共查询到19条相似文献,搜索用时 140 毫秒
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叶片数对喷水推进器性能影响的计算流体动力学分析 总被引:5,自引:0,他引:5
分析和界定了喷水推进器数值计算所需流场控制体。联用结构化网格和非结构化网格对该流场区域进行离散。选择切应力输运(Shear stress transport,SST)二方程紊流模型,采用稳态多参考系方法进行数值计算。根据实船试航时泵转速和航速,计算"船—泵"匹配特性线上六个工况点对应的功率和推力,并与设计单位提供的精确设计值进行比较,在分析网格无关性的基础上检验了数值计算方法的可信性。在此基础上从三个方面分析和比较了该喷水推进器:叶轮叶片数从5叶变化到7叶时对Stodola滑移系数和喷水推进器外特性的影响;导叶体叶片数从9叶变化到13叶时对叶轮出口流体整流结果的影响以及由此引起的流体动力性能的改变;叶轮和导叶体15种不同叶片数匹配时在给定工况下各自对应的流体动力性能数据。结果表明,在给定运动参数工况下,随着叶轮叶片数增加,Stodola滑移系数增加,喷水推进泵扬程增加,产生的轴向推力和消耗的轴功率也增大,效率下降;导叶叶片数增加时,喷口出流的旋转作用减弱,11叶后再增加已无明显改进,导叶为10叶和11叶时喷水推进器性能较接近,对应扬程和推力均较12叶和13叶时大;叶轮为5叶时与9叶导叶组合使整体性能最佳,而6... 相似文献
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为了改善离心泵的汽蚀性能,根据经验,确定了两种叶片进口修缘形式。首先通过原型泵的外特性试验,确定了能量性能和汽蚀性能曲线。基于完整空化模型和混合流体两相流模型,对原型泵运行工况下叶轮内空化流动进行全流道数值计算。预测得到原型泵能量性能和汽蚀性能曲线,与试验曲线吻合良好;同时得到汽蚀发生过程中叶轮流道内空化发展的静态特征,与理论相符。故采用相同的数值分析方法对两种叶片进口修缘后的叶轮进行分析,分析表明:进口修缘后泵的汽蚀性能得到了提高,叶片进口工作面修缘形状越接近流线型,泵的汽蚀性能越好。对较好修缘形式的泵进行试验,得到其能量性能曲线和汽蚀性能曲线,数值分析与试验研究的曲线吻合,修缘后泵的临界汽蚀余量得到改善。研究结果对离心泵汽蚀改善的方法具有一定的指导意义。 相似文献
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《机电产品开发与创新》2016,(3)
喷水推进器常被用在船舶,两栖车辆等作为推进装置。论文应用三维Navier-Stokes方程和两方程湍流模型以及全空化模型,对喷水推进器的空化流动进行数值模拟。介绍了空化流动的模拟方法,并计算了推进器的空化性能指标,通过与试验对比得出:采用数值模拟方法能有效地预测叶片上空化发生的区域和空化流动的发展情况。同时,根据推进器内部流场提出提高抗空化性能的相应设计。 相似文献
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为了分析某型号轴流泵叶轮汽蚀状态下汽液两相流特征,本文基于均相流模型、RNG k-ε湍流模型与SIM-PLEC算法,分别从外特性和内部流场两方面分析了轴流泵叶轮的空化过程,通过定量分析不同NPSH下轴流泵的扬程下降和空泡分布的对应关系,讨论了不同空化状态下叶轮内部速度场和压力场的分布,寻找出轴流泵空化发生破坏的位置和发展趋势。数值模拟结果表明,空化初生时空泡产生于叶片背面进口轮缘处,随着轴流泵进口压力的不断降低,叶片背面外缘处空泡逐渐向轮毂侧发展,且外缘侧空泡不断向前推进,在装置汽蚀余量NPSH为6.62m时,空泡基本覆盖叶片的背面,此时叶片丧失了部分做功能力,且扬程下降明显。计算模型泵进行了现场运行试验,试验结果表明,数值模拟的空泡分布与实际破坏位置一致,验证了数值计算的准确性,也为解决轴流泵汽蚀破坏问题提供了内流流场参考。 相似文献
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以立式自吸泵为研究对象,针对自吸泵的高抗汽蚀性能要求,通过数值模拟、样机试验验证的方法,探究叶轮进口参数对叶轮抗汽蚀性能的影响。研究表明:适当增大叶轮进口直径能有效提高立式泵抗汽蚀性能;增大叶轮前盖板半径有利于立式泵抗汽蚀性能;叶片进口宽度直接影响立式泵抗汽蚀性能。试验结果表明,文中所用设计方法可为立式自吸泵的水力设计提供参考。 相似文献
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《水泵技术》2013,(5)
文献[2]采用两相流全空化模型计算了离心油泵输送粘油的汽蚀性能,但因缺乏试验数据,故无从知道计算的必需汽蚀余量与其试验值的差别。另外,目前还没有关于利用空化模型预测泵初生空化方面的研究;同时,全空化模型预测离心泵汽蚀性能准确度的评估目前还不多见。因此,本文采用全空化模型预测文献[3,4]的试验离心泵输送水时的汽蚀性能,获得了初生空化系数-流量曲线和扬程-有效汽蚀余量曲线,探讨了泵扬程与叶轮内部汽液体积比的关系以及非凝结气体浓度、紊流模型对扬程-有效汽蚀余量关系曲线的影响。本文的计算方法、经验和结果对实际工程中的离心泵汽蚀性能的预测和流动模型的选择有借鉴作用。 相似文献
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半浸式螺旋桨水动力性能的数值模拟研究 总被引:1,自引:0,他引:1
针对半浸式螺旋桨的水动力性能问题,应用CFD方法对其流场进行了数值模拟研究,并把结果与实验进行比较。通过求解雷诺平均方程(RANS)来模拟流场,采用SST k-ω湍流模型来计算RANS方程中的雷诺应力。利用Fluent中的明渠流动(Open Channel Flow)功能模拟空泡水筒中的气液两相流动,采用VOF方法捕捉自由液面。应用滑移网格法完成搅拌桨的转动,实现了对一个五叶右旋半浸式螺旋桨的数值模拟。研究结果表明,桨的尾流场形态与实验结果吻合地较好,证明了CFD方法预测半浸式螺旋桨性能的有效性。在较低浸入深度时,数值模拟可以很好地预测半浸式螺旋桨的性能。随着浸入深度的增加,推力系数和效率的预测结果基本准确,扭矩系数的预测结果有一定偏差。从数值计算结果中,可以获得宏观力的脉动曲线和完全入水桨叶的压力分布,并且可以对桨叶出水和入水过程进行详细的研究。 相似文献
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A CFD code with 2-D cascade model was developed to predict the cavitation behavior around the impeller blades of impeller
in a centrifugal pump. The governing equations are the two-phase Reynolds Averaged Navier-Stokes equations in a homogeneous
form in which both liquid and vapor phases are treated as incompressible fluid. To close the model, a standard k-ɛ turbulence
model is introduced. And the mass transfer rates between liquid and vapor phases are implemented as well. The validations
are carried out by comparing with reference data in impeller of a centrifugal pump impeller. The cavitation characteristics
of current centrifugal pumps is tested at an ondesign point (V=8 m/s) and two off-design points (V=20 m/s and V=30 m/s), respectively.
