Vane Inlet Research Articles

Influence of staggered vane shunt plate on performance characteristics of reactor coolant pump

In order to explore the influence of the axial position of the shunt plate of staggered guide vane on reactor coolant pump(RCP), a mixed-flow RCP was taken as the model for numerical simulation. Based on the entropy production theory, the energy loss in the flow component under different flow conditions was analyzed, and the vortex core distribution in volute and the pressure pulsation at the hydrodynamic interface were studied. The results show the staggered guide vane reduces the head and efficiency slightly, the optimal scheme decreases by 0.9% and 0.6%. Placement of the shunt plate significantly influences entropy production within the guide vane and volute, especially when positioned near the front and back plates. When shunt plate is set centrally, the energy loss due to staggered guide vane is relatively smaller and closer to the original structure. The entropy production rate of guide vane inlet and shunt plate leading edge is higher, but with the increase of flow rate, the shunt plate leading edge is no longer the main location of energy dissipation. Middle placement of staggered guide vanes effectively reduces the outflow vortex band by Omega vortex analysis, and the amplitude of pressure pulsation at the interface decreases obviously.

Evolution mechanism of internal flow in the hump region and hump optimization of axial-flow reactor coolant pump

The Nuclear Reactor Coolant Pump (RCP) serves as a pivotal equipment in nuclear power plants, and its operational reliability is directly linked to the overall safety of the plant. When operating in the hump region, axial-flow reactor coolant pumps inevitably experience significant vibration and noise. Therefore, it is necessary to study the internal flow characteristics in the hump region to achieve effective control and increase the hump margin, keeping it away from the normal operating region. This study conducted analyses of pressure pulsation characteristics under various flow rates through experimentation. Additionally, numerical simulations were employed to scrutinize the internal flow of the pump under corresponding flow rates. Research has found that the disturbance of intermediate frequency signals is the main reason for the increase in pressure fluctuations in the hump region, rooted in the annular flow at the impeller inlet and vortex phenomena in the flow channel. Subsequently, the performance of the hump region was improved by optimizing the design of the vane inlet attack angle. The conclusions drawn from this study provide insights and a foundation for the optimal design of reactor coolant pumps.

DDPM investigation on centrifugal slurry pump with inlet and sideline configuration retrofit

The inlet and sideline configuration modifications are widely investigated to alter regional particle fluid flow conditions, considering pressure, turbulence and erosion, therefore to improve energy saving and compartment longevity of centrifugal slurry pump. This paper aims to analyse pump hydraulic and erosion characteristics with proposed pump sideline and inlet configuration retrofit by the DDPM method. Specifically, the inlet guide vane number () and angle (), and sidelining vane (SDV) curvature are investigated in quantitative manner. Accordingly, by adjusting inlet vane configuration and placement, a trade-off between wall erosion and hydraulic performance is observed. The sidelining vane (SDV) design is suggested to avoid resultant counter-current flow formulation, therefore, to mitigate turbulence induced erosion in impeller and volute. However, the SDV modification effect on pump hydraulic head and efficiency is found marginal. In general, this study offers realistic guideline for performance improvement and device upgrading of centrifugal slurry pumps.

PIV investigation of stalled flow field near the blade rim region of mixed-flow pump under different tip clearances

In order to further explore the physical mechanism of rotating stall induced by different rim leakage flow intensification, the velocity distribution of the stall flow field of the mixed flow pump under different rim clearance scales was obtained by Particle Image Velocimetry technology. By comparing the flow structure under different shooting sections, different phases and different working conditions, the influence of rim clearance scale on the flow field near the wall of the mixed flow pump was revealed. The results show that under the design flow conditions, there is an obvious reflux phenomenon near the hub of the guide vane inlet of the mixed flow pump under the four kinds of rim clearance, but the intensity is weak, and it does not affect the main flow field in the impeller channel. With the increase of rim clearance scale, the leakage flow intensity also increases, and the main flow area affected by the TLV structure also increases. In the deep stall condition, the reflux vortex at the inlet of the guide vane of the mixed flow pump still exists at each clearance, but the unsteady flow structure begins to appear inside, especially the large secondary vortex structure formed at the guide vane inlet, which seriously blocks the main flow. With the increase of the rim clearance, the flow field at the inlet of the guide vane is also obviously affected, and the secondary vortex core gradually moves towards the end wall area, resulting in an increase in the blocked area in the flow field. At the same time, the unsteady flow intensity of the flow field shows a nonlinear increasing trend. The unsteady strength of flow field increases rapidly with small gap impellers, while the unsteady strength changes slowly with large gap impellers. This study provides a reference for optimizing the rim clearance of mixed-flow pump and improving the efficiency of mixed-flow pump.

