• Nuclear Engineering and Technology
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• v.53 no.11
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• pp.3612-3624
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• 2021

At present, in the case of pump fast optimization, there is a problem of rapid, accurate and effective prediction of cavitation performance. In "A Cavitation Performance Prediction Method for Pumps PART1-Proposal and Feasibility" [1], a new cavitation performance prediction method is proposed, and the feasibility of this method is demonstrated in combination with experiments of a mixed flow pump. However, whether this method is applicable to vane pumps with different specific speeds and whether the prediction results of this method are accurate is still worthy of further study. Combined with the experimental results, the research evaluates the sensitivity and accuracy at different flow rates. For a certain operating condition, the method has better sensitivity to different flow rates. This is suitable for multi-parameter multi-objective optimization of pump impeller. For the test mixed flow pump, the method is more accurate when the area ratios are 13.718% and 13.826%. The cavitation vortex flow is obtained through high-speed camera, and the correlation between cavitation flow structure and cavitation performance is established to provide more scientific support for cavitation performance prediction. The method is not only suitable for cavitation performance prediction of the mixed flow pump, but also can be expanded to cavitation performance prediction of blade type hydraulic machinery, which will solve the problem of rapid prediction of hydraulic machinery cavitation performance.

• Nuclear Engineering and Technology
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• v.52 no.11
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• pp.2471-2478
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• 2020

Pumps are essential machinery in the various industries. With the development of high-speed and large-scale pumps, especially high energy density, high requirements have been imposed on the vibration and noise performance of pumps, and cavitation is an important source of vibration and noise excitation in pumps, so it is necessary to improve pumps cavitation performance. The modern pump optimization design method mainly adopts parameterization and artificial intelligence coupling optimization, which requires direct correlation between geometric parameters and pump performance. The existing cavitation performance calculation method is difficult to be integrated into multi-objective automatic coupling optimization. Therefore, a fast prediction method for pump cavitation performance is urgently needed. This paper proposes a novel cavitation prediction method based on impeller pressure isosurface at single-phase media. When the cavitation occurs, the area of pressure isosurface S_iso increases linearly with the NPSH_a decrease. This demonstrates that with the development of cavitation, the variation law of the head with the NPSH_a and the variation law of the head with the area of pressure isosurface are consistent. Therefore, the area of pressure isosurface S_iso can be used to predict cavitation performance. For a certain impeller blade, since the area ratio R_s is proportional to the area of pressure isosurface S_iso, the cavitation performance can be predicted by the R_s. In this paper, a new cavitation performance prediction method is proposed, and the feasibility of this method is demonstrated in combination with experiments, which will greatly accelerate the pump hydraulic optimization design.

• Proceedings of the KSME Conference
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• 2001.06e
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• pp.619-624
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• 2001

A performance test facility for turbopump inducer cavitation was developed and the inducer cavitation performance tests were performed. Major components of the performance test facility are driving unit, test section, piping, water tank, and data acquisition and control system. The maximum of testing capability of this facility are as follows: flow rate - 30kg/s; pressure - 13 bar; rotational speed 10,000rpm. This cavitation test facility is characterized by the booster pump installed at the outlet of the pump that extends the flow rate range, and by the pressure control system that makes the line pressure down to vapor pressure. The vacuum pump is used for removing the dissolved air in the water as well as the line pressure. Performance tests were carried out and preliminary data of test model inducer were obtained. The cavitation performance test and cavitation bubble flow visualization were also made. This facility is originally designed for turbopump inducer performance test and cavitation test. However it can be applied to the pump impeller performance test in the future with little modification.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2004.03a
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• pp.240-244
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• 2004

Characteristics of steady and unsteady cavitation in a turbopump inducer were investigated in this paper. To see the effect of tip clearance on the inducer performance, three cases of tip clearance were tested. The helical inducer, which has two blades with inlet tip blade angle of 7.8 degree and tip solidity of 2.7, was tested in the water. In the non-cavitating condition, the inducer head decreased with increase in the tip clearance. Rotating cavitation and cavitation surge were observed through unsteady pressure measurements at the inducer inlet. The cell number and propagation speed of the rotating cavitation were determined through cross-correlation analysis. During the rotating cavitation one cell rotated at the same rotational speed as that of the inducer rotation and the cavitation surge did not rotate. The critical cavitation number increased with increase in the tip clearance at the same flow rate, but the change of critical cavitation number was small at the nominal flow rate.

• The KSFM Journal of Fluid Machinery
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• v.5 no.1 s.14
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• pp.27-32
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• 2002

The turbopump inducer cavitation is very important for the success of a liquid rocket engine. In this study, the performance test and cavitation performance test were carried out at various rotational speeds with two inducers of different diameter. The rotational speed was varied by 4000, 6000, and 8000 rpm, and the size effect was tested for the normal inducer and twice-enlarged one. The hydraulic performance results showed that the similarity was satisfied over the entire test range of the present study. The blade thickness effect was examined and showed that the increased blade thickness resulted in decreased efficiency and worse cavitation performance for the large tip clearance. The cavitation performance test results showed that the breakdown NPSH increased as the flow coefficient, and was not affected by the rotational speed.

