Performance and Internal Flow of Contra-Rotating Small-Sized Cooling Fan

High pressure and large flow rate small-sized cooling fans are used for servers in data centers and there is a strong demand to increase its performance because of increase of quantity of heat from servers. Contra-rotating rotors have been adopted for some of high pressure and large flow rate cooling fans to meet the demand. The performance curve of the contra-rotating small-sized cooling fan with 40 mm square casing was investigated by an experimental apparatus and its internal flow condition was clarified by the numerical analysis. The fan static pressure of the front rotor was extremely low and it increased significantly at the rear rotor. The uniform flow was achieved at the inlet of the rear rotor because of the special shape of the casing between the front and rear rotors. On the other hand, the tip leakage flow was large enough to influence on the main flow of the test cooling fan by the design specification of high pressure with compact rotor diameter.

INTERNAL FLOW IN CROSS-FLOW FAN FOR AIR CONDITIONER

A numerical analytic process is suggested combining direct boundary element methodwith discrete vortex method and internal flow in cross-flow fan calculated. The process considersnot only function of impeller, but also effect of volute casing. Internal flow field of cross-flow fan ispractically measured, and results compared with that from calculation. It shows that the process isexpected to be used in predicting performances of fluid machinery.

An Approach to Field Test Scheme of Main Fan Performance for the Special Type Mine Fan-House

The field tot of performance of mine main fan is going to become an independance requirement of coal mlue progressively and to be taken seriously. According to the fan-house with air gate closed to the fan inlet, this paper analyses the influence of the rapid changing air flow field upon field test and puts forward a reasonable test scheme.

Numerical Study on Internal Flow of Small Axial Flow Fan with Splitter Blades

The splitter blades are widely used in axial compressors and play an active role in the improvement of the overall performance of compressors. However, little research on the application of splitter blades to small axial flow fans is conducted. This paper designs a splitter blade small axial flow fan (model B) with a small axial flow fan as the prototype fan (model A) by adding short blades at the second half part of the passageway among long blades of model A. The steady simulation for the two models was conducted with the help of RNG k-ε turbulence model provided by software Fluent, and static characteristics and internal flow characteristics of the two models were compared and analyzed. Results show that splitter blades can improve the unsteady flow in the small flow rate region and also have a positive role to increase static pressure rise and efficiency in the higher flow rate region. The variation of static pressure gradient on the meridian plane in model B is well-distributed. The static pressure on the blade surface of model B distributes more uniformly. Splitter blades can suppress the secondary flow from pressure side to suction side in the leading edge because the pressure difference between suction side and pressure side in model B is generally lower than that of model A. And it also can restrain the vortex shedding and flow separation, and further it may be able to get the aerodynamic noise lower because static pressure gradient on the blade surface is well-distributed and the vortex shedding is not developed. Therefore, the performance of the fan with splitter blades is better than that of the prototype fan. The findings of this paper can be a basis for the design of high performance small axial flow fans.

Numerical Investigation on Vortex Structure and Aerodynamic Noise Performance of Small Axial Flow Fan

The details of unsteady flow field in small axial fans are described and the relationship between the internal flow char- acteristics and aerodynamic noise of small axial flow fans are explored in the manuscript. Firstly, the broadband noise model is introduced to calculate the distributions of broadband noise sources in fan’s internal flow field, and further fan’s internal flow characteristics affecting broadband noise sources are analyzed by the main distributions of broad- band noise sources. Secondly, the unsteady characteristics of vortex structure in fan’s internal flow field are analyzed by large eddy simulation, and FH-W acoustic model is introduced to calculate aerodynamic noise affected by the unsteady characteristics of vortex structure. Finally, Monitoring points are set up near and far field of small axial fans, at which sound pressure level and spectral characteristics are analyzed. The results show that broadband noise sources are mainly distributed at the tip clearance close to blade trailing edge and one third of chord length of blade trailing edge of small axial fans. The maximum sound power of broadband noise sources at the tip clearance is greater than that at blade trail- ing edge. Sound power level of broadband noise near one third of blade chord length of blade trailing edge is first in- creasing and then decreasing when the distance between radial planes and the center of fan hub increases. Fan’s internal flow characteristics affecting broadband noise sources are the tip leakage vortex and the trailing edge vortex shedding. The tip leakage vortices at the leading edge of blade tip first integrate and then break down, while vortex cores of the trailing edge vortex shedding gradually move from blade hub to one-third of blade chord length and then move to far field within a one-seventh of the rotation cycle. Within a flow passage of fan rotation period, sound pressure level of the monitoring points is relevant to the unsteady feature of vortex structure and the main bands of aerodynamic noise of monitor points are irrelevant to the unsteady feature of vortex structure, relating to the distance between the monitor points and fan. With the above distance increasing, the main bands of aerodynamic noise are widened and moved from the low bands to high bands. All conclusions in the paper will provide significant references for reducing the noise of small axial flow fans.

