EFFECT OF TIP CLEARANCE ON PERFORMANCE AND FLOW FIELD OF SMALL SIZED HIGH SPEED CENTRIFUGAL FAN

A centrifugal fan with the high speed and compact dimensions is studied numerically and experimentally. The centrifugal fan consists of a shrouded impeller rotating at 34 000 r/min with a small tip clearance 0.7 mm to the fixed outer casing. Computational models with/without the tip clearance are built and the κ-ω shear stress transport （SST） turbulence model and the unstructured mesh are applied to the numerical simulation for unsteady solutions. The overall performance is measured on a standard experimental bench and the major flow feature of each component inside the centrifugal fan is numerically investigated. In the presence of the tip clearance due to the difference of static pressure between leading and trailing edges of the clearance, i. e. , leading and trailing edges of the impeller, a strong return flow exists inside the clearance passage and re-circulates the main stream inside the impeller passage, and produces the strong flow interaction, thus changing the flow field and influencing the overall performance.

Prediction and optimization of aerodynamic noise in an automotive air conditioning centrifugal fan

The high aerodynamic noise induced by automotive air conditioning systems has important effects on the ride comfort, and the centrifugal fan is the largest noise source in these systems. It is very important to reduce the aerodynamic noise generated by the centrifugal fan. The flow field and the sound field on the whole centrifugal fan configuration have been carried out using the computational fluid dynamics. Simulation results show that the sound pressure level near the outlet of the centrifugal fan is too high. Based on the relationship between flow characteristics and the aerodynamic noise, four parameters of the centrifugal fan, i.e., impeller blade＇s outlet angle 0, volute tongue＇s gap t, collector inclination angle fl, and rotating speed n, were selected as design variables and optimized using response surface methodology. While keeping the function of flow rate unchanged, the peak noise level is reduced by 8 dB or 10.8%. The noise level is satisfactorily reduced.

PERFORMANCE IMPROVEMENT OF CENTRIFUGAL FAN BY MEANS OF NUMERICAL SIMULATION

Numerical simulation is used to investigate the flow field in a model centrifugal fan for steam power stations in order to improve the performance. During testing the model fan, it is found that the efficiency is only 62.5% with inlet box, without it the efficiency is 83%. In addition, the strong vibration of test rig is observed with inlet box. It would be highly desirable if the aerodynamics of the fan could be studied. Therefore, numerical simulation is carried out to investigate the internal flow characteristics of a model fan with inlet box. The results from CFD analysis show that the whole region of the inlet box is occupied by a spiral vortex rotating inversely as the rotor＇s direction, which significantly affect the most flow＇region inside the fan. For this reason, a dummy plate is arranged in the inlet box to impede the generation of the spiral vortex, the results from CFD after the reform demonstrate that the modification is quiet effective, the former large spiral vertex has been destroyed effectively, the large one is superseded in favor of two small vortexes. However, two small vortexes have little effect on the inner flow of the rotor and the following parts. Finally, the efficiency of the model fan is improved by the test and the strong vibration of the test rig disappears. This type of modification has been used in steam power stations, the fan efficiency raises to 84% successfully.

Aerodynamic Optimization of a Centrifugal Fan Using Response Surface Methodology

In this paper, the optimization scheme of a centrifugal fan under the constraints of the total pressure difference, efficiency and shaft power was carried out. The blade inlet angle ?1A and the blade outlet angle ?2A of the centrifugal impeller were optimized using the Response Surface Methodology (RSM). Nine optimization cases were presented. The aerodynamic performance and the flow field of the optimized model were carefully compared with the original model. The results show that the total pressure difference and the total-pressure efficiency increase by 5.7% and 4.2% respectively after the optimization. Compared with the original fan, the flow field inside the impeller of the optimized fan has been improved. The flow separation existing around the blade suction surface outlet is suppressed significantly. For fields in the volute, the optimization scheme has reduced the local vortex intensity and weakened the vortex scale. The flow field stability around the volute tongue is also correspondingly improved.

Multi-objective Optimization Design and Experimental Investigation of Centrifugal Fan Performance

Current studies of fan performance optimization mainly focus on two aspects： one is to improve the blade profile, and another is only to consider the influence of single impeller structural parameter on fan performance. However, there are few studies on the comprehensive effect of the key parameters such as blade number, exit stagger angle of blade and the impeller outlet width on the fan performance. The G4-73 backward centrifugal fan widely used in power plants is selected as the research object. Based on orthogonal design and BP neural network, a model for predicting the centrifugal fan performance parameters is established, and the maximum relative errors of the total pressure and efficiency are 0.974% and 0.333%, respectively. Multi-objective optimization of total pressure and efficiency of the fan is conducted with genetic algorithm, and the optimum combination of impeller structural parameters is proposed. The optimized parameters of blade number, exit stagger angle of blade and the impeller outlet width are seperately 14, 43.9~, and 21 cm. The experiments on centrifugal fan performance and noise are conducted before and after the installation of the new impeller The experimental results show that with the new impeller, the total pressure of fan increases significantly in total range of the flow rate, and the fan efficiency is improved when the relative flow is above 75%, also the high efficiency area is broadened. Additionally, in 65% -100% relative flow, the fan noise is reduced. Under the design operating condition, total pressure and efficiency of the fan are improved by 6.91% and 0.5%, respectively. This research sheds light on the considering of comprehensive effect of impeller structrual parameters on fan performance, and a new impeller can be designed to satisfy the engineering demand such as energy-saving, noise reduction or solving air pressure insufficiency for power plants.

