多翼离心风机的内流特性及其噪声研究

结合多翼离心风机各个组成部件的结构特点，回顾了近年来国内外有关多翼离心风机的内流特性及其噪声的研究现状。气流分布不均匀，风机前盘涡流区域、叶道的边界层分离以及从蜗壳逆行回到叶轮进口的回流是影响多翼离心风机性能的主要因素。在试验研究的同时，采用CFD手段进一步深入研究多翼离心风机内流场特征，并在风机设计时反映上述影响因素，从而有效地提高风机效率、降低风机噪声，应是今后研究的一个主要方向。     

偏心叶轮对多翼离心风机气动性能和噪声影响的数值研究

由于多翼离心风机结构及应用条件的特殊性,其设计不能完全采用工业风机的设计方法和经验参数。本文通过不同位置偏心叶轮方案的设计,研究多翼离心风机偏心叶轮的最佳安装位置。与原型风机相比,采用优化的偏心叶轮设计方案,风机流量增加了1.43m3/min,效率提高了2.52%,噪声下降了1.2d B。通过对风机流场和声场的数值分析,指出偏心叶轮可以有效减小叶轮部分叶道内的旋涡,改善由于多翼离心风机强前弯叶片所导致的流道内的流动阻塞,使叶轮的部分通道内的进气状态得到改善,减少叶道内的流动分离,从而有效提高风机效率,降低风机噪声。     

蜗壳与叶轮相对位置对多翼离心风机性能的影响

为探索蜗壳与叶轮轴向相对位置对多翼离心风机气动性能的影响,在保持其它参数不变的情况下,分别对仅改变蜗壳前端面与叶轮前盘间距、仅改变蜗壳后端面与叶轮后盘间距的改造风机进行数值计算,然后选取2个阶段中性能较好的方案进行组合从而确定最佳的蜗壳与叶轮轴向相对位置。研究结果表明:当叶轮出口宽度和蜗壳总宽度的相对值为0.81时其气动性能最佳,与原风机相比,效率提高了2.34%,静压提高了3.61%,噪声下降0.75 dB。     

叶轮结构对离心风机流动特性及性能影响的研究现状

通过回顾近年来国内外对叶轮性能的研究现状,结合叶轮结构形式及参数对离心风机不同方面的影响,得出离心风机叶轮内的损失主要是叶道内沿程摩擦损失,叶片上边界层分离,叶轮径向出口速度分布不均匀引起的尾迹流,轴向涡流,叶道进口冲击损失等。并指出今后的研究应以试验研究与采用CFD相结合的方法,在风机设计时考虑上述影响因素,从而降低叶轮内损失,提高离心风机性能。     

前向离心风机采用串列叶片叶轮降噪的试验研究

针对T9-19No.4A前向离心风机,使用等距串列叶片叶轮和不等距串列叶片叶轮取代原叶轮进行降噪试验研究,并对使用不同叶轮时风机的气动性能和噪声特性进行了比较分析。试验结果表明:使用等距串列叶片叶轮能够使风机在保持气动性能基本不变的条件下,在风机高效点附近的工况范围内降低前向离心风机的气动噪声,而使用不等距串列叶片叶轮则使风机气动性能和噪声特性均变差,主要原因之一是由于叶轮叶片沿圆周不均匀分布导致叶轮流场沿周向分布不均匀。建议在进一步的改进研究中仍可考虑使用等距串列叶片叶轮而暂不考虑使用不等距串列叶片叶轮。     

幅流风机叶轮参数对内流特性的影响研究

针对幅流风机风抗过大导致风量低,全压效率过低.基于FLUENT结合双圆弧叶片设计理论对原叶轮叶片结构进行了优化设计,分析其内流特性细节,实现了风量提升.仿真结果表明,改变叶片弯度角影响风机静压,改善风机风抗;厚度减少风量明显提升;增大部分端部圆风量减小.叶片弯度角、厚度和端部厚度均对风量影响很敏感,是影响幅流风机内流特...     

