| Popis: |
The article presents the results of numerical simulation and experimental study of fluid flow in the jet pump, and, in particular, near the nozzle. It considers the influence of possible manufacturing errors of the pump on its characteristics, such as head and efficiency.Numerical simulation is based on the calculation method of control volume discrete analogs of the Reynolds averaged Navies-Stokes and continuity equations of a continuous medium (method RANS). The closure of the system of equations is performed by k-ω SST turbulence model. The number of cells of the computational grid is about 2 million. The boundary conditions are a fluid velocity at both pump inlets and a pressure at the outlet. In this case the calculated value is the pressure at both inlets.An experimental study is conducted on a hydraulic test bench. The data obtained by experiment are used to discharge characteristic of the pump and its efficiency. Given comparison of design and experimental characteristics shows a significant difference resulting from the manufacturing inaccuracies of the inner shape of the pump nozzle.The paper reports results of modeling a flow in the pump with a shape of the nozzle corresponding to that of really manufactured and several models more with intermediate forms of the nozzle.The simulation results obtain good agreement between the calculation of the corresponding real prototype model with experimental data, and it is shown that a small taper of the inner shape of the nozzle significantly affect the pump head, namely it increases with insignificant change of pressure at the pump inlet, which gives an indication of increasing pump efficiency.This work complements the existing studies of the effect of various factors on the operation of jet devices, such as the scale factor, the change in the axial position of the nozzle and the surface roughness.From the results of the study several conclusions can be drawn. In contrast to the accepted recommendations of designing the jet pump nozzle should be made slightly conical (no straight section) to improve the efficiency of the pump. In preparing design documentation and conducting control, one should focus on the tolerances of the nozzle shape. |
