scholarly journals Variations of Performance and Pressure Pulsation During Cavitation in Centrifugal Pumps with Entrained Air

2021 ◽  
Vol 321 ◽  
pp. 04017
Author(s):  
Fanjie Deng ◽  
Jianping Yuan ◽  
Minquan Liao ◽  
Mengfei Chen ◽  
Han Zhu ◽  
...  
Keyword(s):  
Pressure Pulsation ◽  
Cavitation Number ◽  
Incoming Flow ◽  
Centrifugal Pumps ◽  
Cavitation Performance ◽  
Basic Law ◽  
Natural Cavitation ◽  
Blade Frequency ◽  
Entrained Air ◽  
The Military

Most of the research on the cavitation with entrained air has focused on the military direction, but it ,about centrifugal pumps, which is relevant to people's livelihood, is still relatively lacking. In order to study the basic law of the development of cavitation inside centrifugal pumps under aeration conditions, a test bench suitable for cavitation experiments with incoming flow containing gas was obtained. Furthermore, a single-stage single-suction 6-blade centrifugal pump was used as the research object to conduct pressure pulsation experiments under cavitation condition when the incoming flow was 1.0% air viod fraction at 2900r/min-50m3/h. The results showed that: After cavitation happened, the greater aeration content will deteriorate the pump's anti-cavitation performance, but the head curve is more gentle in falling down compared to natural cavitation. Hence aeration has a beneficial effect on the performance degradation of the pump under the cavitation condition. At the same time, before the cavitation number drops to the fracture cavitation number of the pump, aeration has improvement in the efficiency of the pump in different degrees , especially in the situation with the ventilated rate of 1.0%. The main frequency of pressure pulsation at the inlet and outlet of the test pump after aeration is dominated by the blade frequency. The shaft frequency signal at the outlet gradually decreases with the cavitation number lessened. Moreover the amplitude of the blade frequency grows slightly with the reduction of the cavitation number. But it tends to soar when the cavitation number is less than the fracture cavitation number.

scholarly journals Effect of Impeller Inlet Geometry on Cavitation Performance of Centrifugal Pumps Based on Radial Basis Function

2016 ◽  
Vol 2016 ◽  
pp. 1-9 ◽  
Author(s):  
Shuwei Zhang ◽  
Renhui Zhang ◽  
Sidai Zhang ◽  
Junhu Yang
Keyword(s):  
Radial Basis Function ◽  
Basis Function ◽  
Pressure Pulsation ◽  
Leading Edge ◽  
Suction Side ◽  
Response Model ◽  
Centrifugal Pumps ◽  
Cavitation Performance ◽  
Radial Basis ◽  
Blade Leading Edge

Aiming at the cavitation problem, the blade leading edge shape has been changed to analyze its impact on the cavitation performance for centrifugal pumps. And the response model has been established based on the Radial Basis Function. The calculation case results show that the leading edge extending forward along the shroud can improve the inlet flow condition and cavitation performance. But the cavitation performance has been reduced immensely when the leading edge extends backward along the shroud. Along with the leading edge which extends forward along the hub, the cavitation performance increases at first and then decreases. A better cavitation performance for centrifugal pumps has lower load of blade inlet and higher pressure of blade suction side. The pressure pulsation is affected by the vortex out of the impeller and the falling-off and collapsing of the cavitation bubbles. The lower the pressure pulsation for blade passing frequency and the second harmonics of the samples is, the better the cavitation performance is. A relatively accurate response model based on the Radial Basis Function has been established to predict the effect of the shape of blade leading edge on the cavitation performance of centrifugal pumps.

scholarly journals A Study on the Cavitation and Pressure Pulsation Characteristics in the Impeller of an LNG Submerged Pump

Machines ◽  
2021 ◽  
Vol 10 (1) ◽  
pp. 14
Author(s):  
Wei Li ◽  
Shuo Li ◽  
Leilei Ji ◽  
Xiaofan Zhao ◽  
Weidong Shi ◽  
...  
Keyword(s):  
Pressure Pulsation ◽  
Pressure Coefficient ◽  
Low Frequency ◽  
Signal Amplitude ◽  
Cfd Analysis ◽  
Frequency Signal ◽  
Cavitation Performance ◽  
Blade Frequency ◽  
Waveform Amplitude ◽  
Critical Cavitation

