轴流风机的内部流场。在研究的工况范围内,原始的轴流风机在小的体积流量工况下,存在压力不足、效率偏低的状况。通过增加叶轮叶片的安装角度可以提高轴流风机压力,能够满足风机全压的性能要求,但是风机效率更低。而且在研究的流量范围内风机的内功率比较大,在体积流量为Qv=24000m3/h时内功率为7.559kw,大于轴流风机使用的电机的功率7.5kw,就会出现超功率、超电流的现象。以CLARK y翼型为基本翼型,从叶轮叶片的翼型中线形式和厚度两方面进行研究。首次将离心式压缩机的叶片加载方法——控制载荷法应用于轴流风机,并对不同的加载方法进行了研究。研究表明从提高轴流风机的压力角度而言,三角形卸载方法构造的单弧线的翼型中线生成的风机模型更为有利,优于轴流风机常用的单圆弧中线翼型。翼型厚度的变化是通过在翼型弦长和厚度方向上按比例放大或缩小来实现的,适当减薄翼型厚度对于轴流风机的全压和效率的提高都是有利的。在轴流风机的性能改进过程中,设计目标为以满足风机压力要求为前提,尽量提高轴流风机的效率。由于所研究的轴流风机的全压要求比较高,常用的等环量和变环量设计不适合于本文的研究对象,所以提出了一种改进的变环量设计方法。轴流风机导流段的叶片对风机的性能有很大的影响,考虑到原始模型中静叶片的数量过少,进口角偏小,对导流段叶片进行了简单的改进。导流段叶片为圆弧板叶片和直叶片的组合,本文中增加了进口处的圆弧板叶片的进口角和叶片数目,提高了轴流风机的全压和效率。综合上述数值模拟计算结果,得到了一组比较好的风机模型。在满足风机压力性能要求的前提下,达到了提高风机效率的目的,并且不会有超电流的危险。轴流风机的全压效率随体积流量的增加而增加,体积流量最小为Qv=21000m3/h时,风机全压效率在研究的流量工况下最小,为66.61%。与风机原始模型1相比,风机全压增加了 138.3Pa,全压效率增加了 12.69个百分点。与风机原始模型2相比,风机全压增加了 74.42Pa,风机全压效率增加了 14.45个百分点。体积流量Qv=30000m3/h时,风机全压效率在研究的流量工况下最大,为79.48%,与原始模型1相比风机的全压效率增加了 8.066个百分点,与原始模型2相比风机的全压效率增加了 10.56个百分点。更多还原

【Abstract】 Fan is conveying gas equipment,which has widely application in the areas of economy departments.From the point of energy transformation,the fan is a machine that can transform the prime mover’s mechanical energy into gas’s kinetic energy and the pressure.According to the requirements of industry,the fan has variety of forms.The object of research is based on axial flow fan of marine.We mainly discussed how to achieve the numerical simulation and performance improvement of axial flow fan.We tried to develop the numerical simulation firstly,exploring the inner flow field of axial flow fan.In the working range of fan,the original axial flow fan has the performances of sufficient pressure and low efficiency.As we all known,we can achieve the purpose of raising the pressure of axial fan by the way of increasing the installation angle of impeller.In this way,the axial fan can meet the requirements of the total pressure,but with lower internal efficiency and higher power in the flow scope of fan.In the point of volume flow for Qv=24000m3/h,the fan internal power is 7.559kw,which is more than the motor power 7.5kw.Thus,there will be super power over current phenomenon.The research is based on CLARK y profile.The study on profiles contains the following two aspects:the center line forms and the thickness.One method is put forward,that is suitable for the center line of axial fan’s profile.From the aspects of improving the axial fan’pressure,triangle discharge method is better than that of shaft.Of course,triangle discharge method is better than the commonly used single arc center line.Profile thickness change is achieved through the airfoil chord length and thickness direction enlarged or reduced in proportion.Appropriate minus the thickness of profile is favorable for axial flow fan,the total pressure and efficiency.Our designing goal is to meeting the pressure required for premise,with the found of improve the efficiency of axial flow fan as far as possible.Due to the higher demand of total pressure of axial fan researched,the commonly used equal circulation and variable circulation method don’t fit with this situation any more.So this research proposes an improved variable circulation designing method.The fan blade of guide section of axial flow fan has great influence on fan performance.The original model of stator blade is too little in quantity,and the inlet angle is small,so we improved the guide section.The stator blade is the combination of straight blade and circular plate blade.We increased the inlet angle and number of inlet arc blade,with the result of higher total pressure and efficiency.The above numerical simulations show that the purpose model is better in fan performance,without super current risk.Axial flow fan’s total pressure efficiency decreases with the increasing of volume flow.When the volume flow is 21000m3/h,the pressure efficiency is the worst,66.61%.Compared with the original model 1fan,the total pressure increased 138.3Pa,the total pressure efficiency increased by 12.69%.And compared with the original model 2 fan,the total pressure increased 74.42Pa,the total pressure efficiency increased by 14.45%.When the volume flow is 30000m3/h,the pressure efficiency is the best,79.48%.Compared with the original model 1fan,the total pressure efficiency increased 8.066%.And compared with the original model 2 fan,the total pressure efficiency increased 10.56%.更多还原