Mechanism of the impact of sediment particles on energy loss in mixed-flow pumps

Numerical simulations were performed on the fluid domain of the mixed-flow pump with different solid-phase volume fractions to examine the influence of the sediment particles on internal energy dissipation. The energy properties of the mixed-flow pump were analyzed using the entropy production theory, considering the various flow rates and the solid particle conditions. The research examined the impact of the proportion of the solid particles in the flow on the performance and effectiveness, uncovering the complexities of the energy dissipation in the channel. The results showed that incorporating solid particle media resulted in the decrease in both the performance and effectiveness of the mixed-flow pump compared to water conditions. The mixed-flow pump's head decreased by 0.56 % and its efficiency declined by 2.74 % due to the change in particle volume fraction (Cv) from 5 % to 7.5 %. Upon transitioning from Cv = 7.5 % to Cv = 10 %, the head exhibited a 2.54 % decrease, coupled with a 7.22 % efficiency reduction, signifying pronounced energy loss. The findings highlight that the increase in the quantity of the solid particles enhances the pump's energy dissipation. Solid particles tend to be mainly concentrated in the impeller inlet, blade outer edge, guide vane inlet, and guide vane outer edge regions at varying solid-phase volume fractions. The main dissipation in the fluid region of the mixed flow pump mainly occurs in the impeller and the guide vane, the total energy loss in the guide vane is more than 500 W under the three volume fractions, the total energy loss in the impeller is also about 500 W, and the inlet and outlet losses are small. These research outcomes lay the groundwork for further enhancements in the energy characteristics of mixed-flow pumps.

Impact of rotor–stator axial spacing on the gas–liquid–solid flow characteristics of a multiphase rotodynamic pump based on the Euler multi-fluid model

Multiphase rotodynamic pumps are used by the oil and gas industry to transport mixed media in pipelines. The characteristics of gas–liquid–solid flow in such pumps are significantly affected by the rotor–stator axial spacing so that further investigation is required. Based on the Euler multi-fluid model, the Computational Fluid Dynamics simulations were conducted in this study on the gas–liquid–solid multiphase rotodynamic pump at the rotor–stator axial spacings of 8, 10, 12, 14, and 16 mm, respectively. Changes in the pump's characteristics of external, multiphase flow, and pressure fluctuation were systematically analyzed by using ANSYS-CFX. The results showed that, an overall decreasing trend for the efficiency and head of the multiphase rotodynamic pump were demonstrated with increases in the rotor–stator axial spacing from 8 to 16 mm, which can be categorized into plummets I, moderation, and plummets II. As the rotor–stator axial spacing increased, the pressurization decreased from the inlet to outlet of guide vane while the aggregation of gas and solid increased. Additionally, vorticity increased and vortex structure was found to be more significant. As a result, the overall performance of the multiphase rotodynamic pump deteriorated. The pressure fluctuation in the multiphase rotodynamic pump was determined by the rotor–stator interaction and multiphase flow under gas–liquid–solid flow conditions, resulting in a non-positive correlation between the pressure fluctuation and the pump's external and internal flow characteristics. The location of maximum pressure fluctuation in the multiphase rotodynamic pump was changed from the impeller outlet to the guide vane inlet with increases in rotor–stator axial spacing.

Improving part-load performance of combined-cycle gas turbines by optimizing variable geometry control strategy for compressor and power turbine combined adjustment

The variable geometry methods currently used in combined-cycle gas turbines are compressor variable inlet guide vanes (VIGV) or power turbine variable area nozzles (VAN). On this basis, this study presents the optimal variable geometry control strategy for compressor and power turbine combined adjustment ([Formula: see text]) using the Differential Evolutionary Algorithm with the LM2500+ gas turbine. The aim is to further improve the part-load performance of the combined-cycle gas turbine. Firstly, a part-load performance prediction model for variable geometry gas turbines is established based on the component method. Subsequently, a variable geometry gas turbine part-load performance optimization model is developed by combining the Differential Evolution Algorithm. Finally, the optimum combination of stagger angles for the compressor inlet vane and power turbine nozzle is calculated at each part-load condition. Compared to the VIGV and VAN control strategies, the [Formula: see text] control strategy proposed in this paper shows a higher stability margin and better economy. The [Formula: see text] control strategy maintains a constant exhaust temperature within a part load range from 20% to 100% with the stability margin exceeding 14%. In comparison with the VAN control strategy, the fuel flow rate decreases by 1.152% at 45% relative load power and by 3.435% at 20.0% relative load power with the [Formula: see text] control strategy.

