The World's First Test Facility That Enables the Experimental Visualization of Cavitation on a Rotating Inducer in Both Cryogenic and Ordinary Fluids

Abstract

It is well known that cavitation breakdown, which is a phenomenon in which the pump head suddenly drops with a decrease in the inlet cavitation number, occurs in turbopumps. Especially in cryogenic pumps, cavitation breakdown occurs at a lower inlet cavitation number than that of ordinary fluids such as water. This phenomenon is referred to as a thermodynamic effect, as Stepanoff reported. The thermodynamic properties of the working fluid affect the sizes of cavitation elements, and the sizes affect cavitation breakdown; therefore, experimental flow visualization is an effective approach to realize a more efficient and more reliable cryogenic pump. In 2010, the author and colleagues developed the worldߣs first test facility to enable the visualization of cavitation on a rotating inducer in both cryogenic and ordinary fluids. At that time, only two reports on the flow visualization of a rotating cryogenic impeller had been published: one on flow visualization in liquid hydrogen by NASA in 1967 and the other in liquid nitrogen by JAXA in 2010. The present facility employs a triple-thread helical inducer with a diameter of 65.3 mm and a rotation rate of up to 8000 rpm with both liquid nitrogen and water available as working fluids. Unsteady visualization experiments for cavitation on an inducer in liquid nitrogen and water have revealed the characteristics of tip vortex cavitation, backflow vortex cavitation, and cavitation element size based on comparisons between cryogenic fluids that exhibit a stronger thermodynamic effect and ordinary fluids such as water.

Research on the cavitation characteristics and structural optimisation of spiral grooved thrust bearing lubricated by liquid hydrogen

“…The photos taken by the visualisation experiment have reference significance for the investigation of cavitation in inducer. Moreover, Ito et al 18 experimentally investigated the difference between liquid nitrogen cavitation and ordinary fluids around inducer. The difference between tip and reflux vortex cavitation of water and liquid nitrogen is investigated by unsteady visualisation experiment.…”

Influence of Rotating Speeds and Thermodynamic Effects on LOX Turbopump Performance

“…Nontoxic and nonpolluting propellants, such as liquid oxygen (LOX), kerosene, and liquid hydrogen, have been widely applied, owing to the environmental protection and staff health [2,3]. Moreover, a centrifugal pump is an energy conversion device that is widely used in the cryogenic refrigeration industry and petrochemical industry [4,5]. A common feature of the above components is that the media pumped are all cryogenic media.…”

Structural selection of liquid hydrogen lubricated herringbone spiral-grooved thrust bearing considering viscous dissipative heat

“…[22][23][24][25] Feng et al introduced the bubble-bubble interaction effect into the Keller-Miksis equation, established the cavitation model of bubbles in an ultrasonic field, and obtained the dynamic characteristics of bubbles. 26 In addition, Ito et al 27,28 and Lai et al 29 numerically researched the growth process and temperature distribution of individual bubbles in LH 2 and LN 2 . Considering the thermophysical properties of cryogenic media, this research has successfully promoted the research on cavitation.…”