Numerical Analysis of Cavitation Instabilities and the Suppression in Cascade

Iga, Yuka; Hiranuma, Makoto; Yoshida, Yoshiki; Ikohagi, Toshiaki

doi:10.1299/jee.3.240

Cited by 6 publications

(3 citation statements)

References 10 publications

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“…(1). The terms a x and a y in source term vector S are acceleration terms, and Γ in S represents the evaporation speed by the instantaneous equilibrium evaporation model [3] . Since empirical constants for evaporation speed are not necessary, the evaporation model is robust for pressure wave propagation with a rapid pressure jump accompanied by a pulsation phenomenon.…”

Section: Locally Homogeneous Model For a Compressible Gas-liquid Two-mentioning

confidence: 99%

“…In the previous study, the occurrence conditions or propagation velocity ratio, which have been well documented based on experimental results, were reproduced qualitatively. In addition, the possibility of the suppression of cavitation instabilities by a jet flow through a slit on cascade blades was reported [3] . Furthermore, we have classified three types of cavitation surges in cascade and the frequency characteristics of the cavitation surges [4] and have suggested a mechanism for the propagation direction of rotating cavitations in cascade [5] .…”

Section: Introductionmentioning

confidence: 99%

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Numerical Analysis of the Influence of Acceleration on Cavitation Instabilities that arise in Cascade

Iga

Konno

2012

International Journal of Fluid Machinery and Systems

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In the turbopump inducer of a liquid propellant rocket engine, cavitation is affected by acceleration that occurs during an actual launch sequence. Since cavitation instabilities such as rotating cavitations and cavitation surges are suppressed during launch, it is difficult to obtain data on the influence of acceleration on cavitation instabilities. Therefore, as a fundamental investigation, in the present study, a three-blade cyclic cascade is simulated numerically in order to investigate the influence of acceleration on time-averaged and unsteady characteristics of cavitation that arise in cascade. Several cases of acceleration in the axial direction of the cascade, including accelerations in the upstream and downstream directions, are considered. The numerical results reveal that cavity volume is suppressed in low cavitation number condition and cavitation performance increases as a result of high acceleration in the axial-downstream direction, also, the inverse tendency is observed in the axial-upstream acceleration. Then, the regions in which the individual cavitation instabilities occur shift slightly to a low-cavitation-number region as the acceleration increases downstream. In addition, in a downstream acceleration field, neither sub-synchronous rotating cavitation nor rotating-stall cavitation are observed. On the other hand, rotating-stall cavitation occurs in a relatively higher-cavitationnumber region in an upstream acceleration field. Then, acceleration downstream is robust against cavitation instabilities, whereas cavitation instabilities easily occur in the case of acceleration upstream. Additionally, comparison with the Froude number under the actual launch conditions of a Japanese liquid propellant rocket reveals that the cavitation performance will not be affected by the acceleration under the current launch conditions.

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Section: Locally Homogeneous Model For a Compressible Gas-liquid Two-mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Numerical Analysis of the Influence of Acceleration on Cavitation Instabilities that arise in Cascade

Iga

Konno

2012

International Journal of Fluid Machinery and Systems

Self Cite

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“…In the study, the occurrence condition or propagation velocity ratio, which have been well documented based on experimental results, were reproduced qualitatively. Furthermore, the possibility of the suppression of cavitation instabilities by a jet flow through a slit on cascade blades was reported (7) . The numerical method developed by present authors was confirmed to be applicable for numerical simulation of cavitation instabilities that occur due to mutual interference between the oscillation of unsteady cavitation and the fluid machinery.…”

Section: Introductionmentioning

confidence: 99%

Occurrence Mechanism and Oscillation Characteristics of Pulsation Phenomenon Arising in Cavitation Surge in Cascade

Iga

Hashizume

Yoshida

et al. 2009

JEE

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In this study, numerical analysis of cavitating three-blade cyclic flat-plate cascade is performed with paying attention to cavitation surge which is a type of cavitation instabilities. A numerical method employing "locally homogeneous model for compressible gas-liquid two-phase medium" is applied to solve the unsteady cavitating flowfield. From results of numerical analysis, few typical tendency of cavitation surge which is well known in experiments was reproduced numericaly, that frequency of cavitation surge decreases with lowering σ, and that cavitation surge is easy to occur at low flow rate condition. Additionaly, mechanism of pulsation phenomenon of cavitation surge in flat-plate cascade was clarified, that collapse pressure of cloud cavity in downstream of cascade propagates upstream on contact with re-entrant jet which is flowing backward inside a sheet cavity and causes oscillation in upstream pressure, also that negative angle of attack and choking of cascade throat are considered to cause of oscillation in flow rate. About dynamic transfer function of cavitation, certain degree of possibility is confirmed in quasi-steady mass flow gain factor M quasi and cavitation compliance K quasi for prediction of occurrence limit of cavitation instabilities. Additionally, for prediction of frequency of cavitation surge, it was confirmed that local cavitation compliance K local is more available than quasi-steady one.

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Numerical Analysis of Three Types of Cavitation Surge in Cascade

Iga¹,

Hashizume

Yoshida

2011

Journal of Fluids Engineering

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In the present study, numerical analysis of a cavitating three-blade cyclic flat-plate cascade was performed considering cavitation surge, which is a type of cavitation instability in pumping machinery. A numerical method employing a uniquely developed gas-liquid two-phase model was applied to solve the unsteady cavitating flow field, where compressibility is considered in the liquid phase of the model. From the numerical results, the surging oscillations by cavitation represented in the present cascade system can be classified into three types of cavitation surge based on the oscillation characteristics and the flow fields. In the first type, oscillation is composed of small-vortex cavitation and large scale pulsation, which correspond to “surge mode oscillation” whose frequency is not affected by cavity volume. The second type of oscillation is composed of sheet cavitation with a re-entrant jet, which corresponds to so-called “cavitation surge.” The final type of oscillation is subsynchronous rotating cavitation accompanied by pulsation, which is considered as superposition of system and local instability. In addition, the locking phenomenon of break-off frequency of cavitation in the surging oscillations and the mechanism of the pulsation phenomenon accompanied by re-entrant jet in the present cascade were investigated.

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Numerical Analysis of Cavitation Instabilities and the Suppression in Cascade

Cited by 6 publications

References 10 publications

Numerical Analysis of the Influence of Acceleration on Cavitation Instabilities that arise in Cascade

Numerical Analysis of the Influence of Acceleration on Cavitation Instabilities that arise in Cascade

Occurrence Mechanism and Oscillation Characteristics of Pulsation Phenomenon Arising in Cavitation Surge in Cascade

Numerical Analysis of Three Types of Cavitation Surge in Cascade

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