Method of energy efficiency increase of low power radial impeller micromachines

Abstract

The article is dedicated to the analysis of possibilities of hydrodynamically feasible velocity and pressure field formation in the impeller of low power radial impeller micromachines, up to 50 W, by means of flow control by methods of the border layer theory described in Schlichting’s papers. The purpose of the control is to reduce the extent of energetically unfavorable factors reducing the machine’s specific power. These factors include flow separation zones, secondary currents, and corner vortexes, “slippage” at the output of the impeller interblade channels. It is stated that the basic methods of flow structure control include blowing, suction, and turbulence formation, in particular, turbulence formation of local different energy flow areas existing in channels of radial impeller machines. The article covers the layout of such areas and ways of possible exchange between them. Besides, the working energy efficiency decrease of interblade channel slanted cut of machine impellers is analyzed. The method of turbulence formation is recognized as the most acceptable method of control of flow structure for micromachines. The experimental part of the study was to check the efficiency of flow turbulence formation in the impeller of a radial impeller machine in order to increase its specific power. Comparative hydraulic tests of the same centrifugal micropump with flow turbulence formation in the impeller and without turbulence formation were performed. A metal mesh with a free area ratio of 0.51 fixed on periphery of the impeller was used as a turbulator. The tests showed that installation of mesh increases specific power of the pump featured by head coefficient value, by 28.4%. This allows reducing the diameter of machine impeller by 5.3% while retaining the original power.