斜沟槽机匣处理对轴流风机性能影响的数值研究

为研究斜沟槽机匣处理对风机气动性能的影响,以OB-84型动叶可调式轴流风机为对象,基于FLUENT数值软件,模拟风机在原壁面和六种不同斜沟槽情况下的性能,分析叶顶与吸力面湍动能和涡量分布及不同叶高处的静压和静压差分布。研究表明:斜沟槽开槽位置与动叶叶顶前缘的距离及沟槽斜度对风机性能均有明显影响,斜沟槽机匣处理结构改变了叶顶泄漏流场的分布,缓解了泄漏流的发展,削弱了泄漏流与主流的掺混;与原壁面相比,经斜沟槽机匣处理的风机在设计流量下全压和效率均有一定程度提高。综合考虑效率与安全性,方案5具有最优的气动性能,设计流量下效率较原风机提高了0.59%。     

长短复合导叶对两级动叶可调轴流风机 性能的影响

为研究长短复合导叶对动叶可调轴流风机性能的影响,以某大型两级动叶可调轴流风机为对象,构建了第二级导叶后部和前部长分别依次缩短10%等10种长短复合导叶方案,采用FLUENT软件对不同方案下的轴流风机进行了三维定常数值模拟,分析了复合导叶对风机性能、内流特征和静力结构的影响。研究表明:长短复合导叶对轴流风机的性能有显著影响,在中小流量侧导叶后部缩短10%和20%方案气动性能得到提升,在大流量侧则与之相反;其他缩短方案其性能均低于原风机,导叶后部缩短风机性能优于导叶前部缩短情形;在设计工况下,导叶后部缩短10%时第二级动叶表面压力发生变化、做功能力增强,整机熵产率有所增加,第二级动叶应力和总变形有所增大,振动减弱,但满足使用要求。     

自循环机匣对高速离心叶轮性能及稳定性影响的研究

本文以某高速离心压气机为研究对象,通过数值模拟的方法,研究了叶轮失稳流场和两种自循环机匣对其性能的影响,以期揭示自循环机匣影响叶轮性能和内部流场的内在机理。研究首先模拟叶轮在实壁机匣下的情景,发现小流量工况下的叶片表面二次流强度明显增大,在叶轮前缘和叶顶泄漏流大量掺混,以至于在分流叶片通道进口出现了大范围堵塞,形成大范围"尾迹区",引起叶片失速。针对上述现象,研究模拟叶轮在两种不同后槽位置的自循环机匣下的情景。采用自循环机匣结构后,最高能使失速裕度提升6%,设计点效率下降0.5%。在小流量工况下,气流主要由主叶片压力面附近流入机匣结构中。有效降低了叶顶泄漏流强度和压力面叶顶通道涡强度,同时还增加叶轮进口的流量,减小叶轮进口的气流攻角,降低了流动损失。     

弦向掠叶片对动叶可调轴流风机性能影响模拟

叶片弦向弯掠技术是提升轴流风机气动性能的有效手段。针对带后置导叶的OB-84型单级动叶可调轴流风机,利用Ansys数值软件,对比叶片掠设计前后风机的性能曲线和内流特征,开展静力结构特性分析并进行了噪声预估,探究了前掠角度在不同动叶安装角下的影响。结果表明:设计安装角下,前掠叶片能有效提高叶轮做功能力和导叶扩压能力,减少泄漏损失,提升风机整体性能,在小流量侧和大流量侧效果更明显;设计流量下前掠8.3°性能最优,全压和效率分别提升2.1%和1.68%,但气动噪声有所增大;叶片掠向改型后虽变形增大,但仍满足材料强度要求;在变安装角下,前掠叶片风机性能均有所降低。设计安装角下所得最佳前掠角度适用于长期带基本负荷的轴流风机。     

离心压气机机匣处理多工况性能预测与分析

机匣处理作为一种高效、经济的扩稳技术,越来越多的被用以提高压气机的稳定工作裕度。为了研究机匣处理对离心压气机多工况性能的影响,本文对3种进气回流机匣结构的压气机模型和无机匣处理的实壁压气机模型分别进行了数值仿真分析。数值计算结果与最优模型的试验结果吻合较好,比较准确的预测了喘振边界的位置,验证了计算方法的可靠性。结果表明,只有结构合理的进气回流机匣处理才能在各个转速下均显著扩大压气机小流量的稳定工作范围,其中机匣处理的开槽位置和前置导流挡板对其性能有着重要影响。     

蜗壳及叶片外形对双吸式多翼离心风机性能影响的试验研究

以某款效率低、全压低的双吸式多翼离心风机为实验对象,通过试验研究蜗壳型线,叶片外形以及增加叶片数对风机性能的影响。试验结果表明:蜗壳型线的变化趋势对双吸式多翼离心风机的性能有着很大的影响,良好的蜗壳型线不仅提高了风机效率以及全压,还改变了流量-压力曲线的变化趋势;相比原风机,采用改型蜗壳及改型叶轮的方案2风机能够大幅提升风机性能,使效率提升幅度达到10.93%,风机全压提升近40Pa;当叶片数从46片增加至56片,风机在大流量工况下提升了风机静压,但风机效率会略有下降。     

