Validation of Numerical Simulation for Rotating Stall in a Transonic Fan

2012 ◽  
Vol 135 (2) ◽  
Author(s):  
Minsuk Choi ◽  
Nigel H. S. Smith ◽  
Mehdi Vahdati
Keyword(s):  
Mass Flow ◽  
Transient Flow ◽  
Rotating Stall ◽  
Navier Stokes ◽  
Implicit Time ◽  
Stall Inception ◽  
Rotating Speed ◽  
Design Speed ◽  
Loading Parameter ◽  
Transonic Fan

This paper addresses a comparison of numerical stall simulations with experimental data at 60% (subsonic) and 95% (supersonic) of the design speed in a modern transonic fan rig. The unsteady static pressures were obtained with high frequency Kulite transducers mounted on the casing upstream and downstream of the fan. The casing pressure variation was clearly visible in the measurements when a stall cell passed below the transducers. Numerical stall simulations were conducted using an implicit, time-accurate, 3D compressible Reynolds-averaged Navier-Stokes (RANS) solver. The comparisons between the experiment and simulation mainly cover performance curves and time-domain pressure traces of Kulites during rotating stall. At two different fan speeds, the stall characteristics such as the number and rotating speed of the stall cells were well-matched to the experimental values. The mass flow rate and the loading parameter under the fully-developed rotating stall also showed good agreement with the experiment. In both the numerical and experimental results, a large stall cell was eventually formed after stall inception regardless of the fan speed. Based on the validation, the detailed flow has been evaluated to understand rotating stall in a transonic fan. In addition, it was found that the mass flow measurement using casing static pressure might be wrong during transient flow if the Kulites were mounted too close to the fan blade.

Validation of Numerical Simulation for Rotating Stall in a Transonic Fan

2011 ◽  
Author(s):  
Minsuk Choi ◽  
Nigel H. S. Smith ◽  
Mehdi Vahdati
Keyword(s):  
Mass Flow ◽  
Transient Flow ◽  
Rotating Stall ◽  
Implicit Time ◽  
Stall Inception ◽  
Rotating Speed ◽  
Design Speed ◽  
Fan Speed ◽  
Loading Parameter ◽  
Transonic Fan

This paper addresses a comparison of numerical stall simulations with experimental data at 60% (subsonic) and 95% (supersonic) of the design speed in a modern transonic fan rig. The unsteady static pressures were obtained with high frequency Kulite transducers mounted on the casing upstream and downstream of the fan. The casing pressure variation was clearly visible in the measurements when a stall cell passed below the transducers. Numerical stall simulations were conducted using an implicit, time-accurate 3D compressible RANS solver. The comparisons between the experiment and simulation mainly cover performance curves and time-domain pressure traces of Kulites during rotating stall. At two different fan speeds, the stall characteristics such as the number and rotating speed of the stall cells were well-matched to the experimental values. The mass flow rate and the loading parameter under the fully-developed rotating stall also showed good agreement with the experiment. In both numerical and experimental results, a large stall cell was eventually formed after stall inception regardless of the fan speed. Based on the validation, the detailed flow has been evaluated to understand rotating stall in a transonic fan. In addition, it was found that the mass flow measurement using casing static pressure might be wrong during transient flow if the Kulites were mounted too close to the fan blade.

Computations of bladerow stall inception in transonic flows

1999 ◽  
Vol 103 (1025) ◽  
pp. 317-324 ◽  
Author(s):  
L. He ◽  
J. O. Ismael
Keyword(s):  
Three Dimensional ◽  
Rotating Stall ◽  
Navier Stokes ◽  
Flow Conditions ◽  
Stall Inception ◽  
Tip Leakage ◽  
Blade Row ◽  
Inflow Condition ◽  
Shock Oscillation ◽  
Transonic Fan

Abstract A three-dimensional unsteady Navier-Stokes solver has been used to simulate stall inception in a single row ten passage segment of a transonic fan, the NASA rotor-67. At subsonic flow conditions, the 3D results illustrate a rotating stall inception with short scale part-span cells rotating at around 80% rotor speed, similar to that observed in some low speed experiments. However, at a supersonic relative inflow condition, the results show that an isolated blade row tends to stall in a one-dimensional breakdown pattern without first experiencing rotating stall. At near-stall conditions, significant self-excited unsteadiness is generated by the interaction between the tip-leakage vortex and the passage shock wave. Further computations for two-dimensional configurations indicate that it is possible to have a rotating pattern of instability in transonic blade rows associated with circumferential synchronised shock oscillation.

