scholarly journals Experimental Investigation on Rotating Stall in a Centrifugal Blower With Two and Four Stages and Vaneless Diffusers

1996 ◽  
Author(s):  
Gianmario L. Arnulfi ◽  
Diego Micheli ◽  
Piero Pinamonti
Keyword(s):  
Experimental Investigation ◽  
Flow Field ◽  
Rotating Stall ◽  
Test Plant ◽  
Hot Wire ◽  
Centrifugal Blower ◽  
Stall Inception ◽  
Wire Probe ◽  
Instantaneous Flow Field ◽  
Vaneless Diffusers

The paper presents the results of an experimental investigation on a multistage centrifugal blower, during rotating stall. The test plant allows to change the turbomachine characteristics; in this research the blower has been tested in two different configurations: two-stage and four-stage, with vaneless diffusers. The unsteady flow field inside the blower has been measured by means of hot-wire anemometers. Three single hot-wire probes have been utilised to measure the development of the rotating stall, while a crossed hot-wire probe has been utilised to obtain the instantaneous flow field behind the impellers. The measurements have been done at different flow rate values, including stall inception.

Velocity Measurements Downstream of the Impellers in a Multistage Centrifugal Blower

1994 ◽  
Author(s):  
G. L. Amulfi ◽  
D. Micheli ◽  
P. Pinamonti
Keyword(s):  
Flow Field ◽  
Unsteady Flow ◽  
Flow Rate ◽  
Rotating Stall ◽  
Operating Conditions ◽  
Field Analysis ◽  
Test Plant ◽  
Hot Wire ◽  
Centrifugal Blower ◽  
Ensemble Averaging

The paper presents the results of an experimental investigation on a four-stage centrifugal blower, having the aim of obtaining an accurate description of the flow field behind the impellers in several operative conditions and for different geometrical configurations. Actually, the test plant allows to change the turbomachinery characteristics assembling one, two, three or four stages and three different types of diffusers. In this first research step, the blower has been tested in the four-stage vaneless diffuser configuration. The unsteady flow field behind the impellers and in the diffusers has been measured by means of a hot-wire anemometer. A Phase Locked Ensemble Averaging Technique has been utilised to obtain the relative flow field from the instantaneous signals of the stationary hot-wire probes. Several detailed measurements sets have been performed using both single and crossed hot-wire probe, to obtain the velocity vectors and turbulence trends, just behind the blower impellers and in several radial positions of the vaneless diffusers. These measurements have been done at different flow rate conditions, covering unsteady flow rate phenomena (rotating stall) too. The results obtained allowed to get a detailed flow field analysis in the multistage centrifugal blower, in relation to the geometrical configuration and to the differing operating conditions.

Velocity Measurements Downstream of the Impellers in a Multistage Centrifugal Blower

1995 ◽  
Vol 117 (4) ◽  
pp. 593-601 ◽  
Author(s):  
G. L. Arnulfi ◽  
D. Micheli ◽  
P. Pinamonti
Keyword(s):  
Flow Field ◽  
Unsteady Flow ◽  
Flow Rate ◽  
Rotating Stall ◽  
Operating Conditions ◽  
Field Analysis ◽  
Test Plant ◽  
Hot Wire ◽  
Centrifugal Blower ◽  
Detailed Measurement

The paper presents the results of an experimental investigation on a four-stage centrifugal blower, having the aim of obtaining an accurate description of the flow field behind the impellers in several operative conditions and for different geometric configurations. Actually, the test plant allows one to change the turbomachinery characteristics assembling one, two, three, or four stages and three different types of diffuser. In this first research step, the blower has been tested in the four-stage vaneless diffuser configuration. The unsteady flow field behind the impellers and in the diffusers has been measured by means of a hot-wire anemometer. A phase-locked ensemble-averaging technique has been utilized to obtain the relative flow field from the instantaneous signals of the stationary hot-wire probes. Several detailed measurement sets have been performed using both single and crossed hot-wire probes, to obtain the velocity vectors and turbulence trends, just behind the blower impellers and in several radial positions of the vaneless diffusers. These measurements have been done at different flow rate conditions, covering unsteady flow rate phenomena (rotating stall) also. The results obtained allowed us to get a detailed flow field analysis in the multistage centrifugal blower, in relation to the geometric configuration and to the differing operating conditions.

