Impeller Outlet Research Articles

A novel method for work capacity calculation of centrifugal compressor impellers in energy storage systems

As the basis for centrifugal compressor design, the traditional one-dimensional scheme assumes that there is no flow prewhirl at the impeller inlet (i.e., C1u=0) when inlet guide vanes (IGVs) are absent. However, various experiments have proved that a natural prewhirl does exist at the impeller inlet even there is no IGV. In this study, a novel method is proposed to calculate the Euler work of impellers considering the natural prewhirl, and firstly applied to centrifugal compressors without IGVs. Stodola’s approach dealing with the slip velocity at the impeller outlet is adopted to the flow at the impeller inlet. A new formula for the Euler work calculation is deduced to evaluate the effect of natural prewhirl on centrifugal impellers. Then, this method is applied in two different model stages of industrial centrifugal compressors to verify against the experimental and numerical data. The results indicate that, compared to the traditional scheme assuming C1u=0, the novel method with modified formula considering the influence of C1u≠ 0 is more feasible for high-speed centrifugal compressors. With the aid of the novel calculation method proposed in this paper, the one-dimensional design accuracies of centrifugal compressor stages are improved by 7% compared with the traditional method.

Numerical Investigation and Experiment on Natural Circulation Resistance and Energy Characteristics in a Circulating Axial Pump

Abstract The influence of angle matching in rotor–stator interference (RSI) zone on natural circulation resistance (NCR) of circulating pump in natural circulation condition is illustrated by numerical method, and the analysis and optimization method of natural circulation based on loss coefficient curve are established through experiments. The mechanism and analysis formula of runaway speed are extracted, and the distribution diagram of Euler head density function (EHDF) is obtained to carry out image processing and analysis of secondary flow. Then, the optimal design interval of setting angle of impeller outlet under low flow resistance is acquired. As for the natural circulation loss of static parts, the optimal design interval of guide vane inlet angle and outlet angle with low flow resistance is obtained by analyzing the EHDF distribution diagram of the whole flow parts, which accounts for the position and reason of resistance. In this paper, the mechanism between runaway speed and loss coefficient curve is revealed and the resistance is optimized through the design and analysis of the RSI region, which provides theoretical methods for the analysis of the impeller performance of axial-flow circulating pump. Furthermore, it is a reference for the optimization design of natural circulation system.

Orthogonal Optimization Design of the Compound Impeller for a New Type of Dishwasher Pump

A new type of dishwasher pump without a pipeline system was invented for the first time to form an original sink-type dishwasher avoiding the accumulation of dirt in the hydraulic system. In order to improve the hydraulic performance of this new type of dishwasher pump with twin-volute passive rotation driven by a compound impeller, an orthogonal optimal design method was first introduced to optimize the compound impeller composed of axial cascades and radial blades. Six geometric parameters were selected as the main factors to design the orthogonal table L18(36). All impeller models were manufactured via high-precision 3D printing and tested to determine the optimal solution. Firstly, the hydraulic performance was measured using a specially designed test bench under the assumption of static-volute conditions. Then, the optimization scheme was verified in real machine experiments under the rotating-volute condition, and numerical calculations were used to assess the performance improvement due to optimization under the static- and rotating-volute conditions. The results show that the main factors affecting the pump head and efficiency are impeller outlet diameter D2 and profile line L. The optimized pump head and efficiency are significantly higher than those of the original scheme. Furthermore, the entropy production of each flow passage component of this new type of dishwasher pump is significantly reduced after optimization. Under the static-volute condition, the scheme obtained using the range analysis displays an increase of 0.3 m in the pump head and 2.99% in pump efficiency. Under the rotating-volute condition, the optimization scheme is also effective (pump head increased by 0.54 m, and pump efficiency by 7.46%). At the same time, the passive rotation speed of the twin-volute increases from 60 rpm to 70 rpm, verifying that both the optimization method is reliable and can be used when developing and optimizing dishwasher pumps.