Effects of Fan Speed on Rotating Stall Inception and Recovery

2011 ◽  
Vol 133 (4) ◽  
Author(s):  
Minsuk Choi ◽  
Mehdi Vahdati ◽  
Mehmet Imregun
Keyword(s):  
Aspect Ratio ◽  
Flow Rate ◽  
Reverse Flow ◽  
Recovery Process ◽  
Rotating Stall ◽  
Navier Stokes ◽  
Implicit Time ◽  
Stall Inception ◽  
Stall Cells ◽  
Fan Speed

An implicit, time-accurate 3D compressible Reynolds-averaged Navier-Stokes (RANS) solver is used to simulate rotating stall inception and recovery, the so-called rotating stall hysteresis, in the case of a modern fan geometry. In the first instance, rotating stall was simulated for 70%, 80%, and 90% fan speeds using a whole-annulus fan model with a variable-area nozzle downstream. As the fan speed is increased, the stall cells also increase in size but their number decreases. One large stall cell is predicted to rotate along the annulus at 80% and 90% speeds, while there are three smaller cells at 70% speed. In all cases, the reverse flow is confined to the near-tip region and the rotating stall does not develop into a full-span stall because of the fan blade’s high-aspect ratio. To simulate stall recovery, the nozzle area was increased gradually at 70% and 90% speeds and the flow was seen to recover from rotating stall to reach an unstalled operating condition. The recovery process was found to be affected by the fan speed. At 70% speed, the large disturbances decay first to form almost symmetric stall cells. Thereafter, the stall cells shrink into smaller ones as the mass flow rate increases further. At 90% fan speed, a single stall cell rotates along the annulus, the disappearance of which results in recovery. An attempt has been made to explain the dependence of the stall inception and recovery patterns on the fan speed.

Effect of Circumferential Grooves on the Aerodynamic Performance of an Axial Single-Stage Transonic Compressor

2007 ◽  
Author(s):  
Martin W. Mu¨ller ◽  
Heinz-Peter Schiffer ◽  
Chunill Hah
Keyword(s):  
Mass Flow ◽  
Pressure Ratio ◽  
Rotating Stall ◽  
Single Stage ◽  
Tip Leakage Flow ◽  
Stall Inception ◽  
Tip Leakage ◽  
Transonic Compressor ◽  
Favorable Change ◽  
Design Speed

This paper reports on experimental and numerical investigations on circumferential grooves in an axial single-stage transonic compressor. Total pressure ratio and efficiency speedlines were taken at design speed and three off-design conditions. The experiments comprise four different configurations with deep and shallow grooves and variable coverage of the projected rotor axial chord. All casing treatments proved to have a beneficial effect on stall range while maintaining high levels of efficiency, even at off-design operation. Deep grooves extending almost to the trailing edge showed the biggest potential: the mass flow at stall inception for design speed could be strongly reduced, and the operating range could be enlarged by 56.1%. When three shallow grooves were applied to the compressor, the stage efficiency at design speed was shifted to slightly higher values. A possible explanation could be a favorable change in stator aerodynamics due to the reduction of corner separation. For a closer look into the physical effects of grooves on the tip leakage flow, a rotor-only CFD analysis has been carried out using a steady state calculation. A multi-block grid with approximately 1.2 million nodes was used. The numerical simulations reveal strong effects of circumferential grooves on the rotor flow field at tip. Mach-number contours, axial velocity distributions and particle traces for the smooth casing and six deep grooves are presented at stall mass flow. Compared to the smooth wall case, the treated casing significantly reduces blockage in the tip area and weakens the roll-up of the core vortex. These mechanisms prevent an early spillage of low momentum fluid into the adjacent blade passage and delay the onset of rotating stall.

