Transient Behavior of a Cavitating Centrifugal Pump at Rapid Change in Operating Conditions—Part 3: Classifications of Transient Phenomena

1999 ◽  
Vol 121 (4) ◽  
pp. 857-865 ◽  
Author(s):  
T. Tanaka ◽  
H. Tsukamoto
Keyword(s):  
Water Column ◽  
Centrifugal Pump ◽  
Rapid Change ◽  
Transient Behavior ◽  
Operating Conditions ◽  
Critical Conditions ◽  
Pump System ◽  
Column Separation ◽  
Cavitation Bubbles ◽  
Flow Mechanisms

Analytical studies were developed on the transient behavior of a cavitating centrifugal pump during the transient operations, including the sudden opening/closure of the discharge valve and the pump startup/shutdown. In order to investigate the mechanism of the low cycle oscillations of both the pressure and the flowrate at a rapid change of the pump system conditions, an unsteady flow analysis was made for the cavitating pump-system by assuming the transient pump performance to be quasi-steady. The calculated unsteady pressure and flowrate during the transient period agree with the corresponding measured time histories. It is shown that the fluctuations of delivery pressure and discharge flowrate at pump rapid startup or sudden valve opening are caused by peculiar oscillating cavitation dynamics inside the pump at rapid increase in flowrate, while the fluctuations at pump rapid shutdown or sudden valve closure are related to the collapse of cavitation bubbles or water column separation in the suction pipe at rapid decrease in flowrate. Moreover, the occurrence of transient fluctuations in pressure and flowrate was predicted by examining the critical condition which creates the occurrence of two different flow mechanisms i.e., (A) oscillating cavitation and (B) water column separation including also the collapse of the cavitation bubbles. These flow mechanisms were represented with two flow models i.e., (A) unsteady cavitating flow incorporating effects of cavitation compliance and mass flow gain factor and expressed by a set of ordinary differential equations solved with the Cardano Method and (B) water-hammer type model including Discrete Free Gas Model and solved with method of characteristics. The calculated critical conditions for the occurrence of the oscillating cavitation and water column separation agree qualitatively with measured ones.

Transient Behavior of a Cavitating Centrifugal Pump at Rapid Change in Operating Conditions—Part 1: Transient Phenomena at Opening/Closure of Discharge Valve

1999 ◽  
Vol 121 (4) ◽  
pp. 841-849 ◽  
Author(s):  
T. Tanaka ◽  
H. Tsukamoto
Keyword(s):  
Centrifugal Pump ◽  
High Speed ◽  
Rapid Change ◽  
Transient Behavior ◽  
Video Camera ◽  
Operating Conditions ◽  
Centrifugal Pumps ◽  
Transient Period ◽  
Discharge Valve ◽  
Cavitation Behavior

A series of studies on the dynamic characteristics of noncavitating centrifugal pumps were extended to the cavitating case. An experimental study was carried out on the transient behavior of a cavitating centrifugal pump at the sudden opening/closure of the discharge valve. Cavitation behavior in the centrifugal pump was visualized during the transient period by using high speed video camera, and instantaneous pressure and flowrate were measured at the pump suction and discharge section with rotational speed during the transient period. Unsteady pressure, as well as flowrate, was related to the time-dependent cavitation behavior. As a result of the present study, pressure and flowrate fluctuations were found to occur due to oscillating cavitation or water column separation at rapid transient operations.

Transient Behavior of a Cavitating Centrifugal Pump at Rapid Change in Operating Conditions—Part 2: Transient Phenomena at Pump Startup/Shutdown

1999 ◽  
Vol 121 (4) ◽  
pp. 850-856 ◽  
Author(s):  
T. Tanaka ◽  
H. Tsukamoto
Keyword(s):  
Centrifugal Pump ◽  
Pressure Fluctuations ◽  
Rapid Change ◽  
Transient Behavior ◽  
Operating Conditions ◽  
Pressure Oscillations ◽  
Transient Phenomena ◽  
Discharge Valve ◽  
Delivery Pressure ◽  
Cavitation Behavior

In the 1st report, the dynamic behavior of a cavitating centrifugal pump was related to the transient phenomena at the sudden opening/closure of the discharge valve. In this paper, the experimental study was extended to the transient behavior of the cavitating centrifugal pump at rapid starting/stopping of the pump. Unsteady pressures and flowrate were related to time-dependent cavitation behavior in a similar manner as for the rapid operation of the discharge valve. As a result of the present study, pressure fluctuations were found to occur due to water column separation at the sudden stop of the pump similarly to pressure oscillations associated with the sudden closure of the discharge valve. Moreover, the experimental results on the transient behavior at pump startup indicated that the transient fluctuations of delivery pressure and discharge flowrate are caused by oscillating cavitation similarly to the ones occurring at the opening of the discharge valve.

