Experimental comparison of backflow-vortex cavitation on pump inducer between cryogen and water

Ito, Yutaka; Tsunoda, Atsuhiro; Nagasaki, Takao

doi:10.1088/1742-6596/656/1/012063

Cited by 8 publications

(14 citation statements)

References 9 publications

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“…Small effects of r are observed on N cav in the studied parameter ranges (0:20 /=/ max 0:55 and 3 N 10). This tendency was previously reported by the author and colleagues [14]. Because significantly accurate and stable measurements are possible due to the several modifications made to the experimental facility, the dispersion of collected data is smaller than that in the previous studies [14].…”

Section: Quantitativesupporting

confidence: 59%

“…2015, the present author and colleagues [14] theoretically determined the exact number of secondary vortices from the flow field. In that study, however, we did not specify the reasons for choosing the assumed equations.…”

Section: (C)mentioning

confidence: 87%

“…Later, Aoki and Yamamoto [16], Tsujimoto et al [17], Yokota et al [13], and Tan et al [18] focused on water backflow-vortex cavitation. The author and colleagues [14,19] studied backflow-vortex cavitation in water and also liquid nitrogen to clarify the mechanism of backflow-vortex cavitation and the effect of working fluids on backflow-vortex cavitation, as shown in Fig. 3.…”

Section: (C)mentioning

confidence: 99%

“…Figure 3 shows that the amount of water cavitation is far larger than the amount of nitrogen cavitation and that the size of the nitrogen cavitation component is much smaller than the size of the water cavitation component. The author and colleagues [14,19] previously quantitatively measured backflow-vortex cavitation, including the number of backflow-vortex cavitations (N cav ), x=x imp , and d=d cas , and found no differences in the values for nitrogen and water. In Fig.…”

Section: (C)mentioning

confidence: 99%

“…1, backflow-vortex cavitation can be used as a noninvasive sensor during visualization to determine the number of backflow vortices; therefore, we observe the number, revolving angular velocity, and revolving diameter of the backflow-vortex cavitations. The experimental facility is the same as the one used by the author and colleagues in our previous studies [14,19]. Figure 10(a) shows an overview of the cavitation tunnel, and Fig.…”

Section: Effect Of the Forced Vortex Ratio Of Each Secondarymentioning

confidence: 99%

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Theoretical Analyses of the Number of Backflow Vortices on an Axial Pump or Compressor

Ito

Sato

Nagasaki

2020

Journal of Fluids Engineering

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Backflow vortices occasionally occur in the annular mixing zone between the main and axially reverse whirling flows from the impeller tip clearance on an axial pump or compressor. A number (N) of tornado-like backflow vortices rotate around themselves and revolve around the casing axis with a diameter (d) and a revolving angular velocity (ω). To investigate the factors determining N and the movement of the backflow vortices, theoretical analyses are performed. Each backflow vortex is generated in the mixing zone; the core region of each backflow vortex is considered to be a forced vortex, while the outer region is considered to be a free vortex. The ratio (f) of the forced vortex to the distance between the backflow-vortex center and the casing is defined. Each backflow vortex has a circulation and induces movements of all the other backflow vortices depending on the distance between the vortices. The casing restricts the movements of all the backflow vortices, and imaginary image vortices are considered on the other side of the casing. Consequently, for d, ω, N, and f, any parameter can be determined if the other three parameters are specified. As an application of the present theory to an inducer representing an axial pump or compressor, the number (Ncav) of “backflow-vortex cavitations,” which occur around the backflow-vortex center, is predicted. Cavitation is visible; therefore, Ncav is quantitatively measurable. In the parameter ranges studied for the tested inducer, the predicted value of N accurately agrees with the experimentally measured value of Ncav.

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Section: Quantitativesupporting

confidence: 59%

Section: (C)mentioning

confidence: 87%

Section: (C)mentioning

confidence: 99%

Section: (C)mentioning

confidence: 99%

Section: Effect Of the Forced Vortex Ratio Of Each Secondarymentioning

confidence: 99%

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Theoretical Analyses of the Number of Backflow Vortices on an Axial Pump or Compressor

Ito

Sato

Nagasaki

2020

Journal of Fluids Engineering

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Numerical investigation of compressible cryogenic cavitating flows by a modified mass transport model

et al. 2023

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The objectives of this study are to propose exact numerical methods for the compressible cryogenic cavitating flows and investigate the cavitation behaviors and vortex structures. A numerical modeling framework including large eddy simulations, vapor-liquid equations of state and a modified mass transport model is presented in this paper. The modified transport model is proposed based on the convective heat transfer, in which the convective heat transfer coefficient is associated with the material properties and local temperature. To validate the applicability of the modified model, the liquid nitrogen cavitating flows in the inertial and thermal modes ( s ≈0.50, Tthroat =77.24K and Tthroat =85.23K) are simulated respectively. Meanwhile, the influence of thermodynamic effects on the compressibility is investigated. The numerical method is further utilized to visualize the detailed cavity and vortex structures in the different cavitating flow patterns ( Tthroat ≈77K, s =0.58, 0.39, 0.18). The results show that the predicted cavity structures with the modified mass transport model agree better with the corresponding experimental data. For the thermal mode, since the significant thermal effects restrain the development of cavity, the area of the low sound speed region is smaller than that of the inertial model. And the value of the minimum sound speed is larger. So that the Mach number in the cavitation region is reduced. Therefore, the compressibility of the liquid nitrogen cavitation in the thermal mode is weaker. For the different cavitating flow patterns, the core region of attached cavities near the throat remains stable during an evolutionary cycle.

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

Ito

2021

Journal of Fluids Engineering

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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.

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Experimental comparison of backflow-vortex cavitation on pump inducer between cryogen and water

Cited by 8 publications

References 9 publications

Theoretical Analyses of the Number of Backflow Vortices on an Axial Pump or Compressor

Theoretical Analyses of the Number of Backflow Vortices on an Axial Pump or Compressor

Numerical investigation of compressible cryogenic cavitating flows by a modified mass transport model

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

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