进口弯管对前向离心通风机性能影响的研究

以高压小流量前向离心通风机为研究对象,通过气体动力性能试验和流体动力学数值模拟研究了在不同进口位置连接90°弯管后对风机性能的影响。研究表明,风机进口直接接弯管基本不会对风机性能造成影响;附加D(接管的通流直径)和2D长度直管段对风机性能的影响较大,且大流量段性能恶化明显;附加4D长度直管段时风机性能有所改善。     

集流器形式对轴流式风机性能影响的研究

采用CFD数值模拟方法研究了不同结构形式集流器对大型轴流式风机性能的影响.计算得到了风机压升和效率随流量变化的性能曲线,对比分析了不同结构形式集流器对风机性能影响的原因,为合理设计与选择集流器形式改善风机性能提供了依据.     

带加强盘的交错叶片型风机结构及流动特性

为提高大流量离心风机的气动性能,运用计算流体动力学研究了加强盘位置及叶轮型式对叶轮结构强度、风机性能及压力脉动的影响。结果表明：加强盘居中时风机设计点效率与原型机相比提升3.9%,叶轮最大总变形量减小56.5%,蜗壳流域压力脉动降低5.4%;表面加强盘居中有利于增强叶轮结构强度,提升风机气动性能并降低蜗壳流域压力脉动;采用交错叶片能降低70%以上蜗壳流域压力脉动,有利于风机离散噪声控制;受高低能流体掺混产生的湍动能耗散影响,交错叶片型风机气动损失增加,且叶道内压力脉动幅值增大。加强盘居中和采用交错叶片是提高大流量离心风机气动性能和降低离散噪声的有效方法,但需注意其对气动损失的影响。研究结果可为大流量风机加强盘设计提供理论依据。     

不同进口角度面板对贯流风幕机内流与噪声特性的影响

针对风幕机用贯流风机的降噪问题,采用了数值模拟与噪声试验结合的方法对其进行研究。将风机气动噪声作为优化目标,通过调整贯流风机进口面板的结构参数,改善贯流风机内部流动特性,达到降低气动噪声的目的。对4种不同进口面板结构的贯流风机,建立了三维CFD模型,模拟内部流动,分析其内流特性变化。在消声室进行噪声试验、在设计工况下,测试不同进口面板风机噪声,分析噪声频谱特性,探究进口面板改变所导致的内流与噪声频谱特性之间的关系。研究结果表明,在特定转速下,进口结构参数的改变会影响贯流风机进口回流涡的强度和范围,从而影响气动性能与噪声。模型B气动性能提升,流量提升1.5%,全压提升3%。模型C降噪效果明显,噪声降低3.3 dB(A)。     

Experimental study on the mean flow characteristics of forward-curved centrifugal fans

Measurements have been made in an automotive HVAC blower for two different centrifugal fans. This work is directed at improving the performance of a conventional forward-curved centrifugal fan for a given small blower casing. Mean velocities and pressure have been measured using a miniature five-hole probe and a pressure scanning unit connected to an online data acquisition system. First, we obtained the fan performance curves versus flow rates showing a significant attenuation of unstable nature achieved with the new fan rotor in the surging operation range. Second, aerodynamic characterizations were carried out by investigating the velocity and pressure fields in the casing flow passage for different fan operating conditions. The measurements showed that performance coefficients are strongly influenced by flow characteristics at the throat region. The main flow features were common in both fans, but improved performance is achieved with the new fan rotor, particularly in lower flow rate regions. Based on the measured results, design improvements were carried out in an acceptable operation range, which gave considerable insight into what features of flow behavior were most important.     

EXPERIMENTAL INVESTIGATION OF PASSIVE CONTROL ON UNSTABLE CHARACTERISTICS IN AXIAL FLOW FAN

ＥＸＰＥＲＩＭＥＮＴＡＬＩＮＶＥＳＴＩＧＡＴＩＯＮＯＦＰＡＳＳＩＶＥＣＯＮＴＲＯＬＯＮＵＮＳＴＡＢＬＥＣＨＡＲＡＣＴＥＲＩＳＴＩＣＳＩＮＡＸＩＡＬＦＬＯＷＦＡＮ①ＬｉａｎｇＸｉｚｈｉＷｕＨａｉＣｈｉｎｅｓｅＡｃａｄｅｍｙｏｆＳｃｉｅｎｃｅｓＡｂｓｔｒ...     

