Static pressure recovery analysis in the vane island diffuser of a centrifugal pump

The overall performance of a vane-island type diffuser of a centrifugal pump model was obtained by means of directional probe traverses. These measurements were performed in an air model of a real hydraulic pump for five volume flow rates. Directional probe traverses are performed with a classical three-hole probe to cover most of the complete inlet section of the diffuser from hub to shroud and from pressure to suction side. Existing Particle image velocimetry (PIV) measurement results are also used to compare probe measurement results between the inlet and outlet throats of vane island diffuser at mid-span. Some assistance from already existing unsteady calculation, including leakage effects, is used to evaluate the numerical approach capability and to correctly define the mean initial conditions at impeller’s outlet section. Pressure recovery and the measured total pressure loss levels inside this particular vane diffuser geometry are then calculated. Detailed analysis of the flow structure at the inlet section of the vane island diffuser is presented to focus on pressure evolution inside the entire diffuser section for different flow rates. The combined effects of incidence angle and blockage distributions along hub to shroud direction are found to play an important role on loss distribution in such a diffuser

Data reduction problems using a 3 holes directional pressure probe to investigate mean flow characteristics in the vaneless gap between impeller and diffuser radial pump

Among several different measurement techniques that have been already performed and presented in a radial impeller pump model including PIV, a directional pressure probe has been used to obtain mean velocity field and stagnation pressure between impeller outlet and the inlet vaned diffuser sections. These measurements are supposed to get more information not only about global pump head coefficient including vaned diffuser ones but also about impeller performances itself. Pressure probe information is affected by rotor-stator interactions and impeller rotation, and this paper presents a way to explain and correct pressure probe indications in order to achieve a better evaluation of overall impeller mean performances. The use of unsteady RANS calculation results is found to be a useful way to perform better data reduction analysis for this purpos

Efficient Reduction on the Jacobian Variety of

Abstract In this paper, a system of coordinates for the elements on the Jacobian Variety of Picard curves is presented. These coordinates possess a nice geometric interpretation and provide us with an unifying environment to obtain an explicit structure of abelian variety for the Jacobian, as well as an efficient algorithm for the reduction and addition of divisors. Exploiting the geometry of the Picard curves, a completely effective reduction algorithm is developed, which works for curves defined over any ground field k, with char(k) = 0 or char(k) 6 = 3

Analysis of the unsteady flow velocity fields inside the impeller of a radial flow pump: PIV measurements and numerical calculation comparisons

PIV measurements were performed at mid hub to shroud section inside the impeller of a vaned diffuser pump model working with air. The measurements were restricted to the outlet section of the impeller where the diffuser blades interacted with the impeller flow. Each PIV measuring plane was related to one particular impeller blade to blade channel and analysed according to different relative positions of the vaned diffuser. Two frame change models were considered: the so-called frozen rotor approach for different impeller passage positions relative to the vaned diffuser and a fully unsteady calculation of the whole pump. Comparisons between numerical and experimental results are presented and discussed for a specific mass flow rate corresponding to an off-design point for the impeller and a design point for the vaned diffuser

Numerical and Experimental Investigations in a Vaned Diffuser of SHF Impeller: Fluid Leakage Effect

The paper presents the analysis of the performance and the internal flow behaviour in the vaned diffuser of a radial flow pump using PIV technique, pressure probe traverses and numerical simulations. PIV measurements have been performed at different heights inside one diffuser channel passage for a given speed of rotation and various flow rates. For each operating condition, PIV measurements have been made for different angular positions of the impeller. For each angular position, instantaneous velocities charts have been obtained on two simultaneous views, which allows, firstly, to cover the space between the leading edge of the impeller and the diffuser throat and secondly, to get a rather good evaluation of phase averaged velocity charts and \u201cfluctuating rates". Probe traverses have also been performed using a 3 holes pressure probe from hub to shroud diffuser width at different radial locations in between the two diffuser geometrical throats. The numerical simulations were realized with the two commercial codes: i-Star CCM+ 7.02.011 (at LML), ii-CFX 10.0 (at University of Padova). Fully unsteady calculations of the whole pump were performed. Comparisons between numerical and experimental results are presented and discussed for two flow rates. In this respect, the effects of fluid leakage due to the gap between the rotating and fixed part of the pump model are analysed and discussed

Comparisons between numerical calculations and measurements in vaned diffuser of SHF impeller

The paper presents analysis of the performance and the internal flow behaviour in the vaned diffuser of a radial flow pump using PIV (particle image velocimetry) and pressure probe traverses. PIV measurements have already been performed at middle height inside one diffuser channel passage for a given speed of rotation and various mass flow rates. These results have been already presented in several previous communications. New experiments have been performed using a three\ue011hole pressure probe traverses from hub to shroud diffuser width at different radial locations between the two diffuser geometrical throats. Numerical simulations are also realized with the commercial codes Star CCM+7\ue01002\ue010011 and CFX. Frozen rotor and fully unsteady calculations of the whole pump have been performed. Comparisons between numerical results, previous experimental PIV results and new probe traverses one\u2032s are presented and discussed for one mass flow rate. In this respect, a first attempt to take into account fluid leakages between the rotating and fixed part of the pump has been checked since it may affects the real flow structure inside the diffuser

Investigations in a vaned radial diffuser of SHF impeller

The paper presents the numerical and experimental analysis of performance and internal flow behaviour in the vaned diffuser of a radial flow pump (Fig. 1) using PIV technique (Fig. 2), pressure probe traverses and numerical simulations. PIV measurements have been performed at different heights inside one diffuser channel passage for a given speed of rotation and various mass flow rates. For each operating condition, PIV measurements have been made for different angular positions of the impeller. For each angular position, instantaneous velocities charts have been obtained on two simultaneous views, which allows, firstly, to cover the space between the leading edge of the impeller and the diffuser throat and secondly, to get a rather good evaluation of phase averaged velocity charts and \u201cfluctuating rates \u201c. Hub to shroud directional probe traverses (Fig. 3) have also been performed using a 3 holes pressure probe along the diffuser width at different radial locations between the two diffuser geometrical throats. The numerical simulations were realized with the two commercial codes: i-Star CCM+ 7.02.011 (at LML), ii-CFX 10.0 (at University of Padova). Fully unsteady calculations of the whole pump were performed. Comparisons between numerical and experimental results are presented and discussed for different mass flow rates. In this respect, the effects of fluid leakage due to the gap between the rotating and fixed part of the pump model are analysed and discussed. Experimental results strongly depend on impeller position during its rotation. Pressure probe results are also depending on unsteady effects and this has to be taken into account for further data reduction analysis. The contours of radial and tangential velocity at mid high (Fig. 4) as well as the time-averaged values of radial and tangential velocity distributions allow leakage to be an important parameter that has to be taken into account in order to make comparisons between numerical and experiments. Henceforth, simulations with fluid leakages will be realized and unsteady probes will be used in order to confirm these previous results