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1.
Flow instability in a centrifugal fan was studied using energy gradient theory. Numerical simulation was performed for the threedimensional turbulent flow field in a centrifugal fan. The flow is governed by the three-dimensional incompressible Navier-Stokes equations coupled with the RNG k-ε turbulent model. The finite volume method was used to discretize the governing equations and the Semi-implicit method for pressure linked equation (SIMPLE) algorithm is employed to iterate the system of the equations. The interior flow field in the centrifugal fan and the distribution of the energy gradient function K are obtained at different flow rates. According to the energy gradient method, the area with larger value of K is the place where the flow loses stability easier. The results show that instability is easier to generate in the regions of impeller outlet and volute tongue. The air flow near the hub is more stable than that near the shroud. That is due to the influences of variations of the velocity and the inlet angle along the axial direction. With the decrease of the flow rate, instability zone in a blade channel moves to the impeller inlet from the outlet and the unstable regions in different channels develop in opposite direction to the rotation of impeller.  相似文献   

2.
We performed numerical simulations to study the flow characteristic in a centrifugal pump based on the RANS equations and the RNG k-ε turbulent model. The flow field, including the front and back pump chambers, the impeller wear-ring, the impeller passage, the volute casing, the inlet section and outlet section was calculated to obtain accurate numerical results of fluid flow in a centrifugal pump. The flow characteristic was studied from the internal flow structure in pump chambers, the radial velocity at impeller outlet as well as the pressure inside of the pump, the circumferential velocity and the radial velocity in front pump chamber. The variation of flow parameters in internal flow versus flow rate in the centrifugal pump was analyzed. The results show that the overall performance of the pump is in good agreement with the experimental data. The simulation results show that the distribution of flow field in the front pump chamber is axial asymmetry. The energy dissipation at the impeller outlet is larger than other areas. The distribution of the circumferential velocity and that of radial velocity are similar along the axial direction in the front pump chamber, but the distribution of flow is different along the circumferential and the radial directions. It was also found that the vorticity is large at the impeller inlet compared with other areas.  相似文献   

3.
离心通风机整机三维流场的数值模拟   总被引:4,自引:0,他引:4  
对前弯型离心通风机整机三维内流场进行了数值模拟,预测了叶轮的做功效率,通过与试验结果比较表明了计算的可信性.详细分析了风机内部流场情况,发现轮盖附近的流动分离现象使叶轮对流体的做功能力受到很大影响.通过对不同工况的计算,揭示了叶轮和蜗壳内部的二次流现象及其发展规律.通过比较,分析了蜗壳子午截面涡流产生的机理及其影响因素.  相似文献   

4.
A wide operating band is important for a pump to safely perform at maximum efficiency while saving energy. To widen the operating range, a multi-point optimization process based on numerical simulations in order to improve impeller performance of a centrifugal pump used in nuclear plant applications is proposed by this research. The Reynolds average Navier Stokes equations are utilized to perform the calculations. The meridional shape of the impeller was optimized based on the following four parameters; shroud arc radius, hub arc radius, shroud angle, and hub angle as the design variables. Efficiencies calculated under 0.6Q d, 1.0Q d and 1.62Q d were selected as the three optimized objectives. The Design of experiment method was applied to generate various impellers while 35 impellers were generated by the Latin hypercube sampling method. A Response surface function based on a second order function was applied to construct a mathematical relationship between the objectives and design variables. A multi-objective genetic algorithm was utilized to solve the response surface function to obtain the best optimized objectives as well as the best combination of design parameters. The results indicated that the pump performance predicted by numerical simulation was in agreement with the experimental performance. The optimized efficiencies based on the three operating conditions were increased by 3.9 %, 6.1 % and 2.6 %, respectively. In addition, the velocity distribution, pressure distribution, streamline and turbulence kinetic energy distribution of the optimized and reference impeller were compared and analyzed to illustrate the performance improvement.  相似文献   

