毕业论文（设计）基于OPTIMUS 的通风机进风口集成优化计算.doc

基于OPTIMUS的通风机进风口集成优化计算 赵立峰 王东屏/大连交通大学 摘要：利用三维数值模拟的方法，对离心式通风机进风口流场进行了计算分析，运用多学科优化平台软件OPTIMUS，集成流体计算软件对通风机进风口进行了优化计算。结果表明，通风机的进风口形状对其性能有明显影响，在改动较小的情况下，可以显著提高通风机性能。 关键词：离心式通风机 进风口 集成优化中图分类号：TH432 文献标识码：B文章编号：1006-8155（2006）01-0029-03Integrated and optimum Calculation for Inlet of Fan Based on OPTIMUS FlatAbstract：Inlet flow field of centrifugal fan is calculated and analyzed using 3D numerical simulation, and optimization design of inlet is completed with OPTIMUS flat. The result shows the shape of inlet affects its performance remarkably, and fan performance can be improved remarkably by slight change.Key words：Centrifugal Fan Inlet Optimization1 引言离心式通风机的空气动力特性除了取决于叶轮内部的结构之外，还与通风机的进风口形状密切相关，进风口又称为集风器，其形状对风机的性能有很大的影响。传统上，多是依据经验公式设计其尺寸，对设计者的经验要求很高，设计效果不理想，不能满足日益提高的节能和环保要求。现在，在国外使用多学科优化软件平台，集成计算流体力学的软件进行数值模拟，已经成为设计流体机械的先进手段。本文采用FLUENT6.1计算通风机流场,但是FLUENT软件本身并不具有优化功能，为了达到优化风机进口形状的目的，可借助集成优化平台OPTIMUS5.0。OPTIMUS5.0是多学科多目标优化软件，具有强大的集成优化能力，可以集成多种CAE/CAD软件。本文用其集成GAMBIT2.1 和FLUENT6.1，对北京某厂的离心式通风机的进风口优化设计，以达到提高其性能的目的。2 计算模型2.1 模型的建立和网格生成 现以北京某厂的离心通风机为研究对象，该风机的叶轮半径224mm，32个叶片，在CAD软件中建立几何模型，然后输入到FLUENT的前处理软件GAMBIT中，其整体模型如图1所示。图1 通风机模型 由于几何模型复杂，网格划分采用三维非结构化网格。相对于结构化网格，非结构化网格的适应能力强，局部加密也比较容易，网格质量直接影响结果的收敛性。在梯度大的地方，网格必须保证足够细密。同时，为了减少网格总数，加快计算，还应减少小网格的数量，对通风机不同区域分割时，叶轮部分的网格较小，蜗壳的部分较大。由于叶片数目较多，所以网格总数已有40多万个。2.2 模型定义 在FLUENT中，离心通风机一类的旋转设备问题可以通过旋转参考坐标系来处理，因此要把模型分成定子和转子两类区域。旋转叶轮区域和蜗壳区域的相互作用，通过多参考坐标系模型（Mulitiple Reference Frame,简称MRF）来解决。在MRF方法中，转子区域的网格在计算时应保持静止，在惯性坐标系中是以作用的哥氏力和离心力来进行定常计算，而定子区域则是在惯性坐标系中进行定常计算。在两个区域的交界面处交换惯性坐标系下的流体参数，保证了交界面的连续性，也达到了用定常计算来研究非定常问题的目的。流动进口：定义为压力进口边界，它适合于可压缩流体，也可以用于不可压缩流体。定义总压为0。由于是亚声速，静压可忽略。流动出口：定义为压力出口边界，定义出口压力相对于大气压力为0，即没有附加的压力作用。湍流模型采用双方程模型。叶片、蜗壳、进风口均取壁面边界条件。离心通风机的进口气流为轴向，出口为径向，气流为稳定流，由于气流流动的最大马赫数小于0.3，可按不可压缩流体处理。叶轮和蜗壳、其他界面上均采用了无滑移壁面条件及标准壁面函数。2.3 计算结果及分析该模型在工作站级计算机上，迭代500次，并行计算大约1h就基本收敛了，若继续计算，结果也不会有多大差别。计算得到的出口流量为5.515kg/s,出口总压为2588.54Pa，与试验风机的试验数据基本吻合。进风口为圆锥形，空气进入叶轮前，必须由进风管的轴向转一个90的角，气流才会产生分离，这种分离间接影响了叶轮的功能。如图2所示，气流通过进风口后，气流冲向叶轮后部，发生不应有的冲击，而且叶轮前部发生回流，会出现很大的涡区，能量损失很大。可以预见，通过改变进风口的形状，可改变气流进入叶轮的流动，减小涡区，还可提高叶轮前部的利用效率及通风机的效率。图2 优化前模型子午面流场3 集成优化3.1 在OPTIMUS中建立集成流程通风机进风口几何尺寸为设计变量，以通风机的效率为目标，设计Optimus流程。求解器1是Gambit的求解器，求解器2是Fluent的求解器，jou文件1是Gambit使用的命令文件，jou文件2是Fluent使用的命令文件(见图3)。图3 风机计算集成流程3.2 建立命令文件 建立可以提供给前处理软件的命令流，其中应包含所有必要的信息，同时还须保证内容简洁，注意设计变量调整变化时不发生干涉，命令无法执行等可能由于变量变化带来的影响。准备好 Gambit使用的“jou文件1”，包含进风口的几何尺寸参数，将其作为设计变量。在Optimus中，默认的变量变化范围为其上下变化10。同时输出mesh文件作为Fluent的输入文件。在“求解器1”中写入仿真代码，调用Gambit程序。 在前处理结束后，得到了所需要的流体计算模型，就可以通过Fluent的命令流（text command）控制Fluent，把包含读入模型、写出文件、设置边界条件、设置求解器等信息的Fluent的jou文件作为控制求解器2的“jou文件2”。为了加快计算速度，使用了并行计算，写入了初始化、求解、显示残差、输出结果等命令。在求解器2中写入仿真代码，用来控制Fluent软件的调用。通过计算得出计算结果，在Fluent中可以直接得到的结果有：出口流量、出口压力、进口压力以及叶轮的扭矩。3.3 建立结果处理文件 最后是处理计算结果，可以取绝对值，也可以运用公式加工，Optimus提供了多种处理方法。把输出的结果汇集到“最后结果”,通过在其中写入效率公式，就可以计算得到通风机的效率。3.4 优化方法和结果分析采用设计试验方法（DOE）进行计算，可以通过较少的试验次数，比较准确地反映设计变量和目标函数的关系。设计试验方法是一种设计空间探索技术，用来对设计空间进行初步探索，可以减小优化问题的计算规模。在OPTIMUS中提供多种DOE技术，包括拉丁方、随机试验设计、全参数、部分参数等。