A Method for Preliminary Design of Variable Geometry Vaned Diffuser for Centrifugal Compressor

Abstract Centrifugal compressors require a wide operating range as well as high efficiency. Typical active control forms to enhance the operating range are suction throttling with a valve in a suction line, discharge throttling with a ring installed in a vaneless diffuser, variable inlet guide vanes, and variable geometry vaned diffuser (VVD). This study focuses on the design of a VVD whose vane rotates around a pivot to adjust its opening and proposes a method to estimate the main parameters of the VVD at the preliminary design stage. The design method here is based on matching the diffuser vane inlet angles with the flow angles at the diffuser inlet. If the designed VVD can maintain low incidence at the diffuser vane leading edge over the whole movable range of the vane is evaluated. A graph, which indicates the relation between the diffuser vane inlet angles and the flow angles at the diffuser inlet at diffuser choking and diffuser stalling, makes the evaluation easy. The proposed procedures were applied to select the number of vanes of the VVD for a turbocharger compressor. Tests for the validation of the design procedures were conducted by using fixed vaned diffusers that simulated the VVDs installed on the turbocharger with an 85 mm-diameter impeller. The results showed the effectiveness of the proposed design procedures. This paper first presents examples of applications of the typical active methods extending centrifugal compressors’ operating range for real machines and then discusses the design of VVD.

Understanding Thermal Unsteadiness in Engine Representative Flows and Improved Methodologies for Derived Heat Transfer Calculations Using Thin-Film Gauges

Abstract The Oxford Turbine Research Facility (OTRF) is a high-speed rotating transient test facility, which allows unsteady aerodynamic and heat transfer measurements at engine representative conditions. In addition, a variety of inlet temperature profiles can be simulated in the rig including radial distortion, circumferential distortion, and swirl. However, the engine representative flows cause complications in the processing of heat transfer data. The unsteadiness in temperature data was found to significantly rise as temperature distortions were introduced in the nozzle guide vane (NGV) inlet profile, to model a lean-burn combustor exit. Using the NGV inlet temperature profile survey data, the thermal unsteadiness has been quantified and compared with a uniform inlet. The experiments with a radially varying NGV inlet temperature profile showed up to nine times higher thermal unsteadiness, compared to the uniform inlet. The second part of the paper is a continuation of the work presented in a previous paper by Singh et al. and describes improved methodologies for derived heat transfer calculations using thin-film gauges. In addition, the uncertainty associated with the derived heat transfer parameters, such as the heat transfer coefficient and adiabatic wall temperature has been quantified. The refined processing techniques have been demonstrated on casing heat transfer measurements, acquired in the OTRF with two inlet temperature profiles.

Effect of Inlet Vane Angle of a Partial Vane Diffuser on the Performance and Flow Filed of a Centrifugal Compressor

The paper presents experimental results on the effect of inlet vane angle on the performance and flow field of Partial Vane Diffuser (PVD) of a low speed centrifugal compressor. Performance tests are conducted for eight configurations of PVDs. From these tests, an optimum configuration with 5° increase in inlet angle of partial diffuser vanes on shroud (PVDHS5) is selected for further measurements i.e. static pressure on the diffuser hub and shroud and diffuser passage flow field at four flow coefficients. From passage flow measurements flow parameters are obtained within the diffuser flow passage. Flow parameters are axially averaged and their contours are presented. Radial variation of these flow parameters is also presented. PVDHS5 gives 2.3% increase in peak energy coefficient and 4.9% increase in efficiency compared to that of vane less diffuser. The flow at the exit of PVDHS5 is more uniform.

Analysis of pressure pulsation and energy characteristics of guide vane for axial flow pump based on Hilbert-Huang transform considering impeller-guide vane interaction.

