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The substantiation of the choice of design parameters characterizing the mutual orientation of the mixed flows and the ratio of the geometric dimensions of the elements of the flow path of the jet pump that provide an increase in the energy characteristics of borehole ejection systems is given. Depending on the mutual orientation of the mixed flows, three variants of the design of the jet pump are possible, viz. the one with a parallel orientation of the working and ejected flows, the one with the inlet of the ejected flow at a sharp angle, and the one with a perpendicular orientation of the working and ejected flows. The magnitude of the angle between the velocity vectors of the mixed flows directly affects the intensity of vortex formation in the mixing chamber, the amount of energy loss and the efficiency of the jet pump; however, the simplicity of their manufacture remains the determining condition for choosing the design variant of the elements of ejection systems. Based on the use of the laws of conservation of energy, the amount of motion and continuity of the flow, it is determined that the level of energy loss during mixing flows is directly proportional to the magnitude of the angle of entry of the ejected medium. In the course of computer simulation of the jet pump workflow, an asymmetric distribution of hydrodynamic parameters for the non-parallel orientation of the mixed flows has been obtained. In order to reduce energy losses when mixing flows, the value of the angle of entry of the ejected flow must be taken in the range from 0 to 15°. In the case of the implementation of the zero head mode and the maximum ejection coefficient, minimal energy losses during mixing of flows are provided for the main geometric parameter of the jet pump equal to 2.375. In the course of experimental studies, the inverse dependence of the maximum value of the efficiency of a borehole jet pump on the value of its main geometric parameter represented as a power function, has been established. When using ejection systems that implement long-term technological processes (e. g., during oil production), it is necessary to take the minimum possible value of the main geometric parameter of the jet pump for the specified operating conditions.

The article presents rationales for choosing the depth of installation of an oil jet pump in the borehole that which ensures maximum efficiency of its operation. The operating parameters of the ejection system are determined by the joint solution of the characteristic equations of the high-pressure jet pump and the hydraulic system. In the process of solving the system of equations, the method of successive approximations, the Delphi software environment and PTC Mathcad resources were used. The equation of the characteristics of the jet pump hydraulic system was obtained by determining the pressures in its distinctive cross-sections and then presenting their values as the relative (dimensionless) head of the ejection system. Alteration the installation depth of the jet pump changes the characteristics of its hydraulic system, the parameters of the operating point of the pumping unit and its efficiency. In this case, the minimum permissible installation depth of the jet pump is determined by the value of the minimum pressure in the elements of the ejection system, which must exceed the value of the elastic pressure of saturated vapors of the oil and gas flow and ensure its operation in pre-cavitation mode. The probability of operation of a jet pump in cavitation mode was studied using the Bernoulli, Darcy – Weisbach and flow continity equations. The inversely dependence of the ejection coefficient and efficiency of the jet pump on the depth of its installation in the borehole has been revealed. If the jet pump is installed in the borehole at the optimal depth, its efficiency is increased by 30 %.

Jet pumps are widely used in the power industry as well as in many others. Their main disadvantage is low operating efficiency which aggravates when the jet pump is working with a low ejection coefficient. Such modes are sometimes unavoidable being conditioned by the character of technological process. The article considers methods of improving the operation of central ejectors at small ejection coefficients.The authors use mathematical simulation approach to study the particularities of kinematic structure of the flow in the mixing chamber of the central ejector operating with low ejection coefficients. They utilize Solid Works Cosmos Flo application-program package for the mathematical simulation. The study shows that areas of reverse flows appear alongside the walls of the mixing chamber under the above conditions which reduces the efficiency of the jet apparatus. The more is the extent of the discovered areas the more is the loss of energy. The study detects the regime zones where detached flows areas appear. The authors propose to replace such areas with solid surface (substitution bodies) for preventing them from emerging. The mathematical simulation results determine the geometric parameters of the substitution bodies for the central ejectors with different modules and ejection coefficients and yield mathematical description of their shape. Mathematical and physical simulation of the centralejector operation with the substitution bodies shows the increase in pressure-head and efficiency coefficients in such apparatuses as compared to ejectors of the conventional form. Efficiency increase is the case in quite a wide range of operating modes.The proposed method of the efficiency increase for the central ejectors is rather straightforward and does not require substantial financial expenditures for its implementation.