Method for Calculating Torque-Rate Characteristics of Feed Pump in Pumping, Turbining and Return Flow Mode

The paper presents an improved method to calculate the torque-rate characteristics of the feed pump of thermal power plant of industrial enterprise in return flow and turbining mode. Torque mechanical losses are taken into account when calculating the return flow mode. The return flow mode occurs when the feed pump disrupts the flow and, consequently, the rotation rate of the pump impeller reduces. The torque mechanical losses are loss of energy to the pump impeller wall operating fluid friction. The pump goes into a turbining mode when the rotation rate becomes inverse. In this mode, the calculation also involves mechanical losses. In simplified calculations of the torque-rate characteristics in the return flow mode, the universal curves of reversible hydraulic machines are used in contrast to the proposed method that takes into account the mechanism design parameters, main losses and the pipeline network characteristics. The paper presents a comparison of the torque-rate characteristics in the return flow mode obtained from the universal curves of a reversible hydraulic machine and using the improved technique that takes into account the mechanical losses. The analysis of induction motor rundown is carried out on the basis of the obtained characteristics. This allows us to estimate the success of the self-starting of induction motors.