Measurement of Temperature Effects on Cavitation in a Turbopump Inducer

Abstract

Temperature effects on the critical cavitation number and rotating cavitation in a turbopump inducer have been experimentally investigated in water. Static pressures upstream and downstream of the inducer have been measured to determine the cavitation performance, and cavitation instabilities have been detected using unsteady pressure sensors and a high-speed camera. Two kinds of cavitation instabilities have been identified—rotating cavitation and asymmetric attached cavitation. To quantify temperature effects, nondimensional thermal parameter has been adopted. Increasing water temperature, or increasing nondimensional thermal parameter, lowers the critical cavitation number. Increasing nondimensional thermal parameter also shifts the onset of rotating cavitation to a lower cavitation number and reduces the intensity of rotating cavitation. However, for values larger than 0.540 (340 K, 5000 rpm), the critical cavitation number and the rotating cavitation onset cavitation number become independent of the nondimensional thermal parameter. The onset of the head coefficient degradation correlates with the onset of rotating cavitation regardless of temperature.

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

“…However, when either the liquid temperature or rotational speed is changed, not only Σ * but also the Reynolds number (Re = 2ρ 1 rΩ 2 /μ l ) is simultaneously changed. In Kim and Song (2016), as Σ * was increased from 0.0116 to 1.80, the Reynolds number ranged from 2.6 × 10 6 to 6.4 × 10 6 as well. It indicates that Reynolds number possibly affects the occurrence of rotating cavitation.…”

“…In water, they found that decreasing DB completely suppressed rotating cavitation. Kim and Song (2016) investigated rotating cavitation onset trends for varying Σ * by changing the water temperature at a given rotational speed. The onset cavitation number decreased as Σ * was increased for Σ * < 0.54.…”

“…Increasing inducer blade tip velocity increases Re but decreases Σ * . Figure 2 shows a schematic of the turbopump inducer water test facility at Seoul National University (Kim and Song, 2016). The test facility has been designed to measure cavitating and noncavitating inducer/pump performance over a wide range of operating conditions.…”

“…Rotating parts are composed of the Figure 1. The rotating cavitation onset cavitation number versus the non-dimensional thermal parameter at 5,000 rpm and φ/φ d = 1.0 (Kim and Song, 2016).…”

The Correction and Evaluation of Cavitation Model considering the Thermodynamic Effect

“…The influence of the dimensionless thermodynamic coefficient on the critical cavitation number in inducer and its cavitation states under different temperature was studied. When the thermodynamic coefficient is lower than 0.54, the critical cavitation number decreases along with the increase of thermodynamic coefficient; and vice versa: when it is higher than 0.54, the critical cavitation number is not related to the thermodynamic coefficient [8].…”