Influence of a Closely Coupled Throttle on the Stalling Behavior of a Radial Compressor Stage

1985 ◽  
Vol 107 (2) ◽  
pp. 522-527 ◽  
Author(s):  
J. W. Railly ◽  
H. Ekerol
Keyword(s):  
Rotating Stall ◽  
Compressor Blade ◽  
Compressor Stage ◽  
Slow Speed ◽  
Radial Compressor ◽  
Pressure Characteristic ◽  
Static Instability ◽  
The Stability ◽  
Stage Characteristic ◽  
Radial Gap

On the basis of the classical discussion of the stability of compressor blade rows, a treatment is given of the stability of a stage consisting of a radial impeller followed by a vaned radial diffuser with a small radial gap between them. At the exit of the diffuser a radial array of adjustable vanes serves either to throttle the flow or to offer no resistance. In the latter case, throttling takes place by means of restrictions at inlet situated well upstream. The theory demonstrates that instability in the former case can only occur at the point of static instability, i.e., when the stage pressure characteristic slope becomes so positive that the throttle pressure characteristic is tangential to it. With the conventional throttling arrangement, instability is predicted as expected, when the stage characteristic has zero slope. Experimental confirmation of these predictions was obtained from tests on a slow speed radial compressor stage employing the above arrangement at exit, dischanging to atmosphere. When the vanes were used for throttling no rotating stall appeared but with throttling situated remotely from the stage a vigorous rotating stall mode developed.

Numerical Investigation of Inlet Distortion on the Stall Inception of a Radial Compressor

2014 ◽  
Author(s):  
S. Vagnoli ◽  
T. Verstraete
Keyword(s):  
High Performance ◽  
Stability Limit ◽  
Rotating Stall ◽  
Radial Compressor ◽  
Stall Inception ◽  
Compressor Inlet ◽  
Unstable Solutions ◽  
Unsteady Rans ◽  
Inlet Conditions ◽  
The Stability

In this paper unsteady CFD computations are used to study the stability and the rotating stall inception of a transonic radial compressor, considering two different configurations influencing the inlet flow. The prediction of the surge and stall limit for a centrifugal compressor is a key parameter for operating such machines, and hence requires attention already in the early design phase. Moreover, the operating margin can be dramatically influenced by non-uniform inlet conditions due to for example bended pipes mounted close to the inlet, as found more often today due to space limitation and optimization. In this case, it is not trivial to understand how the performance of the machine will be affected. The influence on the stability limit of an elbow installed in front of the compressor inlet is analyzed in this paper by means of unsteady RANS simulations: results for two different configurations, with elbow and with straight inlet placed in front of the compressor, are compared. All simulations are done modeling the whole annulus of the radial machine, using high performance computing, in order to accurately take into account the non-periodic phenomena leading to stall inception. Moreover, mechanisms leading to flow separation for unstable solutions are studied, pointing out how they are influenced by the unsteady interactions of the tip leakage vortices with the main flow and by the distorted flow from the inlet elbow.

Roles of vanes in diffuser on stability of centrifugal compressor

2019 ◽  
Vol 233 (14) ◽  
pp. 5380-5392
Author(s):  
Wangzhi Zou ◽  
Xiao He ◽  
Wenchao Zhang ◽  
Zitian Niu ◽  
Xinqian Zheng
Keyword(s):  
High Pressure ◽  
Centrifugal Compressor ◽  
Dynamic Pressure ◽  
Pressure Ratio ◽  
Pressure Rise ◽  
Rotating Stall ◽  
Centrifugal Compressors ◽  
Compression System ◽  
The Stability ◽  
Rotating Instability

