Fangping Tang

Flow Measurements in a Transparent Centrifugal Pump by Using 3-D PIV Technique

With the development of laser measurement technique, LDV (Laser Doppler Velocimeter) and PIV (Particle Image Velocimetry) have been widely used to measure the flow fields. Comparison with LDV, PIV is a multiple point measurement technique and the flow fields can be measured convenient. Nowadays, 2-D (two Dimensional) PIV have been used to investigate the flow fields in the centrifugal pump, while 3-D (three Dimensional) PIV is seldom to be used. The reason is that the calibration for 3-D PIV in a small space of centrifugal pumps in very difficult. In this paper, a special water tank was used for 3-D PIV calibration in rotation impeller. The 3-D transient relative velocity in one impeller passage at three axial sections were obtained, when the pump run under the design flow rate. The radial component velocity Wr showed a concave distribution except R = 45 mm. With the increase of radius, the circumference location of minimum Wr moved from the pressure side to the suction side and the tangential component velocity Wθ on the suction side decreases, while on the pressure side increases gradually. The PIV measurement error was investigated based on the mass conservation equation. The maximum error of the PIV measurement was 3.14%, it showed that the test results have higher accuracy and the measured data was reliable.Copyright

PIV Measurements and CFD Analysis in an Axial-Flow Pump

In this study, an axial flow pump impeller without guide vanes is experimentally investigated. The impeller used in the experiments consists of four blades. The particle image velocimetry technique and a five-hole probe have been used. Measurements of flow velocities in the outer part of the impeller have been made. PIV measurements have been realized in 12 meridian planes between blade-to-blade for design and off-design operating conditions. The meridian velocity is obtained with phase averaged method and the total circumferential mean velocity is obtained with an arithmetical average over the 12 circumferential data. The calculation is based on the CFX-TASC flow CFD code solving the three-dimensional Reynolds-averaged Navier-Stokes equation with RNG k–e model of turbulence. The paper focuses on the comparisons of the results. Difference for the flow field between numerical and experimental results is small at large and design flow rate, while big difference occurs at small flow rate. It indicates that the numerical model is not suitable for separation flow.Copyright

Research on the performance of low-lift diving tubular pumping system by CFD and Test

Post-diving tubular pump is always used in large-discharge & low-head irrigation or storm drainage pumping station, its impeller and motor share the same shaft. Considering diving tubular pump systems excellent hydraulic performance, compact structure, good noise resistance and low operating cost, it is used in Chinese pump stations. To study the hydraulic performance and pressure fluctuation of inlet and outlet passage in diving tubular pump system, both of steady and unsteady full flow fields are numerically simulated at three flow rate conditions by using CFD commercial software. The asymmetry of the longitudinal structure of inlet passage affects the flow pattern on outlet. Especially at small flow rate condition, structural asymmetry will result in the uneven velocity distribution on the outlet of passage inlet. The axial velocity distribution uniformity increases as the flow rate increases on the inlet of passage inlet, and there is a positive correlation between hydraulic loss in the passage inlet and flow rates quadratic. The axial velocity distribution uniformity on the outlet of passage inlet is 90% at design flow rate condition. The predicted result shows the same trend with test result, and the range of high efficiency area between predicted result and test result is almost identical. The dominant frequency of pressure pulsation is low frequency in inlet passage at design condition. The dominant frequency is high frequency in inlet passage at small and large flow rate condition. At large flow rate condition, the flow pattern is significantly affected by the rotation of impeller in inlet passage. At off-design condition, the pressure pulsation is strong at outlet passage. At design condition, the dominant frequency is 35.57Hz, which is double rotation frequency.

Computational Investigation of the Flow Field Inside an Submersible Tubular Pump

Submersible tubular pump is particularly suitable for ultra-low head (net head less than 2 m) pumping station which can reduce the excavation depth, lower engine room height, simplify hydraulic structure, and save civil engineering costs. Submersible tubular pump with smaller motor unit can reduce the flow resistance. The flow field inside the submersible tubular pump is simulated in a commercial computation fluid dynamics (CFD) code FLUENT. The RNG k-e turbulent model and SIMPLE algorithm are applied to analyze the full passage of a submersible tubular pump, the performance of pump such as head, shaft power and efficiency are predicted based on the calculation of different operating conditions. The simulations are carried out over a wide range of operating points, from 0.8 of the reference mass flow rate at the best efficiency point (BEP) to the 1.28 of the BEP flow rate at the same rotating speed. For verifying the accuracy and reliability of the calculation results, a model test is conducted. The comparison of simulation results and the experiment data show that the calculation performances are agree with the experiment results in the high efficiency area and large discharge condition, but in the condition of low discharge, it exists deviations between the two results. Compare with the numerical simulation and experiment, which can provide more evidences for the hydraulic performance prediction and optimization design of submersible tubular pump pumping system.Copyright

Numerical Simulation and Experimental Study of a Two-Floor Structure Pumping System

