Vibration and speed envelope analysis of cryogenic pumps induced during cavitation

Cavitation is the undesirable phenomenon that has to be avoided in cryogenic pumps for any successful launch. It is very essential to study the effect of cavitation on cryogenic pumps at various process conditions a priori to ensure a successful flight. The objective of this paper is to analyze the cavitation inception, its intensification and several instabilities induced during cavitation. The ground level testing with varied conditions of flow rate and speed using actual propellants (LH₂ and LOX) were carried to investigate thevibration and speed characteristics. The speed and vibration levels has increased significantly from that of rated speed during cavitation inception. Significant broadband pump vibration frequency of 2 kHz to 10 kHz is observed during cavitation. High frequency signals are also noticed which are more sensitive at the start of cavitation. The results were used for predicting the sufficient margins (critical NPSH) required for the cryogenic tanks during flight.