Investigation on Pressure Fluctuation Related to Mild Surge in Multistage Centrifugal Blower With Inlet Guide Vane

2016 ◽  
Vol 138 (11) ◽  
Author(s):  
Kiyotaka Hiradate ◽  
Satoshi Joukou ◽  
Kiyohide Sakamoto ◽  
Yasushi Shinkawa ◽  
Takeshi Uchiyama
Keyword(s):  
Pressure Fluctuation ◽  
Pressure Fluctuations ◽  
Pressure Rise ◽  
Generation Mechanism ◽  
System Dynamic ◽  
Total System ◽  
Positive Slope ◽  
Centrifugal Blower ◽  
Operating Range ◽  
Last Stage

Centrifugal blowers are widely used for gas compression in a variety of industrial fields; however, a wider operating range is required in these machines. Investigations on the generation mechanism of unsteady flow (i.e., surge) are very important to improve the operating range. The purpose of this study is to clarify the generation mechanism of pressure fluctuations in a multistage centrifugal blower equipped with inlet guide vanes (IGVs) upstream during the first stage under the IGVs partially open condition. These pressure fluctuations occur at flowrates when the slope of the total system head curve is steeply negative. According to our previous study on the detailed unsteady pressure measurements, this pressure oscillation is supposed to be the mild surge caused by the positive slope of the head curves at the second to the last stages. The slope of the total system head curve was kept negative due to the steeply negative slope of the head curve during the first stage. Thus, the whole compression system seemed to be stable. To confirm the validity of this hypothesis, system dynamic simulations based on Greitzer's lumped-parameter model were conducted using newly measured static pressure-rise characteristic curves of each stage in a four-stage centrifugal blower. In these simulations, the pressure-rise characteristic curves of the first stage and the second to last stages were modeled as two different actuator disks, and the stabilization/destabilization effects of each stage on the system dynamic characteristics were separately taken into account under the IGVs partially open condition. The system dynamic simulation reproduced the mild surge behavior of the system under the IGVs partially open condition when the slope of the total system head curve was still kept steeply negative. The calculated amplitude and frequency of the pressure fluctuations caused by the mild surge showed satisfactory agreement with the measured ones. However, the inception flowrate of the system instability in the simulation was approximately 7% smaller than that in the measurement. From these results, we confirmed that the pressure fluctuation occurred under the IGVs partially open condition was caused by the mild surge due to the positive slope of the pressure-rise characteristic during the second to last stage. In addition, we found that this mild surge was caused by the stall of the vaned diffusers during the second to last stage.

Investigation on Pressure Fluctuation Related to Mild Surge in Multi-Stage Centrifugal Blower With Inlet Guide Vane

2015 ◽  
Author(s):  
Kiyotaka Hiradate ◽  
Kiyohide Sakamoto ◽  
Yasushi Shinkawa ◽  
Satoshi Joukou ◽  
Takeshi Uchiyama
Keyword(s):  
Pressure Fluctuation ◽  
Pressure Fluctuations ◽  
Pressure Rise ◽  
Generation Mechanism ◽  
System Dynamic ◽  
Total System ◽  
Positive Slope ◽  
Centrifugal Blower ◽  
Operating Range ◽  
Multi Stage

Centrifugal blowers are widely used for gas compression in various industrial fields. Wider operating range is required in these machines. Investigations on the generation mechanism of unsteady flow (i.e., surge) are very important to improve the operating range of these machines. Purpose of this study is to clarify the generation mechanism of pressure fluctuations in a multi-stage centrifugal blower equipped with inlet guide vanes (IGVs) upstream of the first stage under the IGVs partially open condition. These pressure fluctuations occur at flowrates when the slope of total system head curve is steeply negative. According to our previous study on the detailed unsteady pressure measurements, this pressure oscillation is supposed to be the mild surge caused by the positive slope of the head curves at the second to the last stages. The slope of the total system head curve was kept negative due to the steeply negative slope of the head curve at the first stage. Thus, the whole compression system seemed to be stable. To confirm the validity of this hypothesis, system dynamic simulations based on Greitzer’s lumped-parameter model were conducted using newly measured static-pressure-rise characteristic curves of each stage in a four-stage centrifugal blower. In these simulations, the pressure-rise characteristic curves of the first stage and the second to last stages were modeled as two different actuator disks, and the stabilization/destabilization effects of each stage on the system dynamic characteristics were separately taken into account under the IGVs partially open condition. The system dynamic simulation reproduced the mild surge behavior of the system under the IGVs partially open condition when the slope of the total system head curve was still kept steeply negative. The calculated amplitude and frequency of the pressure fluctuations caused by the mild surge showed satisfactory agreement with the measured ones. However, the inception flowrate of the system instability in the simulation was approximately 7% smaller than that in the measurement. From these results, we confirmed that the pressure fluctuation occurred under the IGVs partially open condition was caused by the mild surge due to the positive slope of the pressure-rise characteristic at the second to the last stages. In addition, we found that this mild surge was caused by the stall of the vaned diffusers at the second to the last stage.