子午加速轴流风机的全三维优化设计

采用流场结构分析和叶片造型调整结合的全三维优化设计方法，对子午加速轴流风机进行了优化设计。结果表明：在不改变风机外径、转速和间隙的情况下，风机的性能得到大幅改善，设计工况下风机效率达到83．3％，提高了18．2％；风机的内部流场合理，没有明显的分离和回流；风机出口全压分布均匀，除叶片尾迹外无明显低压区；同时，风机的性能曲线比较平滑，变工况性能好；经性能实验验证，优化设计后的风机各项指标均达到了设计要求，说明该风机的全三维优化设计是成功的。     

完全可逆地铁风机的三维优化设计

采用试验设计、流场结构分析和叶片造型调整相结合的方法,对完全可逆地铁风机进行三维优化设计。结果表明在不改变风机外径、转速和叶尖间隙的情况下,风机的性能得到大幅改善。设计工况下,风机正转全压效率达到82.3%,比初始设计提高9.1%;风机反转全压效率达到79.1%,比初始设计提高3.3%;风机的内部流场合理,没有明显的分离和回流;风机出口低压区得到明显改善。风机的性能曲线比较平滑,变工况性能好;经性能试验验证,优化设计后的风机各项指标均达到了设计要求。     

Numerical study on the effect of the tip clearance of a 100 HP axial fan on the aerodynamic performance and unsteady stall characteristics

In this study, a numerical analysis was conducted to investigate the effect of the tip clearance on the aerodynamic performance, internal flow characteristics, and stall region characteristics of an axial fan. Three-dimensional steady and unsteady Reynolds-averaged Navier-Stokes (RANS) calculations were conducted with a shear stress transport (SST) turbulence model. Tip clearance ratios of 0, 0.01, and 0.02 were applied to the impeller. As the tip clearance ratio increased, the aerodynamic performance of the axial fan decreased at both the design and the off-design conditions. The correlation between the tip leakage vortex (TLV) and the flow angle of the velocity triangle was presented for the difference in the tip clearance and flow rate. As the flow rate increased, the differences in the aerodynamic performance induced by the tip clearance ratio decreased. As the tip clearance ratio increased, the size of the TLV increased and gradually moved in the circumferential direction to interfere with the main flow at the low flow rate. Meanwhile, the size of the TLV was similar and gradually moved in the axial direction even if the tip clearance ratio increased at the high flow rate. The pressure fluctuations were observed by the fast Fourier transformation (FFT) analysis to compare and analyze internal flow characteristics at the stall region and design point. The static pressure was converted to the appropriate magnitude. The locations of the highest magnitude were shown to be different at the stall region and the design point, respectively.

     

A numerical investigation of flow and performance characteristics of a small propeller fan using viscous flow calculations

The present work is aimed at investigating an unusual variation in flow and performance characteristics of a small propeller fan at low flow rates. A performance test of the fan showed dual performance characteristics, i.e., radial type characteristics at low flow rates and axial type at high flow rates. Dual performance characteristics of the fan are numerically investigated using viscous flow calculations. The Finite Volume Method is used to solve the continuity and Navier-Stokes equations in the flow domain around a fan. The performance parameters and the circumferentially averaged velocity components obtained from the calculations are compared with the experimental results. Numerical values of the performance parameters show good agreement with the measured values. The calculation simulates the steep variations of performance parameters at low flow rates and shows the difference in the flow structure between high and low flow rates. At a low flow coefficient of ϕ=0.2, the flow enters the fan in an axial direction and is discharged radially outward at its tip, which is much like the flow characteristics of a centrifugal fan. The centrifugal effect at low flow rates makes a significant difference in performance characteristics of the fan. As the inlet flow rate increases, flow around the fan changes into the mixed type at ϕ=0.24 and the axial discharge at ϕ=0.4.     

轴流风机叶片展向结构变化对性能影响的数值分析

基于电站风机裕量普遍较高的现象,本文以OB-84轴流风机为对象,采用Fluent模拟了叶顶切割和轮毂加粗后的风机性能,分析了2种改造方式对风机性能、内流特征及轴功率的影响。结果表明:体积流量qv≥33 m3/s时,叶轮改造后的全压和效率均随叶高减小而降低,但轮毂加粗后的风机性能优于叶顶切割情形;qv<33 m3/s时,2种改造方式均可使不稳定区变缓甚至消失;叶轮改造后动叶总压升系数小于原风机,但导叶扩压能力增强,且叶轮改造能改善中小流量下风机噪声特性;叶顶切割后,轴功率均小于原风机;在高于设计流量下,与原风机相比,轮毂加粗后的轴功率呈减小趋势,但叶顶切割方式的降幅更大。     

对旋轴流风机叶顶间隙对其性能的影响

为了探究改变对旋轴流风机两级叶轮的叶顶间隙对其性能的影响，建立不同叶顶间隙下风机三维模型，利用Fluent进行数值模拟，并结合风机性能试验验证仿真的正确性。分析压升、效率、轴功率、湍流动能和叶顶泄漏涡随两级叶轮叶顶间隙的变化情况，结果表明：在相同流量下，压升、效率随间隙的增大而减小；与第一级叶轮相比，间隙对第二级叶轮的轴功率、湍流动能及泄漏涡影响更加显著；随间隙增大，叶顶泄漏涡的强度和影响区域越大。     

对旋式轴流风机变环量流型的改进设计

为进一步提高对旋式轴流风机设计性能,在采用等环量设计方法优选得到的高压比、高效率风机设计方案基础上,在保证设计点两级等负载分配前提下,采用变环量流型设计方法,分别对比研究了两级转子不同展向载荷分配规律对对旋式轴流风机性能的影响,从中确定了性能最佳的两级转子径向载荷分布规律,并给出了近似描述该变化规律的数学表达式.