scholarly journals Effect of the Discharge Piping Scheme on the Pressure Fluctuations Induced from A Laboratory Pump

Proceedings ◽  
2018 ◽  
Vol 2 (23) ◽  
pp. 1488
Author(s):  
Guidong Li ◽  
Jorge Parrondo ◽  
Yang Wang
Keyword(s):  
Fluid Dynamic ◽  
Pressure Fluctuations ◽  
Negative Influence ◽  
Design Flow ◽  
Acoustic Properties ◽  
Characteristic Parameters ◽  
Pump Operation ◽  
Dynamic Noise ◽  
Unsteady Fluid ◽  
Opening And Closing

Fluid-dynamic noise induced by the unsteady fluid phenomena usually causes a negative influence on the hydraulic circuit system during the pump operation, especially at off-design flow rates. The spectrum of the pressure signals measured directly in the pipeline of the pump is usually employed to reflect the acoustic characteristic parameters of the fluid-dynamic noise of the pump itself. However, there exists a large difference between the spectrum characteristics directly measured and the actual characteristics of the acoustic source inside the pump due to the effects of the acoustic properties of the piping. Therefore, in order to verify the effect of the discharge piping on the pressure fluctuations of a laboratory pump, three different discharge piping schemes connected to the pump outlet were studied by opening and closing different valves. The results showed that the amplitude of the pressure pulsations in a constant monitor point changed with the shaft frequency and blade passing frequency. The variation range of the pressure pulsation magnitudes for the points monitored at the pump outlet is evidently larger than that for the points close to the cutwater of the volute.

scholarly journals Experimental Investigation on the Acoustic Scattering Matrix for a Centrifugal Pump

Proceedings ◽  
2018 ◽  
Vol 2 (23) ◽  
pp. 1489
Author(s):  
Guidong Li ◽  
Jorge Parrondo ◽  
Yang Wang
Keyword(s):  
Centrifugal Pump ◽  
Sound Source ◽  
Acoustic Pressure ◽  
Fluid Dynamic ◽  
Acoustic Scattering ◽  
Scattering Matrix ◽  
Acoustic Properties ◽  
Pressure Waves ◽  
Centrifugal Pumps ◽  
Dynamic Noise

Fluid-dynamic noise in centrifugal pumps as a significant sound source in piping systems has gained high attention due to the requirements of vibration and noise reduction in many fields. The acoustic characteristics of the fluid-dynamic noise from pumps are bound to be affected by the pipe ports and other piping components during the operation of the pump system. Therefore, the direct measurement of pressure pulsations in the pipeline of a test pump does not directly reflect the acoustic properties of the pump itself, because the coupling effects of the hydraulic system, which can even cause standing waves, may be seriously misleading in some situations. In this paper, an alternative experimental method has been applied to identify the so-called acoustic scattering matrix of a laboratory centrifugal pump. The elements of the scattering matrix characterize how the acoustic pressure waves are transmitted or reflected from the pump ports, i.e., it summarizes the passive acoustic properties of the pumps. For the tests, the test pump was connected in parallel to another auxiliary pump driven with a variable-frequency that played the role of an external sound source. The acoustic pressure waves induced in the suction and discharge pipes were mathematically decomposed into the corresponding incoming and exiting pressure waves travelling in the positive (P+) and negative (P−) directions respectively, by means of the two-microphone procedure. This paper shows the elements of the scattering matrix determined for the test pump as a function of frequency. These results represent a reference for subsequent theoretical research on the acoustic scattering matrix of centrifugal pumps.

Effects of short blades on performance and inner flow characteristics of a low-specific-speed centrifugal pump

2017 ◽  
Vol 231 (4) ◽  
pp. 290-302 ◽  
Author(s):  
Can Kang ◽  
Ning Mao ◽  
Chen Pan ◽  
Yang Zhu ◽  
Bing Li
Keyword(s):  
Centrifugal Pump ◽  
Flow Rate ◽  
Pressure Fluctuations ◽  
Flow Characteristics ◽  
Low Flow ◽  
Back Surface ◽  
Flow Rates ◽  
Pump Operation ◽  
Low Specific Speed ◽  
Specific Speed

A low-specific-speed centrifugal pump equipped with long and short blades is studied. Emphasis is placed on the pump performance and inner flow characteristics at low flow rates. Each short blade is intentionally shifted towards the back surface of the neighboring long blade, and the outlet parts of the short blades are uniformly shortened. Unsteady numerical simulation is conducted to disclose inner flow patterns associated with the modified design. Thereby, a comparison is enabled between the two schemes featured by different short blades. Both practical operation data and numerical results support that the deviation and cutting of the short blades can eliminate the positive slope of pump head curve at low flow rates. Therefore, the modification of short blades improves the pump operation stability. Due to the shortening of the outlet parts of the short blades, velocity distributions between impeller outlet and radial diffuser inlet exhibit explicitly altered circumferential flow periodicity. Pressure fluctuations in the radial diffuser are complex in terms of diversified periodicity and amplitudes. Flow rate influences pressure fluctuations in the radial diffuser considerably. As flow rate decreases, the regularity of the orbit of hydraulic loads exerted upon the impeller collapses while hydraulic loads exerted upon the short blades remain circumferentially periodic.