Experimental Investigation on Unstable Flow in Multi-Stage Centrifugal Blower With Inlet Guide Vane

2013 ◽  
Author(s):  
Kiyotaka Hiradate ◽  
Kiyohide Sakamoto ◽  
Toshio Kanno ◽  
Yasushi Shinkawa ◽  
Satoshi Joukou ◽  
...  
Keyword(s):  
Rotation Frequency ◽  
Rotating Stall ◽  
Negative Slope ◽  
Inlet Guide Vane ◽  
Total System ◽  
Positive Slope ◽  
Centrifugal Blower ◽  
Unstable Flow ◽  
Pressure Transducers ◽  
Second Stage

This study experimentally examines unstable flow phenomena occur in a five-stage centrifugal blower equipped with inlet guide vanes (IGVs) before the first stage. High response pressure transducers were mounted on a suction nozzle, an U-turn bend between a diffuser and return channel in the second stage, and a discharge nozzle to detect surge. Moreover, at a vaneless space between an impeller and a vaned diffuser in the second stage, three pressure transducers were located thirty degrees apart in the circumferential direction to distinguish rotating stall in the diffuser from surge. Measurements were performed at several flowrates changing the IGVs from fully opening condition to partially opening conditions. We confirmed three types of pressure fluctuation in low flowrate region. The first is the fluctuation showing the largest amplitude and the lowest frequency (about 7–9 percent of impeller rotation frequency) and observed at all the sensors. This appears in the positive slope region of the total system head curve. The second is the spike-like fluctuation intermittently observed only in the vaneless space. This occurs at the IGVs partially opening conditions and shows observed time lag among the three sensors. The last is the fluctuation with smaller amplitude and higher frequency (about 14–23 percent of impeller rotation frequency) than that of the first and observed at all the sensors. This occurs at the IGVs partially opening conditions. At 4.5 percent IGVs opening, this fluctuation is observed in the steep negative slope region of the total system head curve, where the whole compression system is supposed to be stable. Moreover, this fluctuation is measured at the same phase in the vaneless space. We concluded that the first-mentioned fluctuation is deep surge and the second-mentioned fluctuation is rotating stall in the diffuser. On the other hand, we have considered the last-mentioned fluctuation to be mild surge and the reason why this occurs in the negative slope region to be as follows. At 4.5 percent IGVs opening, slope of the first stage head curve becomes steeply negative by prewhirl and this negative slope stabilizes the system. By contrast, at the second to the last stage, the slope of the head curve becomes positive in low flowrate region and this positive slope destabilizes the system. Therefore, even if the total system head curve maintains a steep negative slope, the system operating point oscillates slightly (mild surge situation) due to a balance of these stabilization and destabilization effects.

Experimental Investigation of Pressure Fluctuations on Inner Wall of a Centrifugal Pump

2019 ◽  
Vol 36 (4) ◽  
pp. 401-410 ◽  
Author(s):  
Xiao-Qi Jia ◽  
Bao-Ling Cui ◽  
Zu-Chao Zhu ◽  
Yu-Liang Zhang
Keyword(s):  
Centrifugal Pump ◽  
Flow Rate ◽  
Pressure Fluctuation ◽  
Pressure Fluctuations ◽  
High Flow ◽  
Low Flow ◽  
Centrifugal Pumps ◽  
Flow Rates ◽  
Pressure Distributions ◽  
Blade Passing Frequency