吸油烟机用多翼离心风机错齿叶轮设计研究

提高吸油烟机气动和噪声性能对改善人们的生活品质具有十分重要的意义。本文首先针对某型号吸油烟机的气动和噪声性能进行了数值模拟,并将数值模拟结果与试验结果进行了对比,验证了数值计算模型和计算方法的有效性。其次将贯流风机常用的叶轮分节交错结构应用到吸油烟机的风机叶轮中,得到了一种新型的错齿叶轮,并对错齿叶轮吸油烟机的气动和噪声性能进行了数值和试验研究。数值和试验研究表明,相比于原型吸油烟机,带错齿叶轮的吸油烟机总压和效率基本保持不变,风量增大0.89 m~3/min,噪声降低0.78 dB。分析其作用机理,发现多翼离心风机的蜗舌处的压力变小,压力梯度降低,蜗壳出口处的速度变大,因此整机的流量得到提高,噪声有所下降。错齿叶轮能够在0～2 000 Hz的低频段有效降低烟机噪声,在2 000 Hz以上的高频段降噪效果不明显。     

多翼离心风机噪声分析的试验及数值研究

通过传声器搭建的压力脉动测试系统,测量了某多翼离心风机蜗壳壁面一周的压力脉动值及风机进口的噪声频谱,并结合FLUENT计算分析风机内部的流场,分析得出所研究多翼风机的噪声主要以涡流噪声为主,同时旋转噪声也是不容忽视的一部分,最后为该多翼风机提出了降噪的改进方案。     

不同工况对离心叶轮内部流场特性影响的实验研究

利用激光多普勒测速系统(LDV)在设计和非设计等3种工况下对后弯闭式离心叶轮内部气流流动的影响进行了实验测量。利用测量数据对比描述了不同流量下流道出口主流速度分布的特点。径向面上的速度矢量图说明了不同进口条件下流道内气流流动产生分离的位置、强度以及发展。二次流矢量图表明流量的改变导致在垂直于主流方向引起截然不同的二次涡旋流动。     

蜗舌深度对离心风机气动性能和噪声影响研究

针对新风空调离心风机功率高、噪声大的问题,基于CFD仿真与试验研究了不同蜗舌深度对离心风机气动性能和噪声的影响,并着重对A10,A30,A40共3种方案蜗壳在25～60 m³/h流量范围内风机性能和噪声水平进行了分析。结果表明,蜗舌深度优化后,在额定流量45 m³/h工况下,仿真全压值提高5 Pa,全压效率提高17.28%,试验测试功率降低7.8 W,噪声降低1.7 dB;合理选择蜗舌深度能够改善蜗壳扩压段处流动,提高风机气动性能,同时降低风机噪声。研究结果可为离心风机设计提供指导。     

Experimental and theoretical analysis of stresses, noise and flow in centrifugal fan impeller

Stress analysis of fan impeller by experimental and finite element method has shown that, the stress pattern in impeller components is highly complex. The stresses in the impeller components can be reduced, by using the stiffening rings on the blades. In this paper, experimental and finite element approaches have been discussed to study the stresses in centrifugal fan impeller. The flow of centrifugal fan has been also determined by using the set-up as per AMCA and NAFM guidelines. The effect of the stiffening rings on the stresses, noise and fluid flow has been also investigated and discussed.     

Influence of blade thickness on transient flow characteristics of centrifugal slurry pump with semi-open impeller

As the critical component, the impellers of the slurry pumps usually have blades of a large thickness. The increasing excretion coefficient of the blades affects the flow in the impeller resulting in a relatively higher hydraulic loss, which is rarely reported. In order to investigate the influence of blade thickness on the transient flow characteristics of a centrifugal slurry pump with a semi-open impeller, transient numerical simulations were carried out on six impellers, of which the meridional blade thickness from the leading edge to trailing edge varied from 5-10 mm, 5-15 mm, 5-20 mm, 10-10 mm, 10-15 mm, and 10-20 mm, respectively. Then, two of the six impellers, namely cases 4 and 6, were manufactured and experimentally tested for hydraulic performance to verify the simulation results. Results of these tests agreed reasonably well with those of the numerical simulation. The results demonstrate that when blade thickness increases, pressure fluctuations at the outlet of the impeller become severe. Moreover, the standard deviation of the relative velocity in the middle portion of the suction sides of the blades decreases and that at the outlet of the impeller increases. Thus, the amplitude of the impeller head pulsation for each case increases. Meanwhile, the distribution of the time-averaged relative flow angle becomes less uniform and decreases at the outlet of the impeller. Hence, as the impeller blade thickness increases, the pump head drops rapidly and the maximum efficiency point is offset to a lower flow rate condition. As the thickness of blade trailing edge increases by 10 mm, the head of the pump drops by approximately 5 m, which is approximately 10 % of the original pump head. Futhermore, it is for the first time that the time-averaged relative flow angle is being considered for the analysis of transient flow in centrifugal pump. The presented work could be a useful guideline in engineering practice when designing a centrifugal slurry pump with thick impeller blades.