The criteria of cavitation and flow instability around blades are presented. The results show that the current centrifugal
pump can safely operate without cavitation at on-design point. Also, the simulation shows cavitation develops inhomogeneously
among the blades at off-design points. Moreover, the effects of additional blades in the impeller are studied as well. From
the numerical results, it is expected that a half-length blade is the optimum configuration as additional blades in cavitation
point of view. 相似文献
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《机械工程学报(英文版)》2010,(6)
The blade number of impeller is an important design parameter of pumps,which affects the characteristics of pump heavily.At present,the investigation focuses mostly on the performance characteristics of axis flow pumps,the influence of blade number on inner flow filed and characteristics of centrifugal pump has not been understood completely.Therefore,the methods of numerical simulation and experimental verification are used to investigate the effects of blade number on flow field and characteristics of a centrifugal pump.The model pump has a design specific speed of 92.7 and an impeller with 5 blades.The blade number is varied to 4,6,7 with the casing and other geometric parameters keep constant.The inner flow fields and characteristics of the centrifugal pumps with different blade number are simulated and predicted in non-cavitation and cavitation conditions by using commercial code FLUENT.The impellers with different blade number are made by using rapid prototyping,and their characteristics are tested in an open loop.The comparison between prediction values and experimental results indicates that the prediction results are satisfied.The maximum discrepancy of prediction results for head,efficiency and required net positive suction head are 4.83%,3.9% and 0.36 m,respectively.The flow analysis displays that blade number change has an important effect on the area of low pressure region behind the blade inlet and jet-wake structure in impellers.With the increase of blade number,the head of the model pumps increases too,the variable regulation of efficiency and cavitation characteristics are complicated,but there are optimum values of blade number for each one.The research results are helpful for hydraulic design of centrifugal pump. 相似文献
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Blade number effect for a ducted wind turbine 总被引:1,自引:0,他引:1
Sheng-Huan Wang Shih-Hsiung Chen 《Journal of Mechanical Science and Technology》2008,22(10):1984-1992
Ducted wind turbine with multiple blades installed was believed to have a good wind power energy conversion effect. However,
little information was available on how to design a good ducted wind turbine. In this paper the effects of blade number on
a ducted wind turbine performance is studied. Numerical studies using CFD method to simulate the wind turbine performance
were adopted. The duct is a converging-diverging nozzle with the turbine blades located at the throat. A rated output of a
1-kW turbine is adopted as the baseline design. It was found that the blade geometry, stagger angle, and number of blades
have different duct blockage effects, and do affect the turbine performance (specifically the power coefficient and torque
coefficient, etc.). The fewer number of blades has higher through flow speed, while the larger number of blades provides larger
torque. The best power coefficient lies in between the two extremes. The appropriate number of blades is important to match
the generator performance curve for optimal overall performance and efficiency.