Transient Process of Rotating Stall in Radial Vaneless Diffusers

1994 ◽  
Author(s):  
H. Watanabe ◽  
S. Konomi ◽  
I. Ariga
Keyword(s):  
Flow Rate ◽  
Reverse Flow ◽  
Flow Region ◽  
Rotating Stall ◽  
Lower Side ◽  
Hot Wire ◽  
Vaneless Diffuser ◽  
Reversed Flow ◽  
Stall Inception ◽  
Wire Probe

This paper describes the process of rotating stall inception in a radial vaneless diffuser. Unsteady flow and rotating stall were investigated by measuring the wall static pressures and velocity distributions using X hot-wire probe. From the measurements of the velocity fluctuation, it is confirmed that the periodical disturbance in the reverse flow region as the prestall symptom occurs prior to the onset of stall and then the growth of that periodical disturbance leads to the rotating stall with fully developed non axisymmetric reversed flow. On the process of the rotating stall inception, reverse flow regions in the diffuser grow from the diffuser exit toward the inlet along the shroud and hub wall, and the rotating stall occurs when the reverse flow region on the shroud wall reaches to the impeller exit. In this paper, the effects of the diffuser exit blockage on the process of stall inception were also described. The flow rate of stall onset is moved to the lower side by the restriction of the diffuser exit width, however, this restriction does not affect the distribution of the reverse flow regions. That restriction suppresses the prestall disturbance in the reverse flow regions and then stabilize the flow in the diffuser.

Control of Rotating Stall in the Diffuser of a Low Speed Centrifugal Compressor

2003 ◽  
Author(s):  
Saad A. Ahmed ◽  
Mohamed A. Gadalla
Keyword(s):  
Experimental Investigation ◽  
Centrifugal Compressor ◽  
Flow Instability ◽  
Rotating Stall ◽  
Flow Coefficient ◽  
Centrifugal Blower ◽  
Flow Area ◽  
Lower Flow ◽  
Preliminary Results ◽  
Control Delay

An experimental investigation to delay the onset of the rotating stall in the radial diffuser of a centrifugal blower was carried out. The method involved reducing the flow area by 50% at the diffuser exit using throttle rings attached to either diffuser shroud wall, or the diffuser hub wall. Simultaneous attachments of the throttle rings to both the diffuser’s shroud and the hub walls were also made. The following blockage ratios were used: 25% from both walls, 50% from the diffuser shroud and 0% from the diffuser hub and vice versa. The preliminary results suggest that the onset of the flow instability in the diffuser (stall) could be delayed (i.e., lower flow coefficient) when throttle rings were attached to the diffuser walls to reduce its exit flow area. The results also confirmed that the throttle rings could be an effective method to control/delay the stall in the vaneless radial diffuser.

Sensitivity of Three Sensor Hot Wire Probe to Yaw and Pitch Angle Variation

1988 ◽  
Vol 110 (2) ◽  
pp. 120-122 ◽  
Author(s):  
B. Lakshminarayana ◽  
R. Davino
Keyword(s):  
Flow Field ◽  
Systematic Study ◽  
Pitch Angle ◽  
Three Dimensional ◽  
Hot Wire ◽  
Three Dimensional Flow ◽  
Angle Variation ◽  
Wire Probe ◽  
Response Equation ◽  
Single Sensor

The use of a three sensor hot wire probe for the measurement of three-dimensional flow field is increasing rapidly. This probe is very sensitive to yaw and pitch angle variations and existing laws for single sensor wires cannot be utilized to provide the correct hotwire response equations. A systematic study at various yaw and pitch angles (maximum values of ± 40 deg, nearly 220 different yaw and pitch angles) is carried out to determine the nature of response of a triple sensor hot wire probe. These results are analyzed to provide a correlation for the hot wire response equation which includes both pitch and yaw angles as variables.

Experimental Investigation and Characterization of the Rotating Stall in a High Pressure Centrifugal Compressor: Part IV — Impeller Influence on Diffuser Stability

2003 ◽  
Author(s):  
A. Cellai ◽  
G. Ferrara ◽  
L. Ferrari ◽  
C. P. Mengoni ◽  
L. Baldassarre
Keyword(s):  
Experimental Investigation ◽  
High Pressure ◽  
Centrifugal Compressor ◽  
Rotating Stall ◽  
Radius Ratio ◽  
Vaneless Diffuser ◽  
Stall Inception ◽  
Last Stage ◽  
And Diffusion

Vaneless diffuser rotating stall is a major problem for centrifugal compressors since it is a limit to their working range. In particular the last stage seems to be the most critical. In the literature some good correlations for predicting stall inception can be found but they do not adequately cover the case of the last stage configuration, especially for very low blade-outlet-width-to-impeller-radius-ratio impellers typically used in high-pressure applications. Extensive research has been performed to define diffuser stall limits for this family of stages: three impellers characterized by different blade-outlet-width-to-impeller-radius-ratios are tested with different diffuser configurations (different pinch shapes, diffuser widths and diffusion ratios). Part I and II report the results of these geometry modifications on diffuser stability for the first impeller. Part III, those for the second impeller. In this part the comparison of these results in terms of impeller influence on diffuser stability is reported.