Fluent-based numerical simulation of flow centrifugal fan

Testing centrifugal fan flow field by physical laboratory is difficult because the testing system is complex and the workload is heavy, and the results observed by naked-eye deviates far from the actual value. To address this problem, the computational fluid dynamics software FLUENT was applied to establish three-dimensional model of the centrifugal fan. The numeral model was verified by comparing simulation data to experimental data. The pressure centrifugal fan and the speed changes in distribution in centrifugal fan was simulated by computational fluid dynamics soft-ware FLUENT. The simulation results show that the gas flow velocity in the impeller increases with impeller radius increase. Static pressure gradually increases when gas from the fan access is imported through fan impeller leaving fans.

Design of a Three-Dimensional Centrifugal Fan with Controlled Blade Loading Approach

The high flow-rate centrifugal fan needs a three-dimensional impeller to achieve a high efficiency. In this paper, the design procedure of a high-efficiency three-dimensional centrifugal fan is presented. First, the main dimensions of the fan were calculated by using the conventional one-dimensional method. Then, the blade loading or the angular momentum distribution along the meridional streamline on the blade surfaces is prescribed. After that, the three-dimensional blade is determined by using the streamline curvature method. With the aid of numerical simulations, the performance of the three-dimensional fan was improved and some of the key influence factors were investigated. The analyses indicate that, as to the high flow-rate centrifugal fan, the Stanitz modified formula is recommended to calculate the separation radius, rb. A proper increase in the separation radius is beneficial for the fan’s performance. It is also indicated that a decrease in the angular momentum on the hub leads to an increase in total pressure efficiency, under the condition of a given constant mean angular momentum at the outlet of the blade. In addition, the installation of a fairing on the hub plate can improve the fan’s efficiency evidently when the streamline curvature method is adopted to design the three-dimensional impeller.

Aerodynamic Noise Characteristics During Evolution of Rotating Stall in Centrifugal Fan

基于节流阀函数及宽带噪声源模型，对电厂常用的G4？73型后向式离心风机在旋转失速状态下的气动噪声特性进行了数值研究。分析离心风机分别在设计工况、失速先兆的产生过程、失速先兆发展为失速团的三维演化过程及失速团沿周向传播过程中风机内部的气动噪声特性，揭示了旋转失速非稳定流动现象对气动噪声分布的影响规律。结果表明，失速先兆发生后叶轮附近旋涡噪声对应的高噪区经历了沿径向、周向和轴向的三维非定常演化过程，高噪区从两个变为一个；失速发生后，旋涡噪声占主要部分，高噪区保持与失速团相同的速度沿周向传播。文中分析了失速团与蜗舌对离心风机气动噪声的影响机制。研究结果对完善旋转失速的理论体系及通过噪声对旋转失速进行预估具有重要意义。

Application of a Cleaning System Made up of a Centrifugal Fan with Double Channel and One Sieve to Combine

In this paper the application of a cleaning system which was made up of a centrifugal fan with double channel and one sieve to 4LZ-3.5 combine was introduced. This cleaning system with double channel compared with the traditional air-sieve cleaning system of combines may omit one two sieves and simplify the transmission mechanism. It is also compared with the present cleaning system with double channel applied to some combines, such as the Commandor 112CS/ 228CS combines of Claas Corporation in Germany and the MAXIMIZERTMombincs of John Deerc company in U.S.A. It may omit one sieve and the preclcaner and simlify the transmission mechanism. The measuring results indicated that the cleaning ratio of wheat grain is 99.1% and the cleaning loss ratio of wheat is 0.17% when the feed rate is 4.01 kg/ s.