5.
提出在离心叶轮吸力面尾部开缝抽吸的方法,在叶片吸力面尾部对低速流体区域进行抽吸,以减弱由叶轮内二次流所导致的射流—尾迹结构。以Krain高速离心叶轮为例,建立抽吸模型,并进行了数值计算。数值仿真结果表明,在压气机流量范围内,叶轮尾部开缝抽吸可以减少叶片表面的分离区域,改善叶轮内部流场的流动状况,有效地提高离心叶轮性能。  相似文献   

6.
Cavitation is one of the most important performance of centrifugal pumps. However, the current optimization works of centrifugal pump are mostly focusing on hydraulic efficiency only, which may result in poor cavitation performance. Therefore, it is necessary to find an appropriate solution to improve cavitation performance with acceptable efficiency. In this paper, to improve the cavitation performance of a centrifugal pump with a vaned diffuser, the influence of impeller geometric parameters on the cavitation of the pump is investigated using the orthogonal design of experiment(DOE) based on computational fluid dynamics. The impeller inlet diameter D_1, inlet incidence angle Δβ, and blade wrap angle φ are selected as the main impeller geometric parameters and the orthogonal experiment of L_9(3*3) is performed. Three-dimensional steady simulations for cavitation are conducted by using constant gas mass fraction model with second-order upwind, and the predicated cavitation performance is validated by laboratory experiment. The optimization results are obtained by the range analysis method to improve cavitation performance without obvious decreasing the efficiency of the centrifugal pump. The internal flow of the pump is analyzed in order to identify the flow behavior that can affect cavitation performance. The results show that D_1 has the greatest influence on the pump cavitation and the final optimized impeller provides better flow distribution at blade leading edge. The final optimized impeller accomplishes better cavitation and hydraulic performance and the NPSHR decreases by 0.63 m compared with the original one. The presented work supplies a feasible route in engineering practice to optimize a centrifugal pump impeller for better cavitation performance.  相似文献   

7.
对离心风机叶片进行打孔处理,分析叶片打孔位置对风机噪声的影响.首先在稳态流场的计算结果上加载宽频噪声模型,得到不同工况下离心风机蜗壳和叶片上噪声分布情况,然后在瞬态分析的基础上加载FW-H噪声模块,利用LES/FW-H匹配技术分析叶片打孔对离心风机的气动噪声特性及声压级的影响.研究结果表明:离心风机结构表面声压主要集中...  相似文献   

8.
针对某离心通风机模型,研究了防涡圈对风机性能的影响。数值模拟和试验结果都说明了加装防涡圈后全压升和效率有所下降,这与以往的认知不完全一致。设计工况下,未加装防涡圈的通风机全压升比加装长防涡圈的风机高出约4%,效率高出约3%,内泄漏情况也会随防涡圈长度的增加变得严重;从内部流场可以看出,加装防涡圈减小了蜗壳内部的扩压空间,叶轮出口大尺度漩涡更加剧烈,影响了叶轮出口气流方向,并在叶轮出口产生回流现象,降低了通风机的全压和效率。因此认为对于不同压力系数和流量系数的风机,防涡圈对风机性能的影响规律是不一样的。  相似文献   

9.
通过设计离心泵水力模型,分析了在能量传递过程中能量损失的原因,介绍了提高效率和汽蚀性能所采取的措施。通过试验检测发现,其效率和汽蚀指标均达到要求,同时提出直线型叶轮出口前后盖板具有消除驼峰和提高流量扬程的作用。  相似文献   

10.
In order to widen the high-efficiency operating range of a low-specific-speed centrifugal pump, an optimization process for considering efficiencies under 1.0Q_d and 1.4Q_d is proposed. Three parameters, namely, the blade outlet width b_2, blade outlet angle β_2, and blade wrap angle φ, are selected as design variables. Impellers are generated using the optimal Latin hypercube sampling method. The pump efficiencies are calculated using the software CFX 14.5 at two operating points selected as objectives. Surrogate models are also constructed to analyze the relationship between the objectives and the design variables. Finally, the particle swarm optimization algorithm is applied to calculate the surrogate model to determine the best combination of the impeller parameters. The results show that the performance curve predicted by numerical simulation has a good agreement with the experimental results. Compared with the efficiencies of the original impeller, the hydraulic efficiencies of the optimized impeller are increased by 4.18% and 0.62% under 1.0Q_d and 1.4Q_d, respectively. The comparison of inner flow between the original pump and optimized one illustrates the improvement of performance. The optimization process can provide a useful reference on performance improvement of other pumps, even on reduction of pressure fluctuations.  相似文献   