The two-floor flow passages pumping system with the simple structure is well practical in the Basin of Yangzi River downstream. However, this kind of pumping system has some disadvantages, such as low efficiency, easy to appear submerse vortex in discharge flow passages which causes the unit vibration and does harm to the operating of pump unit. In order to solve these problems, the design scheme with a new curve of diffusing outlet structure and inlet cone put forward, which are used in the renovation of the two-floor flow passages pumping station. With the numerical simulation of the two-floor flow passages pumping system, the flow fields are analyzed, and the external performance curves are obtained. To verify the calculation, a model tests were done using the standard model of pump. The test results are compared with the performance curves of numerical simulation. Good agreement of two results is found in the high efficiency area, which can show the calculation is believable. The new design improves the efficiency of pumping system significantly and eliminates the submerse vortex, also can guarantees the economy and security of operating.Copyright

Influence of Support Shapes on the Efficiency of Bulb Tubular Pumps

With the characteristics of high efficiency, small hydraulic loss, compact unit structure, simple construction arrangement and low cost both for construction and operation, bulb tubular pumps are especially suitable for large discharge and low lift head pumping stations of the east route of South to North Water Diversion Project in China. It is important to analyze the flow characteristics and performance of bulb tubular pumps.

Three Dimensional Numerical Simulation of Flow Field Inside a Reversible Pumping Station With Symmetric Aerofoil Blade

The pumping station with symmetric aerofoil can achieve reversible pumping function. It can keep high reversible efficiency and its flow coefficient is approaching to normal one. At same time, it has the simple structure and is easy to operate and maintain. The flow inside reversible pumping station is very complex and dominated by three dimensional viscous effects. With the rapid progress of computational fluid dynamics, CFD has become an important tool to help to make full understanding of flow. In order to recognize the characteristic of pumping station, the control volume method is used to simulation the flow filed. The RNG k-e turbulent model and SIMPLEC algorithm are applied to do analysis. Flow field inside symmetric aerofoil blade and passage of pumping station are analyzed in detail. Some computational data, such as computational contour of sections, streamline of pumping system, flow vectors of blade and pressure contour of blade for two different rotate directional, are given in the paper. On the based of the simulation results, efficiency prediction of the pumping station is applied. By calculating the useful power and the hydraulic efficiency at the 11 different discharge points, capabilities of pumping station are predicted. A set of model pumping station with a 300mm blade are made for test. Using the laboratory test loop of which the total uncertainty of measured efficiency is ±0.39%, the hydraulic performance is evaluated and demonstrated. The numerical performances agree well with experiment data.Copyright

Study on the Hydraulic Performance of Elbow-Inlet Passage by CFD

The Elbow-inlet passage with low loss and little width is a typical passage of pumping station. A new optimization criterion for hydraulic design is put forward. The incompressible N-S equations are solved by the finite volume method. Base on the RNG k-e model with Wall-Function Law, the SIMPLEC algorithm is applied for the solution of the discretization governing equation. Using CFD, the flow pattern in passage is revealed. The flow patterns in the elbow-inlet passage are classified as three patterns phases: horizontal contraction, elbow bend and vertical phase. According to axial velocity of ten sections, the new criteria of named height of pump (NHP) and other control parameters for Elbow-inlet passage is suggested. A good agreement is achieved between the numerical simulation and experimental results. The computational model is much more effective for hydraulic performance study. The optimum hydraulic design method was established: First, the shape of passage is designed on the optimum control parameters. Second, the sections of passage are designed according to the smooth average velocity. Finally, flow patterns are studied in order to find its hydrodynamic characteristics. This method could simply the design of Elbow-inlet Passage.Copyright

Analysis of the Influence of Passage Components on the Efficiency of Bulb Tubular Pumps

For large discharge and low lift head, it is especially suitable to use tubular pumps for their economic characteristics. Tubular pumps have high efficiency, small hydraulic loss, compact unit structure, simple construction arrangement and low cost both for construction and running. Recently, in the east route of South to North Water Diversion Project in China, there are many low head and large discharge pump stations using tubular pumps. It is important to analyze the flow characteristics and performance of tubular pump. In this paper CFD method is used to simulate the whole flow passage in a bulb tubular pump which includes inlet passage, outlet passage, guide vane, bulb unit and supportings. Based on the RNG k–e turbulent model with Wall-Function Law, the SIMPLE algorithm is applied for the solution of the discrete governing equations. The results of the calculation indicate that all of the flow passage components influence the efficiency of the tubular pump, especially the parts of guide vane unit and bulb section. The shape of the bulb and relative position of guide vanes and bulb supportings have important effects on total hydraulic losses of the pump. Reasonable supportings not only improve the turbulent flow, but also reduce circumference velocity. The efficiency of the pump after improving can be increased about 6%.Copyright

The Study on the Flow Fields and Hydraulic Performance in the Pump Sump

The pump sump, which connects forebay and intake of pump station, supplies good flow condition for the intake of the pump. The flow inside pump sump is very complex and dominated by three dimensional viscous effects. In order to recognize the characteristic of pump sump, the control volume method is used to simulation the flow filed. The RNG k-e turbulent model and SIMPLEC algorithm are applied to do analysis. Flow fields inside pump sump are analyzed in details. A lot of computational data, such as computational contour of sections, streamline, flow vectors and pressure contour, are given in the paper. On the based of the simulation results, best plane shapes and suitable dimensions of sump are presented. Relationship between flow patterns and dimensions of sump, such as back wall clearance, bellmouth height and shape of back wall etc, was discussed. The recommenced parameters are brought out. The results show that numerical flow fields agree well with experiment data measured by 3D-PIV model test.Copyright