输送水时离心油泵不同出口角叶轮切割性能实验

选取常用的65Y60型离心油泵为研究对象,对叶片出口角分别为15°、25°、45°和60°的4个叶轮进行切割试验,研究了泵性能随叶片出口角和叶轮直径的变化规律。研究表明,扬程曲线和轴功率曲线随叶轮直径的减小而下移。当叶轮直径切割到205mm时,泵效率出现不降反而升高现象;以后,随直径的减小而迅速下降。最优工况流量、扬程和轴功率随叶轮直径的减小而下降。叶片出口角对滑移系数、水力效率和机械效率的影响较大,对容积效率的影响较小。叶轮直径对水力效率和机械效率的影响较大,对滑移系数和容积效率的影响较小。切割指数同时受叶轮直径和叶片出口角的影响。对小出口角叶轮,流量切割指数、扬程切割指数和轴功率切割指数随叶轮直径的减小而下降;对大出口角叶轮,流量切割指数、扬程切割指数和轴功率切割指数随叶轮直径的减小而升高。效率切割指数随叶轮直径的减小而升高,并趋向某个值。由实验结果得到的4个切割指数都与现有的理论值不同。

超厚叶片离心泵叶轮与蜗壳之间性能匹配的研究

在研究低比转速无过载潜水排污泵中,针对一个直径385 mm的3叶片叶轮,分别设计了D_3=390 mm、435mm、460 mm3种蜗壳,通过对3种不同基圆直径蜗壳内部三维非定常流动的数值计算,得到监测点的压力脉动。计算表明,D_3值的不同,是影响蜗壳内部压力脉动的重要因素,由此造成的脉动幅值相差3倍。本研究结果为解决低比转速无过载潜水排污泵的振动和噪声,提供了理论依据。

双流道泵叶轮切割定律方程的建立与试验

为了找出适用于双流道泵叶轮的切割定律,选用比转数为77和122的两种双流道泵,分别对其叶轮进行了5次切割,并进行了泵外特性试验。通过分析双流道泵在最优工况及关死点工况下性能参数与叶轮直径的变化规律,确定了相应的切割指数取值范围,最终建立了双流道泵叶轮的切割定律指数方程。研究结果表明,双流道泵的流量、扬程、轴功率和效率随叶轮直径的减小而降低,但随叶轮切割百分比的增加,最优工况性能参数的变化规律及下降幅度并不相同,关死点扬程和轴功率随叶轮直径的减小下降明显;双流道泵关死工况点的切割指数可以近似认为与比转数的变化无关;最优工况和一般工况点的流量切割指数随比转数的变化较明显。建立的双流道泵叶轮切割定律预测值与试验值吻合性好。

离心油泵叶轮切割后效率升高现象

对65Y60型离心油泵进行了一系列输送不同粘度液体的叶轮切割性能实验,实验发现了叶轮切割以后泵效率升高现象,利用水力效率比、容积效率比和机械效率随直径和粘度的变化曲线,分析了效率升高的原因。研究表明,在直径为205mm时,泵效率出现升高现象,效率高与液体粘度有关,较高的液体粘度有助于诱发效率升高。容积效率的升高和机械效率的增大是离心油泵叶轮切割后效率升高的原因。

叶片数与分流叶片长度对小型压缩机性能影响研究

以一种小型压缩机的叶轮为研究对象,运用数值模拟的方法研究叶片数和分流叶片长度对叶轮性能的影响。研究发现:叶片数较少,会增大叶片的当量脚,使得叶片边界层增厚,叶轮效率下降;叶片数过多,叶片在做功过程中会使得气体的摩擦损失和叶片阻塞增加,因此存在一个最佳叶片数,以该叶轮而言,最佳稠密度为1.9,叶片数为18时,叶轮的性能最好;分流叶片的长度对叶轮性能也有一定的影响,当短叶片与长叶片垂直长度比为0.7时,叶轮性能较好。

基于CFD技术的离心泵出口流态模拟及分析

以应用较为广泛且低转速比的离心泵作为研究对象,在当前流体力学发展的理论基础之上,根据离心泵的工作流态特征,给出离心泵内部流体与构件间的数学模型,对泵体的工作状态进行模拟分析。同时,通过建立离心泵的三维实体造型,并将其与相适应的CFD技术相衔接,进而通过对离心泵过流关键部件网格划分与优化处理,选取合适的湍流模型,进行泵体的出口流态更接近实际的数值模拟,有利于观察泵内出入口的流场、压力等参数的变化情况。该研究对于深入理解其内部流动的机理,改进离心泵的结构组成、叶轮性能及参数优化有一定参考价值,从而达到最终提高泵的水力效能目标,是一种值得推广的分析方法。