Numerical Study of Unsteady Pressure Fluctuation at Impeller Outlet of a Centrifugal Pump

Intense fluid-dynamic interaction at the impeller outlet strongly affects the unsteady flow and pressure stability within the centrifugal pump. In order to have a better understanding of the pressure fluctuation of centrifugal pumps, a numerical calculation is carried out by using the RNG k-epsilon turbulence model under various flow rates. The numerical calculation results are compared with the experimental results in order to verify the reliability of the calculation model. The amplitude and frequency distribution of pressure fluctuation at the impeller outlet is obtained and analyzed in the time and frequency domain. The research results show that the blade passing frequency is the dominant frequency of the pressure fluctuation. And the pressure fluctuation is a periodic fluctuation. As the flow rate decreases, the periodicity of the pressure fluctuation decreases. Besides, the amplitude and intensity of pressure fluctuation are closely related to flow rate and spatial location. At the low flow rate, the amplitude of pressure fluctuation in the time domain and frequency domain is enlarged greatly, especially near the tongue region. The pressure difference distribution on both sides of the blade surface is extremely uneven, and the pressure changes significantly.

Investigation on flow mechanism of an advanced transonic centrifugal compressor with free-form impeller at design and off-design speeds

A transonic centrifugal compressor with a ruled-impeller (that is, impeller blades are generated by a set of points swept by a moving straight line) was used as the baseline, and the impeller blades were redesigned using non-ruled surfaces (referred to as the ‘free-form impeller’) in this study to reveal the potential of this design approach to improve the performance of high-pressure-ratio centrifugal compressors. By using the method of Computational Fluid Dynamics (CFD) simulation, the performance characteristic and the flow field inside the impeller and diffuser of the baseline compressor and the free-form one were comparatively analyzed in detail. The results show that the free-form impeller design can improve the performance of the compressor in many aspects no matter at design or off-design speeds. The barreled-sweep inducer can reduce the losses from the shock wave at design speed and extend the compressor stable operating range at off-design speeds. The positive compound-lean impeller blades can suppress the reverse flow at impeller outlet. The flow downstream of the free-form impeller was also improved due to a more uniform outlet flow field provided by it at. This study aims to provide a valuable reference for applying free-form design methods to future advanced centrifugal compressors.

Numerical Study for Flow Loss Characteristic of an Axial-Flow Pump as Turbine via Entropy Production Analysis

Low-head vertical axial-flow pump as turbine (PAT) devices play a vital part in the development of clean energy for hydropower in plain areas. The traditional method of evaluating the flow loss in hydraulic machinery is calculated by the pressure drop method, the limitation of which is that the location of the occurrence of large losses cannot be accurately determined. In this paper, entropy production theory is introduced to evaluate the irreversible losses in the axial-flow PAT from the perspective of the second law of thermodynamics. A three-dimensional model of the axial-flow PAT is established and solved numerically using the Reynolds time-averaged equation, and the turbulence model is adopted as Shear Stress Transport–Curvature Correction (SST-CC) model. The validity of the entropy production theory to evaluate the energy loss distribution of the axial-flow PAT is illustrated by comparing the flow loss calculated by the pressure drop and the entropy production theory, respectively. The entropy production by turbulent dissipative dominates the total entropy production in the whole flow conduit, and the turbulent dissipative entropy accounts for the smallest percentage of the whole conduit entropy production at the optimal working condition Qbep, which is 51%. The impeller and the dustpan-shaped conduit are the essential sources of hydraulic loss in the entire flow conduit of the axial-flow PAT, and most of the energy loss of the impeller occurs at the blade leading edge, the trailing edge, and the flow separation zone near the suction surface. The energy loss of the dustpan-shaped conduit results from the high-speed flow from the impeller outlet to dustpan-shaped conduit to form a vortex, backflow and other chaotic flow patterns. Flow impact, flow separation, vortex and backflow are the main causes of high entropy production and energy loss.

Mechanism of the rotor−stator interaction in a centrifugal pump with guided vanes based on dynamic mode decomposition

In this paper, the mechanism of the rotor–stator interaction in a centrifugal pump with guide vanes is studied numerically and theoretically. The dynamic mode decomposition method is employed to decouple and reconstruct the unsteady flow. A diametrical mode theory suitable for centrifugal pumps with guided vanes is proposed to determine the source of harmonics with higher amplitudes quickly. The results show that the dominant frequencies of the pressure pulsation in the volute and guide vanes are the blade passing frequency and its harmonic frequencies, and the corresponding flow structure is stable and has higher modal energy. The rotor–stator interaction effect around the impeller outlet is most pronounced. The potential flow effect works on the impeller and guide vanes but decays rapidly. The pressure pulsation caused by the wake effect propagates downstream and persists for long distances, which is the main reason for forming the modal pressure field in the volute. The modal reconstruction can reproduce the dynamic evolution process of the pressure field at the characteristic frequencies. The propagation characteristics of the modal pressure field in the volute can be accurately predicted by theoretical analysis. This research can provide an essential reference for fault diagnosis and vibration control of the centrifugal pump.

