Performance of Wells Turbine with Guide Vanes for Wave Energy Conversion

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Experimental Studies on Heat Transfer in the Tip Gap of a Sectorial Turbine Cascade

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Application of Numerical Simulation Method to Predict the Performance of Wave Energy Device with Impulse Turbine

This paper presents the work carried out to predict the behavior of a 0.6 m Impulse turbine with fixed guide vanes with 0.6 hub-to-tip (H/T) ratio under real sea conditions. In order to predict the true performance of the actual Oscillating Water Column (OWC), the numerical technique has been fine tuned by incorporating the compressibility effect. Water surface elevation verses time history based on Pierson Moskowitz Spectra was used as the input data. Standard numerical techniques were employed to solve the non-linear behavior of the sea waves. The effect due to compressibility inside the air chamber and turbine performance under unsteady and irregular flow condition has been analyzed numerically. Considering the quasi-steady assumptions, unidirectional steady flow experimental data was used to simulate the turbine characteristics under irregular unsteady flow conditions. The results show that the performance of this type of turbine is quite stable and efficiency of air chamber and the mean conversion     

Experimental Study of Endwall and Tip Clearance Flows in a Two—Dimensional Turbine Rotor Blade Cascade—Effect of Incidence Angle

IntroductionA ttirbomachinery rotor must have a slhall hilt finite clearance relative to its surrounding casing. Theflow, which leaks thlough this fililte gap, has a surprisingly large effect on the aerodynamics of the flow.The loss produced due to the tip clearance is an.unavoidable loss. The presence of tip clearance ajtersthe endwall flow siglilflcaotly. The normal secondaryflow interacts with the leakage fluid ajs it easts fromthe suction surface. The leakage fluid rolls into whatis known…     

On the Controlling Factor of Catalyst Temperature in C3H8—Air Mixture

Catalytic combustion of propane-air mixture was investigated.Platinum catalysts over a flat stainless steel with γ-alumina washcoat were employed.The employed burner has three catalysts set parallel to the mixture flow,spaced at an interval of 5,10 and 15 mm.Both experiment and numerical simulation were made at inlet temperature of 553 K,inlet velocity of 3 to 7 m/s and equivalence ratio of 0.3 to 0.5.In the numerical simulation,two-dimensional,steady state model was developed to calculate the temperature and species concentration in gas-phase.In this model.chemical reaction on the catalyst surface and that in the gas phase were assumed to occur in three-steps.The numerical results show good agreement with experimental results.It was found that the properties of the catalyst strongly affect the catalyst surface temperature.Especially,the thermal conductivity of catalyst has a great effect,while the emissivity of catalyst has less effect.     

2D CFD Analysis and Experimental Analysis on the Effect of Hub to Tip Ratios on the Performance of 0.6 m Impulse Turbine

The objective of this paper is to present the performance comparison of 2D Computational Fluid Dynamics (CFD) analysis with experimental analysis of 0.6 m impulse turbine with fixed guide vanes for both 0.6 and 0.7 hub to tip ratio (H/T). Also the comparison of 2D CFD analysis of the said turbine with different values of H/T ranging from 0.5 to 0.7. A 2D-cascade model was used for CFD analysis while uni-directional steady flow was used for experimental analysis. The blade and guide vane geometries are based on 0.6 m rotor diameter, with optimum profile, and different H/T of 0.5, 0.6 and 0.7. It was concluded from 2D CFD analysis that 0.5 H/T ratio performances was higher than that of 0.6 and 0.7 H/T at peak efficiency and the operational flow range for 0.5 H/T was found to be wider than that of 0.6 and 0.7 H/T ratio.     

Effect of Nonequilibrium Condensation of Moist Air on the Boundary Layer in a Supersonic Nozzle

INTRODUCTIONMapstudies[1-13lonthecondensationshockwaveoccurringinthecaseoftherapidexpansionofmoistairorsteaminasupersonicnozzlehavebeenper-formed,andthecharacteristicsofcondensationshockwavhavenearlybeenclarified.Acondensationshockwavalsooccursinthebladepassageinasteamturbinel14'15].Suchacondensationshockwavethatinteractswiththeboundary1ayeronthesurfaceofthettirbineblade,affectsthellowinthebladepas-sageinasteamturbine.However,thefiowinthebladepaJssagewiththecondensationshockwaveisnotyetun…     

Effects of Various Geometric Features on the Performance of a 7:1 Pressure Ratio Deeply Scalloped and Split Radial Turbine in a Gas Turbine Engine

A 2 MW gas turbine engine has been developed for the distributed power market.This engine features a 7:1 pressure ratio radial inflow turbine.In this paper,influences of various geometry features are investigated including turbine tip and backface clearances.In addition to the clearances,the effects of the inducer deep scallop and exducer rounded trailing edge are investigated.Finally,geometric features associated with a split rotor(separate inducer and exducer)are studied.These geometry features are investigated numerically using CFD.Part of the numerical results is also compared to experimental data acquired during engine test to validate the CFD results.     

