Thermodynamic Effect and Cavitation Performance of a Cavitating Centrifugal Pump

2011 ◽  
Author(s):  
Teiichi Tanaka
Keyword(s):  
Centrifugal Pump ◽  
Liquid Nitrogen ◽  
Cold Water ◽  
Experimental Results ◽  
Flow Coefficient ◽  
Test Setup ◽  
Cavitation Performance ◽  
Thermodynamic Effect ◽  
Delivery Pressure ◽  
Temperature Depression

The thermodynamic effect which affects the cavitation performance of a cavitating centrifugal pump was investigated experimentally using liquid nitrogen. To measure the pump cavitation performance, a test setup which could carry out experiments using both liquid nitrogen and cold water was constructed. The test setup consisted of a suction tank, a test pump, a mass flow meter, a ball valve and pipes. Vacuum-insulated pipes were used. The test pump was a centrifugal type magnetic pump, and two impellers, which differed in cavitation performance, were used in experiments. Cavitation performance using liquid nitrogen or cold water could be obtained from the measurement of the pump suction and delivery pressure, the pump suction and delivery temperature, and the discharge flow rate. And an improvement in pump cavitation performance could be seen when comparing the experimental results from using liquid nitrogen with those from using cold water. The experimental results indicated that cavitation performance using liquid nitrogen was better than that using cold water. This improvement in cavitation performance was thought to be due to the thermodynamic effect of cavitation. And the estimated temperature depression due to the thermodynamic effect decreased with a decreasing flow coefficient. Moreover, it was shown that the estimated temperature depression due to the thermodynamic effect on the low cavitation performance impeller was larger than that on the high cavitation performance impeller at the same flow coefficient.

Thermodynamic Effect on a Cavitating Inducer in Liquid Nitrogen

2006 ◽  
Vol 129 (3) ◽  
pp. 273-278 ◽  
Author(s):  
Yoshiki Yoshida ◽  
Kengo Kikuta ◽  
Satoshi Hasegawa ◽  
Mitsuru Shimagaki ◽  
Takashi Tokumasu
Keyword(s):  
Liquid Nitrogen ◽  
Cavity Length ◽  
Cold Water ◽  
Cavitation Number ◽  
Experimental Investigations ◽  
Thermodynamic Effect ◽  
Blade Tip ◽  
Cryogenic Flow ◽  
The Difference ◽  
Temperature Depression

For experimental investigations of the thermodynamic effect on a cavitating inducer, it is nesessary to observe the cavitation. However, visualizations of the cavitation are not so easy in cryogenic flow. For this reason, we estimated the cavity region in liquid nitrogen based on measurements of the pressure fluctuation near the blade tip. In the present study, we focused on the length of the tip cavitation as a cavitation indicator. Comparison of the tip cavity length in liquid nitrogen (80K) with that in cold water (296K) allowed us to estimate the strength of the thermodynamic effect. The degree of thermodynamic effect was found to increase with an increase of the cavity length. The temperature depression was estimated from the difference of the cavitation number of corresponding cavity condition (i.e., cavity length) between in liquid nitrogen and in cold water. The estimated temperature depression caused by vaporization increased rapidly when the cavity length extended over the throat. In addition, the estimated temperature inside the bubble nearly reached the temperature of the triple point when the pump performance deteriorated.

Influence of Rotational Speed on Thermodynamic Effect in a Cavitating Inducer

2009 ◽  
Author(s):  
Kengo Kikuta ◽  
Yoshiki Yoshida ◽  
Tomoyuki Hashimoto ◽  
Hideaki Nanri ◽  
Tsutomu Mizuno ◽  
...  
Keyword(s):  
Liquid Nitrogen ◽  
Rotational Speed ◽  
Cavity Length ◽  
Cold Water ◽  
Thermodynamic Effect ◽  
Suction Performance ◽  
Temperature Depression

To estimate the influence of velocity on the thermodynamic effect, we conducted experiments in which the inducer rotational speed was changed in liquid nitrogen. The experiments in liquid nitrogen and in cold water allowed us to estimate the amplitude of the thermodynamic effect. In the experiment with lower rotational speed, suction performance was improved. The cavity length at lower rotational speed was shorter than that at higher speed. Thus, we confirmed that the degree of the thermodynamic effect depends on the rotational speed as lower rotational speed suppresses cavity length. Temperature depression was estimated based on a comparison of cavity length in liquid nitrogen and that in water. We found that the degree of temperature depression became smaller when the rotational speed was lower.