Centrifugal Pump Leak-Free Technology Introduction and Its Applications in EPR Nuclear Power Plant

2010 ◽  
Author(s):  
Guohui Cong ◽  
Ling Zhang
Keyword(s):  
Power Plant ◽  
Nuclear Power Plant ◽  
Centrifugal Pump ◽  
Nuclear Power ◽  
Operating Conditions ◽  
Critical Conditions ◽  
Mechanical Seal ◽  
Centrifugal Pumps ◽  
Canned Motor ◽  
Magnetic Drive

Environmental protection requirement is more and more critical now, and it increases the request to prevent dangerous liquid to leak outside in nuclear power plant too. Centrifugal pumps are the most important active equipments in nuclear power plant, but there is a shaft clearance between rotor and stator of centrifugal pump. The shaft clearance can lead pumped fluid to the outside, so the environment may be polluted by the leakage. In some critical conditions such as transferring high radioactive fluid in the pump, the leakage shall be totally forbidden. So solutions have to be found to make centrifugal pumps totally leak-free for applications in nuclear power plant. Normally there are three leak-free technologies for centrifugal pumps: mechanical seal with auxiliary system, canned motor and magnetic drive. In this paper, all the three leak-free technologies and some of their applications in EPR 3rd generation PWR nuclear power plants are presented and discussed. The results show that in EPR nuclear power plant, canned motor pumps can be preferably used for strict environmental requirement of leak-free if the pump power and operating conditions are applicable. For other conditions, pumps with double mechanical seal can also be used with additional sealing water system support. For centrifugal pumps with magnetic drive are not so applicable in high pressure condition, and the safety aspect is weaker than canned motor pumps, generally they are not used in EPR nuclear power plant at present.

scholarly journals X-Ray Measurements in a Cavitating Centrifugal Pump During Fast Start-Ups

2013 ◽  
Vol 135 (4) ◽  
Author(s):  
S. Duplaa ◽  
O. Coutier-Delgosha ◽  
A. Dazin ◽  
G. Bois
Keyword(s):  
Centrifugal Pump ◽  
Rocket Engine ◽  
Transient Behavior ◽  
Operating Conditions ◽  
Centrifugal Impeller ◽  
X Ray ◽  
Speed Increase ◽  
Start Up ◽  
Fast Start ◽  
Start Ups

The start-up of rocket engine turbopumps is generally performed in a few seconds or even less. It implies that these pumps reach their nominal operating conditions after a few rotations only. During the start-up, the flow evolution within the pump is governed by transient phenomena, based mainly on the flow rate and rotation speed increase. Significant pressure fluctuations, which may result in the development of cavitation, are observed. A centrifugal impeller whose transient behavior during start-ups has been detailed in a previous publication is considered. Three different cases of fast start-ups have been identified according the final operating point (Duplaa et al., 2010, “Experimental Study of a Cavitating Centrifugal Pump During Fast Start-Ups,” ASME J. Fluids Eng., 132(2), p. 021301). The aim of this paper is to analyze the evolution during the start-ups of the local amount of vapor in the blade to blade channels of the pump by fast X-ray imaging. This technique has enabled to calculate the time-evolution of the fluid density within the pump, which appears to be correlated with pressure time-evolutions. For each investigated start-up, X-ray measurements have been performed at three different sections of the impeller height. For each investigated start-up and section tested, measurements have been performed for several initial positions of the impeller, to estimate the measurement uncertainty, and to obtain records from different beam angles, like in tomography.

scholarly journals Experimental Study of a Cavitating Centrifugal Pump During Fast Startups

2010 ◽  
Vol 132 (2) ◽  
Author(s):  
S. Duplaa ◽  
O. Coutier-Delgosha ◽  
A. Dazin ◽  
O. Roussette ◽  
G. Bois ◽  
...  
Keyword(s):  
Centrifugal Pump ◽  
Flow Rate ◽  
Transient Flow ◽  
Flow Behavior ◽  
Rocket Engine ◽  
Rotation Velocity ◽  
Transient Behavior ◽  
Operating Conditions ◽  
Physical Analysis ◽  
Different Types

