Suppresson of Cavitation Surge in a Turbopump Inducer by the Backflow Restriction Step

Tomaru, Hiroshi; Ugajin, Hiroki; Kawasaki, Shigeo; Nakano, Masataka

doi:10.2514/6.2007-5538

Cited by 9 publications

(4 citation statements)

References 2 publications

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“…The so-called backflow vortex cavitation, which is a rotating instability with multiple cells formed in backflow vortices, was detected for the first time in 1997 [19] for two separated ranges of values of the cavitation number: at high cavitation numbers (three to four times the breakdown cavitation number), when the tip vortex cavitation is the principal form of cavitation, and around the head breakdown for low flow coefficient, where the backflow is particularly strong. It has been recently shown in the open literature that the extent of the cavitation backflow and, consequently, of the surge instability associated to it can be significantly reduced by adding a backflow restriction step to the inducer casing [20].…”

mentioning

confidence: 99%

Effect of Tip Clearance on the Performance of a Three-Bladed Axial Inducer

Torre¹,

Pasini²,

Cervone³

et al. 2011

Journal of Propulsion and Power

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This paper illustrates the results of an experimental campaign conducted in the Cavitating Pump Rotordynamic Test Facility. Tests have been carried out at two values of the blade tip clearance on the three-bladed DAPAMITO3 inducer, designed by means of a reduced-order model, with geometry and noncavitating performance representative of typical space rocket inducers. Different cavitating behaviors have been observed at different values of the blade tip clearance, particularly near breakdown conditions. The intensity of pressure oscillations tends to decrease as the tip blade clearance increases, and cavitation-induced azimuthal flow instabilities appear to be more sensitive to changes of the blade tip clearance than axial flow instabilities. Finally, the presence of backflow seems to have a stabilizing effect on rotating cavitation instabilities. Nomenclature c % = tip clearance/mean blade height ratio c % =h m f1; 2; . . . = name of instability h m = mean blade height, m n = number of lobes p in = inlet static pressure, Pa p V = vapor pressure, Pa Q = volumetric flow rate, m 3 =s Re = Reynolds number; 2r 2 T = r T = inducer tip radius, m b = blade angle evaluated with respect to the azimuthal direction, rad xy = coherence function p = static pressure rise across inducer, Pa = angular spacing between transducers, rad = tip clearance, m = kinematic viscosity, m 2 =s = liquid density, kg=m 3 = cavitation number; p 1 p V =0:5 2 r 2 T = flow coefficient; Q=r 3 T D = design flow coefficient ' = phase of cross spectrum, rad = static head coefficient; p= 2 r 2 T = inducer rotational speed, rad=s

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mentioning

confidence: 99%

Effect of Tip Clearance on the Performance of a Three-Bladed Axial Inducer

Torre¹,

Pasini²,

Cervone³

et al. 2011

Journal of Propulsion and Power

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“…In the future, combinations with backflow reversal [4], which is effective in controlling backflow in low flow conditions, should be considered.…”

Section: Discussionmentioning

confidence: 99%

“…As methods to suppress cavitation instability, J-Groove [3] and the Backflow Restriction Step [4] have been studied, but while they are effective for certain instability phenomena, they have not been able to prevent them completely. In addition, issues remain from the viewpoints of simplicity of processing and miniaturization.…”

Section: Introductionmentioning

confidence: 99%

Effect of the difference in slit locations on the suppression of cavitation instabilities in an inducer.

Ishikawa,

Nakura,

Kawasaki

et al. 2024

J. Phys.: Conf. Ser.

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Cavitation instabilities are caused by unsteady cavitation in the inducer in liquid rocket turbopumps. This phenomenon has a negative impact on pumps and must be suppressed. Our research group has proposed a method to suppress the instabilities by adding slits to the inducer blades, and previous studies was shown the effectiveness of this method. In this study, water experiments of inducers with slits at different locations were conducted. As a results, the vibration characteristics of cavitation in the slit inducers changed when the location of the slit was changed although the cavitation instabilities were successfully suppressed in all slit inducer. The visualized image of cylindrical surface of the axial flow pump was expanded into a two-dimensional plane to determine the time variation of the area of the tip leakage vortex cavitation generated in each blade. The suppression mechanism of cavitation instabilities in each slit location was discussed from the obtained unsteady image of cavity area in each blade in the slit inducers.

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“…Because of easy implementation of this method, it seems to be a common one in modern rocket engine turbopumps. To enlarge the range of operation flow rate of inducer, various kinds of casing treatments such as J-Groove [14], circumferential groove [15] and backflow restriction step [16] have been proposed and have contributed to extend our 5 FE- Watanabe knowledge in terms of the suppression of cavitation instabilities. However, the effectiveness of them were examined in the limited range of the flow rate, from slightly partial flow rate to the design or over flow rate, and some of them seem to be not effective at extremely low flow rates, at which a large flow recirculation due to strong inlet backflow from inducer occurs in nature [17].…”

Section: Introductionmentioning

confidence: 99%

Suppression of Cavitation Surge in Turbopump With Inducer by Reduced-Diameter Suction Pipe With Swirl Brake

Tanaka

Kitabata

Nasu

et al. 2022

Journal of Fluids Engineering

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Downsizing and high power density of turbopumps are achieved by increasing their rotational speed. Cavitation often becomes a problem while the influence of cavitation will be generally relieved by employing an inducer before the impeller. For general-use turbopumps with inducer, instability-free operation as well as high suction performance are required in wide flow rate range including extremely low flow rate. However, the low frequency and large amplitude of cavitation surge is often be a serious problem even with inducer when operated at very low flow rates. In this study, a reduced-diameter suction pipe (RSP) equipped with swirl brake (SB) was proposed for a suppression device of the inlet backflow as well as of the cavitation surge through removing swirling velocity component. The effectiveness of this device was investigated by CFD and experiments. First, several geometries of RSP with SB were examined by CFD, and it was found that the extension of inlet backflow was stopped at this device provided that the swirl brake had a sufficient radial or axial length. Then, one of the proposed RSP with SB was manufactured, and the experimental evaluation of the effectiveness of this device was conducted. It seemed that RSP with SB could well prevent the extension of inlet backflow. The cavitation surge was completely suppressed even at extremely low flow rates. As a result, the suction performance was also improved at low flow rates.

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Suppresson of Cavitation Surge in a Turbopump Inducer by the Backflow Restriction Step

Cited by 9 publications

References 2 publications

Effect of Tip Clearance on the Performance of a Three-Bladed Axial Inducer

Effect of Tip Clearance on the Performance of a Three-Bladed Axial Inducer

Effect of the difference in slit locations on the suppression of cavitation instabilities in an inducer.

Suppression of Cavitation Surge in Turbopump With Inducer by Reduced-Diameter Suction Pipe With Swirl Brake

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