Effect of Hub-Ratio on Performance of Asymmetric Dual-Rotor Small Axial Fan

Currently, domestic and abroad scholars put more attention on contra-rotating dual-rotor axial fan. But there is less scholars study on asymmetric dual-rotor small axial fan, which is one of the contra-rotating dual-rotor axial fans. Like axial fan, many factors have influence on the performance of the asymmetric dual-rotor small axial flow fan, such as the wheel hub ratio, blade shape, blade number, stagger angle and the tip clearance. Because wheel hub ratio has great impact on the performance of the fan, we choose the size of wheel hub ratio as a variable factor to study the model change. There is a different wheel hub ratio between front stage impeller and rear stage of asymmetric dual-rotor small axial fan, so it is very beneficial to select the greater wind area that the fan area of external diameter minuses the area occupied by the blades and the hub as front stage impeller. In this paper, the hub-ratio of front stage impeller is 0.72, and that of rear stage is 0.72, 0.67 and 0.62 respectively along with the front stage impeller. Three kinds of models with different hub ratio of rear stage are simulated using the CFD software and the static characteristics are obtained. Based on the experimental test results, the internal flow field of the asymmetric dual-rotor small axial fan is analyzed in detail, the impact trends of different hub-ratio on the performance of asymmetric dual-rotor small axial fan are obtained and the argument of structure optimization for dual-rotor small axial fan is provided.

EXPERIMENTAL RESEARCH ON AERODYNAMIC PERFORMANCE AND EXIT FLOW FIELD OF LOW PRESSURE AXIAL FLOW FAN WITH CIRCUMFERENTIAL SKEWED BLADES

In this article, the low pressure axial flow fan with circumferential skewed rotor blade, including the radial blade, the forward-skewed blade and the backward-skewed blade, was studied with experimental methods. The aerodynamic performance of the rotors was measured. At the design condition at outlet of the rotors, detailed flow measurements were performed with a five-hole probe and a Hot-Wire Anemometer （HWA）. The results show that compared to the radial rotor, the forward-skewed rotor demonstrates a wider Stable Operating Range （SOR）, is able to reduce the total pressure loss in the hub region and make main loading of blade accumulating in the mid-span region. There is a wider wake in the upper mid-span region of the forward-skewed rotor. Compared to the radial rotor, in the backward-skewed rotor there is higher total pressure loss near the hub and shroud regions and lower loss in the mid-span region. In addition, the velocity deficit in the wake is lower at mid-span of the backward-skewed rotor than the forward-skewed rotor.

仿鹰翼型叶片幅流风机气动噪声性能研究

为进一步优化幅流风机气动噪声性能,以某地铁空调系统中幅流风机为研究对象,提取雀鹰羽翼展向40%截面处作为参考,重构风机叶片。基于Fluent软件,采用Realizable K-ε模型,利用数值模拟方法和声类比FW-H方程,对仿鹰翼型叶片风机进行流场及气动噪声分析。结果表明,仿鹰翼型叶片风机较原风机风量增加2.67 m^(3)/min,叶轮效率提高3.07%,噪声降低2.34 dB。仿鹰翼型叶片可有效抑制漩涡噪声,改善幅流风机气动性能和声学性能。