Stall Warning Using the Rotor Tip Pressure in a Transonic Axial Compressor With Circumferential Grooves

2018 ◽  
Author(s):  
Byeung Jun Lim ◽  
Tae Choon Park ◽  
Young Seok Kang
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Axial Compressor ◽  
Rotating Stall ◽  
Single Stage ◽  
Stall Inception ◽  
Casing Treatment ◽  
Stall Warning ◽  
Transonic Axial Compressor

In this study, characteristics of stall inception in a single-stage transonic axial compressor with circumferential grooves casing treatment were investigated experimentally. Additionally, the characteristic of increasing irregularity in the pressure inside circumferential grooves as the compressor approaches the stall limit was applied to the stall warning method. Spike-type rotating stall was observed in the single-stage transonic axial compressor with smooth casing. When circumferential grooves were applied, the stall inception was suppressed and the operating point of the compressor moved to lower flow rate than the stall limit. A spike-like disturbance was developed into a rotating stall cell and then the Helmholtz perturbation was overlapped on it at N = 80%. At N = 70 %, the Helmholtz perturbation was observed first and the amplitude of the wave gradually increased as mass flow rate decreased. At N = 60%, spike type stall inceptions were observed intermittently and then developed into continuous rotating stall at lower mass flow rate. Pressure measured at the bottom of circumferential grooves showed that the level of irregularity of pressure increased as flow rate decreased. Based on the characteristic of increasing irregularity of the pressure signals inside the circumferential grooves as stall approaches, an autocorrelation technique was applied to the stall warning. This technique could be used to provide warning against stall and estimate real-time stall margins in compressors with casing treatments.

scholarly journals Simulation and Experimental Investigation of the Stay Vane Channel Flow in a Reversible Pump Turbine at Off-Design Conditions

2017 ◽  
Vol 61 (2) ◽  
pp. 94 ◽  
Author(s):  
Sandro Erne ◽  
Gernot Edinger ◽  
Anton Maly ◽  
Christian Bauer
Keyword(s):  
Transient Flow ◽  
Guide Vane ◽  
Low Frequency ◽  
Rotating Stall ◽  
Design Flow ◽  
Flow State ◽  
Mean Flow ◽  
Load Range ◽  
Pump Turbine ◽  
Stall Inception

This work presents the assessment of the mean flow field and low frequency disturbances in the stay vane channel of a model pump turbine using transient numerical simulations and LDV-based measurements. The focus is laid on transient CFD simulations of characteristic flow states in the stay vane channel when operating at off-design conditions in pump mode. Experimental and numerical investigations obtained a shifting velocity distribution between the shroud and hub of the distributor when continuously increasing the discharge in the part-load range. Simulations captured the occurrence of this changing flow state in the stay vane channel reasonably well. A further increase of the discharge showed a uniformly redistributed mean flow of both hub and shroud side. Monitoring points and integral quantities from measurements and transient simulations were used to interpret the development of transient flow patterns in the stay vane channel at the operating point of strongest asymmetrical flow. During simulation and measurement, a dominant rotating stall inception was observed near the design flow of the pump turbine. At this point where the stall becomes severe, a high level of correlation between the signals of the upper and lower stalled flow in the stay vane channel was calculated. Further simulations for different guide vane positions predicted a strong influence of the guide vane position on the structure of rotating stall.

1997 Best Paper Award—Controls and Diagnostics Committee: Active Stabilization of Rotating Stall and Surge in a Transonic Single-Stage Axial Compressor

1998 ◽  
Vol 120 (4) ◽  
pp. 625-636 ◽  
Author(s):  
H. J. Weigl ◽  
J. D. Paduano ◽  
L. G. Fre´chette ◽  
A. H. Epstein ◽  
E. M. Greitzer ◽  
...  
Keyword(s):  
Mass Flow ◽  
Control Strategies ◽  
Axial Compressor ◽  
Gain Control ◽  
Rotating Stall ◽  
Forced Response ◽  
Single Stage ◽  
Rotor Speed ◽  
Stall Inception ◽  
Spatial Harmonics