Fluid Energy Conversion Analysis in Hydraulic Channels of reactor coolant pump under flow coastdown transient

Conversion between dynamic energy and static pressure energy is complex in reactor coolant pump (RCP) hydraulic channel in nuclear plant station, especially under flow coastdown transient. The performance was calculated by numerical simulation. The performance of RCP under flow coastdown is studied, and the energy conversion characteristics of hydraulic components are analyzed. The results investigated show that with increasing of coastdown time head loss decreases sharply from coastdown starting. After the coastdown time of 10 s, the head loss in the channel of impeller, guide vane and volute decrease to 50% below. In the process of coastdown, dynamic pressure head of the inlet flow domain drops rapidly from 6.8 m, and finally decreases to 0 m, while static pressure head gradually increases from −7 m, and closes to 0 m after coastdown time is 140 s. When coastdown starts, dynamic energy above 24.33 m is mainly distributed at the outlet of impeller, the inlet of guide vane and the outlet of volute. When t= 110 s, the dynamic energy in most area is below 12.17 m, and when t= 200 s, the dynamic energy is small, distributed in the range of 0 m∼6.08 m. With coastdown time increasing the dynamic energy on pressure and suction surfaces of impeller and guide vane blade decreases. At t= 90 s, dynamic energy is lower at leading edge of blade than that at trailing of impeller blade, and the maximum energy of guide vane blade is located at the root of leading edge. As the coastdown time increases, static pressure energy of RCP inlet flow domain and impeller inlet continues to increase, while the larger static pressure energy distribution area in the volute gradually decreases.

Investigation on the Effect of the Shaft Transition Form on the Inflow Pattern and Hydrodynamic Characteristics of the Pre-Shaft Tubular Pump Device

The shaft tubular pump device is widely used in low head pumping stations in plain areas. The N-S equation and the SST k-ω turbulence model are adopted. Then, the investigation on the influence of the shaft transition form on the inflow pattern and hydrodynamic characteristics of the pre-shaft tubular pump device is carried out. By designing three transition forms of shafts, different inflow patterns are provided for the tubular pump device. The characteristic parameters of the shafts and external and internal flow characteristics of the pumping device under different inflow patterns are compared and analyzed. Finally, the optimal transition form is selected for model tests, and unsteady pressure pulsation characteristics are studied. The results show that the flow pattern in the inlet passage of each case is relatively uniform and smooth, and the range of the high-efficiency zone of the pump device is roughly within 0.9Qd–1.2Qd. The energy loss and the weighted average angle on the outlet of each case are similar. The axial velocity distribution uniformity on the impeller inlet of case 1 is better than that of the other cases. The numerical simulation results are consistent with the experimental results, and the numerical simulation method is reliable. Under the design condition, the pressure pulsation amplitude at the impeller inlet is the largest. It gradually increases from the hub to the shroud. The main frequency of pressure pulsation is the blade frequency. The pressure pulsation amplitude at the impeller outlet decreases from the hub to the shroud. The main frequency is not constant due to the rotor–stator interaction between the impeller and the guide vane. The outcome will be beneficial to the design and optimization of the shaft tubular pump device, which is helpful for broadening the corresponding theory and applying it to the actual project.

Optimization design of hump phenomenon of low specific speed centrifugal pump based on CFD and orthogonal test