The stability considerations of centrifugal compressors become increasingly severe with the high pressure ratios, especially in aero-engines. Diffuser is the major subcomponent of centrifugal compressor, and its performance greatly influences the stability of compressor. This paper experimentally investigates the roles of vanes in diffuser on component instability and compression system instability. High pressure ratio centrifugal compressors with and without vanes in diffuser are tested and analyzed. Rig tests are carried out to obtain the compressor performance map. Dynamic pressure measurements and relevant Fourier analysis are performed to identify complex instability phenomena in the time domain and frequency domain, including rotating instability, stall, and surge. For component instability, vanes in diffuser are capable of suppressing the emergence of rotating stall in the diffuser at full speeds, but barely affect the characteristics of rotating instability in the impeller at low and middle speeds. For compression system instability, it is shown that the use of vanes in diffuser can effectively postpone the occurrence of compression system surge at full speeds. According to the experimental results and the one-dimensional flow theory, vanes in diffuser turn the diffuser pressure rise slope more negative and thus improve the stability of compressor stage, which means lower surge mass flow rate.

An Investigation of the Stability Enhancement of a Centrifugal Compressor Stage Using a Porous Throat Diffuser

2017 ◽  
Vol 140 (1) ◽  
Author(s):  
Lee Galloway ◽  
Stephen Spence ◽  
Sung In Kim ◽  
Daniel Rusch ◽  
Klemens Vogel ◽  
...  
Keyword(s):  
Centrifugal Compressor ◽  
Compressor Stage ◽  
Vaned Diffuser ◽  
Flow Rates ◽  
Stall Inception ◽  
Centrifugal Compressor Stage ◽  
Operating Range ◽  
Stable Operating ◽  
The Stability ◽  
Circumferential Pressure

The stable operating range of a centrifugal compressor stage of an engine turbocharger is limited at low mass flow rates by aerodynamic instabilities which can lead to the onset of rotating stall or surge. There have been many techniques employed to increase the stable operating range of centrifugal compressor stages. The literature demonstrates that there are various possibilities for adding special treatments to the nominal diffuser vane geometry, or including injection or bleed flows to modify the diffuser flow field in order to influence diffuser stability. One such treatment is the porous throat diffuser (PTD). Although the benefits of this technique have been proven in the existing literature, a comprehensive understanding of how this technique operates is not yet available. This paper uses experimental measurements from a high pressure ratio (PR) compressor stage to acquire a sound understanding of the flow features within the vaned diffuser which affect the stability of the overall compression system and investigate the stabilizing mechanism of the porous throat diffuser. The nonuniform circumferential pressure imposed by the asymmetric volute is experimentally and numerically examined to understand if this provides a preferential location for stall inception in the diffuser. The following hypothesis is confirmed: linking of the diffuser throats via the side cavity equalizes the diffuser throat pressure, thus creating a more homogeneous circumferential pressure distribution, which delays stall inception to lower flow rates. The results of the porous throat diffuser configuration are compared to a standard vaned diffuser compressor stage in terms of overall compressor performance parameters, circumferential pressure nonuniformity at various locations through the compressor stage and diffuser subcomponent analysis. The diffuser inlet region was found to be the element most influenced by the porous throat diffuser, and the stability limit is mainly governed by this element.

scholarly journals Experimental investigation and numerical modelling of 3D radial compressor stage and influence of the technological holes on the working characteristics

2018 ◽  
Vol 180 ◽  
pp. 02060 ◽  
Author(s):  
Richard Matas ◽  
Tomáš Syka ◽  
Lukáš Hurda
Keyword(s):  
Experimental Investigation ◽  
Numerical Modelling ◽  
Research And Development ◽  
Evaluation Process ◽  
Rotor Blades ◽  
Compressor Stage ◽  
Experimental Facility ◽  
Radial Compressor ◽  
Measurement And Evaluation

The article deals with a description of results from research and development of a radial compressor stage with 3D rotor blades. The experimental facility and the measurement and evaluation process is described briefly in the first part. The comparison of measured and computed characteristics can be found in the second part. The last part of this contribution is the evaluation of the rotor blades technological holes influence on the compressor stage characteristics.