Study on the Effect of the Side Secondary Air Velocity on the Aerodynamic Field in a Tangentially Fired Furnace with HBC—SSA Burner

INTroDUCTIONThe Horizontal Bias Combustioll Pulverized Coal(HBC) burner for tangential firing system has advantages of improving flame stabilization, slaggingresistance, pollution control and high combustionefficiency[']. However, in the thin and tall furnace firedwith coal with strong slagging telldency) it is possiblethat slagging occurred on water-cooled wall, especiallywhen the cross-sectional and volumetric heat releaserate are very high in the burner domain.The HBC burner with Si…     

Effect of Nonequilibrium Homogenous Condensation on Flow Fields in a Supersonic Nozzle

INTRODUCTIONManystudies[1-131onthecondensationshockwaveoccurringinthecaseoftheraPidexPansionofmoistairorsteaminasupersonicnozzlehavebeenper-formed,andthecharacteristicsofcondensationshock'wavehavenearlybeenclarilied.Acondensationshockwavealsooccursinthebladepassageinasteamturbinel14,15]andsuchacondensationshockwavinteractswiththeboundarylayeronthesurfaceoftheblade.Thus,thefiowinthebladepassageofthesteamturbinewiththecondensationshockwavehasnotyetbeenclariliedl16'17].InthepreseDtstudythee…     

Effect of guide vanes on the performance of a self-rectifying air turbine with constant and variable chord rotors

A Wells turbine is a self-rectifying air flow turbine capable of converting pneumatic power of the periodically reversing air stream in Oscillating Water Column into mechanical energy. The Wells turbine has inherent disadvantages; lower efficiency, poorer starting characteristics, higher axial force and low tangential force in comparison with conventional turbines. Guide vanes before and after the rotor suggest a means to improve the tangential force, hence its efficiency. Experimental investigations are carried out on a Wells turbine with the constant chord and variable chord blade rotors fitted with inlet and outlet guide vanes to understand the aerodynamics. Experiments were also conducted for the above said rotors with various stagger angles to validate the design stagger angle. In addition, the starting and running characteristics of the rotors have been studied and compared with the case without guide vanes. Studies were done at various flow coefficients covering the entire range of flow coefficients over which the turbine is operable. The efficiency, starting characteristics of the turbines with guide vanes have improved when compared with the respective turbines without guide vanes.     

带可调进口导叶的多级轴流压气机非设计点性能计算

多级轴流压气机为保证非设计转速下的性能,通常采用进口导叶(IGV)以及静叶可调的扩稳方法。为获得可靠的进口导叶性能以用于压气机初步设计和扩稳方案的初步筛选,基于Banjac和Petrovic等提出的IGV损失和落后角模型与平均中径计算相结合,开发了带有IGV的多级轴流压气机性能分析工具。选用E3压气机作为算例进行计算分析,结果表明,所选用的IGV模型在较大开度内具有较好的精度和有效性。研究结果可以为多级轴流压气机初步设计和扩稳方案确定提供参考。     

Performance analysis of a centrifugal compressor with variable inlet guide vanes

The flow in a centrifugal compressor stage with variable inlet guide vanes (VIGVs) is investigated by numerical simulation in this paper. Analysis of the performance curves and relative velocity vectograms indicates that performance curves shift toward small flow domain when VIGVs turn positively, and toward large flow domain when VIGVs turn negatively. Stage efficiency drops quickly after work condition enters a small flow domain through the peak efficiency point. Under the circumstance of large setting angles of the guide vanes, there exist obvious flow separations in guide vane passages within wide flow ranges, and back flow regions can be located at the front of splitter suction surfaces under large flow conditions, while under the condition of small flow, flow separations occur on suction surfaces of long blades. __________ Translated from Journal of Power Engineering, 2006, 26(6): 804–807 [译自: 动力工程]     

Impulse turbine with 3D guide vanes for wave energy conversion

In this study, in order to achieve further improvement of the performance of an impulse turbine with fixed guide vanes for wave energy conversion, the effect of guide vane shape on the performance was investigated by experiment. The investigation was performed by model testing under steady flow condition. As a result, it was found that the efficiency of the turbine with 3D guide vanes are slightly superior to that of the turbine with 2D guide vanes because of the increase of torque by means of 3D guide vane, though pressure drop across the turbine for the 3D case is slightly higher than that for the 2D case.     