Abstract Affected by rotor–stator interaction and unstable inner flow, asymmetric pressure distributions and pressure fluctuations cannot be avoided in centrifugal pumps. To study the pressure distributions on volute and front casing walls, dynamic pressure tests are carried out on a centrifugal pump. Frequency spectrum analysis of pressure fluctuation is presented based on Fast Fourier transform and steady pressure distribution is obtained based on time-average method. The results show that amplitudes of pressure fluctuation and blade-passing frequency are sensitive to the flow rate. At low flow rates, high-pressure region and large pressure gradients near the volute tongue are observed, and the main factors contributing to the pressure fluctuation are fluctuations in blade-passing frequency and high-frequency fluctuations. By contrast, at high flow rates, fluctuations of rotating-frequency and low frequencies are the main contributors to pressure fluctuation. Moreover, at low flow rates, pressure near volute tongue increases rapidly at first and thereafter increases slowly, whereas at high flow rates, pressure decreases sharply. Asymmetries are observed in the pressure distributions on both volute and front casing walls. With increasing of flow rate, both asymmetries in the pressure distributions and magnitude of the pressure decrease.

The Cavitation-Induced Pressure Fluctuations in a Mixed-Flow Pump under Impeller Inflow Distortion

Machines ◽  
2021 ◽  
Vol 9 (12) ◽  
pp. 326
Author(s):  
Huiyan Zhang ◽  
Fan Meng ◽  
Yunhao Zheng ◽  
Yanjun Li
Keyword(s):  
Frequency Domain ◽  
Pressure Fluctuation ◽  
Dynamic Pressure ◽  
Pressure Fluctuations ◽  
Pressure Sensors ◽  
Mixed Flow ◽  
Guide Vanes ◽  
Time Frequency ◽  
Critical Cavitation ◽  
Flow Pump

To reduce cavitation-induced pressure fluctuations in a mixed-flow pump under impeller inflow distortion, the dynamic pressure signal at different monitoring points of a mixed-flow pump with a dustpan-shaped inlet conduit under normal and critical cavitation conditions was collected using high-precision digital pressure sensors. Firstly, the nonuniformity of the impeller inflow caused by inlet conduit shape was characterized by the time–frequency-domain spectra and statistical characteristics of pressure fluctuation at four monitoring points (P4–P7) circumferentially distributed at the outlet of the inlet conduit. Then, the cavity distribution on the blade surface was captured by a stroboscope. Lastly, the characteristics of cavitation-induced pressure fluctuation were obtained by analyzing the time–frequency-domain spectra and statistical characteristic values of dynamic pressure signals at the impeller inlet (P1), guide vanes inlet (P2), and guide vanes outlet (P3). The results show that the flow distribution of impeller inflow is asymmetric. The pav values at P4 and P6 were the smallest and largest, respectively. Compared with normal conditions, the impeller inlet pressure is lower under critical cavitation conditions, which leads to low pav, pp-p and a main frequency amplitude at P1. In addition, the cavity covered the whole suction side under H = 13.6 m and 15.5 m, which led the pp-p and dominant frequency amplitude of pressure fluctuation at P2 and P3 under critical cavitation to be higher than that under normal conditions.

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.

Proper Orthogonal Decomposition and Extended- Proper Orthogonal Decomposition Analysis of Pressure Fluctuations and Vortex Structures Inside a Steam Turbine Control Valve

2018 ◽  
Vol 141 (4) ◽  
Author(s):  
Peng Wang ◽  
Hongyu Ma ◽  
Yingzheng Liu
Keyword(s):  
Proper Orthogonal Decomposition ◽  
Steam Turbine ◽  
Pressure Fluctuation ◽  
Pressure Field ◽  
Pressure Fluctuations ◽  
Control Valve ◽  
Vortex Structures ◽  
Orthogonal Decomposition ◽  
Pod Analysis ◽  
Proper Orthogonal