Thermodynamic Effect on a Cavitating Inducer in Liquid Nitrogen

2005 ◽  
Author(s):  
Yoshiki Yoshida ◽  
Kengo Kikuta ◽  
Satoshi Hasegawa ◽  
Mitsuru Shimagaki ◽  
Noriaki Nakamura ◽  
...  
Keyword(s):  
Liquid Nitrogen ◽  
Triple Point ◽  
Cavity Length ◽  
Cold Water ◽  
Experimental Investigations ◽  
Pump Performance ◽  
Thermodynamic Effect ◽  
Blade Tip ◽  
Cryogenic Flow ◽  
Temperature Depression

For experimental investigations of the thermodynamic effect on a cavitating inducer, it is nesessary to observe the cavitation. However, visualizations of the cavitation are not so easy in cryogenic flow. For this reason, we estimated the cavity region in liquid nitrogen based on measurements of the pressure fluctuation near the blade tip. In the present study, we focused on the length of the tip cavitation as a cavitation parameter. Comparison of the tip cavity length in liquid nitrogen (80 K) with that in cold water (296 K) allowed us to estimate the strength of the thermodynamic effect. The degree of thermodynamic effect was found to increase with an increase of the cavity length. The estimated temperature depression caused by vaporization increased rapidly when the cavity length extended over the throat. In addition, the estimated temperature inside the bubble nearly reached the temperature of the triple point when the pump performance deteriorated.

Thermodynamic Effect on Cavitation Performances and Cavitation Instabilities in an Inducer

2008 ◽  
Vol 130 (11) ◽  
Author(s):  
Kengo Kikuta ◽  
Yoshiki Yoshida ◽  
Mitsuo Watanabe ◽  
Tomoyuki Hashimoto ◽  
Katsuji Nagaura ◽  
...  
Keyword(s):  
Liquid Nitrogen ◽  
Temperature Difference ◽  
Cavity Length ◽  
Cold Water ◽  
Experimental Results ◽  
Working Fluid ◽  
Blade Passage ◽  
Thermodynamic Effect

Based on the length of the tip cavitation as an indication of cavitation, we focused on the effect of thermodynamics on cavitation performances and cavitation instabilities in an inducer. Comparison of the tip cavity length in liquid nitrogen (76K and 80K) as working fluid with that in cold water (296K) allowed us to estimate the strength of the thermodynamic effect on the cavitations. The degree of thermodynamic effect was found to increase with an increase of the cavity length, particularly when the cavity length extended over the throat of the blade passage. In addition, cavitation instabilities occurred both in liquid nitrogen and in cold water when the cavity length increased. Subsynchronous rotating cavitation appeared both in liquid nitrogen and in cold water. In the experiment using liquid nitrogen, the temperature difference between 76K and 80K affected the range in which the subsynchronous rotating cavitation occurred. In contrast, deep cavitation surge appeared only in cold water at lower cavitation numbers. From these experimental results, it was concluded that when the cavity length extends over the throat, the thermodynamic effect also affects the cavitation instabilities as a “thermal damping” through the unsteady cavitation characteristics.

scholarly journals Influence of Thermodynamic Effect on Blade Load in a Cavitating Inducer

2010 ◽  
Vol 2010 ◽  
pp. 1-7 ◽  
Author(s):  
Kengo Kikuta ◽  
Noriyuki Shimiya ◽  
Tomoyuki Hashimoto ◽  
Mitsuru Shimagaki ◽  
Hideaki Nanri ◽  
...  
Keyword(s):  
Pressure Distribution ◽  
Liquid Nitrogen ◽  
Cavity Length ◽  
Cold Water ◽  
Pressure Rise ◽  
Cavitation Number ◽  
Design Parameters ◽  
Trailing Edge ◽  
Thermodynamic Effect ◽  
Blade Tip

Distribution of the blade load is one of the design parameters for a cavitating inducer. For experimental investigation of the thermodynamic effect on the blade load, we conducted experiments in both cold water and liquid nitrogen. The thermodynamic effect on cavitation notably appears in this cryogenic fluid although it can be disregarded in cold water. In these experiments, the pressure rise along the blade tip was measured. In water, the pressure increased almost linearly from the leading edge to the trailing edge at higher cavitation number. After that, with a decrease of cavitation number, pressure rise occurred only near the trailing edge. On the other hand, in liquid nitrogen, the pressure distribution was similar to that in water at a higher cavitation number, even if the cavitation number as a cavitation parameter decreased. Because the cavitation growth is suppressed by the thermodynamic effect, the distribution of the blade load does not change even at lower cavitation number. By contrast, the pressure distribution in liquid nitrogen has the same tendency as that in water if the cavity length at the blade tip is taken as a cavitation indication. From these results, it was found that the shift of the blade load to the trailing edge depended on the increase of cavity length, and that the distribution of blade load was indicated only by the cavity length independent of the thermodynamic effect.