变几何涡轮可调导叶瞬时转动气动特性研究

为探究单级变几何涡轮(VGT)在导叶转动过程中的过渡态性能,对某动力涡轮进行了非定常数值计算,应用动网格技术实现导叶转角的改变,并对导叶通道开大或关小过渡过程中涡轮性能进行了分析。结果表明：导叶转角从0°变化到-5°时,单级涡轮效率逐渐下降1.6%,从0°变化到6°时,效率逐渐提高0.5%;质量流量和导叶出口绝对气流角随转角改变接近线性变化,而动叶出口相对气流角、熵增、效率和导叶出口总压损失等随转角改变呈抛物线型变化;过渡态下导叶流场内损失变化主要受上、下端壁处间隙泄漏涡影响,动叶出口熵增变化规律主要受动叶吸力侧泄漏涡和下部通道涡影响,其中下部通道涡的改变是引起熵增变化的主要原因。     

Effect of interior guide tubes in cross‐flow turbine runner on turbine performance

The cross‐flow turbine has attracted much attention as a source of hydropower generation for small and micro‐systems, especially for low head establishments. Such turbines have a distinct advantage of lower initial and operating costs over other small scale turbines, but their efficiency is lower than others. Efficiency predictions of these turbines are generally based on the assumption that the entire flow crosses from the first stage to the second stage of the turbine runner. In this study, interior guide tubes were designed and used inside the runner of a cross‐flow turbine to collect and guide the crossing flow towards the second stage of the runner. The interior guide tubes were designed on the basis of observed flow patterns inside the runner. Experimentally, three different types of tubes were tested. The laboratory tests were conducted to calculate the turbine efficiency with different gate openings of nozzle and different positions of interior guide tubes. Results of this work with and without interior tubes have been presented in this paper. When the experiments were done with and without interior guide tubes, it has been found that turbine efficiency with the interior guide tube decreased about 5 per cent. Copyright © 2000 John Wiley & Sons, Ltd.     

Forced responses on a radial turbine with nozzle guide vanes

Radial turbines with nozzle guide vanes are widely used in various size turbochargers. However, due to the inter- ferences with guide vanes, the blades of impellers are exposed to intense unsteady aerodynamic excitations, which cause blade vibrations and lead to high cycle failures （HCF）.Moreover, the harmonic resonance in some frequency regions are unavoidable due to the wide operation conditions. Aiming to achieve a detail insight into vibration characteristics of radial flow turbine, a numerical method based on fluid .structure interaction （FSI） is presented. Firstly, the unsteady aerodynamic loads are determined by computational fluid dynamics （CFD）.And the fluctuating pressures are transformed from time domain to frequency domain by fast Fourier-transform （FFT）. Then, the entire rotor model is adopted to analyze frequencies and mode shapes considering mistuning in finite element （FE） method. Meanwhile, harmonic analyses, applying the pressure fluctuation from CFD, are conducted to investigate the impeller vibration behavior and blade forced response in frequency domain. The prediction of the vibration dynamic stress shows acceptable agreement to the blade actual damage in consistent tendency.     

前置导叶对双吸离心泵性能影响试验研究

为了优化离心泵运行工况,运用叶轮机械设计、前置导叶预旋调节的基本理论,并结合诱导轮设计理论,设计了两种不同叶高的双吸泵前置诱导叶片.对带有不同叶高前置叶片的双吸泵进行了试验研究.研究结果表明:带有诱导叶片的双吸泵虽然扬程略有降低,且在大流量区域效率降低,但其功率消耗降低,最大可节能3.34%,且高效区往小流量偏移;14 mm叶高诱导叶片调节效果明显优于20 mm叶高诱导叶片,且能够有效地将双吸泵高效区往小流量偏移,同时降低离心泵功率消耗.     

分流导叶垂直轴风力机气动性能研究

为提高垂直轴风力机气动性能,提出一种随相位角变化而改变相对夹角的分流导叶结构。以NACA0021为基础翼型,采用计算流体力学方法对分流导叶作用下垂直轴风力机风能利用系数、单叶片瞬时转矩、压力系数及速度场进行数值分析。结果表明：静态和动态分流导叶均可提高垂直轴风力机气动性能,且动态分流导叶提升效果更为显著;相较于静态分流导叶,动态分流导叶垂直轴风力机在尖速比为2.33时风能利用系数最高可提升23%,在尖速比为2.03时静态分流导叶垂直轴风力机较原始垂直轴风力机风能利用系数提高37%;分流导叶也可使最佳尖速比前移,稳定叶片转矩波动,提升垂直轴风力机的运行稳定性。