Engineering Calculation of Axial Force Acting on Rotor of Electric Pumping Unit of Space Thermal Regulation Systems

The article covers the method of calculating the axial force acting on the rotor of centrifugal electric pumping units used in spacecraft thermal regulation systems. The units shall have a long operational life numbering tens of thousands of hours of continuous operation. Their reliability of the design, precise calculation of radial and axial forces acting on the unit rotor are subject to increased requirements. Precise calculation of forces ensures a correct selection of the type and geometry of bearings in which the rotor is installed. The existing methods of calculating axial force in centrifugal blowers are based on the model of the non-flow type current of working medium in lateral gaps between the unit impeller and body. They use the assumption that the working medium behaves like a solid rotating body. In real designs of centrifugal electric pumping units used in spacecraft thermal regulation systems, current in the gaps is from the periphery to the center of the impeller, so the current is flow type. This essentially changes the nature of the static pressure distribution over the impeller radius, on which the value of axial force depends. Incorrect assumption of the non-flow type of working medium in lateral gaps results in large errors upon calculating the axial force. This paper provides the results of the experimental determination of the static pressure distribution diagram in the lateral gaps between the impeller and the unit body. The approximation of experimental data had been made, on the basis of which a simple algorithm of calculation of axial force was developed increasing the accuracy of calculations.