Influence of Thermodynamic Effect on Synchronous Rotating Cavitation

Abstract

Synchronous rotating cavitation is known as one type of cavitation instability, which causes synchronous shaft vibration or head loss. On the other hand, cavitation in cryogenic fluids has a thermodynamic effect on cavitating inducers because of thermal imbalance around the cavity. It improves cavitation performances due to delay of cavity growth. However, relationships between the thermodynamic effect and cavitation instabilities are still unknown. To investigate the influence of the thermodynamic effect on synchronous rotating cavitation, we conducted experiments in which liquid nitrogen was set at different temperatures (74K, 78K, and 83K). We clarified the thermodynamic effect on synchronous rotating cavitation in terms of cavity length, fluid force, and liquid temperature. Synchronous rotating cavitation occurs at the critical cavity length of Lc∕h≅0.8, and the onset cavitation number shifts to a lower level due to the lag of cavity growth by the thermodynamic effect, which appears significantly with rising liquid temperature. Furthermore, we confirmed that the fluid force acting on the inducer notably increases under conditions of synchronous rotating cavitation.

Measurement of Temperature Effects on Cavitation in a Turbopump Inducer

“…Cavity length and onset cavitation number of alternate blade cavitation and rotating cavitation all decreased as the temperature increased. Yoshida et al [10] found that increasing the liquid nitrogen temperature slowed down the growth rate of cavity length of inducer tip cavitation and lowered the onset cavitation number of asymmetric attached cavitation. Kikuta et al [11] found that cavitation surge occurred in water at 296 K (R Ã % 0.01), whereas cavitation surge did not occur in liquid nitrogen at 76 K (R Ã % 7).…”

Analysis of Flow Instabilities on a Three-Bladed Axial Inducer in Fixed and Rotating Frames

“…More specifically, present experiments focused on refining the characterization of the cavitation phenomena developing inside the inducer blade channels and their interactions with the flow instabilities occurring in the impeller eye. Earlier experiments to this purpose, like those carried out by Yoshida and his collaborators ( [38], [39], [40]), suitably multiplexed at the frequency of the impeller rotation the measurements of pressure transducers flush-mounted on the impeller casing in order to extract the information on the flow behavior in the blade channels. A peculiar aspect of present experiments is that the pressure transducers have been mounted both on the casing and on the hub of the inducer, in order to allow for the simultaneous analysis of the flow instabilities in the stationary and rotating reference frames.…”

Measurement of thermal parameter and Reynolds number effects on cavitation instability onset in a turbopump inducer

“…In R-114 (in which the thermal effect existed), the cavitation region was lengthened as the rotational speed increased, but the cavitation region length was insensitive to the rotational speed in cold water (in which the thermal effect was negligible). Yoshida et al (2007Yoshida et al ( , 2009 investigated cavitation instabilities at different liquid nitrogen temperatures. They found the followings.…”