Wind Field Flow Characteristics Analysis of T4-72 Type Centrifugal Fan

In order to explore the internal wind field flow characteristics of T4-72 type centrifugal fan, the three-dimensional model was established based on PRO/E software. Combined with computational fluid Dynamics Software Fluent 6.3, the standard model and SIMPLEC algorithm were used to simulate the wind field inside the fan. Analysis of the flow characteristics, velocity distributed and pressure distributed of the internal fluid model of the T4-72 centrifugal fan, combined with the theoretical formula to obtain the full pressure, power and efficiency performance parameters of the fan. The centrifugal fan performance curve is drawn. While compared with the experimental data, it is found that the internal flow disturbance is strong when the fan is running under low load condition and high load condition, which affects the performance of the fan and reduces the life of the fan. The numerical simulation results are consistent with the experimental results. The overall performance parameters of the fan are in good agreement, verifying the reliability of the simulation results;when the fan works between 1 - 1.4 times the rated flow rate, it can obtain a more stable flow field while maintaining higher efficiency, which provides a new idea for the optimization of the subsequent fan.

多翼离心风机蜗壳气动性能与出风均匀性优化设计

以某型号风暖浴霸吹风系统的多翼离心风机为研究对象,利用ANSYS Fluent 2020 R2对原型风机的出口风量与均匀度进行仿真分析,结果显示仿真与实测误差在5%以内,验证了用CFD数值模拟方法来优化浴霸多翼离心风机的可靠性.将蜗壳型线参数化,通过正交试验设计,针对蜗舌放置角α、蜗舌半径R、等角螺线常数A(蜗壳周向面积)与风轮移动距离L(蜗舌与叶轮间隙)4个因素,制定了16组参数组合方案并进行了CFD数值模拟,得到各方案的出口风量与均匀度,并由均值与极差分析确定了最优参数组合.通过数值计算结果可知,优化后的风机在蜗舌附近区域湍流强度减小,内部流动改善.测试结果显示,优化后的风机出口风量提升7.3%,均匀度提升4.5%,全压效率提升5.9%.显著提升了风暖浴霸离心风机的出风性能和出口风速分布均匀性,对提高风暖浴霸取暖效率和增强人体舒适性有重要意义.

多翼离心风机旋转失速阶段压力脉动分析

为了研究多翼离心风机在旋转失速阶段的压力脉动特性,以多翼离心风机为研究对象,利用Creo软件对其进行三维建模,并对模型进行网格划分,进行非定常数值计算.在叶轮出口不同周向、径向以及轴向位置设置监测点,分析旋转失速工况下风机内部压力脉动规律,计算结果表明:隔舌处监测点的压力系数最大,且随着流量的减小,压力脉动剧烈程度增大;叶轮出口受叶轮与蜗壳之间动静干涉影响,压力系数幅值最大,往蜗壳壁面径向移动,压力脉动程度减弱;压力脉动规律受轴向位置变化影响较小,旋转失速程度的变化会引起压力脉动的变化,旋转失速越强,压力脉动越剧烈,低频脉动范围越广,失速频率幅值越高.

煤矿用离心通风机导叶叶型结构的优化设计研究

对煤矿中使用的离心通风机结构及相关参数进行介绍,阐述了前导器内导叶结构参数对设备性能的重要性。基于CFD有限元软件构建离心通风机的模型,模型中选用SSTκ-ω湍流模型,将数值模拟结果与试验结果进行对比,验证了有限元模型的正确性。对平板形、弧形和对称翼形3种导叶结构进行对比研究,发现对称翼形结构下的通风机效率最佳。在原有翼形结构的基础上,设计了4种翼形导叶结构,主要是改变了叶根和叶尾的形状、叶根与叶尾之间的扭转角。数值模拟结果表明,翼形3导叶结构的全压、效率、压力损失、湍动能等均处于最佳状态。所以将翼形3导叶结构确定为最优的结构,能够显著提升离心通风机的综合性能。

多翼离心风机气动噪声数值预测

文章采用计算流体力学软件Fluent对多翼离心风机的内部流场进行三维的定常和非定常数值模拟,并对数值结果进行了分析。数值结果与试验结果的对比分析表明了数值模拟具有较好的准确性和可信度。随后,基于流场的计算结果进行声场的数值计算,结果表明:基于非定常流动的FW-H声压模型可获得多翼离心风机气动噪声主要噪声源在声学接收点处的噪声频谱,有助于更深层地了解声源的噪声特性以及明确噪声峰值所对应的频率段,为下一步进行有针对性的噪声控制研究提供有力的依据。

多翼离心风机叶轮内油性粒子沉积特性的数值研究

为了揭示多翼离心风机内部油性粒子沉积分布规律,减少风机内粒子沉积,采用Fluent离散相模型描述粒子运动,同时结合临界速度模型和用户自定义函数(UDF)建模油性粒子在壁面上的沉积,模拟研究了多翼离心风机内油性粒子的运动轨迹和沉积特性,并探究了颗粒直径对沉积分布的影响。结果表明:油性粒子沉积主要分布在叶片压力面,且靠近出口尾缘段尤为严重;由于进气条件不稳定,整机下内部流场更为紊乱,沉积情况也更为严重;大直径粒子受惯性力主导更容易沉积在叶片表面。针对油性粒子沉积分布规律及成因,提出了切割叶片减小叶片出口安装角从而减少叶轮内油性粒子沉积的方法。对于切割后的叶片,叶轮出口处流动分离区域减小,叶片尾缘段涡量减小,通过数值模拟和实验研究发现,叶轮内油性粒子沉积率分别下降了30.75%和30.66%,两者吻合良好,证实了提出的减小叶轮油性粒子沉积方法的有效性。