In order to explore the characteristics of pressure pulsation signals and energy distribution of water flow at the guide vane considering impeller-guide vane interaction. The numerical simulation of the vertical axial flow pump device's steady and unsteady three-dimensional flow fields was carried out. The Hilbert-Huang method was used to conduct empirical mode decomposition decomposition and Hilbert spectrum analysis of pressure pulsation signal at each monitoring point in the inlet and outlet regions of the guide vane. The results show: Under the condition of 0.3Qbep, the internal pressure of the guide vane is obviously affected by the impeller, and there are large block-shaped vortex structures in the guide vane. Under the operating conditions of 1.0Qbep and 1.2Qbep, the size of the pressure area in the guide vane is basically not affected by the impeller, and the vortex structures in the guide vane are concentrated near the outlet of the guide vanes, and there are long strip-shaped vortex structures at the edge of the guide vane. The size and number of vortex structures decrease with the increase in flow rate. The pressure pulsation signal at the inlet of the guide vane is affected by the rotation of the impeller and exhibits good periodicity, with the main frequency centered around 146 Hz, and the energy ratio of the main frequency is up to 97.7%. There are low-frequency signals below 100 Hz and high-frequency signals fluctuating around 146 Hz in all three flow conditions. When the flow rate increases, the fluctuation amplitude of the high-frequency signal increases. The flow rate has a significant impact on the water flow at the outlet of the guide vane. At 0.3Qbep, its frequency is distributed in the range of 0-500 Hz, mainly concentrated in the area below 400 Hz. At 1.0Qbep, the frequency of pressure pulsation is distributed below 250 Hz after the guiding function of the guide vane. At 1.2Qbep, the water flow is mainly controlled by the rotation of the impeller, and after the energy recovery of the guide vane, its main frequency is still concentrated around 150 Hz, which is 337.2% and 268.5% of 0.3Qbep and 1.0Qbep. Under the working condition of 0.3Qbep, the proportion of intrinsic mode function energy corresponding to the dominant frequency at the center of the guide vane inlet is as high as 95.9%, and the proportion of intrinsic mode function energy corresponding to the dominant frequency at the shroud side and hub side of the guide vane is rather low. If the flow rate rises from 0.3Qbep to 1.2Qbep, the proportion of intrinsic mode function energy increases by more than 42%. Under the working conditions of 0.3Qbep and 1.0Qbep, the main frequency of pressure pulsation signal of water flow at the guide vane outlet is less affected by the impeller and the corresponding energy proportion is low. Under the working condition of 1.2Qbep, the main frequency of pressure pulsation signal is 4 times the rotational frequency and the corresponding energy proportion is higher than 60%.

Design Impacts on Ram Air Vane Cooling in an Ultra-Compact Combustor

Abstract The ultra-compact combustor (UCC) aims to decrease the length of gas turbine combustors using a unique design geometry which wraps a combustion chamber around the central axial flow. This distinctive design enables an out of the box type of cooling scheme to be investigated for the turbine inlet vanes, termed the hybrid guide vane (HGV) in the UCC. The leading edge of the HGV experiences only compressor exit air as combustion products do not interact with the vane upstream of the 14% axial chord location. Previous studies were conducted which computationally evaluated the viability of taking in freestream flow through the HGV stagnation region for use as coolant. Based on these studies, a six vane HGV was manufactured which incorporated a solid vane and five hollow vanes. Each of these vanes incorporated different features to vary the size of the internal plug, trailing edge exit, and film cooling holes. In the present study, the cooled HGV was experimentally analyzed using pressure, thermocouple, and infrared (IR) thermography measurements to evaluate internal coolant flowrates and pressure loss along with cooling performance. Furthermore, the vanes were compared to isolate the impact of design differences on vane cooling. It was found that the location of the internal plug and incorporation of film cooling holes had a minor impact on coolant flow and cooling. Additionally, results showed exit area had the largest impact on surface temperature and coolant mass flow where the largest exit area allowed less restricted coolant flow resulting in the lowest average surface temperature. However, completely blocking the exit slot forced coolant to exit only through film cooling holes, stagnating the majority of the internal flow, resulting in surface temperatures higher than the uncooled, solid vane.

Influence of Inlet Vane and Wrap Angles on Cavitation Behavior of a Centrifugal Pump

This comprehensive study focuses on the relationship between the inlet vane and wrap angles of a centrifugal pump impeller and its cavitation behavior. The objective is to propose a new design for cavitation performance enhancement of the pump by reducing the required net positive suction head (NPSHR). To render a detailed study, the variations of the mentioned angles were examined both at hub and shroud. A three-dimensional two-phase parametric computational fluid dynamics (CFD) study was conducted and variations of inlet blade and wrap angles at hub and shroud were investigated separately. After validating the experimental results with the pump model, the pump parameterization process was carried out, and pump geometry was re-defined with its geometrical properties. The characteristic curves of the parameterized pump and pump model were in agreement with each other. Numerical cavitation tests were performed and the NPSHR values of each design were calculated for four different operating conditions. Results showed that cavitation performance increase was achieved with angle variations at the best efficiency point (BEP) but, this situation led the pump to operate exposed to cavitation at high flows (HF) for some designs. Therefore, the design with the best cavitation performance increased at BEP and HF was proposed as a new design. During numerical simulations, shear stress transport (SST) turbulence model and Rayleigh–Plesset equation were used.

