Determination of the characteristics of a jet pump during its asymmetric rotation in a well

Abstract

The hydraulic model of low-pressure jet pump working process for conditions of its asymmetric rotation is proposed on the basis of law of conservation of liquid momentum of parallel mixed potential flows with linear distribution of tangential velocities and radial displacement relative to borehole axis. In the process of derivation of the equation of pressure characteristic of low pressure jet pump at its asymmetrical rotation in a borehole the law of conservation of flow energy in the form of Bernoulli's equation and the law of continuity conservation of mixed currents have been used. To characterize uneven distribution of kinematic parameters in the mixing chamber of jet pump, the unevenness coefficient in the form of ratio of average and axial circumferential velocities of mixed flows is introduced. Flow rates of working, ejected and mixed streams are determined by integration of the adopted velocity profiles in the inlet and outlet sections of the mixing chamber of the jet pump. The developed hydraulic model allowed obtaining a dimensionless relative form of equation for determining the additional head of the jet pump caused by its asymmetric rotation in the borehole. The magnitude of the additional dynamic head increases as the peripheral velocity increases and the operating flow rate decreases. The total head produced by the jet pump is calculated by summing the additional head and the head obtained for the stationary ejector system. The rotation of the borehole ejection system causes the head and the efficiency of the jet pump to increase. The proposed hydraulic model can be used to improve the efficiency of jet pump mode prediction as a part of assemblies for drilling and bottomhole cleaning.