Aiming to eliminate the hump phenomenon in a low specific speed centrifugal pump, its structural parameters were optimized using the computational fluid dynamics method. Based on the k - varepsilon turbulence model, a 3D steady analysis of the internal flow field was carried out. The L_{9} left( {3^{4} } right) orthogonal table was established, and four structural parameters, including the impeller outlet diameter, impeller outlet width, number of blades, and blade outlet angle, were selected as influencing factors. Nine orthogonal test schemes were developed and the results were analyzed through the weight matrix analysis method, obtaining the weight of the selected factors on the test results. The optimal scheme was selected according to the weight and the weight matrix analysis results have shown that the impeller outlet width had the dominant influence on the head, shaft power, and efficiency. Further, the blade number was the main influencing factor for shaft power and efficiency. The centrifugal pump flow control test bench was built to carry out the numerical simulation and test all the prototype and optimization pump indexes. Through the external characteristic test, it can be seen that the beta_{2} Z^{0.773} of the optimized pump is 87.889, which is 24.89% lower than that of the prototype pump, which effectively optimizes the hump phenomenon of the centrifugal pump. The experimental results have shown that in underrated working conditions, the working performance of the optimized pump was improved significantly. The head size was reduced by 1.424%, and the efficiency was increased by 7.896%. By optimizing the structural pump parameters, its jet-wake hydraulic loss was reduced, and the head curve hump phenomenon was effectively eliminated. All the performance indexes of the optimized pump were higher than those of the prototype, verifying both the accuracy and reliability of the orthogonal test and weight matrix analysis method. Finally, obtained results provide a reference for the structural design of high-performance centrifugal pumps.

Study on vortex flow and pressure fluctuation in dustpan-shaped conduit of a low head axial-flow pump as turbine

In the plain river network area, the constructed axial-flow pumping station is used to generate electricity by reversing as turbine when the upstream water is abundant, which can reduce the environmental pollution caused by coal-fired power generation while making full use of water resources. When the axial-flow pump as turbine (PAT) operates, there are severe flow instability and obvious pressure pulsation in the dustpan-shaped conduit. In this paper, the transient numerical simulation method is used to study the evolution characteristics and pressure pulsation of the vortex in the dustpan-shaped conduit when the axial-flow PAT runs, and the pressure pulsation signal of simulation is compared with the pressure pulsation result of model test. The formation of the spiral vortex rope in the dustpan-shaped conduit is related to the velocity circulation at the impeller outlet and the axial velocity of the fluid. The axial velocity and tangential velocity near the vortex center are close to zero. The inlet of the dustpan-shaped conduit is subjected to the dynamic and static interaction effect of impeller domain and conduit domain. Further downstream, rotor and static interaction effect weakens gradually. As the distance from the impeller increases, the dominant frequency of pressure pulsation changes from 3 times the rotational frequency to 0.5 times the rotational frequency. The dominant frequency of pressure pulsation at the monitoring points near the vortex rope are 0.5 times the rotational frequency, and massive low frequency near the vortex rope are generated by the vortex rope rotation.

The Cavitation Characteristics of High Speed Centrifugal Pumps With Different Impeller Types

Addressing the cavitation prevention requirements for a longer service life of the high-speed centrifugal pump in the temperature control system of aerospace, the effect of blade inlet width on cavitation performance is studied on the premise of consistency of impeller outlet diameter D2, impeller outlet width b2, volute inlet diameter D3, pump interface and other structural parameters. Therefore, the corrected coefficient k1 of blade inlet exclusion coefficient is introduced; four groups of centrifugal impellers with inlets of different geometric structures blades are put forward. To begin with, based on the D# pump performance test and Pumplinx simulation, the cavitation performance of high-speed pump with four different groups of impellers is studied under five working conditions of negative inlet pressure (Pj=(−20, −30, −40, −50, −60)kPa) on the premise that energy characteristics agree well with cavitation performance. According to the results, when Pj drops from −50 kPa to −60 kPa, the cavitation perform changes the most significantly. This indicates that the method of twisting the centrifugal impeller of the suspended forward-extended blade shows a significant effect in preventing cavitation performance under such working conditions of high speed and negative pressure. Its application in aerospace power systems can effectively reduce the impact of low pressure in the system and significantly improve the cavitation performance.

MODIFICATION OF MOMENTUM DISTRIBUTION WITHIN THE THREE NOZZLES OF THE WATERJET AZIMUTH PROPULSION SYSTEM

This paper focuses on the thrust direction misalignment and lateral force caused by the rotational flow at the impeller outlet of the waterjet azimuth propulsion system. Momentum distribution within the three nozzles is found to be the direct reason. Two methods, i.e. area match between the left nozzle and right nozzle and adding guide vanes inside the middle nozzle are proposed and their effects are analysed respectively based on numerical simulation. Results show that an appropriate area ratio can eliminate thrust direction misalignment with a small increase in lateral force. Guide vanes can effectively reduce lateral force by 56% without affecting aligned thrust direction.