通过对DOE结果分析得知，只有减小截面尺寸的分析才是有效的，可以提高效率。因此，把变量的变化范围缩小，可以提高计算效率，减少计算时间。在DOE的基础上进行优化，OPTIMUS中提供了局部优化算法，如梯度算法和序列二次规划算法、全局搜索算法如自适应遗传算法；模拟退火法等。采用序列二次规划算法，在设定的空间内进行了7次迭代，图4为迭代过程。图4 优化迭代 通过优化计算，优化目标效率有了显著的提高，主要是出口的总压提高较多。计算得到的进风口形状见图5的右图。图5 优化前、后进风口形状图6 优化后模型子午面流场 图5中左边的圆锥形进风口为原模型的进风口，右边为优化计算得到的进风口形状。图6中得到的是优化后流场，与优化前的模型流场对比（见图2）可以看出，在叶轮进风口其他部位产生的“回流”明显减小，减少了能量损失，同时也有更多气流由叶轮前部流出，提高了叶轮前部的利用，改善了气流在涡壳内部的流动。通过对通风机进风口的优化，在对原通风机改动很小的情况下，可以有效提高通风机的性能（见表1），出口总压、流量等指标也都有所提高，效率提高了11.41。表1 出口压力/Pa流量/(kg/s)效率/%优化前模型2707.995.49634.78优化后模型3288.525.98746.19 4 结束语利用Fluent软件可以有效模拟通风机的流场，计算出通风机的性能参数。本文提出了使用多学科优化软件与流体计算软件集成，对离心式通风机的进风口进行优化计算。可以看出进风口的形状对通风机性能有明显的影响，尤其是进风口形状与其他部件的匹配，只有很好地匹配，才能减少能量损失。通过优化分析，可以在对原机型改动较小的情况下，明显提高通风机的性能。由于只对通风机的进风口进行了优化，没有分析叶轮、蜗壳，所以性能提高有限。如果对叶片也进行优化分析，可以预见，将会使通风机的性能有更大的提高。 参 考 文 献1 B.埃克 ,通风机.机械工业出版社，1983.2 沈阳鼓风机研究所，东北工学院.离心式通风机.机械工业出版社，1984.3 FLUENT6.1 Documentation,Fluent Inc 2003.4 OPTIMUS5.0 Documentation,Nosis Inc 2004.Editor's note: Judson Jones is a meteorologist, journalist and photographer. He has freelanced with CNN for four years, covering severe weather from tornadoes to typhoons. Follow him on Twitter: jnjonesjr (CNN) - I will always wonder what it was like to huddle around a shortwave radio and through the crackling static from space hear the faint beeps of the world's first satellite - Sputnik. I also missed watching Neil Armstrong step foot on the moon and the first space shuttle take off for the stars. Those events were way before my time.As a kid, I was fascinated with what goes on in the sky, and when NASA pulled the plug on the shuttle program I was heartbroken. Yet the privatized space race has renewed my childhood dreams to reach for the stars.As a meteorologist, I've still seen many important weather and space events, but right now, if you were sitting next to me, you'd hear my foot tapping rapidly under my desk. I'm anxious for the next one: a space capsule hanging from a crane in the New Mexico desert.It's like the set for a George Lucas movie floating to the edge of space.You and I will have the chance to watch a man take a leap into an unimaginable free fall from the edge of space - live.The (lack of) air up there Watch man jump from 96,000 feet Tuesday, I sat at work glued to the live stream of the Red Bull Stratos Mission. I watched the balloons positioned at different altitudes in the sky to test the winds, knowing that if they would just line up in a vertical straight line "we" would be go for launch.I feel this mission was created for me because I am also a journalist and a photographer, but above all I live for taking a leap of faith - the feeling of pushing the envelope into uncharted territory.The guy who is going to do this, Felix Baumgartner, must have that same feeling, at a level I will never reach. However, it did not stop me from feeling his pain when a gust of swirling wind kicked up and twisted the partially filled balloon that would take him to the upper end of our