Sub-synchronous rotating cavitations were observed in severalinducers in cold water and liquid nitrogen. The propagation speed ratio of the sub-synchronous rotating cavitation is 0.9〜0.9 rotated in the same direction as the inducer rotation. It occurs al lower cavittation number without the head break. The mean cavity length is so long, and the cavity oscillates at the inter-blade, not at the inducer inlet. It could be estimated that the phase delay of the mass flow gain factor and the cavitation compliance plays a major role to occur the sub-synchronous rotating cavitation.

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Cryogenic Inducer Test Facility(CITF) was constructed in JAXA kakuda Rocket Engine Research Center. The test facility gas been operated since 2003. Liquid nitrogen and liquid gydrogen are used as working fluid for the experiments of rocket engine turbopump inducers, therefore the themodynamic effect on cavitation could be examinged. The faculty of CITF was verified from the elemental and comprehensive tests. In this paper, the vilification test results and the future programs are presented.

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For experimantally investigation of themodynamic effect on cavitation, it is of value to observe the cavitation in cryogenic flow, but the visualization is difficult. For this reasen, we tried to estimate the cavitating region in liquid nitrogen based on unsteady pressure distribution. Unsteady pressure was measured by placing sensors on casing of inducer. By this method, it succeeded in grasping of the cavitating rejion in relation to cavitation number. The comparison of the expriments in liquid nitrogen and in cold water allowed us to estimate theamplitude of the themodynamic effect. Consequently, it turns out that the amplitude of themodynamic effectis changing with the cavity length. The amount of temperature depression increases rapidly when the cavity extends over the throat.

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