Transient phenomena in low-head pump station with free-surface discharge

Abstract

1. With regard to starting capacity, the most favorable is a pump start with the rotor blades set at minimum regulating angle. The minimum head at starting is secured by opening the gate at the instant of equalization of water levels upstream and downstream of the gate, with a rate of vg=0.08–0.10 m/sec. 2. The storage volume of the gate forebay can be reduced 1.5–2 times, according to the starting conditions (Mres≤0.7Mn.e, the moment of resistance during synchronization should not exceed the nominal moment of the motor; S/Sopt≤1.5–1.75). 3. Stoppage of the pump should be effected at large regulating angles of the blades,ϕ=0°. For the given gate-forebay volume (Wfor/Qopt=20 sec) the motor should be switched off at the instant that the gate is closed down toag/a=0.5, with vg=0.4 m/sec. With the volume reduced 1.5–2 times, the motor should be switched off at the instantag/a=0.25, with vg=0.4 m/sec. 4. Pump stoppage without the prior closure of the gate is not permissible because, in the acceleration stage, the magnitudes of the vibrations and dynamic loadings increase 10–12 times compared with normal pumping regimes.