Based on CFD analysis technology, this paper studies the cavitation performance of an LNG submerged pump and the pressure pulsation characteristics under cavitation excitation. The variation laws of the waveform, amplitude and frequency of the pressure pulsation in the impeller of the LNG submerged pump under different flow rates and NPSHa are also analysed. By calculating the root mean square of the pressure coefficient of the low-frequency pulsation, the influence of the aggravation process of cavitation on the low-frequency pulsation in the LNG submerged pump is quantitatively analysed, and the characteristics of the pressure pulsation in the LNG submerged pump under the cavitation condition are revealed. The results show that with the increase in flow rate, the pressure pulsation in the impeller becomes stronger, periodically, and the amplitude decreases. The influence of cavitation on the pressure pulsation in the primary impeller is greater than that in the secondary impeller. When critical cavitation occurs, the low-frequency signal amplitude of pressure pulsation in the primary impeller increases and exceeds the blade frequency, becoming the main frequency.

scholarly journals Influence of wall roughness on cavitation performance of centrifugal pump

2021 ◽  
Vol 43 (6) ◽  
Author(s):  
Weihui Xu ◽  
Xiaoke He ◽  
Xiao Hou ◽  
Zhihao Huang ◽  
Weishu Wang
Keyword(s):  
Flow Field ◽  
Centrifugal Pump ◽  
Internal Flow ◽  
Wall Roughness ◽  
Blade Surface ◽  
Centrifugal Pumps ◽  
Three Dimensional Model ◽  
Cavitation Inception ◽  
Cavitation Performance ◽  
Critical Cavitation

AbstractCavitation is a phenomenon that occurs easily during rotation of fluid machinery and can decrease the performance of a pump, thereby resulting in damage to flow passage components. To study the influence of wall roughness on the cavitation performance of a centrifugal pump, a three-dimensional model of internal flow field of a centrifugal pump was constructed and a numerical simulation of cavitation in the flow field was conducted with ANSYS CFX software based on the Reynolds normalization group k-epsilon turbulence model and Zwart cavitation model. The cavitation can be further divided into four stages: cavitation inception, cavitation development, critical cavitation, and fracture cavitation. Influencing laws of wall roughness of the blade surface on the cavitation performance of a centrifugal pump were analyzed. Research results demonstrate that in the design process of centrifugal pumps, decreasing the wall roughness appropriately during the cavitation development and critical cavitation is important to effectively improve the cavitation performance of pumps. Moreover, a number of nucleation sites on the blade surface increase with the increase in wall roughness, thereby expanding the low-pressure area of the blade. Research conclusions can provide theoretical references to improve cavitation performance and optimize the structural design of the pump.

scholarly journals Investigation of Unsteady Pressure Pulsation in New Type Dishwasher Pump with Special Double Tongue Volute

2022 ◽  
Vol 2022 ◽  
pp. 1-11
Author(s):  
Jinfeng Zhang ◽  
Yilei Zhu ◽  
Yalin Li ◽  
Ping Huang ◽  
Hui Xu ◽  
...  
Keyword(s):  
Pressure Pulsation ◽  
Rotation Speed ◽  
Performance Tests ◽  
Unsteady Pressure ◽  
Passive Rotation ◽  
Impeller Outlet ◽  
Tongue Position ◽  
New Type ◽  
Reference Scheme ◽  
Blade Frequency

Through numerical simulations, this work analyzes the unsteady pressure pulsation characteristics in new type of dishwasher pump with double tongue volute and single tongue volute, under volute static and rotation conditions. Likewise, the performance tests were also carried out to verify the numerical results. Multiple monitoring points were set at the various positions of new type dishwasher pump to collect the pressure pulsation signals, and the relevant frequency signals were obtained via Fast Fourier Transform, to analyze the influence of volute tongue and its passive speed on the pump performance. The results reveal that when the double tongue volute is stationary, the pressure pulsation amplitudes increase from the impeller inlet to the impeller outlet. Under the influence of shedding vortex, the pressure pulsation in the lateral region of tongue becomes disorganized, and the main frequency of pressure pulsation changes from blade frequency to shaft frequency. In addition, compared with the static volute, double tongue volute can effectively guide the water flow out of the tongue during the rotation process, thus ensuring good periodicity for pressure pulsation in the tongue region. Accordingly, a volute reference scheme with passive rotation speed is proposed in this study, which can effectively improve the pressure pulsation at tongue position, and provides a new idea for rotor-stator interference to guide the innovation of dishwasher.

scholarly journals Cavitating flow-induced unsteady pressure pulsations in a low specific speed centrifugal pump

2018 ◽  
Vol 5 (7) ◽  
pp. 180408 ◽  
Author(s):  
Ning Zhang ◽  
Bo Gao ◽  
Zhong Li ◽  
Qifeng Jiang
Keyword(s):  
Critical Point ◽  
Cavitation Bubble ◽  
Pressure Wave ◽  
High Energy ◽  
Cavitation Number ◽  
Centrifugal Pumps ◽  
Pressure Pulsations ◽  
Measuring Point ◽  
Number Range ◽  
Cavitation Region

