低速风机内部非定常流动分离控制及应用研究

发布时间：2018-01-08 01:29

本文关键词：低速风机内部非定常流动分离控制及应用研究　出处：《华中科技大学》2015年博士论文　论文类型：学位论文

【摘要】：低速风机广泛应用于国防、民用领域,其内部包含着复杂的三维、非定常的粘性流动问题,对其分离流动的控制是研究的热点之一。基于对低速轴流／离心风机内流动机理与设计方法研究,试图通过叶片改型设计、动静部件匹配性研究对叶轮流道内的压力梯度分布进行控制,从而起到抑制叶片端部分离流动,减少端部低能流体聚集的作用,实现低速风机气动性能的提升与降噪。论文主要围绕低速轴流风扇\前弯离心风机叶片前缘分离流动、多翼离心风机叶片尾缘及蜗壳舌部的仿生设计等方面开展工作,采用数值计算方法对分离流动演变过程进行分析,结合试验对分离流动控制方案进行验证,探索提高低速风机气动-声学性能的途径。主要工作和研究成果如下：一、在γ-Reθ转捩模型中引入基于当地变量的应变率雷诺数Rev,并将求解的间歇因子耦合进SST湍流模型能量方程,对三种不同厚度翼型表面分离诱导转捩进行数值求解,分析不同攻角、雷诺数影响下的前缘、尾缘分离流动结构特征及涡系演变过程；对NACA0006翼型前缘型线进行改型,给出不同前缘形状对吸力峰、压力损失及边界层内速度梯度分布的影响。二、在低速轴流风机中引入了叶片前缘保凸设计方法,对某半开式轴流风扇叶片进行前缘改型设计应用研究。通过控制多边形各点坐标调节叶型前缘形状,采用双三次Bezier曲面及Casteljau算法完成曲面拟合。探讨数值预测中前缘变型对抑制叶栅截面流动分离的内在机制。试验对比改型前、后风机外特性与噪声性能,验证了采用前缘保凸法设计的低速轴流风叶性能方面的优越性。三、基于SST k-ω湍流模型,发展一种求解强旋流、弯曲叶片表面流动问题的非线性模型。运用模型对90°弯管内流场进行仿真预测,对比试验结果评估改进模型的准确性。应用改进湍流模型对具有狭长流道特征的前弯离心风机内流场进行性能预测,分析叶片前缘时均化涡量云图,发现分离涡呈现不均匀分布,采用非对称进气控制方案抑制叶片前缘分离流动,结果表明：该方案减小了分离涡大小,改善了气动性能,研究过程中结合外特性试验及噪声测试进行方案验证。四、基于多翼离心叶轮出口速度分布特征,建立尾迹相似模型,引用速度及周向位置无量纲因子对速度尾迹分布进行曲线拟合,结合分布特征对叶片尾缘进行改型设计。改型的多翼离心叶片出口速度分布变得过渡均匀,未出现原风机类似跌宕分布。其压力在设计流量周围覆盖原机,设计工况下效率提升2%左右。同时,探讨了仿鹗翼蜗舌在偏工况点运行时出现的分离流动问题,结合倾斜蜗舌设计方法,设计并制作带倾斜特征仿鹗翼蜗舌,在半消音室内进行声学测试发现：改型后风机在高频段声压级幅值下降明显,低频段噪声也低于原风机,整机降噪2.0dB。
[Abstract]:Civil field low speed wind machine is widely used in national defense, and its interior contains complex three-dimensional, unsteady viscous flow problems, the separation flow control is one of the hot research. Research on the flow mechanism and design method of axial flow and centrifugal fan based on attempts by the blade modification design, static and dynamic components matching control of pressure gradient on the impeller in the distribution, thus inhibiting the blade tip flow separation, reducing the end of low-energy fluid accumulation, and enhance the implementation of the low noise fan aerodynamic performance.
This paper mainly focuses on the low speed axial flow fan forward curved centrifugal fan blade leading edge separation flow, multi blade centrifugal fan blade and volute tongue of bionic design work, by using the numerical method for analysis of the evolution of flow separation, combined with the test of separation flow control scheme is verified, explore a way to improve the low speed fan aerodynamic and acoustic performance. The main work and research results are as follows:
A local variable, strain rate of Reynolds number Rev based on the -Re gamma theta transition model, and the intermittency factor of coupling into the SST turbulence model and energy equation, three kinds of different thickness of the airfoil surface separation induced transition for numerical analysis of different angles of attack, the front Reynolds number under the influence of the trailing edge separation flow the structure characteristics and vortex evolution process; modified NACA0006 airfoil leading edge profile, given different leading edge shape of suction peak impact pressure loss and velocity gradient in the boundary layer.
Two, in a low speed axial flow fan is introduced in the leading edge of the blade convexity design method of a semi open axial flow fan blade leading edge modification design applied research. Through the control polygon coordinates of each point blade leading edge shape adjustment, double three Bezier surface and Casteljau surface fitting algorithm. Numerical study on the prediction of frontal variant the inner mechanism of blade section flow separation suppression. Contrast modification before the test, after the fan performance and noise performance, verify the superiority of low speed axial fan performance using the front convex design method.
Three, the SST k- turbulence model is based on the development of a solution of strong swirl, the nonlinear model of curved blade surface flow problem. By using the model to simulate flow field of 90 degree bend, improve the model accuracy evaluation test results. The application of improved model performance on the flow field of centrifugal fan with forward curved narrow flow channel characteristics in the prediction, analysis of blade leading edge averaged vorticity nephogram, found vortex were not evenly distributed, suppressing blade leading edge separation flow, the asymmetric inlet control scheme shows that the scheme reduces the vortex size, improve the aerodynamic performance of the research process with experiments and the noise characteristics of test program verification.
Four, multi blade centrifugal impeller velocity distribution based on the establishment of wake similarity model, the reference speed and the circumferential position of the dimensionless factor on the velocity distribution of wake curve fitting, combined with the distribution characteristics of blade trailing edge modification design. The modified multi blade centrifugal impeller outlet velocity distribution becomes uniform transition, not the original fan like the ups and the pressure distribution. The coverage of the original machine in the design flow around design conditions to enhance the efficiency of about 2%. At the same time, discusses the problem of separation flow in the volute tongue imitation wing Osprey partial point run when, with inclined volute tongue design method, made with inclined volute tongue characteristics of wing design and imitation osprey, acoustic test found in the semi anechoic chamber: the modification of fan in the sound pressure level amplitude frequency decreased significantly, the low-frequency noise is lower than that of the original fan, the noise reduction of 2.0dB.

【学位授予单位】：华中科技大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TH43

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