• 유체기계공업학회:학술대회논문집
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• 2001.11a
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• pp.229-234
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• 2001

The turbopump inducer cavitation is very important for the success of a Liquid rocket engine. In this study the performance test and cavitation performance test were carried out at various rotational speed with two different diameter inducers. The rotational speed were varied 4000, 6000, 8000 rpm and the variation to the diameter of an inducer were taken as design size and 2 times enlarged size. The major results of the present study were as follows. 1. The hydraulic performance results showed that the similarity was met over the entire test range of the present study. 2. The blade thickness effect was examined and showed that the increased blade thickness resulted in decreased efficiency and worse cavitation performance for large tip clearance. 3. The cavitation performance test results showed that the breakdown NPSH increases as the flow coefficient and does not affected by the rotational speed.

• Journal of the Society of Naval Architects of Korea
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• v.60 no.1
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• pp.1-9
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• 2023

In order to improve the propeller cavitation performance composed of Cavitation Inception Speed (CIS), cavitation extent and pressure fluctuation, it needs to improve the wake distribution that flows into the propeller. The warship propeller cavitation is strongly influenced by the wake created at the V-strut of various appendages. The inflow characteristics of the V-strut were investigated using Computational Fluid Dynamics (CFD) and the twisted angles of the V-strut were aligned with upstream flow. The resistance and self-propulsion tests for the model ship with the existing and modified V-struts were conducted in Towing Tank (TT), and wake distribution, CIS, cavitation observation and pressure fluctuation tests were conducted in Large Cavitation Tunnel (LCT). The propeller behind the modified V-strut showed better cavitation characteristics than that behind the existing V-strut. Another model test was conducted to investigate rudder cavitation performance by the change of the V-strut. The rudder cavitation characteristics were not improved by the change of the operating conditions. On the basis of the present study, it is thought that the stern appendages for better propeller cavitation performance would be developed.

• Tribology and Lubricants
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• v.26 no.4
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• pp.209-218
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• 2010

In this study, the effect of dimensions and location of oil grooves on the static performance of a cylindrical journal bearing is analyzed numerically. Axial length, circumferential length and location of oil grooves are considered as parameters. Cavitation occurs within the diverging region of a journal bearing. The distribution of cavitation region where cavitation occurs varies with dimensions and location of oil grooves and affects the performance of a journal bearing. Elrod's cavitation algorithm which implements JFO boundary conditions based on the principle of mass conservation at the interfaces between cavitation and full film region is adopted in order to consider the effect of cavitation. The result shows that parameters, especially location of oil grooves have a great effect on the static performance of a journal bearing.

• Proceedings of the KSME Conference
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• 2008.11b
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• pp.2434-2439
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• 2008

This paper was studied on the cavitation instability of a Solution Pump Inducer in an absorption chiller-heater. Inlet pressure of LiBr and rotational speed at nominal mode are 2,800 Pa and 3,500 rpm respectively. Due to the marginal operation of available NPSH, the cavitation performance of the inducer is critical for the stable operation without the deterioration of head performance. In the study, cavitation performance and its mode of instability was investigated experimentally. Water was used as the working fluid and the test inducer was scaled up as 1.75 times for detail measurements and flow visualization. Inlet pressure was controlled by a vacuum pump. This research focused on types of cavitation instability and phenomena to investigate the possibility of harmful damage due to cavitation instability. Casing wall pressure and instantaneous inlet pressure was measured to observe the unsteady flow characteristics. Through the visualization and spectrum analysis of pressure, the occurrence region and intensity of asymmetric cavitation and cavitation surge are analyzed in the test inducer.

• 유체기계공업학회:학술대회논문집
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• 2001.11a
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• pp.185-190
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• 2001

The cavitation causes suction performance and efficiency of the high-speed pump to be reduced significantly To diminish these effects, the inducer has been used. Most of the inducer is designed at a maximum efficiency point of the pump, therefore suction performance drop due to effects of flow separation and inlet inverse flow is often observed at off-design point. The objective of this study is to find out the cavitation modes at various conditions by applying event detection technique and to design an inducer reducing cavitation. The pressure fluctuations at each cavitating condition were measured at inducer inlet and outlet locations using pressure transducers, which were located 90 degrees apart from each other to identify the cavitation modes. The time-frequency characteristics were analyzed by using Choi-williams distribution. In the second part of this paper, the inducer design method which uses nominal performance characteristic and onset condition of cavitation is introduced and applied to real situation.