Direct Measurement of Unsteady Fluid Dynamic Forces for a Hovering Dragonfly

AIAA Journal ◽  
2005 ◽  
Vol 43 (12) ◽  
pp. 2475-2480 ◽  
Author(s):  
Manabu Yamamoto ◽  
Koji Isogai
Keyword(s):  
Direct Measurement ◽  
Fluid Dynamic ◽  
Dynamic Forces ◽  
Unsteady Fluid

Increasing Inducer Stability and Suction Performance With a Stability Control Device

2018 ◽  
Vol 141 (1) ◽  
Author(s):  
R. Lundgreen ◽  
D. Maynes ◽  
S. Gorrell ◽  
K. Oliphant
Keyword(s):  
Fluid Dynamic ◽  
Leading Edge ◽  
High Energy ◽  
Stability Control ◽  
Control Device ◽  
Design Flow ◽  
Flow Coefficient ◽  
Blade Tip ◽  
Rotordynamic Forces ◽  
Suction Performance

An inducer is used as the first stage of high suction performance pump. It pressurizes the fluid to delay the onset of cavitation, which can adversely affect performance in a centrifugal pump. In this paper, the performance of a water pump inducer has been explored with and without the implementation of a stability control device (SCD). This device is an inlet cover bleed system that removes high-energy fluid near the blade leading edge and reinjects it back upstream. The research was conducted by running multiphase, time-accurate computational fluid dynamic (CFD) simulations at the design flow coefficient and at low, off-design flow coefficients. The suction performance and stability for the same inducer with and without the implementation of the SCD has been explored. An improvement in stability and suction performance was observed when the SCD was implemented. Without the SCD, the inducer developed backflow at the blade tip, which led to rotating cavitation and larger rotordynamic forces. With the SCD, no significant cavitation instabilities developed, and the rotordynamic forces remained small. The lack of cavitation instabilities also allowed the inducer to operate at lower inlet pressures, increasing the suction performance of the inducer.

Influence of wall roughness on the static performance and pressure fluctuation characteristics of a double-suction centrifugal pump

2018 ◽  
Vol 232 (7) ◽  
pp. 826-840 ◽  
Author(s):  
Zhifeng Yao ◽  
Min Yang ◽  
Ruofu Xiao ◽  
Fujun Wang
Keyword(s):  
Centrifugal Pump ◽  
Pressure Fluctuation ◽  
Pressure Fluctuations ◽  
Design Flow ◽  
Experimental Investigations ◽  
Wall Roughness ◽  
Detached Eddy Simulation ◽  
Centrifugal Pumps ◽  
Eddy Simulation ◽  
Static Performance

The unsteady flow field and pressure fluctuations in double-suction centrifugal pumps are greatly affected by the wall roughness of internal surfaces. To determine the wall roughness effect, numerical and experimental investigations were carried out. Three impeller schemes for different wall roughness were solved using detached eddy simulation, and the performance and pressure fluctuations resolved by detached eddy simulation were compared with the experimental data. The results show that the effects of wall roughness on the static performance of a pump are remarkable. The head and efficiency of the tested double-suction centrifugal pump are raised by 2.53% and 6.60% respectively as the wall roughness is reduced by means of sand blasting and coating treatments. The detached eddy simulation method has been proven to be accurate for the prediction of the head and efficiency of the double-suction centrifugal pump with roughness effects. The influence of the roughness on pressure fluctuation is greatly dependent on the location relative to the volute tongue region. For locations close to the volute tongue, the peak-to-peak value of the pressure fluctuations of a wall roughness of Ra = 0.10 mm may be 23.27% larger than the case where Ra = 0.02 mm at design flow rate.

Based on the Principle of Approximate Model Established Model Test Rig Simulation of the Actual Test Bench

2012 ◽  
Vol 614-615 ◽  
pp. 14-19
Author(s):  
Min Xue ◽  
Zhu Ma ◽  
Yan Jun Li ◽  
Long Bin Yang ◽  
Fang Zhu
Keyword(s):  
Wave Phenomenon ◽  
Fluid Dynamic ◽  
Pressure Fluctuations ◽  
Steam Pressure ◽  
Approximate Model ◽  
Two Phase ◽  
Small Model ◽  
Main Steam ◽  
Relationship Of ◽  
Physical Phenomena

For Marine pressurization boiler dynamic system, when the boiler provide steam for air storage, boiler drum pressure and steam pressure will have produced a wave phenomenon; In order to research this a wave phenomenon, considering similar principles , establish the model experiments to simulate the wave process. Due to boiler provide steam for air storage that involves in many complex physical processes, including two phase flow, heat transfer, braising physical phenomena. By a simple analysis, to be completely similar to the model, model must be the same as the real situation; it will lose the small model experimental significance. According to this problem, we consider use approximate modeling method which usually used in engineering, seize the pressure fluctuations of the main contradictions; Put forward in the process of considering only reflect pressure fluctuations of local fluid dynamic field project of similar approximation, Finally we get the fluctuation relationship of the actual conditions and small model experiment of main steam pressure.