11.
在基于控制速度分布的离心叶轮优化设计方法基础上,建立了前盘子午面成型和蜗壳设计方法,形成了离心风机的优化设计系统。在前盘子午面成型时,用叶片型线与叶轮进口直径和叶片进口角相结合进行优化,使总体参数优化、前盘子午型线及叶片成型三者有机结合。蜗壳设计中考虑了粘性影响,使蜗壳的设计更加高效实用。使用C语言将优化系统编写成程序,并对某型号风机进行优化设计,结果表明,在全工况下优化后的风机效率有明显提高,说明本文建立的离心通风机优化设计方法是可行的。  相似文献   

12.
气固两相流风机磨损率的数值预测研究   总被引:4,自引:0,他引:4  
梅丹  幸福堂 《流体机械》2007,35(10):25-28
利用数值模拟技术,基于雷诺应力湍流模型和Tabakoff and Grant的磨损模型,实现了叶轮磨损的可视化预测.揭示了不同粒径的颗粒对叶片不同的磨损方式以及叶轮各部分的磨损现象,并以此为理论基础,提出了有针对性的防磨措施,为工程实践提供有益的参考.  相似文献   

13.
《流体机械》2013,(3):5-9
为分析射流式自吸离心泵的半开式叶轮与导流器前盖之间的间隙大小对其性能的影响,采用数值模拟的方法得到了4种不同间隙下射流式自吸离心泵水力性能、径向力变化规律、自吸过程泵内部气液两相分布及流动情况,结果表明:间隙大小对射流式自吸离心泵水力性能影响明显,随着间隙增大,泵扬程和效率呈明显下降趋势,额定工况点间隙为0.5时的扬程和效率相对于间隙2mm时的扬程和效率分别下降14.43%、7.07%;叶轮与导流器上径向力也随间隙增大而减小;叶轮含气率、导流器两个不对称出口及泵体出口的气相质量流率随间隙增大而降低.兼顾考虑水力性能、自吸性能及加工装配工艺,最终确定叶轮与导流器前盖的间隙为0.5mm.样机试验结果表明:在额定工况点扬程34.21m,效率55.29%,当自吸高度为5m时,自吸时间45s,达到设计要求。  相似文献   

14.
This work developed improved slip factor model and correction method to predict flow through impeller in forward-curved centrifugal fan. Both steady and unsteady three-dimensional CFD analyses were performed to validate the slip factor model and the correction method. The results show that the improved slip factor model presented in this paper could provide more accurate predictions for forward-curved centrifugal impeller than the other slip factor models since the present model takes into account the effect of blade curvature. The correction method is provided to predict mass-averaged absolute circumferential velocity at the exit of impeller by taking account of blockage effects induced by the large-scale backflow near the front plate and flow separation within blade passage. The comparison with CFD results also shows that the improved slip factor model coupled with the present correction method provides accurate predictions for mass-averaged absolute circumferential velocity at the exit of impeller near and above the flow rate of peak total pressure coefficient.  相似文献   

15.
基于CFD的离心通风机结构优化方法与试验对比   总被引:1,自引:1,他引:0  
利用三维数值模拟的CFD方法,对某型号离心通风机的内流特性进行了分析,找出其结构存在的问题,运用CFD方法对其叶轮结构进行了优化设计,将改进前后的内流特性进行了数值和试验对比。结果表明,通风机的叶轮形状对其性能有明显影响,在改动较小的情况下,可显著提高通风机性能。  相似文献   