Theoretical Analysis of Isentropic Exponent Effects on the Internal Flow of Supercritical CO2 Centrifugal Compressors

The isentropic exponent in the near-critical region can sharply change with operation condition transitions of a closed Brayton cycle, thus having significant impacts on the compressor aerodynamic performance and the internal flow of the compressor embedded into the cycle. This paper investigates the isentropic exponent effects of the supercritical carbon dioxide (CO2) using theoretical analyses and three-dimensional computational fluid dynamic (CFD) simulations. The theoretical analysis reveals that the increasing isentropic exponent mitigates the impeller work coefficient and the impeller outlet Mach number but raises the suction side Mach number of the impeller blade and blade loading at the leading edge. The CFD results provide validations for the theoretical results. Based on the findings, a suggestion is offered to guide the physical experiment design of a centrifugal compressor with supercritical CO2 as its working fluid.

Rotor-stator aerodynamic interaction of centrifugal compressor at pulsating backpressure conditions

The performance of a centrifugal compressor is strongly influenced by pulsating backpressure condition, but little knowledge of the mechanism has been obtained. This study investigates aerodynamic interaction between impeller and volute at pulsating condition via experimentally validated numerical method. Results show that the features of volute-induce distortion at impeller exit are closely coupled with pulsating backpressure at different operational conditions. Specifically, the volute-induce pressure distortion varies out-of-phase with the mass flow rate near surge condition (OP2), but in phase near choke condition (OP1). The circumferential flow distortion at the impeller outlet manifests a notably unsteady effect at pulsating conditions for both OP1 and OP2. Comparing with the quasi-steady cases, the magnitude of the distortion is alleviated maximally by 2.3% and 2.7% for OP1 and OP2, respectively. The evolution of secondary flow patterns in the impeller show that an array of vortex tubes appears in the shroud region of the inducer downstream the main blade leading edge. It is resulted from the rolling-up of vortex sheet due to the K-H instability. The pulsating backpressure can profoundly depress the development of the vortex street. Therefore, the blockage effect by the vortex street in the inducer is alleviated.

Optimization Design for the Centrifugal Pump under Non-Uniform Elbow Inflow Based on Orthogonal Test and GA_PSO

The non-uniform inflow caused by the elbow inlet is one of the main reasons for the low actual operation performance of a centrifugal pump. Orthogonal experiment and GA_PSO algorithm are used to improve the head and efficiency of a centrifugal pump with an elbow inlet based on the method combining numerical simulation and prototype experiment in this paper. The effects of the design parameters, including elbow inlet radius ratio, blade inlet angle, blade number, blade wrap angle, blade outlet angle, impeller outlet diameter, blade outlet width and flow area ratio, on the pump head and efficiency are studied in the orthogonal experiment. The blade inlet angle is the major factor to match the non-uniform inflow and reduce the flow loss in the impeller inlet to contribute to enhancing the pump performance and cavitation characteristics. The particle swarm optimization (PSO) algorithm is optimized by integrating the genetic algorithm (GA), which ensures that the PSO-calculation result avoids falling into the local optimization and the global optimal solution is obtained as quickly as possible. The centrifugal pump with an elbow inlet is optimally designed by the GA_PSO algorithm. According to the performance test results, the efficiency of the optimized pump is 4.7% higher than that of the original pump.

Performance Enhancement of a Centrifugal Compressor by Designing a Tandem Cascade Diffuser

The performance of a vane diffuser plays an important role in transforming the high kinetic energy into pressure energy at the impeller outlet of a centrifugal compressor. In this study, the performance enhancement of a centrifugal compressor is achieved by designing a tandem cascade diffuser. An optimum value of the total bending angle of a tandem cascade diffuser is obtained through numerical simulation. The total bending angle is defined as the angle between the tangent line of the front blade arc line at the leading edge point and the tangent line of the rear blade arc line at the trailing edge point. The range of the total bending angle increases from zero to 21°. The simulation results show that the variation of the total bending angle has a great impact on the performances of the compressor stage. The best performance is achieved by the 10° model, by which the minimum total pressure loss coefficient and the maximum static pressure recovery coefficient are obtained. The mechanism of performance improvement by choosing a reasonable total bending angle is that the separated flow zone in the diffuser is constrained and the distribution of radial velocity at the inlet and outlet of the diffuser is more uniformed. With the 10° model, the separated zone almost completely disappears in the diffuser and a distribution of more uniform radial velocity along the meridional section is obtained. Compared with the stage of the prototype with a single row of vane diffuser, the stage with the newly designed tandem vane diffuser (10° model) achieved performance improvement, the efficiency increased about 6%, and the total pressure ratio increased about 3.5% at the flow coefficient of 0.15.