基于Fluent的小型扫路机内部流场数值分析及优化

针对某小型扫路机箱体内网孔板易堵塞的问题,基于Fluent采用了应用计算流体力学(CFD)方法对该扫路机箱体内流场进行了仿真,采用Realizable k-ε湍流模型和多重坐标系(MRF)进行求解,对风机进气网孔板的网孔数量、风机进气室高度对系统性能的影响进行了分析。仿真结果表明,该型扫路机箱体内网孔板易堵塞的原因为风机进气室空间高度过小,导致网孔处流速过高,垃圾易吸附于网孔板上,从而影响风机进气的通畅性,进而降低了整个系统的性能,单纯靠增加风机进气网孔板的网孔数量并不能大幅提升扫路机的气力系统作业性能。通过计算优化了风机进气室空间距离等关键参数后,风机功率提升6.94%,风机流量提升6.27%,吸嘴负压提升10.15%,整个气力系统的性能得到了显著提升。

Performance and Flow Condition of Small-Sized Axial Fan and Adoption of Contra-Rotating Rotors

Small-sized axial fans are used as air coolers for electric equipments.But there is a strong demand for higher power of fans according to the increase of quantity of heat from electric devices.Therefore,higher rotational speed design is conducted,although it causes the deterioration of the efficiency and the increase of noise.Then the adoption of contra-rotating rotors for the small-sized axial fan is proposed for the improvement of the performance.In the present paper,the performance and the internal flow condition of the small-sized axial fan are shown as a first step of the research for the contra-rotating small-sized axial fan and the important points to apply contra-rotating rotors to the small-sized axial fan are discussed.Furthermore,the numerical flow analysis is conducted to investigate the performance of the contra-rotating small-sized axial fan and internal flow conditions and pressure distributions are clarified and the effect of contra-rotating rotors is considered.

变叶片安装角对旋风机气固两相流特性研究

针对某实际运行的矿用对旋风机叶片存在的磨损问题,采用SST k-ω湍流模型和Finnie磨损模型,对不同叶片安装角下风机内部气固两相流场进行了数值模拟研究。首先,选择风机静压、功率和效率为评价指标,进行了风机性能试验,对数值计算方法和模型的准确性进行了验证;然后,根据设计的6种叶片安装角方案,对叶片压力面的磨损特征和气固两相流风机流场的分布规律进行了分析;最后,对不同叶片安装角下气固两相流风机的性能进行了对比,确定了具有最佳抗磨效果和最优风机性能的叶片安装角方案。研究结果表明:相比于原始的叶片安装角,增大后级安装角后的叶片面平均磨损率降低了6.0×10^(-8)kg/(m^(2)·s);同时,增大后级安装角能够有效地缓解后级叶片前缘和尾缘处的分离涡现象,提高风机的性能,达到叶片抗磨的目的。

高压无气喷涂扇形喷嘴结构参数对内部流场影响的数值模拟

为研究高压无气喷涂中喷嘴内部结构参数对内部涂料流动状态的影响,在Fluent中对不同结构参数(收缩角,出口段长径比,出口切槽夹角)的喷嘴模型分别进行建模及数值模拟计算,黏性模型为层流模型,涂料为乳胶漆。仿真结果表明,在其他条件不变的情况下,喷嘴收缩角,出口段长径比,出口切槽夹角的改变都会对内部涂料的流动状态产生影响。随着喷嘴收缩角的增大,涂料流体的压力衰减和速度梯度也会明显加大;长径比的改变会影响流体的流速。切槽夹角对流体流速的影响较大,随着切槽夹角的增大,流体出口流速也会增加,但集束性会随之降低。

煤矿轴流通风机的数值模拟研究

为充分掌握FBCDNo14型对旋轴流式通风机的特点,指导实践生产中通风机运行参数的设置,在对FBCDNo14型通风机原理及其结构分析的基础上,基于SolidWorks三维软件和Fluent软件构建数值模拟仿真模型,并通过试验验证了模型的准确性。对不同叶片安装角度下的三种工况对通风机内部气流轨迹、速度矢量以及压力云图进行对比,以期指导今后通风机参数的优化和实践生产。