In steam turbine control valves, pressure fluctuations coupled with vortex structures in highly unsteady three-dimensional flows are essential contributors to the aerodynamic forces on the valve components, and are major sources of flow-induced vibrations and acoustic emissions. Advanced turbulence models can capture the detailed flow information of the control valve; however, it is challenging to identify the primary flow structures, due to the massive flow database. In this study, state-of-the-art data-driven analyses, namely, proper orthogonal decomposition (POD) and extended-POD, were used to extract the energetic pressure fluctuations and dominant vortex structures of the control valve. To this end, the typical annular attachment flow inside a steam turbine control valve was investigated by carrying out a detached eddy simulation (DES). Thereafter, the energetic pressure fluctuation modes were determined by conducting POD analysis on the pressure field of the valve. The vortex structures contributing to the energetic pressure fluctuation modes were determined by conducting extended-POD analysis on the pressure–velocity coupling field. Finally, the dominant vortex structures were revealed conducting a direct POD analysis of the velocity field. The results revealed that the flow instabilities inside the control valve were mainly induced by oscillations of the annular wall-attached jet and the derivative flow separations and reattachments. Moreover, the POD analysis of the pressure field revealed that most of the pressure fluctuation intensity comprised the axial, antisymmetric, and asymmetric pressure modes. By conducting extended-POD analysis, the incorporation of the vortex structures with the energetic pressure modes was observed to coincide with the synchronous, alternating, and single-sided oscillation behaviors of the annular attachment flow. However, based on the POD analysis of the unsteady velocity fields, the vortex structures, buried in the dominant modes at St = 0.017, were found to result from the alternating oscillation behaviors of the annular attachment flow.

Pressure and Flow Rate Fluctuations in Single- and Two-Blade Pumps

2020 ◽  
Vol 143 (1) ◽  
Author(s):  
Andreas Pesch ◽  
Steffen Melzer ◽  
Stephan Schepeler ◽  
Tobias Kalkkuhl ◽  
Romuald Skoda
Keyword(s):  
Flow Rate ◽  
Pressure Fluctuation ◽  
Pressure Fluctuations ◽  
Three Dimensional ◽  
Electromagnetic Flowmeter ◽  
Flow Region ◽  
Mean Values ◽  
Wall Pressure Fluctuations ◽  
Simulation Results ◽  
Blade Pump

Abstract A comparative study on the highly unsteady flow field in single- and two-blade pumps is performed. Stationary pump characteristics, as well as pressure and flow rate fluctuations, are presented. Wall pressure fluctuations were measured in the suction and pressure pipe as well as at several locations within the volute casing by piezoresistive transducers. Flow rate fluctuations were evaluated by a recently presented measurement system based on an electromagnetic flowmeter (Melzer et al. 2020, “A System for Time-Fluctuating Flow Rate Measurements in a Single-Blade Pump Circuit,” Flow Meas. Instrum., 71, p. 101675). Measurements were accompanied by three-dimensional (3D) flow simulations with the open-source cfd software foam-extend. A thorough grid study and validation of the simulation were performed. By a complementary analysis of measurement and simulation results, distinctive differences between both pump types were observed, e.g., flow rate and pressure fluctuation magnitudes are significantly higher in the single-blade pump. In relation to the respective mean values, flow rate fluctuation magnitudes are one order lower than pressure fluctuation magnitudes for both pumps. For the two-blade pump, fluctuations attenuate toward overload irrespective of the particular pump circuit, while they rise for the single-blade pump. 3D simulation results yield detailed insight into the spatially and temporally resolved impeller–volute interaction and reveal that the single-blade impeller pushes a high-pressure flow region forward in a way as a positive displacement pump, resulting in an inherently fluctuating velocity and pressure distribution within the volute.

Investigation of Supercritical Flow and Shape of Flip Bucket Spillways on Coefficients of Dynamic Pressure

2020 ◽  
Vol 143 (6) ◽  
Author(s):  
Hessam Vatandoust ◽  
Hamidreza Yarmohammadi ◽  
Mohammadreza Kavianpour
Keyword(s):  
Froude Number ◽  
Pressure Fluctuation ◽  
Dynamic Pressure ◽  
Pressure Coefficient ◽  
Pressure Fluctuations ◽  
Experimental Studies ◽  
Flow Speed ◽  
Middle Part ◽  
Statistical Characteristics ◽  
Pressure Coefficients