Analysis of Transient Characteristics of Submersible Tubular Pump During Runaway Transition

In order to study the transient characteristics of the submersible tubular pump in the process of power failure, the 6DOF model was used to carry out three unsteady numerical values for the whole flow channel of the pump. The results show that the calculation results of the 6DOF model based on the fourth-order multi-point Adams–Moulton formula are in better agreement with the experimental results than the first-order format to predict the impeller motion. When the unit is powered off, the speed and flow of the pump device decrease rapidly with time. At the maximum head 3.41 m, when the unit enters the runaway condition, the speed is about −1.88 times the initial speed and the flow rate is about −1.98 times the initial flow. The axial force and radial force of the impeller increase alternately, and compared with the normal operating condition, the radial force is significantly increased. In the process of the pump device changing from forward flow to reverse flow, the internal flow state of the pump device is relatively chaotic, and there are a large number of vortices in the flow channel, which is easy to cause structural vibration. Before reaching the runaway state, a large number of vortices also appear inside the impeller and guide vane, causing flow blockage, especially when the flow rate is zero. At the same time, the reverse flow impact causes the local pressure on the blade surface to increase, which threatens the stability of the blade structure. The pressure at the impeller inlet, impeller outlet, and guide vane outlet monitoring points is the largest near zero flow, and the smallest during runaway. The main frequency of the pressure pulsation in the pump device is the blade pass frequency (fBRF) and its harmonics (2fBRF, 3fBRF, 5fBRF, etc.), and the pressure pulsation intensity increases with the increase of the impeller speed. The results of this study provide a theoretical reference for the operation of the submersible tubular pump to ensure the safety and stability of the pumping station.

Transportability Improvement of a Gas–Liquid Rotodynamic Pump Using the Two-Step Multi-Objective Optimization Strategy

The development of multiphase pumps is restricted because of low efficiency and poor mixing transportation capacity. In this study, a two-step multi-objective optimization design system for a multiphase pump is constructed using a three-dimensional (3D) design theory and multi-objective optimization techniques. The transportability improvement for the pump impeller is achieved by implementing the optimization variables of its geometry and blade loading and the optimization objectives containing the pump efficiency and gas uniformity. The optimal results of impeller geometry show that the blade wrap angle and control parameters of the hub have remarkable effects on the pump efficiency and gas uniformity. The optimal results of impeller blade loading show that the pump efficiency is improved if the impeller with large loading at the leading edge, large slope at the middle part, and large negative high-pressure edge angle. The gas uniformity is improved if the hub loading at the middle and trailing parts is larger than the shroud loading. Compared to the original test impeller, the pump efficiency with the impeller T-Opt1 and the gas uniformity at the impeller outlet are improved by 10.81% and 6.91%, respectively. The maximum fluctuation amplitudes in T-Opt1 and its corresponding guide vane are reduced by 0.61% and 67.76%, respectively.

Comparative analysis of flow characteristics of different blade inclination outlet schemes of long shaft pumps

Multistage space guide vane long shaft pump is widely used in many important fields because of its compact structure, convenient maintenance and simple pipeline. However, due to the complex flow phenomenon in its channel, the space guide vane long shaft pump has the problem of low performance. This paper takes xb4.3/240-300lc vertical long shaft fire pump as the research object. When the blade outlet width is the same, three schemes of impeller outlet inclination angle (0°, 15°and 25°) are designed, and CFX is used for numerical simulation to analyse the difference of internal flow field of each scheme. The results show that compared with the other two schemes, the scheme with an inclination angle of 15° has better performance in efficiency( η ) and head( H ). The pressure on the working surface of the blade is higher than that on the back of the blade, and the pressure near the front cover plate increases with the growth of the inclination angle. Under the condition of small flow, the velocity at the impeller outlet increases with the growth of inclination angle. Under the condition of large flow, the velocity at the impeller outlet decreases with the growth of inclination angle. Similarly, the turbulent kinetic energy shares the same pattern with the velocity at the impeller outlet. Under all working conditions, small vortex structure appears in impeller and guide vane. It is found that the scheme with impeller outlet inclination angle of 15° has smaller impeller vortex structure under standard working condition.