MODELLING THE INFLUENCE OF CYLINDRICAL THROTTLE EROSION WEAR ON CHARACTERISTICS OF AUTOMATIC BALANCING DEVICE

摘要

Complicated system of forces acts on the rotor of multi-stage centrifugal pump under its exploitation. Axial force is the biggest one for pumps with one-side inlet wheels. This force in many constructions of pumps is balanced by special automatic balancing device (ABD). This device consists of an unloading disk rigidly fixed on the shaft and a non-rotating supporting disk. The corresponding surfaces of these elements form cylindrical and face throttles arranged in series divided with the unloading chamber. Automatic operation of such devices is caused by the interdependence of hydrodynamic characteristics in cylindrical and face throttles. The middle gap value of cylindrical throttle is one of the main characteristics determining the pressure in the chamber and the ABD flow-rate value. The middle gap can increase due to erosive wear under pump operating, and it can result in negative impact on ABD operating. In this work, the intensity of erosion wear is considered as a function of middle velocity of flow and the coefficient of material wear. The middle velocity of flow in the cylindrical throttle is obtained by solving equations of turbulent fluid flow motion jointly with continuity equation. It allows one to determine the changes of the middle gap of cylindrical throttle in time and to estimate the influence of such changes on static and flow-rate characteristics of the ABD.