Computer Simulation Of The Flowpath In Magnetic Sealless Pumps
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For applications that involved fluids with a high rate of change of vapor pressure or low specific heat, it was found that there could be inadequate flow through the thrust bearing. This effect was compounded by the heat generation due to the eddy currents that occur in magnetic drive pumps with metallic shells. This paper describes a computer simulation to predict the flows, pressures, and temperatures in magnetic drive sealless pumps. The program has been developed using both theoretical and test work. The objective of the program was to provide reliable selection of magnetic drive pumps; this was accomplished by taking into account the effects of viscosity, vapor pressure, and other liquid properties on the local pressures in the pump. The goal of this program was thus to simulate a customer’s desired application of a particular fluid at an operating pressure, temperature, NPSH, and speed. The resulting conclusion would be whether the customer’s fluid and operating conditions were applicable for sealless pumps. Warnings are output through the graphical user interface of the program at the various points, should flashing occur using the particular fluid. The testing involved a wide range of pump sizes. Within each size, an extensive matrix involved running at different speeds, different cut impeller diameters, and from shutoff through runout condition. The units were tested with different shell configurations and different materials. These included polyetheretherketone (known as PEEK), Alloy C-276, and a dual containment consisting of both materials. The design of the back shroud influences the magnitude of the hub factor. This is because the traditional affinity laws cannot be applied to the calculation of the axial load for semiopen impeller with a scalloped back shroud, pump out vanes, or pump out slots. One of the important findings was that the impeller hub factor, which is required for the computation of the axial load, changed as a function of speed and cut impeller diameter. It was also found that pump out vanes or pump out slots significantly enhanced the lubrication through the bearings and across magnets. Part of the verification involved performing tests with different bushing clearances and grooving configurations. These were analyzed empirically to confirm the coefficients that were obtained from experimental methods. In order to examine the possible operation of the pump when handling the user’s particular fluid, the flow is simulated in the program using a graphical user interface. A graphical output is given of all the pertinent locations in the systems, such as the thrust collar face or the gap between the driven magnets and the shell. The program currently calculates the pressure, flow, and temperature within the flowpath, along with the axial thrust, at five pump operating flow conditions expressed as a percentage of the best efficiency point.
Guinzburg, Adiel; Buse, Frederic W. (1998). Computer Simulation Of The Flowpath In Magnetic Sealless Pumps. Texas A&M University. Turbomachinery Laboratories. Available electronically from