Improvement on acoustic performance of the accumulator of double-cylinder rotary compressors

2007 ◽  
Vol 221 (11) ◽  
pp. 1391-1396 ◽  
Author(s):  
Z Y Huang ◽  
W K Jiang ◽  
C H Liu ◽  
H S Jin ◽  
Y Zhou
Keyword(s):  
Noise Level ◽  
Fluid Dynamic ◽  
Pressure Fluctuations ◽  
Wall Pressure ◽  
Rotary Compressor ◽  
Acoustic Performance ◽  
Wall Pressure Fluctuations ◽  
Large Pressure ◽  
Flow Phase ◽  
Single Pipe

Since the accumulator is one of main contributors to the overall noise level of the rotary compressor, research on the acoustic performance of accumulators is essential. Numerical analysis based on the computational fluid dynamic method shows that large pressure fluctuations are caused mainly by periodic rotating piston. The idea that the flow phase differences of two pipes could be utilized for suppressing fluctuations is proposed. The double standpipes of an accumulator are changed to the single pipe with two branches and each branch is connected to the inlet of the compressor. Flow structures and wall pressure fluctuations for the two configurations are computed. Computational results show that wall pressure pulsations of the new accumulator are obviously lower than that of the original. The acoustic experiments were carried out under the real working conditions. Compared with the original, the new accumulator shows that the overall noise level is reduced about 1.2 dB(A) and the sound spectrum levels are also lower in a wide frequency domain, which validate the numerical and theoretical analysis.

Theoretical Analysis of Resonance Tube End Wall Heating: Solution of Unsteady Fluid Dynamic and Energy Equations

2015 ◽  
Author(s):  
Ramlala P. Sinha
Keyword(s):  
Heat Transfer ◽  
Fluid Dynamic ◽  
Stable Solution ◽  
Heat Conducting ◽  
Cross Sectional ◽  
Arbitrary Boundary ◽  
Resonance Tube ◽  
Unsteady Fluid ◽  
Energy Equations ◽  
End Wall

A solution of the highly complex unsteady compressible flow field inside a cylindrical resonance tube has been obtained numerically, assuming one dimensional, viscous, and heat conducting flow, by solving the appropriate fluid dynamic and energy equations. The resonance tube is approximated by a right circular cylinder closed at one end with a piston oscillating at resonant frequency at the other end. An iterative implicit finite difference scheme is employed to obtain the solution. The scheme permits arbitrary boundary conditions at the piston and the end wall and allows assumptions for transport properties. For the example considered herein, the solution predicts a rise of 95°F in the mean end wall temperature, from 60°F to 155°F, in 14.313 milliseconds which is in good agreement with the experimentally observed values. The solution would also be valid for tapered tubes if the variations in the cross-sectional area are small. In successfully predicting the resonance tube results, an innovative simple but stable solution of unsteady fluid dynamic and energy equations is provided here for wide ranging research, development, and industrial applications in solving a variety of complex fluid flow heat transfer problems. The method is directly applicable to pulsed or pulsating flow and wave motion thermal energy transport, fluid-structure interaction heat transfer enhancement, and fluidic pyrotechnic initiation devices.

A Study on the Use of Reduced Order Models for Unsteady Fluid Dynamic Analysis of Flexible Structures

2012 ◽  
Author(s):  
L. Ebrahimnejad ◽  
H. Yadollahi Farsani ◽  
D. T. Valentine ◽  
K. D. Janoyan ◽  
P. Marzocca
Keyword(s):  
Dynamic Analysis ◽  
Cross Sections ◽  
Fluid Dynamic ◽  
Flexible Structures ◽  
Reduced Order Models ◽  
Computationally Efficient ◽  
Reduced Order ◽  
Long Span ◽  
Long Span Bridge ◽  
Unsteady Fluid

Reduced order models (ROMs) are computationally efficient techniques, which have been widely used for predicting unsteady aerodynamic response of airfoils and wings. However, they have not been applied extensively to perform unsteady fluid dynamic analysis of flexible structures in civil engineering. This paper discusses the application of reduced order computational fluid dynamics (CFD) model based on the eigensystem realization algorithm (ERA) in the aerodynamic analysis of flexible structures with arbitrary shaped cross sections. As an example of a civil structure we examine the GBB long-span bridge for which there are published experimental data. The aerodynamic impulse responses of the GBB Bridge are used to construct the ROM, and then the aerodynamic forces due to arbitrary inputs are evaluated and compared to those of the model coupled with an advanced CFD code. Results demonstrate reasonable prediction power and high computational efficiency of the technique that can serve for preliminary design, optimization and control purposes. The methodology described in this paper has wide application in many offshore engineering problems where flexible structures interact with unsteady fluid mechanical phenomena.

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