The study of liquid flux coefficient dependence in axial clearance of electrically driven pump unit on operating and structural parameters

Aeronautical and Space-Rocket Engineering

Thermal engines, electric propulsion and power plants for flying vehicles


Аuthors

Malov D. V.*, Shablii L. S.**

Samara National Research University named after Academician S.P. Korolev, 34, Moskovskoye shosse, Samara, 443086, Russia

*e-mail: Animaggg@yandex.ru
**e-mail: shelbi-gt500@mail.ru

Abstract

In the last few years the problems emerge in electrically driven pump unit (EDPU), which disrupt operation of the spacecraft thermo-regulating system (TRS) and disabling EDPU. The EDPU service life and operability depend greatly on the operability of rotor supports, sealing system efficiency, and required lubricating and cooling mode. As a rule, seals and supports are connected with the pump flowing part, and they are connected between each other by the hydraulic path, necessary for the unit normal operation. Large axial loading occurrence is considered the most probable cause of the EDPU failure. Thus, studying hydrodynamics of such auxiliary hydraulic paths is the paramount objective for the enterprises working in this field. For these problems solving, a 3D mathematical model of the working fluid flow in the impeller cavity of the EDPU being studied was developed.

To validate the computational model, hydraulic test bench was assembled, and special hydrodynamic tests of the EDPU under study were performed. The pressure changing behavior in various areas obtained by the tests coincides with the CFX computation, and the error does not exceed 3%.

The pressure force change in the axial clearance along the radius submits to the parabolic law, in which the liquid flux coefficient in the axial clearance φ plays an important part. It depends upon the structural and operating parameters of the pump and changes from 0.5 for the lossless flow to 0.76 with expendable flow from periphery to the center in the form of the working fluid leakages. The force acting from the axial clearance side depends on the φ coefficient, though the suggested recommendations are not enough for correct axial force determining.

To determine the fluid flow rate in the axial clearance, the axial force, obtained with software complex, was being used. The values of the φ coefficient were obtained this way for all modes, tested with the hydraulic test bench. Additional calculations of the EDPU various working modes were performed for the livid illustration of the way the coefficient φ depends on the structural and operating parameters, but without test bench testing since the computational model convergence has been already proved.

The obtained dependencies demonstrate that the φ coefficient depends weakly on the operating parameters, and to the greater extent it depends on structural ones, and more specifically, on the discharge openings diameter. In addition, the range of this parameter changes is wider than it is pointed in the source based on the experimental data, which cannot be always determined precisely due to the structure complexity, and, as a consequence, complex access of measuring devices to the EDPU areas of interest.

Keywords:

electrically driven pump unit, impeller, axial force, CFD modeling, bearing

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