多翼离心风机集流器偏心安装对空调新风系统风量的影响

为了研究集流器对多翼离心风机的影响,基于真实空调新风系统模型,构建了空调新风系统多翼离心风机CFD三维模型。对集流器偏心前后的风机内部流场展开分析,最后得出集流器的合理偏心安装方案,并通过试验对其进行了验证。研究结果表明,当偏心角θ=120°,偏心距L=4.2 mm时,风机流道内流动情况得到明显优化,叶道堵塞情况得到改善,叶轮有效通流面积增大,叶轮出口气流速度提升,叶轮与集流器间的泄漏流减少,风机效率有所提升,蜗壳出口处风量提高3 m3/h,增幅约5.6%。研究结果可为多翼离心风机的优化设计提供参考。

气流染色机用离心通风机的优化设计

离心通风机是气流染色系统的核心部件,其性能优劣直接决定气流染色系统的染色质量和能耗水平。本文针对某气流染色机用离心通风机的气动性能和几何结构开展优化设计,以风机全压PtF和全压效率ηtF最大化为优化目标,利用基于人工神经网络构建的代理模型,结合带精英策略的遗传算法对离心通风机叶轮开展优化设计,同时基于叶轮与蜗壳耦合整机气动匹配条件下对蜗壳几何结构进行优化设计。试验结果表明,优化设计的离心通风机结构更紧凑,其全压PtF提升约500Pa,其全压效率ηtF提升约5%。

基于WPSO-BP和L-MBWO的多翼离心风机优化研究

针对多翼离心风机气动性能、噪声情况难以同时改进的问题,提出了一种基于变权重粒子群优化算法的反向传播神经网络风机性能预测模型(WPSO-BP),以及一种基于逻辑混沌初始化的多目标白鲸优化算法(L-MBWO),并将二者应用于多翼离心风机的优化设计中。首先,选取了叶片进出口角、倾斜蜗舌的最大蜗舌半径、叶片切除角度作为设计变量,把风机的全压、效率、声压级作为优化目标;然后,构建了WPSO-BP预测模型,以反映设计变量与优化目标之间的关系,定量分析对比了该模型与BP神经网络预测模型,预测值用于风机的性能优化;接着,将逻辑混沌初始化引入到白鲸优化算法(BWO),基于第三代非支配排序遗传算法(NSGA-Ⅲ)构建了L-MBWO优化算法;最后,在实验验证仿真可靠的前提下,将提出的预测模型和优化算法应用于风机优化,并对优化效果进行了综合分析。研究结果表明:优化后的风机全压增加了34.79 Pa,效率提高了0.67%,噪声降低了1.73 dB,实现了多个优化目标之间的平衡,有效改善了风机的综合性能,为多翼离心风机的优化设计提供了一种新思路。

采用分组模型的高比转速离心风机改进设计

为了提升某高比转速离心风机的气动性能,采用分组设计的方法,结合试验和数值模拟依次对原始风机的叶轮、蜗壳和集流器进行了改进设计。结果表明:叶轮前盘型线对高比转速离心风机的气动性能影响较大,仅对叶轮前盘型线改进设计后,风机的全压和效率分别提升了9.64%和8.91%;双圆弧叶片相较于单圆弧叶片具有更高的设计自由度,可实现对叶轮内部流动更加精细的控制,当双圆弧叶片的相对半径系数和相对叶片角系数分别取0.7和0.3时,全压效率值为87.43%;经过分组改进设计后的风机在设计工况下的全压和全压效率较原始风机分别提升了17.84%和12.79%,最高效率值为88.58%,内部流场得到优化,流动损失明显减小,性能得到全面提升。采用分组模型的改进设计方法可以有效地提升离心风机的气动性能,具有实际工程应用价值。

采棉机风机叶片优化与流场分析

风机作为采棉机气力输送系统的核心部件,其性能优劣将影响采棉机的作业效率。为提高采棉机气力输送系统的最大风量,针对采棉机用多翼离心风机叶片进行优化设计。为了获得代理模型所需的基本数据,建立了CFD数值模型并采用拉丁超立方实验在设计空间内生成20组样本。基于样本数据,建立了出口风量与设计变量的近似模型,采用智能优化算法获得最优设计方案。优化后的设计方案相较于原型机,出口风速明显增大。CFD数值计算分析风机的动态特性,结果表明,在多转速工况下风量均有明显提升,其在额定转速工况下,风量提升17.27%。