A significant decrease in the efficiency of the submersible installations of electric centrifugal pumps (ESP) accompanies the operation of the mechanized well stock in the presence of the pumped fluid-free gas. Based on photos showing the high-speed shooting the gas-liquid flow in the inter-blade channels of the ESP, the analysis of mixture structure changes depending on the size of the pump supply and the free-gas volume content is presented. It was established that when the ESP is fed with a volume of gas fraction more then 0.05, stagnant zones comprising gas bubbles (transient flow mode of the mixture) form in the flow channels of the impeller of the centrifugal pump, which, with further growth of volume of gas fraction, are transformed into stable gas caverns filling the entire flow section of the impeller (flow mode with a stable gas cavern). Such flow modes of the gas-liquid mixture contribute to an increase in pressure losses on friction, and, as a result, the degradation of the head capacity curve of the pump. Using the balance equation of forces acting on the gas bubble in the inter-blade channel of the centrifugal impeller, a mechanistic correlation is obtained for calculating the boundaries of the transition of gas-liquid structures to the transition flow regime and from the transition regime to the flow with a stable gas cavity. The verification of the obtained mechanistic correlation to determine the conditions that cause a change in the structure of gas-liquid mixture in the inter-blade channels of the ESP’S impeller, based on the comparison of calculated and experimental data at the boundary of the transition of gas-liquid structures to the transition mode and from the transition mode to the stable gas cavity, showed a satisfactory precision of the results, sufficient for engineering calculations.
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