Abstract Pressure fluctuation is one of the major turbulent flow characteristics. It may cause crucial problems for hydraulic structures. This research is based on experimental studies, and it focuses on the measurements of pressure fluctuations along flip bucket spillways with different geometrical characteristics. The function of the flip bucket spillway is discharging floods from reservoir dams which are energy storage source measurements of dynamic pressures on three different models of flip buckets that were performed for this investigation. Pressure fluctuation of the flip buckets have been measured within a range of Froude numbers from 5 to 13 (Fr = u/gy, where u is the flow speed, y is the depth, and g is 9.81 m/s2). Statistical characteristics of pressure fluctuations, the location, and the values of maximum and minimum fluctuations have also supplemented the study. The results show that the coefficients of pressure fluctuations (Cp = RMS/(0.5(u2/g)) where RMS is the root-mean-square of pressure fluctuation, u is the flow speed, and g is 9.81 m/s2) reduce as the Froude number (Fr) of flow increases, except a maximum Froude number. Pressure coefficients increase along the flip bucket with incremental mutations in the transformation area of the flip bucket. In the middle part of the flip bucket spillway, pressure coefficient values decrease. Additionally, as B/r (B is the width of the flip bucket and r is the radius of the flip bucket) ratio increases, pressure coefficients become larger and this process continues along the flip bucket.

Efficient and reliable surge prevention algorithm for centrifugal compressor

2020 ◽  
Vol 92 (1) ◽  
pp. 47-59
Author(s):  
Grzegorz Liśkiewicz
Keyword(s):  
Working Conditions ◽  
High Frequency ◽  
Experimental Studies ◽  
Phase Portraits ◽  
Centrifugal Blower ◽  
Local Flow ◽  
Content Type ◽  
Operating Range ◽  
Surge Margin ◽  
External Conditions

Purpose The paper aims to present an outline of the technology of the active anti-surge algorithm based on high-frequency pressure measurement. The presented system is fast, inexpensive and reliable and does not limit the machine-operating range. Many contemporary anti-surge systems are based on theoretical surge margin. This solution limits machine operating range by about 10-15 per cent in the region of the highest pressure ratios. It is also often sensitive to change in external conditions such as temperature or density, as the system reacts to limits calculated theoretically. Design/methodology/approach This paper presents results of pressure measurements obtained on the low-speed centrifugal blower DP1.12. The pressure signals were presented in the form of phase diagrams, and conclusions were drawn from their phase portraits to develop the surge indication parameter. Findings The presented safety system uses the signal to develop the so-called (rate of derivative fluctuation) RDF parameter. In nominal working conditions, this parameter keeps the value close to 1. When RDF reaches values over 3, the anti-surge procedure should be implemented. Experimental studies have shown that this algorithm assures enough time to incur actions suppressing unstable phenomena. Originality/value The system reacts to real machine working conditions and is hence reliable. The RDF algorithm could also be used to identify local flow instabilities, as well as off-design operation.

Horizontal Pressure Fluctuation in Bubbling Fluidized Bed

2003 ◽  
Author(s):  
Vesa V. Walle´n
Keyword(s):  
Pressure Gradient ◽  
Fluidized Bed ◽  
Pressure Fluctuation ◽  
Pressure Fluctuations ◽  
Middle Part ◽  
Biomass Combustion ◽  
Bottom Part ◽  
Pressure Transducers ◽  
Bubbling Fluidized Bed ◽  
Horizontal Pressure

Pressure measurements were conducted in a two-dimensional hot atmospheric bubbling fluidized bed reactor in the laboratory of Energy and Process Engineering at Tampere University of Technology. A set of six fast pressure transducers was used to detect the rapid pressure fluctuations inside the bubbling bed of the reactor. These pressure transducers were placed both vertically and horizontally into the reactor. From these measurements it was found that the vertical pressure fluctuation took place at the same time at different levels of the bed. Also the same fluctuation could be seen under the air distributor. The horizontal pressure fluctuation was found to vary both by place and time. At the bottom part of the bed the highest pressure peaks was found at centre of the bed. Most of the time there was a pressure gradient the highest pressure being in the centre of the bed. This gradient creates horizontal flow of gases from middle to the sides. The velocity of this flow varies with the size of the pressure gradient. The opposite effect can be found in the upper part of the bed. The highest pressure was no more in the middle part of the bed. Instead, it was found to be between the centre of the bed and left and right walls. The pressure was low at the walls but also rather low at the middle of the bed. There must be flow towards the walls and to the centre axis. These pressure fluctuations can provide an explanation for the well-known “wandering plume” effect. They can also give a tool to better describe the mixing inside a bubbling fluidized bed. This kind of tool is needed when biomass combustion is modelled in bubbling fluidized bed.

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