With the development of cavitation, the high-energy pressure wave from a cavitation bubble collapsing is detrimental to the stable operation of centrifugal pumps. The present paper concentrates on pressure pulsations under cavitation conditions, and pressure amplitudes at the blade-passing frequency ( f BPF ) and RMS values in the 0–500 Hz frequency band are combined to investigate cavitation-induced pressure pulsations. The results show that components at f BPF always dominate the pressure spectrum even at the full cavitation stage. For points P1–P7 on the volute side wall, with a decreasing cavitation number, the pressure energy first remains unchanged and then it rises rapidly after the critical point. For point In1 in a volute suction pipe located close to the cavitation region, the pressure energy changes slightly at high cavitation numbers; then for a particular cavitation number range, the pressure energy decreases, and finally increases again. For different flow rates, the pressure energy at the critical point is much lower than the initial amplitude at the non-cavitation condition for In1. This demonstrates that the cavitation cloud in the typical stage is partially compressible, and the emitted pressure wave from a collapsing cavitation bubble is absorbed and attenuated significantly. Finally, this leads to the pressure energy decreasing rapidly for the measuring point In1 near the cavitation region.

scholarly journals Investigation on centrifugal pump performance degradation under air-water inlet two-phase flow conditions

2018 ◽  
pp. 41-48 ◽  
Author(s):  
Qiaorui Si ◽  
Qianglei Cui ◽  
Keyu Zhang ◽  
Jianping Yuan ◽  
Gérard Bois
Keyword(s):  
Centrifugal Pump ◽  
Pressure Pulsation ◽  
Flow Characteristics ◽  
Performance Degradation ◽  
Inlet Pressure ◽  
Pulsation Frequency ◽  
Centrifugal Pumps ◽  
Two Phase ◽  
Flow Rates ◽  
Pump Performance

In order to study the flow characteristics of centrifugal pumps when transporting the gas-liquid mixture, water and air were chosen as the working medium. Both numerical simulation and experimental tests were conducted on a centrifugal pump under different conditions of inlet air volume fraction (IAVF). The calculation used URANS k-epsilon turbulence model combined with the Euler-Euler inhomogeneous two-phase model. The air distribution and velocity streamline inside the impeller were obtained to discuss the flow characteristics of the pump. The results show that air concentration is high at the inlet pressure side of the blade, where the vortex will exist, indicating that the gas concentration have a great relationship with the vortex aggregation in the impeller passages. In the experimental works, pump performances were measured at different IAVF and compared with numerical results. Contributions to the centrifugal pump performance degradations were analyzed under different air-water inlet flow condition such as IAVF, bubble size, inlet pressure. Results show that pump performance degradation is more pronounced for low flow rates compared to high flow rates. Finally, pressure pulsation and vibration experiments of the pump model under different IAVF were also conducted. Inlet and outlet transient pressure signals under four IAVF were investigated and pressure pulsation frequency of the monitors is near the blade passing frequency at different IAVF, and when IAVF increased, the lower frequency signal is more and more obvious. Vibration signals at five measuring points were also obtained under different IAVF for various flow rates.

scholarly journals Experimental Investigation on Cavitating Flow Induced Vibration Characteristics of a Low Specific Speed Centrifugal Pump

2017 ◽  
Vol 2017 ◽  
pp. 1-12 ◽  
Author(s):  
Bo Gao ◽  
Pengming Guo ◽  
Ning Zhang ◽  
Zhong Li ◽  
Minguan Yang
Keyword(s):  
Frequency Band ◽  
Low Frequency ◽  
Local Maximum ◽  
Cavitation Number ◽  
Cavitating Flow ◽  
Vibration Characteristics ◽  
Vibration Energy ◽  
Stable Operation ◽  
Centrifugal Pumps ◽  
Number Range

Cavitating flow developing in the blade channels is detrimental to the stable operation of centrifugal pumps, so it is essential to detect cavitation and avoid the unexpected results. The present paper concentrates on cavitation induced vibration characteristics, and special attention is laid on vibration energy in low frequency band, 10–500 Hz. The correlation between cavitating evolution and the corresponding vibration energy in 10–500 Hz frequency band is discussed through visualization analysis. Results show that the varying trend of vibration energy in low frequency band is unique compared with the high frequency band. With cavitation number decreasing, vibration energy reaches a local maximum at a cavitation number much larger than the 3% head drop point; after that it decreases. The varying trend is closely associated with the corresponding cavitation status. With cavitation number decreasing, cavitation could be divided into four stages. The decreasing of vibration energy, in particular cavitation number range, is caused by the partial compressible cavitation structure. From cavitation induced vibration characteristics, vibration energy rises much earlier than the usual 3% head drop criterion, and it indicates that cavitation could be detected in advance and effectively by means of cavitation induced vibration characteristics.

