Transient Characteristics of a Closed Loop Pipe System During Pump Stopping Periods

Abstract

In order to study the transient characteristics of a closedloop pipe system with room temperature water, experiments were carried out based on different pump stopping periods from rate rotational speed to zero. Various stopping periods were realized by changing the rotational inertia of the rotors, controlling the frequency of the motor and braking the shaft. Experimental results of different operating schemes were compared, and transient flow rate of the pipe system and transient characteristics of the pump were analyzed. The influences of the kinetic energy of the loop fluid and pump rotors to the stopping periods were summarized. Results show that rapid change of the pump operating conditions occurs during the stopping period and transient flow rate of the pipe system and characteristics of the pump depend largely on the way of stopping. The kinetic energy stored in the pump can drive the impeller keeping rotating for more time after the motor is shutdown. Due to the kinetic energy stored in the loop pipe, the flow rate does not reach zero immediately after the rotational speed reaches zero. The inertia of pump rotor and fluid inertia affect the impact of fluid flow and the duration of the loop during pump stopping period.