DESIGN OF NEW TEST FACILITY FOR MICRO-TURBO-MACHINERY

Micro-turbine engine has no enough space for measuring impeller characteristics,so the design and the construction of a new test facility of micro-turbo-machinery are presented for micro-centrifugal compressors and radial turbines.The facility is used for the full speed compressor test and the long duration hot turbine test.To rapidly adjust the testing condition,all regulations of the operating state are automatically completed by the control system.The facility is also used for testing the impeller performance with a series of diameter from 55 mm to 180 mm as a result of the modular design.A thermal protection system is designed to avoid the heat distortion caused by the high turbine inlet temperature over 1 100 K and provide a proper experimental environment for the electronic components.A photoelectric torque transducer with the accuracy of 1% is designed to measure the torque of rigid shaft at a high speed of 125 000 r/min.The designing techniques for micro-turbo-machineries are verified by the impeller testing of the facility.

排尘风机的选择与改进

论述了选择高浓度尘气排尘风机时必须考虑的一些主要因素。

Effects of the short blade locations on the anti-cavitation performance of the splitter-bladed inducer and the pump

In order to evaluate the effects of the short blade locations on the anti-cavitation performance of the splittel bladed inducer and the pump, 5 inducers with different short blade locations are designed, Cavitation simulatior and experimental tests of the pumps with these inducers are carried out. The algebraic slip mixture model in th CFX software is adopted for cavitation simulation. The results show that there is a vortex at the inlet of the indu（ er. Asymmetric cavitation on the inducer and on the impeller is observed. The analysis shows that the short blad locations have a minor effect on the internal flow field in the inducer and on the external performance of th pump, but have a significant effect on the anti-cavitation performance. It is suggested that the inducer shoul be designed appropriately. The present simulations found an optimal inducer with better anti-cavitatio performance.

Performance Analysis of a Vertical Axis Tidal Turbine With Flexible Blades

In this study, a vertical axis tidal turbine with flexible blades is investigated. The focus is on analyzing the effect of flexible airfoils types and blade flexibility on turbine net output power. To this end, five different flexible airfoils （Symmetric and Non-symmetric） are employed. The results show that the use of a thick flexible symmetric airfoil can effectively increase output power compared to that achievable with a conventional rigid blade. Moreover, the use of highly flexible blades, as opposed to less flexible or rigid blades, is not recommended.

Parametric geometry representations for wind turbine blade shapes

Based on the Joukowsky transformation and Theodorsen method, a novel parametric function （shape function） for wind turbine airfoils has been developed. The airfoil design space and shape control equations also have been studied. Results of the analysis of a typical wind turbine airfoil are shown to illustrate the evaluation process and to demonstrate the rate of convergence of the geometric characteristics. The coordinates and aerodynamic performance of approximate airfoils is rapidly close to the baseline airfoil corresponding to increasing orders of polynomial. Comparison of the RFOIL prediction and experimental results for the baseline airfoil generally show good agreement. A universal method for three-dimensional blade integration-＂ Shape function/Distribution function＂ is presented. By changing the parameters of shape function and distribution functions, a three dimensional blade can be designed and then transformed into the physical space in which the actual geometry is defined. Application of this method to a wind turbine blade is presented and the differences of power performance between the represented blade and original one are less than 0. 5%. This method is particularly simple and convenient for bodies of streamline forms.

Effect of blade pitch angle on aerodynamic performance of straight-bladed vertical axis wind turbine

Wind energy is one of the most promising renewable energy sources, straight-bladed vertical axis wind turbine(S-VAWT) appears to be particularly promising for the shortage of fossil fuel reserves owing to its distinct advantages, but suffers from poor self-starting and low power coefficient. Variable-pitch method was recognized as an attractive solution to performance improvement, thus majority efforts had been devoted into blade pitch angle effect on aerodynamic performance. Taken into account the local flow field of S-VAWT, mathematical model was built to analyze the relationship between power outputs and pitch angle. Numerical simulations on static and dynamic performances of blade were carried out and optimized pitch angle along the rotor were presented. Comparative analyses of fixed pitch and variable-pitch S-VAWT were conducted, and a considerable improvement of the performance was obtained by the optimized blade pitch angle, in particular, a relative increase of the power coefficient by more than 19.3%. It is further demonstrated that the self-starting is greatly improved with the optimized blade pitch angle.