Detection of Precursor Waves Announcing Stall in Two 3-Stage Axial Compressors

1998 ◽  
Author(s):  
F. Grauer ◽  
W. Volgmann ◽  
H. Stoff ◽  
T. Breuer
Keyword(s):  
Pressure Fluctuations ◽  
Safety Margin ◽  
Stability Limit ◽  
Rotating Stall ◽  
Time Dependent ◽  
Axial Compressors ◽  
Performance Map ◽  
Fourier Transform Methods ◽  
The Stability ◽  
Stall Control

Rotating stall and surge limit the operating range of a compressor towards low throughflow and high pressure in the performance map. Usually a safety margin must be observed to prevent the compressor from entering unintentionally aerodynamic instabilities. As the range of highest performance and efficiency lies in the vicinity of the stability limit, efforts concentrate on recognizing imminent onset of unstable operation prior to its occurrence. The present investigation centers on means of detecting information about onsetting instability from signals of pressure fluctuations in two transonic medium-pressure axial compressors of 3 stages. Fourier-transform-methods as well as artificial neural networks are applied for the data reduction of the time-dependent pressure signals. The methods of investigation presented here detected stall precursors announcing the onset of instability. Some of them seem appropriate to be used in connection with active stall control.

Control of Self-Excited Oscillations in Centrifugal Blowers

2007 ◽  
Author(s):  
Saad A. Ahmed
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Critical Mass ◽  
Industrial Applications ◽  
Rotating Stall ◽  
Operating Conditions ◽  
Flow Coefficient ◽  
Flow Area ◽  
The Stability

Centrifugal compressors or blowers are widely used in many industrial applications. However, the operation of such systems is limited at low-mass flow rates by self-excited flow instabilities which could result in rotating stall or surge of the compressor. These instabilities will limit the flow range in which the compressor or the blower can operate, and will also lower their performance and efficiency. Experimental techniques were used to investigate a model of radial vaneless diffuser at stall and stall-free operating conditions. The speed of the impeller was kept constant, while the mass flow rate was reduced gradually to study the steady and unsteady operating conditions of the compressor. Additional experiments were made to investigate the effects of reducing the exit flow area on the inception of stall. The results indicate that the instability in the diffuser was successfully delayed to a lower flow coefficient when throttle rings were attached to either one or both of the diffuser walls (i.e., to reduce the diffuser exit flow area). The results also showed that an increase of the blockage ratio improves the stability of the system (i.e., the critical mass flow rate could be reduced to 50% of its value without blockage). The results indicate that the throttle rings could be an effective method to control stall in radial diffusers.

Numerical Analysis to Investigate the Effect of Swept Rotor on the Overall Performance of a Transonic Compressor Stage

2014 ◽  
Author(s):  
Shobhavathy M. Thimmaiah ◽  
Ramesha Gurikelu ◽  
Nisha Sherief
Keyword(s):  
Flow Field ◽  
Total Pressure ◽  
Pressure Ratio ◽  
Stability Margin ◽  
Compressor Stage ◽  
Operating Range ◽  
Transonic Compressor ◽  
Overall Performance ◽  
Design Speed ◽  
The Stability

This paper presents the steady state numerical analyses carried out to investigate the effect of forward and backward swept rotor on the overall performance and stability margin of single stage transonic axial flow compressor. Initially, the analyses were carried out on a radially stacked rotor/baseline configuration and obtained the overall performance map of the compressor stage. These results were compared with the available experimental data for validation. Further, investigations were carried out on geometrically modified rotor with six configurations having 5, 10 and 15° forward and backward sweep. A commercial 3-Dimensional CFD package, ANSYS FLUENT was used to compute the complex flow field of transonic compressor rotors. The flow field structures were studied with the help of Mach number total pressure contours. The results of modified rotor geometry indicated that the peak adiabatic efficiency and the total pressure ratio for all the tested forward and backward swept rotor configurations are marginally higher than that of the baseline configuration at all speeds. The operating ranges of all the swept rotor configurations are found to be higher than that of the baseline configuration. The operating range is broader at lower operating speeds than at design speed condition. Rotor with 10° forward sweep and 5° backward sweep indicated the noteworthy improvement in the operating range against the baseline configuration. The stability margin of 11.3, 6.6, 5.2 and 3.5% at 60, 80, 90 and 100% of the design speed respectively compared to the baseline configuration obtained from 10° forward sweep. Rotor with 5° backward sweep showed the stability margin of 12, 4, 3.9 and 3% at 60, 80, 90 and 100% of the design speed respectively compared to the baseline configuration.

