АНАЛІЗ ВПЛИВУ КОНСТРУКТИВНИХ ОСОБЛИВОСТЕЙ ПРОТОЧНОЇ ЧАСТИНИ ШНЕК-ВІДЦЕНТРОВОГО НАСОСА НА ЙОГО КАВІТАЦІЙНУ ХАРАКТЕРИСТИКУ

Abstract

The phenomenon of cavitation is inherent in all vane machines, the working medium of which is liquid. With a certain combination of input pressure, flow rate, rotor speed, and the gas saturation of the working fluid in the vane machine, cavitation may occur. Cavitation negatively affects the power characteristics of the vane machines. It leads to a drop in the power parameters for the pumps and damage to their flowing parts. And also at times increases the pulsation of pressure at the pump outlet and vibration. This is especially dangerous for LPRE chambers, as the pulsation of pressure leads to the appearance of low-frequency oscillations of the chamber itself. Therefore, it is so important, even at the design stage, to determine the cavitation perfection of the LPRE vane pump and take measures to increase it.When developing the RD861K engine, high demands were placed on the power perfection of the oxidizer pump. The efficiency of the oxidizer pump RD861K should be 5% higher than that of the oxidizer pump RD861 (pump prototype).To increase the efficiency of the oxidizer pump RD861K, a number of design changes were required in its design, most of which were aimed at improving the flowing part of the pump. These works were successful, the required efficiency was achieved. However, some of the taken measures taken had a negative impact on the cavitation perfection of the pump. Therefore, this study is devoted to a comparative analysis of the cavitation perfection of two designs of oxidizer pumps of RD861 and RD861K engines. During the analysis, it was determined how the design features affect the nature of the cavitation characteristic. It is also established how a concrete design change affects the value of the cavitation specific velocity of the pump. In addition to the above studies, an analysis was made of cavitation characteristics of pumps operating on a gas-containing liquid. Based on the results of the analysis, the dependence of the decrease in the cavitation specific velocity of the pump on the amount of free gas supplied to the inlet to the pump was constructed. The results of this study allow us to estimate the magnitude of cavitation pump failure at the design stage, depending on the design features of its flowing part when working on pure liquid and on the gas-liquid mixture.