Study on the Performance Deterioration of Mixed Flow Impeller due to Change in Tip Clearance

Performance of mixed flow compressor with un-shrouded impeller strongly depends upon unsteady, asymmetrical flow fields in the axial directions. The flow through the mixed flow impeller is complex due to three-dimensional nature of geometry. In mixed flow impeller, there are clearances between the rotating impeller blades and the casing as the high pressure ratio compressors are usually open shrouded impellers. As a result, certain amount of reduction in the performance is unavoidable due to clearance flows. In the present investigations, numerical analysis is performed using a commercial code to investigate tip clearance effects on through flow. The performance of mixed flow impeller with four different clearances between impeller and stationary shroud are evaluated and compared with experimental results. The impeller performance map was obtained for different operating speeds and mass flow rates with different tip clearances. The result shows that the tip leakage flow strongly interacts with mainstream and contributes to total pressure loss and performance reduction. The pressure and performance decrement are approximately linearly proportional to the gap between impeller and stationary shroud.The analysis showed scope for improvement in design of the compressor for better performance in terms of efficiency and operating range.

Performance Enhancement of a Pump Impeller Using Optimal Design Method

This paper presents the performance evaluation of a regenerative pump to increase its efficiency using optimal design method. Two design parameters which define the shape of the pump impeller, are introduced and analyzed. Pump performance is evaluated by numerical simulation and design of experiments(DOE). To analyze three-dimensional flow field in the pump, general analysis code, CFX, is used in the present work. Shear stress turbulence model is employed to estimate the eddy viscosity. Experimental apparatus with an open-loop facility is set up for measuring the pump performance. Pump performance, efficiency and pressure, obtained from numerical simulation are validated by comparison with the results of experiments. Throughout the shape optimization of the pump impeller at the operating flow condition, the pump efficiency is successfully increased by 3 percent compared to the reference pump. It is noted that the pressure increase of the optimum pump is mainly caused by higher momentum force generated inside blade passage due to the optimal blade shape. Comparisons of pump internal flow on the reference and optimum pump are also investigated and discussed in detail.

Influence of axial distance on pre-whirl regulation by the inlet guide vanes for a centrifugal pump

The valuation of the hydraulic performance of a centrifugal pump with pre-whirl regulation of the inlet guide vanes was studied experimentally by varying the pre-whirl angle from -60° to 60° with distances between the inlet guide vanes and the impeller inlet of 280 mm, 380 mm and 460 mm. The efficiency-flow curves and the characteristic curves were obtained for the pump for various operation conditions. The experiment results demonstrated that the pre-whirl regulation widened the high efficiency zone and improved the hydraulic performance for off-design conditions with the proper pre-whirl angle. The axial distance between the inlet guide vanes and the impeller inlet influenced the pre-whirl regulation effect of the inlet guide vanes with the best pre-whirl regulation effect obtained for an axial distance of 380 mm. These results showed that an appropriate axial distance between the inlet guide vanes and the impeller inlet can improve the fluid flow at the impeller entrance with pre-whirl regulation for centrifugal pumps.

Research on Performance of Centrifugal Pump with Different-type Open Impeller

To investigate the influence of impeller type on the performance and inner flow of centrifugal pump, the numeri- cal simulation and experimental research were carried out on the same centrifugal pump with straight-blade and curved-blade open impeller. Based on SIMPLEC algorithm, time-averaged N-S equation and the standard k-e turbulence model, the numerical results are obtained. The pressure distribution in the different type impellers is uniform, while the low pressure area in straight-blade inlet is larger. The vortexes in the passage of impeller exist in both cases. Relative to curved-blade impeller, there are larger vortexes in most of the flow passages except the passage near the tongue in straight-blade impeller. Also some small backflow regions are found at the blade inlet of two impellers. The characteristic curves achieved by numerical simulation basieaUy agree with those by experiment, and straight-blade open impeller centrifugal pump has a better hydraulic performance.

Influence of exit-to-throat width ratio on performance of high pressure convergent-divergent rotor in a vaneless counter-rotating turbine

