Experimental Visualization of Cryogenic Backflow Vortex Cavitation with Thermodynamic Effects

Ito, Yutaka; Tsunoda, Atsuhiro; Kurishita, Yuto; Kitano, Shoko; Nagasaki, Takao

doi:10.2514/1.b35782

Cited by 37 publications

(23 citation statements)

References 22 publications

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“…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: (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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“…A high-speed camera is an essential tool used to capture cavitation development in hydraulic machinery. 14–16 The present paper used a super-high-speed camera (PCO. dimax HD) connected to an imaging acquisition computer to observe cavitating flow in the high-speed inducer.…”

Section: Experimental Facility and Proceduresmentioning

confidence: 99%

Visual experiment and numerical simulation of cavitation instability in a high-speed inducer

Cui

Chen

2019

Proceedings of the Institution of Mechanical Engineers, Part A:

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Cavitation instabilities in a high-speed inducer at a design flow rate were investigated for different cavitation numbers in numerical simulations and visual experiments. On the basis of a shear stress transport k–ω turbulence model and Zwart–Gerber–Belamri cavitation model, the transient cavitating flow in a high-speed centrifugal pump with an inducer is numerically simulated using ANSYS-CFX 15.0 software. Visual experiments were carried out to capture the evolution of cavitating flow in the inducer by using a high-speed camera. The performance and cavitation characteristic curves from numerical simulation agree with those from experiment. With a decreasing cavitation number, the cavitation development in the high-speed inducer goes through incipient cavitation, developing cavitation, critical cavitation, and deteriorated cavitation and presents vortex cavitation, sheet cavitation, cloud cavitation, backflow cavitation, and a cavitation surge. The region having a high vapor volume fraction basically coincides with the region of low local pressure at the same cavitation number. The position of largish blade loading on the inducer changes with the development of cavitation. A cavitation surge as one type of cavitation instability appears in the inducer at lower cavitation numbers. The drop or rise of the head coefficient is affected by an increasing or decreasing cavitation area in the cycle of a cavitation surge.

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“…This cavitation is caused by the blade tip vortex flow. 1 The tornado-like backflow vortex in the inducer will cause the backflow vortex cavitation. 2 Studies have reported that there are two major kinds of cavitation in the inducer.…”

Section: Introductionmentioning

confidence: 99%

Investigation of the cavitation model in an inducer for water and liquid nitrogen

Zhang

Ren

Wang

et al. 2019

Proceedings of the Institution of Mechanical Engineers, Part C:

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Cavitation commonly occurs in the hydraulic machineries like inducers. Cavitation happening in the cryogens is sophisticated due to their complicated thermodynamic properties. Computational fluid dynamics could provide relatively precise prediction for water. However, existing computational fluid dynamics methods may fail to simulate the cryogens cavitation precisely. This study presents a computational fluid dynamics simulation of four major cavitation models in both the liquid nitrogen and the water in an inducer. Four different cavitation models analyzed in this work are full cavitation model, Kunz model, Zwart–Gerber–Belamri, and Schnerr & Sauer. And the computational fluid dynamics simulation results are verified by the experiment to ensure the cavitation model's applicability in both liquid. Comparison of cavitation in water and liquid nitrogen is conducted and analyzed. The four cavitation models can predict cavitation in water, but the Zwart–Gerber–Belamri model and Schnerr & Sauer model also feature high capability to predict tip vortex cavitation. The results show that the full cavitation model is suitable for simulating the liquid nitrogen cavitation without changing of the model constants. The empirical constants of the other models should be adjusted in the liquid nitrogen cavitation simulation. Full cavitation model features high robustness in various liquids. The Schnerr & Sauer model can achieve the best results by adopting different empirical constants. In addition, the inducer performs better in the liquid nitrogen than water at low cavitation number regime as the head coefficient drops smoothly in liquid nitrogen with decreasing cavitation number.

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Experimental Visualization of Cryogenic Backflow Vortex Cavitation with Thermodynamic Effects

Cited by 37 publications

References 22 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

Visual experiment and numerical simulation of cavitation instability in a high-speed inducer

Investigation of the cavitation model in an inducer for water and liquid nitrogen

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