Numerical calculation and finite element calculation on impeller of stainless steel multistage centrifugal pump

In order to save energy and materials, some mechanical structures are very thin. Aiming to study the influence of impeller blade thickness on the performance of stainless steel multistage centrifugal pump, the whole flow field of stainless steel multistage centrifugal pump with different blade thickness were calculated based on ANSYS Fluent. The relationship between the impeller blade thickness and the overall performance of the pump was analyzed. To further study the reliability of the impeller structure for stainless steel multistage centrifugal pump, based on the ANSYS Workbench, the final stage impeller of the pump with different blade thickness were calculated by using the finite element method. Results indicate that with the increase of blade thickness, the maximum stress and deformation of the impeller gradually decreased, while the stability of the impeller structure increased

Leakage flow simulation in a specific pump model

This paper deals with the influence of leakage flow existing in SHF pump model on the analysis of internal flow behaviour inside the vane diffuser of the pump model performance using both experiments and calculations. PIV measurements have been performed at different hub to shroud planes inside one diffuser channel passage for a given speed of rotation and various flow rates. For each operating condition, the PIV measurements have been trigged with different angular impeller positions. The performances and the static pressure rise of the diffuser were also measured using a three-hole probe. The numerical simulations were carried out with Star CCM+ 8.06 code (RANS frozen and unsteady calculations). Comparisons between numerical and experimental results are presented and discussed for three flow rates. The performances of the diffuser obtained by numerical simulation results are compared to the performances obtained by three-hole probe indications. The comparisons show few influence of fluid leakage on global performances but a real improvement concerning the efficiency of the impeller, the pump and the velocity distributions. These results show that leakage is an important parameter that has to be taken into account in order to make improved comparisons between numerical approaches and experiments in such a specific model set up

Antiseismic response research of horizontal residual heat removal pump in different seismic spectrum input directions

A million kilowatt horizontal residual heat removal pump is an essential part of the first loop residual heat removal system in nuclear power plants; it is the second most significant piece of nuclear power equipment. The residual heat removal pump of a nuclear power plant is examined by using a multiseismic spectrum, multiinput direction method to analyze its dynamic characteristics and responses. The aim of this analysis was to determine the seismic responses and possible actions to reduce damage to the integral structure. The favorable and unfavorable spectra are investigated as well. The research focuses on avoiding the damaging effects caused by earthquakes. The maximum value of seismic effect and the corresponding seismic input direction are determined, laying a speculative foundation for structural design and installation. Utilizing a response spectrum method, the antiseismic performance of a pump at SSE seismic load has been analyzed according to an algorithm using the square root of the sum of the squares. The result shows that the deformation of the impeller surface fitted with a wear ring decreases along the direction of flow in different input directions of the seismic spectrum. The largest deformation occurs at an angle of approximately 135 degrees; thus, antiseismic analysis should be conducted at this input angle to conservatively evaluate the antiseismic performance, and the installation angle designed for frequent earthquakes should avoid 135 degrees to decrease the deformation caused by the seismic force. Calculation results prove that the clearance between the rotor and the stator of the horizontal residual heat removal pump shows satisfactory seismic response performance that fulfills the requirements for antiseismic design according to the RCC-M standard; this may reduce seismic damage and avoid environmental disasters

Investigation on the influence of jetting equipment on the characteristics of centrifugal pump

To reduce radial noises from the motor of centrifugal pumps, this study designed a water cooling system called jettingequipment to replace traditional fan cooling systems in pump motors. By measuring radiated noises, head, efficiency, andcavitation performance, the research compared the differences among experimental results of the original pump unit,the one with a normal design jetting pipe and another one with a larger jetting pipe. Results show that the radiatedsound pressure level of the model pump was significantly reduced by 8.3 dB after integrating the jetting pipe. With a nor-mal jetting pipe, no significant changes were observed in the head, efficiency, and shaft power curves, and cavitation per-formance improved under small flow rate. However, the performance with the larger jetting pipe worsened, except thehump phenomenon of the model pump under a small flow rate was enhanced. Computational fluid dynamics methodwas used to calculate the internal flow of three model pumps in order to investigate the jetting flow effect. A compari-son among the flow fields at the inlet of the three types of pumps indicated that high-pressure water injection can effec-tively control inlet recirculation and improve velocity distribution in the inlet flow field with decreased recirculationvortex strength and recirculation onset critical flow rate

Experimental and Numerical Investigation on a Centrifugal Pump under Air-Water Two-Phase Flow Condition

Experimental and numerical investigations have been performed on a single stage, single-suction, horizontal-orientated centrifugal pump under air-water two-phase non condensable flow conditions. Experimental test loop allows performing controlled values of air void fraction for different water flow rates and several rotational speeds. Global pump heads and efficiencies have been measured for several inlet air void fraction values at different rotating speeds up to pump performance breakdown. Similar laws under two-phase flow condition have been investigated at three selected rotating speeds. Numerical calculations have been also performed using URANS approach including k-e turbulence and inhomogeneous two-phase models for nominal rotational speed, the results of which are used to understand some specific experimental results that have been obtained. The results show that the pump performance degradation is more pronounced for low flow rates compared to high flow rates and the similarity laws can also be applied for air-water two phase flow conditions corresponding to the bubbly flow regime, when IVAF is small. Particle fluid model with interface transfer terms looks quite suitable to evaluate pump performance degradation up to IAVF values of 7%. Air bubbles distribute on suction side of the blade and are detained more and more inside the impeller channel near “wake” area when IAVF increase. Bubbles take over 60% part of the channel when IAVF increase to 7% in all three flow rates, which is the reason of the pump performance deterioration

