A.A. Loganov – Ph.D.(Eng.), JSC Academician M.F. Reshetnev «ISS» (Zheleznogorsk)
A.V. Lekanov – Ph.D.(Eng.), Associate Professor, JSC Academician M.F. Reshetnev «ISS» (Zheleznogorsk)
A.A. Melkomukov – Associate Professor, JSC Academician M.F. Reshetnev «ISS» (Zheleznogorsk)
V.A. Levko – Dr.Sc.(Eng.), Professor, Reshetnev Siberian State University of Science and Technology (Krasnoyarsk)
The article considers the problem of resource and reliability of electric pump units of the system thermal control of spacecraft. The primary means of confirming the ability of the electric pump unit to meet the requirements for resource is currently vibration diagnostics. There are difficulties with the interpretation of the results of the registration of vibration during operation of the electric pump unit of the centrifugal type in multiple characteristic frequencies. Not been clearly defined cause local maxima in the spectrum of vibrations at frequencies of passing blades of the impeller. The spectra on the magnitude and nature of these local maxima on the frequency of the long blades and at the frequency of all blades, including the same number of short blades, in the general case differ. There is a need to clarify the general structure of pressure pulsations, install the form and nature of pressure pulsations on the problematic frequencies to develop a means of assessing the magnitude of pulsation. The characteristic of used JSC ISS of impellers of centrifugal pumps from the test in the vast majority of modern published scientific papers is the use of two types of alternating blades, long and short. Therefore, the results obtained in these works may not be fully applicable to the production of the JSC ISS.
As a means of solving the problems chosen two approaches. First, on the basis of modern scientific works on the subject, you need to install the basic dependencies between the parameters enrobing of the pump and the size of the periodic pressure pulsations. On the other hand, based on physical picture of the process of functioning of the centrifugal pump it is necessary to describe the peculiarities of action of impellers used in the JSC ISS.
To obtain the means to assess the magnitude of the pressure pulsations generated on the blades of the impeller have been introduced the value – given pressure drop. This value is proportional to the difference of the tangent velocity squares on the outer diameter of the blades and at the initial diameter. It was the comparison of given differential pressures for short and long blades and calculating the actual pressure differential across the impeller. It was found that the ratio of the pressure drop for each of the blades and the actual differential pressure to the impeller determines the slip angle of the jets of working fluid from the blade. The slip angle of the jet with the long blades in relation to the tangent at the vanishing point is always greater than the angle of descent with short blades. If the differential pressure for short blades below the actual differential pressure to the impeller, the vanishing of the liquid jets with short blades does not occur. The operation of the pump, wherein the pressure drop for short blades is compared and becomes lower than the actual differential pressure at the impeller close to the operating mode electric pump units of the JSC ISS. It should be noted that with increased total level vibration pressure pulsations in the operation of the pump are not the cause of high peaks at the blades passage frequency at a constant rotational speed of the impeller. This is because the dynamic impact from the pressure pulsations are uniquely defined by the frequency of rotation of the impeller and the resistance of the hydraulic circuit in which the pump works. Consequently, the peaks of the vibration acceleration at the frequency of passage of the blades at a constant frequency of rotation of the impeller at high general level of vibratory loads are not a result of hydraulic loads.
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