Numerical analysis of bubble size effect in a gas-liquid two-phase rotodynamic pump by using a bubble coalescence and collapse model

The inlet bubble sizes and their coalescence and collapse behavior are the key factors affecting the performance and transportability of the multiphase pump. In this paper, a bubble coalescence and collapse model is applied for the simulation of a gas-liquid two-phase rotodynamic pump. The external characteristic, gas-liquid flow, phase interaction, and pressure fluctuation are analyzed using computational fluid dynamics (CFD) methods as the inlet bubble diameter d0 varies from 0.1 mm to 2.2 mm. The CFD results show that the pump’s efficiency and pressure rise decrease sharply at 0.1 mm ≤ d0 ≤ 0.4 mm, slow down at 0.4 mm < d0 ≤ 1.3 mm, and become stable at 1.3 mm < d0 ≤ 2.2 mm. The effects of inlet bubble size on flow characteristics in the impeller, such as gas-liquid separation, flow separation, vorticity change rate, and interphase force, are larger than that in the guide vane. The drag is the most significant interphase force at d0 = 0.1 mm, while the lift force plays a dominant role at d0 = 0.7 mm and 1.9 mm. The effect of the turbulent dispersion force is weakest at d0 = 0.1 mm, 0.7 mm, and 1.9 mm. Rotor-stator interaction is the key driver of the pressure fluctuation in the gas-liquid two-phase pump but is restrained by serious phase separation, flow separation, and interphase interaction at the impeller outlet. The most obvious fluctuation occurs near the guide vane inlet at d0 = 0.1 mm, 0.7 mm, and 1.9 mm. The maximum fluctuation at d0 = 0.7 mm and 1.9 mm are 5.98 times and 7.17 times that at d0 = 0.1 mm.

Experimental Analysis of Tangential-Vane Swirl Atomizer Spray Angle

A swirl atomizer is a widely applied spray-generating device. The swirling motion of a swirl atomizer is induced either by a tangential inlet or a swirl-generating vane. The swirling effect produces a spray with a wide angle which is important in various applications such as gas cooling, diesel engine combustion, and automatic hand sanitizer. An intense swirling mechanism was reported to significantly affect the spray angle. An attempt was made by combining tangential inlet and swirl-generating vane in a single embodiment to create a more intense swirling effect. The experiment was conducted with pipe flow in transition and turbulence regimes. The shadowgraph technique was applied to acquire the spray images. The images were processed using image processing software. It was found that the combined swirling mechanism produces a wider spray angle compared to the individual tangential inlet swirl atomizer. It was also found that the swirling intensity has a bigger effect on the spray angle than the Reynolds number.

Effect of Slot Jet Flow on Non-Axisymmetric Endwall Cooling Performance of High-Load Turbines

As vane inlet temperatures and turbine loadings are increasing, the aerodynamic and thermal management for the endwalls of gas turbines have received increased attention. Non-axisymmetric endwalls are becoming popular due to their proficient capabilities to modify the secondary flow fields and to change the film cooling performance on the endwalls. In this study, by considering the interaction between mainstream and purge flow based on non-axisymmetric endwall contouring, the numerical research model used in the present research was established. Based on the validated numerical method, the influence of the non-axisymmetric endwall contouring on the film-cooling effectiveness and aerodynamic characteristics was studied. Furthermore, the effect of different inclination angles on the film-cooling performance of the contoured endwalls was also investigated. The results indicate that for the high-load turbine vane used in this research, various types of non-axisymmetric endwall contouring can alter the aero-dynamic characteristics and cooling performance simultaneously. By inhibiting the secondary flows, non-axisymmetric endwall contouring can reduce the total cascade pressure loss coefficient by 0.305%. In addition, non-axisymmetric endwall contouring can significantly enhance the effective coverage area of purge flow up to 28.29%, and the endwall near the suction side can achieve better cooling performance. Finally, non-axisymmetric endwall contouring can improve the protective effect of large-angle purge flow.