Delay of Rotating Stall in Compressors Using Plasma Actuators

2016 ◽  
Vol 138 (9) ◽  
Author(s):  
Farzad Ashrafi ◽  
Mathias Michaud ◽  
Huu Duc Vo
Keyword(s):  
Centrifugal Compressor ◽  
Leading Edge ◽  
Plasma Actuator ◽  
Rotating Stall ◽  
Tip Clearance ◽  
Compressor Stage ◽  
Dbd Plasma ◽  
Two Stage ◽  
Stall Inception ◽  
Flow Acceleration

Rotating stall is a well-known aerodynamic instability in compressors that limits the operating envelope of aircraft gas turbine engines. An innovative method for delaying the most common form of rotating stall inception using an annular dielectric barrier discharge (DBD) plasma actuator had been proposed. A DBD plasma actuator is a simple solid-state device that converts electricity directly into flow acceleration through partial air ionization. However, the proposed concept had only been preliminarily evaluated with numerical simulations on an isolated axial rotor using a relatively basic CFD code. This paper provides both an experimental and a numerical assessment of this concept for an axial compressor stage as well as a centrifugal compressor stage, with both stages being part of a low-speed two-stage axial-centrifugal compressor test rig. The two configurations studied are the two-stage configuration with a 100 mN/m annular casing plasma actuator placed just upstream of the axial rotor leading edge (LE) and the single-stage centrifugal compressor with the same actuator placed upstream of the impeller LE. The tested configurations were simulated with a commercial RANS CFD code (ansys cfx) in which was implemented the latest engineering DBD plasma model and dynamic throttle boundary condition, using single-passage multiple blade row computational domains. The computational fluid dynamics (CFD) simulations indicate that in both types of compressors, the actuator delays the stall inception by pushing the incoming/tip clearance flow interface downstream into the blade passage. In each case, the predicted reduction in stalling mass flow matches the experimental value reasonably well.

Correlation Analysis of Multiple Sensors for Industrial Gas Turbine Compressor Blade Health Monitoring

2015 ◽  
Vol 137 (11) ◽  
Author(s):  
Brian Kestner ◽  
Tim Lieuwen ◽  
Chris Hill ◽  
Leonard Angello ◽  
Josh Barron ◽  
...  
Keyword(s):  
Gas Turbine ◽  
Acoustic Pressure ◽  
Dynamic Pressure ◽  
Pressure Sensors ◽  
Rotating Stall ◽  
Compressor Blade ◽  
Blade Vibration ◽  
Multiple Sensors ◽  
Dynamic Pressure Measurements ◽  
Industrial Gas Turbine

This paper summarizes an analysis of data obtained from an instrumented compressor of an operational, heavy duty industrial gas turbine; the goal of the aforementioned analysis is to understand some of the fundamental drivers, which may lead to compressor blade vibration. Methodologies are needed to (1) understand the fundamental drivers of compressor blade vibration, (2) quantify the severity of “events,” which accelerate the likelihood of failure and reduce the remaining life of the blade, and (3) proactively detect when these issues are occurring so that the operator can take corrective action. The motivation for this analysis lies in understanding the correlations between different sensors, which may be used to measure the fundamental drivers and blade vibrations. In this study, a variety of dynamic data was acquired from an operating engine, including acoustic pressure, bearing vibration, tip timing, and traditional gas path measurements. The acoustic pressure sensors were installed on the first four compressor stages, while the tip timing was installed on the first stage only. These data show the presence of rotating stall instabilities in the front stages of the compressor, occurring during every startup and shutdown, and manifesting itself as increased amplitude oscillations in the dynamic pressure measurements, which are manifested in blade and bearing vibrations. The data that lead to these observations were acquired during several startup and shutdown events, and clearly show that the amplitude of these instabilities and the rpm at which they occur can vary substantially.

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