atmosphere. As soon as the 40-acre balloon, with skin no thicker than a dry cleaning bag, scraped the ground I knew it was over.How claustrophobia almost grounded supersonic skydiverWith each twist, you could see the wrinkles of disappointment on the face of the current record holder and "capcom" (capsule communications), Col. Joe Kittinger. He hung his head low in mission control as he told Baumgartner the disappointing news: Mission aborted.The supersonic descent could happen as early as Sunday.The weather plays an important role in this mission. Starting at the ground, conditions have to be very calm - winds less than 2 mph, with no precipitation or humidity and limited cloud cover. The balloon, with capsule attached, will move through the lower level of the atmosphere (the troposphere) where our day-to-day weather lives. It will climb higher than the tip of Mount Everest (5.5 miles/8.85 kilometers), drifting even higher than the cruising altitude of commercial airliners (5.6 miles/9.17 kilometers) and into the stratosphere. As he crosses the boundary layer (called the tropopause), he can expect a lot of turbulence.The balloon will slowly drift to the edge of space at 120,000 feet (22.7 miles/36.53 kilometers). Here, "Fearless Felix" will unclip. He will roll back the door.Then, I would assume, he will slowly step out onto something resembling an Olympic diving platform.Below, the Earth becomes the concrete bottom of a swimming pool that he wants to land on, but not too hard. Still, he'll be traveling fast, so despite the distance, it will not be like diving into the deep end of a pool. It will be like he is diving into the shallow end.Skydiver preps for the big jumpWhen he jumps, he is expected to reach the speed of sound - 690 mph (1,110 kph) - in less than 40 seconds. Like hitting the top of the water, he will begin to slow as he approaches the more dense air closer to Earth. But this will not be enough to stop him completely.If he goes too fast or spins out of control, he has a stabilization parachute that can be deployed to slow him down. His team hopes it's not needed. Instead, he plans to deploy his 270-square-foot (25-square-meter) main chute at an altitude of around 5,000 feet (1,524 meters).In order to deploy this chute successfully, he will have to slow to 172 mph (277 kph). He will have a reserve parachute that will open automatically if he loses consciousness at mach speeds.Even if everything goes as planned, it won't. Baumgartner still will free fall at a speed that would cause you and me to pass out, and no parachute is guaranteed to work higher than 25,000 feet (7,620 meters).It might not be the moon, but Kittinger free fell from 102,800 feet in 1960 - at the dawn of an infamous space race that captured the hearts of many. Baumgartner will attempt to break that record, a feat that boggles the mind. This is one of those monumental moments I will always remember, because there is no way I'd miss this.