Understanding the Steady and Transient Behavior of the Moderately Loaded High Speed Axial Flow Compressor Stage at Off-Design Conditions

2014 ◽  
Author(s):  
Dilipkumar B. Alone ◽  
Subramani Satish Kumar ◽  
Shobhavathy M. Thimmaiah ◽  
Janaki Rami Reddy Mudipalli ◽  
A. M. Pradeep ◽  
...  
Keyword(s):  
High Speed ◽  
Axial Flow ◽  
Transient Behavior ◽  
Compressor Stage ◽  
Hot Wire ◽  
Stall Inception ◽  
Wire Probe ◽  
Stable Operating ◽  
Performance Map ◽  
Aero Engines

High performance high speed transonic axial flow compressors and fans are the major components of efficient aero-engines. Engine operating envelope and performance normally depends on the compressor performance and its distortion tolerance. Even though the high speed compressors are favorite amongst modern aero-engines, they are more prone to instabilities like surge and stall, which further restricts the engine operations. The present paper deal with experimental study carried on a moderately loaded high speed single stage axial compressor and is focused on the steady state as well as transient behavior at off-design conditions. The single stage transonic compressor is designed for stage total pressure ratio of 1.35 and delivers 23 kg/s mass flow rate at corrected speed of 12930 rpm. The stall inception phenomenon is studied using high frequency miniature Kulite pressure transducers and hot wire probe. The fluctuations in the wall static pressure were also studied by placing three Kulite transducers, one at rotor inlet, second at rotor exit and the third at stator exit. The unsteady pressure signals from these Kulite transducers are processed and analysed to understand the stall inception process. The FFT was performed to identify the stall frequency and pressure oscillation amplitude. Unsteady pressure signals clearly shows the instabilities occurred at the rotor inlet and then gradually moves towards the rotor exit, while the flow at the stator exit remains undisturbed. The intensity of the instabilities along the blade span was also studied using three point Kulite rakes placed at the rotor inlet. Stable operating margin of the compressor was evaluated by deriving the compressor stage performance map. The compressor stage performance map was derived using conventional instrumentation like total pressure rakes and thermocouples. The compressor stage experienced abrupt stall at higher operating speeds. The turbulence intensity was evaluated using single component hot wire probe. Maximum stable operating range of 22% is obtained at 50% design speed. The flow parameters were also evaluated at the rotor inlet and rotor exit using aerodynamic probe at full flow and near stall conditions.

Unsteady Investigation on Tip Flow Field and Rotating Stall in Counter-Rotating Axial Compressor

2015 ◽  
Vol 137 (7) ◽  
Author(s):  
Limin Gao ◽  
Ruiyu Li ◽  
Fang Miao ◽  
Yutong Cai
Keyword(s):  
Flow Field ◽  
Second Harmonic ◽  
Axial Compressor ◽  
Rotating Stall ◽  
Tip Clearance ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Stall Inception ◽  
Tip Leakage ◽  
Future Goals

Contra-rotating axial compressor/fan (CRAC) is a promising technology to meet the future goals aircraft industry. Massive time accurate simulations are performed to investigate rotating stall in CRAC containing two counter-rotating rotors. Particularly, the back pressure increasing with a very small step to avoid missing flow field transition from stability to instability. Due to the canceling of the stator, the instability of downstream rotor is more stronger. The present studies mostly focus on the downstream rotor. The tip leakage flow field is analyzed in detail under near stall condition, which indicates that a secondary leakage flow plays an important role in the unsteadiness of CRAC's unsteady flow field. The frequency analysis in the tip clearance of downstream rotor under multiple near stall conditions captured the transition of the second harmonic frequency which can be used as stall inception signal. Moreover, the rotating stall onset process in real CRAC is simulated on the numerical stall.

Stall Cell Development in an Axial Compressor

1987 ◽  
Vol 109 (4) ◽  
pp. 492-498 ◽  
Author(s):  
A. D. Jackson
Keyword(s):  
Experimental Investigation ◽  
Cell Growth ◽  
Axial Compressor ◽  
Cell Development ◽  
Rotating Stall ◽  
Small Distance ◽  
Stall Inception ◽  
Full Development ◽  
Radial Extent ◽  
Circumferential Extent

An experimental investigation of stall inception and stall cell development in a single-stage axial compressor is described. The stall inception was found to be naturally nonrandom: By artificially perturbing the flow the inception could be accurately fixed at a known location in the compressor. The stall cell was first detected behind the rotor at a small distance from the tip. The stall cell grew very rapidly in circumferential extent, but slowly in radial extent. After reaching the hub the cell decreased in size before reaching full development as a single full span rotating stall cell. Relationships between various parameters of the stall cell growth are presented. The growth is explained in terms of the cell blockage, and the mechanism for multiple stall inception is discussed.

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