The startup of rocket engine turbopumps is generally performed only in a few seconds. It implies that these pumps reach their nominal operating conditions after only a few rotations. During these first rotations of the blades, the flow evolution in the pump is governed by transient phenomena, based mainly on the flow rate and rotation speed evolution. These phenomena progressively become negligible when the steady behavior is reached. The pump transient behavior induces significant pressure fluctuations, which may result in partial flow vaporization, i.e., cavitation. An existing experimental test rig has been updated in the LML Laboratory (Lille, France) for the startups of a centrifugal pump. The study focuses on the cavitation induced during the pump startup. Instantaneous measurement of torque, flow rate, inlet and outlet unsteady pressures, and pump rotation velocity enable to characterize the pump behavior during rapid starting periods. Three different types of fast startup behaviors have been identified. According to the final operating point, the startup is characterized either by a single drop of the delivery static pressure, by several low-frequency drops, or by a water hammer phenomenon that can be observed in both the inlet and outlet of the pump. A physical analysis is proposed to explain these three different types of transient flow behavior.

Research on Cavitation Induced Noise in a Centrifugal Pump

2011 ◽  
Author(s):  
Bo Gao ◽  
Minguan Yang ◽  
Zhong Li ◽  
Can Kang
Keyword(s):  
Flow Field ◽  
Centrifugal Pump ◽  
High Frequency ◽  
Noise Level ◽  
Volume Fraction ◽  
Operating Conditions ◽  
Frequency Noise ◽  
Cavitation Flow ◽  
Cavitation Noise ◽  
Cavitation Bubbles

To study the cavitation flow field and cavitation induced noise features in a centrifugal pump, a model pump is chosen as the research object. Cavitation flow field at design and off-design operating conditions is visualized by high speed camera. The cavitation bubbles spatial distribution changing with pump net positive suction head (NPSH) value have been captured. Meanwhile, cavitation noise signals from the pump at the corresponding operating conditions have been acquired in the frequency band from 10 up to 8kHz. Noise levels at broadband frequency and discrete frequency, such as rotating frequency (RF) and blade pass frequency (BPF), are discussed. It is of help to recognize the relationship between cavitation bubbles and emitted noise spectrum characteristics. Experimental results indicate that the total noise level is unlikely to raise before and in the cavitation inception period. But sound pressure level (SPL) over high frequency broadband increases obviously, as well as SPL at BPF and half of that. It is hard to change at RF. When the NPSH goes down until to the onset of cavitation damage, cavitation cloud appears. The volume fraction of bubbles in every impeller passage is different. The total and high frequency noise level reach peak values near the NPSH critical point. The discrete tone at half of BPF also raises steeply. Cavitation bubbles are filled both on suction and pressure side of the blades in fully developed cavitation stage. Emitted noise energy fluctuates due to the unsteady features of internal flow in the pump.

Waterhammer Analysis of Pump Discharge Line With Several One-Way Surge Tanks

1967 ◽  
Vol 89 (4) ◽  
pp. 621-627
Author(s):  
H. Miyashiro
Keyword(s):  
Water Column ◽  
Digital Computer ◽  
Pump System ◽  
Column Separation ◽  
Discharge Line ◽  
Fundamental Equations

In some pumping plants several one-way surge tanks are installed to prevent water-column separation in the discharge line caused by failure of power to pumps. This paper describes a method of analysis of waterhammer in a pump system of this type. The analysis is carried out by solving the fundamental equations by a digital computer. An example is calculated and the results are compared with the measurements.

Study of Transient Behavior in Centrifugal Pump During Startup Period

2012 ◽  
Author(s):  
Yu-liang Zhang ◽  
Zu-chao Zhu ◽  
Bao-ling Cui ◽  
Yi Li
Keyword(s):  
Flow Field ◽  
Centrifugal Pump ◽  
Flow Rate ◽  
Transient Flow ◽  
Three Dimensional ◽  
Transient Behavior ◽  
Operating Conditions ◽  
Pipe System ◽  
Rotor Stator Interaction ◽  
Startup Period

To explore the transient characteristic of a centrifugal pump with the specific speed of 90 during startup period, the internal three-dimensional unsteady flow was solved by using CFD. Wherein to overcome the difficulty in implement of boundary conditions in numerical simulation, a closed-loop pipe system that includes a centrifugal pump was built to accomplish self-coupling calculation. The results show that at the very beginning of startup, flow rate rises slowly and non-dimensional head coefficient is much higher than quasi-steady value, the quasi-assumption can not be competent for predicting transient effect well. Moreover, the insufficient of energy conversion makes the evolvement of transient flow field lags behind that of quasi-steady flow field, i.e., kinetic energy can’t convert pressure energy in time during acceleration flow period. Rotor-stator interaction makes flow rate present slight fluctuation characteristic under stable operating conditions.

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