Thermodynamic Effect on Sub-Synchronous Rotating Cavitation and Surge Mode Oscillation in a Space Inducer

2009 ◽  
Author(s):  
Yoshiki Yoshida ◽  
Hideaki Nanri ◽  
Kengo Kikuta ◽  
Yusuke Kazami ◽  
Yuka Iga ◽  
...  
Keyword(s):  
Liquid Nitrogen ◽  
Cold Water ◽  
Acoustic Resonance ◽  
Pipe System ◽  
Thermodynamic Effect ◽  
Mode Oscillation ◽  
Cavitation Instability ◽  
Different Temperatures ◽  
Thermodynamic Effects ◽  
The Relationship

The relationship between the thermodynamic effect and sub-synchronous rotating cavitation was investigated with a focus on cavity fluctuations. Experiments on a three-bladed inducer were conducted with liquid nitrogen at different temperatures (74 K, 78K and 83 K) to confirm the dependence of the thermodynamic effects. Sub-synchronous rotating cavitation appeared at lower cavitation numbers in liquid nitrogen at 74 K, the same as in cold water. In contrast, in liquid nitrogen at 83 K, the occurrence of sub-synchronous rotating cavitation was suppressed because of the increase of the thermodynamic effect due to the rising temperature. Furthermore, unevenness of cavity length under synchronous rotating cavitation at 83 K was also decreased by the thermodynamic effect. However, surge mode oscillation occurred simultaneously under this weakened synchronous rotating cavitation. Cavity lengths on the blades oscillated with the same phase and maintained the uneven cavity pattern. It was inferred that the thermodynamic effect weakened the peripheral cavitation instability, i.e., synchronous rotating cavitation, and thus axial cavitation instability, i.e., surge mode oscillation, was easily induced due to the synchronization of the cavity fluctuation with an acoustic resonance in the present experimental inlet-pipe system.

Comparison of Transport Equation-Based Cavitation Models and Application to Industrial Pumps with Inducers

2021 ◽  
Author(s):  
Enver Karakas ◽  
Nehir Tokgoz ◽  
Hiroyoshi Watanabe ◽  
Matteo Aureli ◽  
Cahit Evrensel
Keyword(s):  
Transport Equation ◽  
Centrifugal Pump ◽  
Experimental Results ◽  
Vaporization Rate ◽  
Centrifugal Pumps ◽  
Cavitation Model ◽  
Cavitation Performance ◽  
High Dependency ◽  
The Impact ◽  
Empirical Constants

Abstract This paper investigates and compares four commonly used flow transport equation-based cavitation models and their applicability to predict the cavitation performance and bubble dynamics of an industrial centrifugal pump with a helical inducer. The main purpose of this study is to identify the most appropriate cavitation model and the associated empirical constants for calculating the cavitation performance of centrifugal pumps with inducers. Each cavitation model is reviewed in detail and the uniqueness of each model is outlined. These cavitation models are incorporated in a computational fluid dynamics code to study the vaporization and condensation transport rate of the fluid. Experimental tests are conducted on the pump to determine the true cavitation performance in terms of Net Positive Suction Head (NPSH). Experimental results are compared to simulation results for different cavitation models to validate accuracy and assumptions of each model, along with the empirical constants. Lastly, bubble formation, cavitation inception, and bubble growth predicted by each cavitation model are compared with the experimental results. A sensitivity analysis is conducted in order to determine the impact of each set of empirical constants to the condensation and the vaporization rate in the centrifugal pump. Results show that two of the cavitation models exhibit high dependency on the empirical constants in terms of change in vaporization rate. Modifications to empirical constants for two of the four cavitation models are suggested to obtain agreement with the experimentally observed cavitation behavior and better predict NPSH performance for the industrial pump studied.

Thermodynamic Effect on Subsynchronous Rotating Cavitation and Surge Mode Oscillation in a Space Inducer

2011 ◽  
Vol 133 (6) ◽  
Author(s):  
Yoshiki Yoshida ◽  
Hideaki Nanri ◽  
Kengo Kikuta ◽  
Yusuke Kazami ◽  
Yuka Iga ◽  
...  
Keyword(s):  
Liquid Nitrogen ◽  
Cold Water ◽  
Acoustic Resonance ◽  
Pipe System ◽  
Thermodynamic Effect ◽  
Mode Oscillation ◽  
Cavitation Instability ◽  
Different Temperatures ◽  
Thermodynamic Effects ◽  
The Relationship

The relationship between the thermodynamic effect and subsynchronous rotating cavitation was investigated with a focus on cavity fluctuations. Experiments on a three-bladed inducer were conducted with liquid nitrogen at different temperatures (74, 78, and 83 K) to confirm the dependence of the thermodynamic effects. Subsynchronous rotating cavitation appeared at lower cavitation numbers in liquid nitrogen at 74 K, the same as in cold water. In contrast, in liquid nitrogen at 83 K the occurrence of subsynchronous rotating cavitation was suppressed because of the increase of the thermodynamic effect due to the rising temperature. Furthermore, unevenness of cavity length under synchronous rotating cavitation at 83 K was also decreased by the thermodynamic effect. However, surge mode oscillation occurred simultaneously under this weakened synchronous rotating cavitation. Cavity lengths on the blades oscillated with the same phase and maintained the uneven cavity pattern. It was inferred that the thermodynamic effect weakened peripheral cavitation instability, i.e., synchronous rotating cavitation, and thus axial cavitation instability, i.e., surge mode oscillation, was easily induced due to the synchronization of the cavity fluctuation with an acoustic resonance in the present experimental inlet-pipe system.

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