空调用贯流风机特性研究及性能优化

贯流风机是小型分体式热泵空调器送风模块的重要组成部件,其流场特性、声场特性以及性能优化受到重点关注。通过整理分析国内外空调贯流风机的研究成果,总结贯流风机的流场特性和声场特性的研究现状,主要围绕贯流风机的流场、声场及其性能优化这3个方面的研究成果展开综述,对贯流风机今后的研究工作提出展望。

Performances and Acoustic Noise of Micro Multi-blade Fan

在这篇论文，表演和传统的类型的声学的噪音，微多片扇子试验性地并且数字地被调查，到为居民情形优化扇子的说明。声学的噪音水平减少，但是效率随 impeller 的片数字的增加稍微败坏。而且，声学的噪音随在 impeller 插头和涡囊舌头之间的距离的增加减少，在随输入的增加和扇子效率的恶化伴随。

双出风口多风道离心风机内部流场数值模拟

针对现有全喂入式水稻联合收获机风筛式清选装置中单风道离心风机的缺点,运用Solidworks软件建立了双出风口多风道离心风机的流道模型,利用ICEM软件进行了网格划分,并用Fluent软件对双出风口多风道离心风机内部流场进行了三维数值模拟,确定了风机的结构尺寸。改进后风机内部流场仿真结果表明:双出风口多风道离心风机的上出风口和叶轮外边缘处气流速度较大,叶轮流道的压力沿径向逐步增大,下出风口Ⅰ、Ⅱ、Ⅲ的气流速度逐步增大,风速衰减距离增加,有利于气流覆盖整个筛面;上出风口处横向气流基本成层状分布,下出风口的3个风道横向气流呈中间高两边低的对称分布,存在明显的边界效应。分析了风机转速、进风口直径和分风板角度的变化对风机内部流场分布、出风口风速、风量的影响:上出风口和下出风口Ⅱ和Ⅲ的风速、风量和压力最大值随风机转速的增加逐步增大;各出风口的风量及风速最大值随进风口直径减小(或增加)而减小(或增加),其中下出风口Ⅰ变化较明显;上、下分风板角度的改变使得下出风口的风速和风量发生了较大变化。

两级动叶可调轴流风机内流特征的数值模拟

采用Fluent软件对某600MW机组配套的两级动叶可调轴流一次风机进行了全三维定常数值模拟,分析了风机第一、第二级叶轮内流特征和动叶安装角对风机性能的影响.结果表明:第二级叶轮出口总压整体呈现高压区和次高压区交替分布的特征,且比第一级叶轮的对称性差;第一、第二级叶轮叶片压力面、吸力面的总压和静压分布规律相似;第二级叶轮叶片压力面和吸力面相应位置上的静压值均大于第一级叶轮叶片;随着动叶安装角的增大,第一、第二级叶轮的总压升系数和静叶的扩压系数均增大,且第二级叶轮大于第一级叶轮,表明第二级叶轮的做功能力和静叶的扩压能力均比第一级叶轮的大.

空调用轴流风扇系统内流特性分析与应用

本文针对分体空调器室外机轴流风扇系统的特点，采用计算流体动力学方法对该系统中的气体流动进行数值模拟，内流分析与性能实验结果比较表明，ＣＦＤ技术能够有效地改进空调器风扇系统设计及其为不同叶型风扇的应用提供依据．

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。

动叶可调轴流风机叶顶间隙形态的优化研究

优化叶顶间隙形态可有效改善轴流风机的性能。以OB-84型动叶可调轴流风机为对象,采用Fluent模拟了均匀间隙及非均匀间隙下的风机性能,探讨了不同间隙形态对间隙内泄漏流场及损失分布的影响。研究表明:在平均叶顶间隙不变的前提下,采用渐缩型间隙的风机全压与效率均高于均匀间隙,高效区范围扩大,且渐缩程度越大,性能提升越显著;渐缩型间隙改变了间隙内涡量场的分布,叶顶泄漏损失减少,叶片中上部做功能力增强。而采用渐扩型间隙后做功能力下降,风机性能均低于均匀间隙。渐缩型叶顶间隙形态可作为一种提高风机性能的重要手段加以实施。