Investigation of Unsteady Pressure Pulsations of Reactor Coolant Pump Passage under Flow Coast-down

In order to obtain the pressure pulsations of a reactor coolant pump during flow coast-down conditions, the time-domain characteristics of the flow passage under different times of flow coast-down were calculated by numerical calculation. Because the unsteady pressure pulsation signals in the RCP under flow coast-down are non-stationary and some phenomena may only occur in a short time, this paper analyzed them with the wavelet transform. The results show that the pressure fluctuation varies dramatically with the flow coast-down process and the variation rate of the pressure fluctuation coefficient can reach more than 60%. With the development of flow coast-down, there is a strong correlation between the pressure pulsation and number of impeller blades. The main frequency of the pressure pulsation gradually changes from high-frequency pulsation to low-frequency pulsation, and the regularity of the pressure pulsation is quickly destroyed, while the change in pressure pulsation regularity of the guide vane passage is more gentle than that of the impeller and pressurized water chamber. The change in wavelet intensity at the impeller outlet, guide vane inlet, and left side of the pressurized water chamber is more intense than at other areas.

Investigation of Transient Characteristics of a Vertical Axial-Flow Pump with Non-Uniform Suction Flow

The aim of this paper is to study the influence of non-uniform suction flow on the transient characteristics of a vertical axial-flow pump device. The unsteady calculation is employed to forecast the unstable flow structure with three inlet deflection angles α, and the calculation accuracy under uniform inlet flow is verified by the external characteristic test. The results depict that a promotion in the α will increase the head and shaft power and thus improve the stress and fatigue failure risk of the impeller. At the impeller inlet, the pressure pulsation intensity (PPI) with α = 40° is lower than that with α = 0° caused by a decline in the axial velocity. The dominant frequency of the unsteady pressure signal is the blade-passing frequency (BPF), and the dominant frequency amplitude rises with the increase in α due to the improvement of the pre-rotation impact intensity. At the guide vanes inlet, the dominant frequency of the unsteady pressure signal at the guide vane inlet is also the blade-passing frequency. An improvement in α magnifies the angle between the trailing edge jet of the impeller and the leading edge of the guide vanes under 0.8Qdes and 1.0Qdes, while it diminishes the angle under 1.2Qdes. Thus, the PPI and dominant frequency amplitude with α = 40° are higher than that with α = 0° under 0.8Qdes and 1.0Qdes, but these are lower than that with α = 0° under 1.2Qdes.

Influence of Guide Vane Slope on Axial-Flow Hydraulic Performance and Internal Flow Characteristics

To comprehensively study the influence of the guide vane inlet slope on the axial-flow pump, eight groups of axial-flow pumps with different guide vane inlet slopes are designed and studied in this paper. Four groups of schemes increase the relative slope at the rim of the guide vane blade, and the other four groups increase the relative slope at the hub. Numerical simulations have been verified experimentally and show good simulation accuracy. The numerical simulation results show that reducing the hub height of the guide vane can improve the head and efficiency of the axial-flow pump. Compared with the original scheme, the scheme H2/S2 is more stable in velocity and turbulent kinetic energy and has fewer vortices and low-speed areas at the guide vane. The scheme H3/S3 also exhibits excellent hydraulic performance and internal flow characteristics. It is recommended that when designing an axial-flow pump, the distance between the impeller and the guide vane at the hub can be appropriately larger than the distance between the impeller and the guide vane at the rim. This helps to reduce the velocity circulation at the outlet of the guide vane and improve the head and efficiency of the axial-flow pump.

Numerical Study on Entropy Generation of the Multi-Stage Centrifugal Pump.

The energy loss of the multi-stage centrifugal pump was investigated by numerical analysis using the entropy generation method with the RNG k-ε turbulence model. Entropy generation due to time-averaged motion and velocity fluctuation was mainly considered. It was found that the entropy generation of guide vanes and impellers account for 71.2% and 23.3% of the total entropy generation under the designed flow condition. The guide vanes are the main hydraulic loss domains and their entropy generation is about 9 W/K, followed by impellers. There are vortices at the tongue of the guide vane inlet as well as flow separations in the impellers, which lead to entropy generation. The fluid impacts the outer surface of the guide vanes, resulting in the increase in entropy generation. There are refluxes near the guide vane tongues which also increase the entropy generation of this part. The entropy generation distribution of the guide vanes and impellers was investigated, which found that the positive guide vane has more entropy generation compared with the reverse guide. The entropy generation of the blade suction surface is higher compared with the pressure surface. This study indicated that the entropy generation method has distinct advantages in the assessment of hydraulic loss.