Research On The Inter-stage Clearance Flow Characteristics Of Submersible Pumps And Its Influence On The Axial Force

Improving the safety and reliability of submersible pumps and optimizing the performance of submersible pumps have always been key issues in the industry.In the submersible pump,after the liquid flows out of the space guide vane,a small part of the liquid flows to the balance cavity through the inter-stage gap,forming an interstage clearance flow.Because of the existence of inter-stage clearance flow,the fluid flow characteristics of the balance chamber of the submersible pump are completely different from the fluid flow characteristics of the balance chamber of the centrifugal pump with a double-sealed impeller with a balance hole.The increase of the inter-stage clearance changes the internal flow field structure of the submersible pump,resulting in greater energy loss,and has an important impact on the axial force.Therefore,the study of the submersible pump inter-stage clearance is important for optimizing the performance of the submersible pump and improving the safety of the submersible pump.Reliability is of great significance.This paper takes 200QJ50 submersible pump for two-stage wells as the research object.On the basis of mutual confirmation of test and numerical simulation,the submersible pump model is studied and relevant conclusions are obtained.(1)Under the condition that the radial clearance of the seal ring behind the impeller remains unchanged,the method of changing the balance hole diameter and the inter-stage clearance is adopted to carry out the full flow field numerical simulation of the 12 sets of submersible pump models,focusing on the study of the leakage characteristics of the inter-stage clearance,The relationship between the radial clearance of the rear seal and the leakage characteristics of the balance hole,the flow characteristics and pressure distribution of the liquid in the inter-stage clearance,and the influence on the pressure of the balance cavity.The results show that with the increase of the inter-stage clearance,the pressure in the balance chamber increases,the turbulent energy dissipation at the position of the balance hole increases,and the efficiency and head of the submersible pump decrease to varying degrees.After the inter-stage clearance increases,the leakage of the inter-stage clearance and balance hole increases,and the leakage of the rear seal ring decreases.In the core area of the inter-stage clearance,the non-dimensional peripheral velocity of the liquid gradually decreases along the axial direction.The non-dimensional circumferential sub-velocity near the inner diameter of the inter-stage clearance is relatively large,and there is almost no radial flow of the liquid.The pressure inside the inter-stage clearance decreases along the axial direction from the inlet to the outlet,and the size is almost constant along the radial direction,showing a uniform distribution.For the studied pump,from the perspective of reducing leakage and preventing the pump shaft from locking up,the diameter of the balance hole is 6mm,and the gap between stages is more suitable to vary between 0.18mm and 0.36mm.(2)Under the condition that the diameter of the balance hole is constant,the four groups of submersible pump models with different inter-stage clearance values are studied,and the flow structure of the balance cavity under different inter-stage clearances,the flow trajectory of the liquid in the balance cavity,and the velocity distribution characteristics are analyzed.And the distribution law of the liquid velocity component in the balance cavity.The results show that the increase of the inter-stage clearance has a great influence on the stability of the liquid flow in the balance cavity.With the increase of the inter-stage clearance,the total area of the vortex area in the balance cavity increases,and the friction loss of the balance cavity disc is gradually reduced,the radial leakage velocity in the balance cavity decreases,and the radial velocity component of the liquid in the balance cavity fluctuates in the radial direction.After the inter-stage clearance increases,the pressure value in the balance cavity area increases,and the pressure distribution inside the balance cavity increases.The degree of unevenness increases,and the uneven area increases.(3)Taking the size of the inter-stage clearance and the diameter of the balance hole of the impeller as variables,and taking the axial component and the resultant force of the impeller as the research object,numerical analysis of the full flow field of 12 sets of model pumps with different interstage clearances and balance hole diameter matching relationships.The results show that the axial force of the submersible pump increases with the increase of the inter-stage clearance,and decreases with the increase of the balance hole diameter.Changing the inter-stage clearance has little effect on the axial force component produced by the fluid inside the impeller.The resultant force of the axial force acting on the two-stage impeller has a greater influence.For the pump studied in this article,from the perspective of reducing the axial force and ensuring the performance of the water pump,the balance hole diameter is 8mm,and the inter-stage clearance is 0.18mm.