This paper was presented at the 9th Asian International Conference on Fluid Machinery (AICFM9), Jeju Korea, October 16–19, 2007. 相似文献
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针对液压阀中的气穴现象会引起液压阀的噪音、性能恶化,甚至导致液压阀失效等问题,对伺服阀前置级喷嘴和挡板之间流场中的气穴现象进行了研究.利用Pro/E软件对流场进行了三维建模,用前处理软件Gambit对三维模型进行了网格划分及边界条件设置,利用标准k-ε模型和混合气穴模型建立流场的数学模型,运用FLUENT软件对不同喷嘴入口流速下流场的分布特性及气穴特征进行了仿真分析;同时利用高速摄像机对喷嘴挡板之间的流场分布进行了观测和记录.研究结果表明,在低雷诺数流动条件下,气穴开始在喷嘴外壁和挡板前端的边缘形成;随着雷诺数的增大,在挡板弯曲的附体气穴逐渐长大并随着射流流速的增加出现云状的气穴.将不同流动条件下流场结构和气穴分布的数值计算结果与试验观测结果进行比较,两者基本吻合,说明伺服阀前置级流场气穴仿真模型和数值计算方法是可靠的. 相似文献
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Considering the lack of theoretical models and ingredients necessary to explain the scaling of the results of propeller cavitation inception and cavitating hydroacoustics from model tests to full scale currently, and the insufficient reflection of the nuclei effects on cavitation in the numerical methods, the cavitating hydrodynamics and cavitation low frequency noise spectrum of three geometrically similar 7-bladed highly skewed propellers with non-uniform inflow are addressed. In this process, a numerical bridge from the multiphase viscous simulation of propeller cavitation hydrodynamics to its hydro-acoustics is built, and the scale effects on performances and the applicability of exist scaling law are analyzed. The effects of non-condensable gas(NCG) on cavitation inception are involved explicitly in the improved Sauer’s cavitation model, and the cavity volume acceleration related to its characteristic length is used to produce the noise spectrum. Results show that, with the same cavitation number, the cavity extension on propeller blades increases with diameter associated with an earlier shift of the beginning point of thrust decline induced by cavitation, while the three decline slopes of thrust breakdown curves are found to be nearly the same. The power of the scaling law based on local Reynolds number around 0.9R section is determined as 0.11. As for the smallest propeller, the predominant tonal noise is located at blade passing frequency(BPF), whereas 2BPF for the middle and both 2BPF and 3BPF for the largest, which shows the cavitating line spectrum is fully related to the interaction between non-uniform inflow and fluctuated cavity volume. The predicted spectrum level exceedance from the middle to the large propeller is 6.65 dB at BPF and 5.94 dB at 2BPF. Since it just differs less than 2 dB to the increment obtained by empirical scaling law, it is inferred that the scale effects on them are acceptable with a sufficient model scale, and so do the scaling law. The numerical implementation of cavitating hydrodynamics and hydro-acoustics prediction of propeller in big scale in wake has been completed. 相似文献
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CFD在计算船舶螺旋桨敞水性能中的应用研究 总被引:1,自引:0,他引:1
对流场中螺旋桨的敞水性能进行研究。利用Pro/E软件对螺旋桨进行三维建模,通过剖面坐标转换绘出桨叶的剖面型线,利用创建实体功能得到螺旋桨实体模型。用CFD软件对螺旋桨在不同进速系数下的推力系数、转矩系数以及推进效率进行模拟,并且对三种湍流模型的计算结果进行比较分析。对采用Fluent软件计算螺旋桨敞水性能的过程进行详细介绍,并给出敞水性能曲线的计算结果。与试验结果的比较分析表明,数值模拟的结果可以满足工程应用要求。 相似文献