16.
Aerodynamic noise is the predominant component of automobile alternator noise at high speed, which directly affects the noise characteristic and noise control of alternator. Based on Lighthill acoustic theory, the aerodynamic noise of an automobile alternator was simulated with three-dimensional, Large eddy simulation (LES) and Ffowcs Williams-Hawkings (FW-H) acoustic model, and the aerodynamic noise reduction research was conducted through optimizing the front fan blade spacing angle of alternator with vector composition method while considering high fan flow and optimal noise frequency components for reduced harmonic rotating noise of alternator. The results show that the sound pressure amplitude of the primary aerodynamic noise components simulated with LES are in good agreement with experimental ones, and the dominant harmonic frequency components of aerodynamic noise are in the 4th, 6th, 8th, 10th, 12th and 18th orders and the A-weighted sound pressure level of one-third octave mainly concentrates in 1120-7000 Hz. The average total noise level of alternator noise is decreased by 2.58 dB, and the mass flow of monitoring surface of fan blade is increased by 1.36 g/s with 5.80 dB decrease in the sound level of the 12th and 18th harmonic orders on average with optimized front fan blade spacing angles, which verifies the effectiveness of the noise reduction method proposed in this paper.  相似文献   

17.
对带内置电机的前向多翼离心通风机进行了三维数值试验。讨论了数值试验中建模参数化思想,分析了CFD应用于多翼离心通风机的精度问题。重点讨论了除叶轮参数外风机的各种结构尺寸对流场以及性能的影响,从气动力学原理解释了造成这些影响的原因,提出了合理选取结构参数的建议。  相似文献   

18.
双流道泵输送固液介质的水力性能及磨损试验研究   总被引:4,自引:1,他引:3  
为分析固液混合物对双流道输送泵性能的影响,采用平均粒径为10 mm和36 mm的固体颗粒对双流道泵在不同浓度和流量下开展输送固液两相介质的水力性能试验,并对泵的磨损进行分析。水力试验结果表明,在一定的流量下,随着输送混合物中固体颗粒浓度的增加,入口表压、出口表压、扬程及效率呈递减趋势。 与输送清水时比较,当输送固液两相介质时,随着流量的增大,轴功率上升较快,扬程的下降量在不同流量下几乎相同;效率曲线在不同流量下比输送清水时效率要低,差值随着流量的增大而增大。在同流量同浓度比工况下,泵的进出口压力、扬程和汽蚀性能在输送较大直径固体颗粒时,明显下降。通过对双流道泵磨损的分析表明,叶轮磨损部位主要在前盖板外缘、流道内偏前盖板的流道表面、压力面进口边,压力面的磨损区域呈三角形;泵体的磨损部位主要在周壁、隔舌及泵体口环处。本研究可为固液两相双流道离心泵的理论研究与设计应用提供试验依据。  相似文献   

19.
首先对某双进气后向叶片的离心风机性能进行试验和数值模拟对比,验证数值模拟结果的精度及有效性;然后在叶轮前盘、轮盘形状和叶片数都相同的情况下,分析了改进叶片型式风机的性能变化。数值模拟结果表明,改进方案风机的全压更高、效率更高,尤其是在大流量区,效率提高5%以上。  相似文献   

20.
《流体机械》2016,(9):25-30
采用数值计算方法,开展混流式核主泵叶轮叶片自前盖板至后盖板方向厚度分布规律对能量性能影响的研究。通过对5种具有不同厚度分布规律叶片的叶轮进行比较分析,探索最佳叶片厚度比值和其对叶片表面静压力分布规律的影响。结果表明:当叶片后盖板处厚度与前盖板处厚度比值L=1.5时,叶轮的水力效率达到最高,当L=1.25时叶片做功能力低,叶轮内能量损失大,水力效率较低;在小流量工况下,随着比值L的增加,相同流量下扬程和水力效率都随之升高;在大流量工况下,扬程和水力效率都随着L的增大而降低;叶轮流道内压能沿着前盖板至后盖板方向增大并且最大压能位置向中间移动。  相似文献   

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