A study of rotating stall in a vaneless diffuser of radial flow pump

Rotating stall in a vaneless diffuser of radial flow pump is studied. The measurements consist of: (i) unsteady pressure measurements delivered by two microphones; and (ii) nine steady pressure taps mounted in one radial line to measure the pressure recovery in the vaneless diffuser. Spectrum analysis was used to identify and characterize rotating stall. An assumption was made to estimate the losses in the vaneless diffuser to evaluate the effect of the instability development on its performance. The result has shown that the arising of rotating stall has a positive effect on the diffuser performance. Two possible reasons are proposed: (1) a blockage in the diffuser due to the unstable cells which shortens the streamlines and decreased the friction losses along the vaneless diffuser; (2) the topology of rotating stall cells results in the convection of fluid coming from outside part of the pump model to the vaneless diffuser.CSC Scolarshi

Investigation on centrifugal pump performance degradation under air-water inlet two-phase flow conditions

In order to study the flow characteristics of centrifugal pumps when transporting the gas-liquid mixture, water and air were chosen as the working medium. Both numerical simulation and experimental tests were conducted on a centrifugal pump under different conditions of inlet air volume fraction (IAVF). The calculation used URANS k-epsilon turbulence model combined with the Euler-Euler inhomogeneous two-phase model. The air distribution and velocity streamline inside the impeller were obtained to discuss the flow characteristics of the pump. The results shows that air concentration is high at the inlet pressure side of the blade, where the vortex will exist, indicating that the gas concentration have a great relationship with the vortex aggregation in the impeller passages. In the experimental works, pump performance were measured at different IAVF and compared with numerical results. Contributions to the centrifugal pump performance degradations were analyzed under different air-water inlet flow condition such as IAVF, bubble size, inlet pressure. Results show that pump performance degradation is more pronounced for low flow rates compared to high flow rates. Finally, pressure pulsation and vibration experiments of the pump model under different IAVF were also conducted. Inlet and outlet transient pressure signals under four IAVF were investigated and pressure pulsation frequency of the monitors is near the blade passing frequency at different IAVF, and when IAVF increased, the lower frequency signal are more and more obvious. Vibration signals at five measuring points were also obtained under different IAVF for various flow rates

A Review of Design Considerations of Centrifugal Pump Capability for Handling Inlet Gas-Liquid Two-Phase Flows

Most of the pumps working under two phase flows conditions are used in petroleum industry applications, like electrical submersible pumps (ESP) for hydrocarbon fluids, in chemistry, nuclear industries and in agriculture for irrigation purposes as well. Two-phase flows always deteriorate overall pump performances compared with single flow conditions. Several papers have been published aiming to understand flow physics and to model all the main mechanisms that govern gas pocket formation and surging phenomena. These mechanisms depend on the pump type, the impeller geometry, the rotational speed, design and off-design liquid flow rate conditions, the volumetric gas fraction, the fluid properties and the inlet pressure. In the present paper, a review on two phase performances from various centrifugal pumps designs is presented, mainly based on experimental results. The main focus is devoted to detect the significant geometrical parameters that: (1) Modify the pump head degradation level under bubbly flow regime assumption; (2) Allow single stage centrifugal pumps keep working under two-phase flow conditions with high inlet void fraction values before pump shut down, whatever the pump performance degradations and liquid production rates should be. Because most of the published experimental studies are performed on dedicated laboratory centrifugal pump models, most of the present review is based on air-water mixtures as the working fluid with inlet pressures close to atmospheric conditions. The following review supposes that gas phase is considered as a non-condensable perfect gas, while the liquid phase is incompressible. Both phases are isolated from external conditions: neither mass nor heat transfer take place between the phases

Experimental and numerical studies on flow characteristics of centrifugal pump under air-water inflow

A two-phase liquid pumping test ring is built to study the flow induced characteristics of centrifugal pump under the air-water flow working condition. Pump performances are measured under different flow rates and different inlet air void fraction (a). Pressure pulsation signal spectrums and their probability density maps are also recorded. The calculations, using URANS k-epsilon turbulence model combined with the Euler-Euler inhomogeneous two-phase model, are also performed to obtain inner flow structure inside the impeller and volute channels under different air-water conditions in order to understand the pump characteristic evolutions. The results show that the performance of centrifugal pump is more sensitive to air inlet injection at low flow rates. The maximum air void fraction of model pump could reach 10% when the pump operates at the highest efficiency point, and the performance drops sharply when the air void fraction is more than 8%. The dominant frequency of pump outlet pressure pulsation is still at the blade passing frequency even under two-phase condition. Frequency amplitude increases with the increase of a. The greater the a, the more low frequency appears in broadband characteristics. With the increase of a, the probability density amplitude of pressure pulsation decreases gradually, and its span becomes gradually wider as well. Comparisons between numerical local results, experimental unsteady pressure can explain part of the phenomena that are found in the present paper

Experimental Investigations on the Inner Flow Behavior of Centrifugal Pumps under Inlet Air-Water Two-Phase Conditions

Centrifugal pumps are widely used and are known to be sensitive to inlet air-water two-phase flow conditions. The pump performance degradation mainly depends on the changes in the two-phase flow behavior inside the pump. In the present paper, experimental overall pump performance tests were performed for two different rotational speeds and several inlet air void fractions (αi) up to pump shut-off condition. Visualizations were also performed on the flow patterns of a whole impeller passage and the volute tongue area to physically understand pump performance degradation. The results showed that liquid flow modification does not follow head modification as described by affinity laws, which are only valid for homogeneous bubbly flow regimes. Three-dimensional effects were more pronounced when inlet void fraction increased up to 3%. Bubbly flow with low mean velocities were observed close to the volute tongue for all αi, and returned back to the impeller blade passages. The starting point of pump break down was related to a strong inward reverse flow that occurred in the vicinity of the shroud gap between the impeller and volute tongue area