     

离心式风机直叶片的应用

对离心式风机叶片形式变化进行研究,系统分析了直叶片在实际应用中的有关问题,结果表明直叶片形式是风机发展的方向。     

Effect of blade tip pattern on blade load and vibration characteristics of a twin-stage axial flow fan

Focusing on a twin-stage axial fan, this paper investigates the effect of blade tip pattern on blade load and vibration characteristics. Steady simulations are first conducted to quantify the aerodynamic performance of various blade tip patterns. The finite element modeling analysis is performed to capture blade load and vibration characteristics, and Campbell diagram is introduced to evaluate resonance margin of different blade tip patterns. Results show that for all selected patterns, the first three mode shapes are mainly the bending of blade tip, which results in stress concentration at the blade root, while the last three are the waving in small range. The proposed blade tip patterns not only increase maximum stress and average deformation, but also significantly increase resonance margin near the rated speed. In addition, based on the harmonic response analysis, we find that the stress and amplitude frequency response will be notably altered by blade tip patterns.

     

Aeroacoustic characteristics and noise reduction of a centrifugal fan for a vacuum cleaner

The aeroacoustic characteristics of a centrifugal fan for a vacuum cleaner and its noise reduction method are studied in this paper. The major noise source of a vacuum cleaner is the centrifugal fan. The impeller of the fan rotates at over 3000 rpm, and generates very high-level noise. It was revealed that the dominant noise source is the aerodynamic interaction between the rotating impeller and stationary diffuser. The directivity of acoustic pressure showed that most of the noise propagates backward direction of the fan-motor assembly. In order to reduce the high tonal sound generated from the aerodynamic interaction, unevenly pitched impeller and diffuser, and tapered impeller designs were proposed and experiments were performed. Uneven pitch design of the impeller changes the sound quality while the overall sound power level (SPL) and the performance remains similar. The effect of the tapered design of impeller was evaluated. The trailing edge of the tapered fan is inclined. This reduces the flow interaction between the rotating impeller and the stationary diffuser because of some phase shifts. The static efficiency of the new impeller design is slightly lower than the previous design. However, the overall SPL is reduced by about 4 dB(A). The SPL of the fundamental blade passing frequency (BPF) is reduced by about 6 dB(A) and the 2^nd BPF is reduced about 20 dB(A). The vacuum cleaner with the tapered impeller design produces lower noise level than the previous one, and the strong tonal sound was dramatically reduced.     

离心式循环压缩机叶轮内部流场的数值模拟

运用大型CFD软件FLUENT采用标准κ-ε湍流模型进行数值模拟,研究了一台离心式循环压缩机叶轮的流场,分析了速度、压力和湍流强度的分布情况,为叶轮的改进提出了参考依据.     

叶片后缘加厚对轴流风机性能的影响

为解决NACA65系列翼型叶片后缘轮廓线内切圆半径收敛至0引起的铸造工艺问题,采用三次多项式函数生成叶片后缘厚度函数,精确调整叶片后缘末端厚度.基于Ansys软件对不同叶片后缘厚度的风机进行流体仿真,并分析其气动性能与静力结构特性.结果表明叶片后缘增厚使得叶片附面层分离损失增加,尾迹与叶栅主流区的掺混损失增大.叶片载荷...     

离心式通风机降噪设计研究

探讨了离心式通风机噪声产生的机理,并详细分析了离心式通风机在设计中常用的降噪设计的方法、思路以及每种设计方法的适用范围.可为解决离心风机降噪问题提供科学的指导.     

Exit flow measurements of a centrifugal pump impeller

Discharge flows from a centrifugal pump impeller with a specific speed of 150 [rpm, m³/min, m] were experimentally investigated. A large axisymmetric collector instead of a volute casing was installed to obtain circumferentially uniform flow, i.e. without interaction of the impeller and the volute. The unsteady flow was measured at the impeller exit and vaneless diffuser using a hot film probe and a pressure transducer. The flow at impeller exit showed pronounced jet-wake flow patterns. The wake, which was on the suction/hub side at high flow rate, became enlarged pitchwisely on both the hub and the shroud side as the flow rate decreases. The pitchwise non-uniformity of the flow rapidly decreased along the downstream and the nonuniformity almost disappeared at radius ratio of 1.18 for medium flow rate. The mean vaneless diffuser flow was reasonably predicted using a one dimensional analysis when an empirical constant was used to specify the skin friction coefficient. The data can be used for a centrifugal pump impeller design and validation of CFD codes and flow modeling.