The Rotating Cavitation Performance of a Centrifugal Pump with a Splitter-Bladed Inducer under Different Rotational Speed

2015 ◽  
Vol 32 (3) ◽  
Author(s):  
XiaoMei Guo ◽  
ZuChao Zhu ◽  
BaoLing Cui ◽  
Yi Li
Keyword(s):  
Centrifugal Pump ◽  
Rotational Speed ◽  
High Speed ◽  
Internal Flow ◽  
Centrifugal Pumps ◽  
Cavitation Flow ◽  
Operation Condition ◽  
Cavitation Performance ◽  
Cavitation Behavior ◽  
Suction Performance

AbstractDesigning inducer is one of the effective ways to improve the suction performance of high-speed centrifugal pumps. The operation condition including rotational speeds can affect the internal flow and external performance of high-speed centrifugal pumps with an inducer. In order to clarify the rotating cavitation performance of a centrifugal pump with a splitter-bladed inducer under different rotational speed, a centrifugal pump with a splitter-bladed inducer is investigated in the work. By using Rayleigh–Plesset equations and Mixture model, the cavitation flow of centrifugal pump is numerically simulated, as well as the external performance experimental test is carried out. It is found that the cavitation area increases with the rotational speeds. The location of the passage where cavitation is easy to appear is explored. Asymmetric cavitation behavior is observed. That, the trail of the inducer is easy to take cavitation when the rotational speed is increased to a degree, is also observed. The trend of

Advances in Design Methods and Characteristics of Internal Flow for Centrifugal Pumps

2010 ◽  
Author(s):  
Shouqi Yuan ◽  
Jianping Yuan ◽  
Houlin Liu ◽  
Yue Tang ◽  
Jinfeng Zhang ◽  
...  
Keyword(s):  
Unsteady Flow ◽  
Pressure Pulsation ◽  
Design Method ◽  
Internal Flow ◽  
Design Methods ◽  
Centrifugal Pumps ◽  
Flow Induced Vibration ◽  
Hydraulic Design ◽  
Piv Measurement ◽  
Engineering And Technology

Centrifugal pump is widely used in various fields of the national economy. Pumps, of which 70% are centrifugal pumps, consume 20.9% of the total electricity generation nationwide in China in 2009, according to the statistics. In this paper, the research advances in design methods and characteristics of internal flow fields for centrifugal pumps, carried out by the Research Center of Fluid Machinery Engineering and Technology of Jiangsu University, is introduced. First of all, the Greater Flow Design method, Non-Overload Design method and Splitter Blade Offset Design method are fully discussed through systematically studies. In addition, three methods of performance prediction for centrifugal pumps are adopted, and a CAD/CFD software for hydraulic design and analysis is initially developed. Secondly, to deepen the understanding of characteristics of internal flow in centrifugal pumps, the numerical simulation and PIV measurement investigation have been done. Then the unsteady flow induced vibration and noise are studied considering fluid-structure interaction and fluid-sound interaction. The control of the unsteady flow in centrifugal pumps is also attempted to optimize the design method for centrifugal pumps. In addition, the pressure pulsation and vibration behaviors under both cavitation and non-cavitation conditions are obtained and analyzed. Finally, some detecting methods and criterion for cavitation incipiency and development are put forward.

Unsteady Pressure Pulsation Measurements and Analysis of a Low Specific Speed Centrifugal Pump

2017 ◽  
Vol 139 (7) ◽  
Author(s):  
Bo Gao ◽  
Pengming Guo ◽  
Ning Zhang ◽  
Zhong Li ◽  
MinGuan Yang
Keyword(s):  
Frequency Band ◽  
Flow Rate ◽  
Pressure Pulsation ◽  
Operating Conditions ◽  
Stable Operation ◽  
Centrifugal Pumps ◽  
Pressure Transducers ◽  
Unsteady Pressure ◽  
Low Specific Speed ◽  
Response Pressure

Intense pressure pulsation, resulted from the flow structure shedding from the blade trailing edge and its interaction with the volute tongue and the casing, is detrimental to the stable operation of centrifugal pumps. In the present study, unsteady pressure pulsation signals at different positions of the volute casing are extracted using high response pressure transducers at flow rate of 0–1.55ΦN. Emphasis is laid upon the influence of measuring position and operating condition on pressure pulsation characteristics, and components at the blade passing frequency fBPF and root-mean-square (RMS) values in 0–20.66fn frequency band are mainly analyzed. Results clearly show that the predominant components in pressure spectra always locate at fBPF. The varying trends versus flow rate of components at fBPF differ significantly for different points, and it is considered to be associated with the corresponding flow structures at particular positions of the volute casing. At the near-tongue region, high pressure amplitudes occur at the position of θ = 36 deg, namely the point at the after tongue region. For different measuring points, angular distributions of amplitudes at fBPF and RMS values in 0–20.66fn frequency band are not consistent and affected significantly by the pump operating conditions.

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