This paper describes the redesign of a high pressure rotor (with exit Mach number around 1.5) for the vaneless counter-rotating turbine by choosing adequate exit-to-throat width ratio. Based on the previous design analysis and test results, effects of the exit-to-throat width ratio on the performance of the transonic turbine cascade were proposed. In order to investigate the influence of the exit-to-throat width ratio on the performance of the turbine cascade, a flow model of the convergent-divergent turbine cascade was constructed by using the theory of Laval nozzle. Then a method on how to choose the adequate exit-to-throat width ratio for the turbine cascade was proposed. To validate the method, it was used to calculate the adequate exit-to-throat width ratio for the high pressure rotor of the vaneless counter-rotating turbine. The high pressure turbine rotor was redesigned with the new exit-to-throat width ratio. Numerical simulation results show that the isentropic efficiency of the redesigned vaneless counter-rotating turbine under the design condition has increased by 0.9% and the efficiencies under the off-design conditions are also improved significantly. On the original design, a group of compressional waves are created from the suction surface after about 60% axial chord in the high pressure turbine rotor. While on the new design the compressional waves are eliminated. Furthermore, on the original design, the inner-extending waves first impinge on the next high pressure turbine rotor suction surface. Its reflection is strong enough and cannot be neglected. However on the new design the inner-extending waves are weakened or even eliminated. Another main progress is that the redesigned high pressure turbine rotor is of practical significance. In the original rotor, a part of the blade (from 60% axial chord to the trailing edge) is thin leading to the intensity problem and difficult arrangement of the cooling system. In the new design, however, the thickness distribution of the rotor airfoil along the chord is relatively reasonable. The intensity of the rotor is enhanced. It is possible to arrange the cooling system reasonably.

Influence of Blade Outlet Angle on Performance of Low-specific-speed Centrifugal Pump

In order to analyze the influence of blade outlet angle on inner flow field and performance of low-specific-speed centrifugal pump, the flow field in the pump with different blade outlet angles 32.5°and 39° was numerically calculated. The external performance experiment was also carried out on the pump. Based on SIMPLEC algorithm, time-average N-S equation and the rectified k-ε turbulent model were adopted during the process of computation. The distributions of velocity and pressure in pumps with different blade outlet angles were obtained by calculation. The numerical results show that backflow areas exist in the two impellers, while the inner flow has a little improvement in the impeller with larger blade outlet angle. Blade outlet angle has a certain influence on the static pressure near the long-blade leading edge and tongue, but it has little influence on the distribution of static pressure in the passages of impeller. The experiment results show that the low-specific-speed centrifugal pump with larger blade outlet angle has better hydraulic performance.

Anti-cavitation performance of a splitter-bladed inducer under different flow rates and different inlet pressures

The anti-cavitation performance of a high-speed centrifugal pump with a splitter-bladed inducer is investigated under different flow rates and different inlet pressures. Simulations and external characteristics experiments are carried out. Static pressure and the vapor volume fraction distributions on the inducer and the impeller of the pump under various operation conditions are obtained. The results show that the cavitation developments on the impeller and on the inducer with the flow rates are reverse, while the development of the inlet pressure on the inducer and the impeller is the same. Cavitation on the impeller increases with the increase of flow rates, and it extends to the near passages with rotating, while cavitation on the inducer is more complex than that on the impeller. Cavitation at the inlet of the inducer decreases with the increase of flow rates, while cavitation at the outlet of the inducer is opposite. The results also show that cavitation development on the impeller and on the inducer with the inlet pressure is the same. Cavitation both decreases with the increase of the inlet pressure at the same flow rate. Furthermore, asymmetric cavitation on the impeller and on the inducer is both observed. And the asymmetric degree of cavitation on the impeller is higher than that on the inducer.

Combined Experimental and Numerical Investigations on the Roughness Effects on the Aerodynamic Performances of LPT Blades

The aerodynamic performance of a high-load low-pressure turbine blade cascade has been analyzed for three different distributed surface roughness levels(Ra) for steady and unsteady inflows. Results from CFD simulations and experiments are presented for two different Reynolds numbers(300000 and 70000 representative of take-off and cruise conditions, respectively) in order to evaluate the roughness effects for two typical operating conditions. Computational fluid dynamics has been used to support and interpret experimental results, analyzing in detail the flow field on the blade surface and evaluating the non-dimensional local roughness parameters, further contributing to understand how and where roughness have some influence on the aerodynamic performance of the blade. The total pressure distributions in the wake region have been measured by means of a five-hole miniaturized pressure probe for the different flow conditions, allowing the evaluation of profile losses and of their dependence on the surface finish, as well as a direct comparison with the simulations. Results reported in the paper clearly highlight that only at the highest Reynolds number tested(Re=300000) surface roughness have some influence on the blade performance, both for steady and unsteady incoming flows. In this flow condition profile losses grow as the surface roughness increases, while no appreciable variations have been found at the lowest Reynolds number. The boundary layer evolution and the wake structure have shown that this trend is due to a thickening of the suction side boundary layer associated to an anticipation of transition process. On the other side, no effects have been observed on the pressure side boundary layer.