Rotating stall and surge have been stabilized in a transonic single-stage axial compressor using active feedback control. The control strategy is to sense upstream wall static pressure patterns and feed back the signal to an annular array of twelve separately modulated air injectors. At tip relative Mach numbers of 1.0 and 1.5 the control achieved 11 and 3.5 percent reductions in stalling mass flow, respectively, with injection adding 3.6 percent of the design compressor mass flow. The aerodynamic effects of the injection have also been examined. At a tip Mach number, Mtip, of 1.0, the stall inception dynamics and effective active control strategies are similar to results for low-speed axial compressors. The range extension was achieved by individually damping the first and second spatial harmonics of the prestall perturbations using constant gain feedback. At a Mtip of 1.5 (design rotor speed), the prestall dynamics are different than at the lower speed. Both one-dimensional (surge) and two-dimensional (rotating stall) perturbations needed to be stabilized to increase the compressor operating range. At design speed, the instability was initiated by approximately ten rotor revolutions of rotating stall followed by classic surge cycles. In accord with the results from a compressible stall inception analysis, the zeroth, first, and second spatial harmonics each include more than one lightly damped mode, which can grow into the large amplitude instability. Forced response testing identified several modes traveling up to 150 percent of rotor speed for the first three spatial harmonics; simple constant gain control cannot damp all of these modes and thus cannot stabilize the compressor at this speed. A dynamic, model-based robust controller was therefore used to stabilize the multiple modes that comprise the first three harmonic perturbations in this transonic region of operation.

scholarly journals Flow and Noise Characteristics of Centrifugal Fan under Different Stall Conditions

2014 ◽  
Vol 2014 ◽  
pp. 1-9 ◽  
Author(s):  
Lei Zhang ◽  
Shoufang Liang ◽  
Chenxing Hu
Keyword(s):  
Flow Field ◽  
Power Level ◽  
Aerodynamic Characteristics ◽  
Rotating Stall ◽  
Field Analysis ◽  
Aerodynamic Noise ◽  
Navier Stokes ◽  
Implicit Time ◽  
Centrifugal Fan ◽  
Noise Characteristics

An implicit, time-accurate 3D Reynolds-averaged Navier-Stokes (RANS) solver is used to simulate the rotating stall phenomenon in a centrifugal fan. The goal of the present work is to shed light on the flow field and particularly the aerodynamic noise at different stall conditions. Aerodynamic characteristics, frequency domain characteristics, and the contours of sound power level under two different stall conditions are discussed in this paper. The results show that, with the decrease of valve opening, the amplitude of full pressure and flow fluctuations tends to be larger and the stall frequency remains the same. The flow field analysis indicates that the area occupied by stall cells expands with the decrease of flow rate. The noise calculation based on the simulation underlines the role of vortex noise after the occurrence of rotating stall, showing that the high noise area rotates along with the stall cell in the circumferential direction.

Modeling for the Development and Evaluation of Strategies for Controlling Flow Instabilities in Transonic Compressors

2007 ◽  
Author(s):  
John N. Chi
Keyword(s):  
Gas Turbine ◽  
Mass Flow ◽  
High Speed ◽  
Rotating Stall ◽  
Air Injection ◽  
Stall Inception ◽  
Operating Range ◽  
Transonic Compressor ◽  
Hot Air ◽  
Injection Model

A gas turbine engine consists of three primary components: a compressor, a combustion chamber, and a turbine. The operating range, performance, and reliability of gas turbine engines are limited by aerodynamic instabilities that occur in the compressor at low mass flow rates. Two of such compressor instabilities are rotating stall and surge. The stabilization of compression systems by means of active control has been demonstrated on several research compressors using different actuators such as inlet guide vanes, bleed valves, and air injection to manipulate the compressor flow field. This paper presents validated models of the steady and unsteady behaviors of air injection in high speed axial flow compressors that can be used for feasibility studies and control algorithm development. The steady air injection model consists of a control volume analysis coupled with wind tunnel measurements to characterize the changes in flow profiles entering the compressor and a streamline curvature analysis to model the response of the compressor blade rows to the different inlet span-wise profiles generated by the jet actuator. The steady air injection model was validated with experimentally measured span-wise profiles and compressor speed-lines, and then used to study the effect of hot air injection on the performance of a transonic compressor. The results show that injecting hot air into a transonic compressor has a potential increase in the operating range (i.e., decrease in the stalling mass flow rate) and a decrease in the total pressure rise across the transonic compressor. A modified theoretical stall inception model for high speed machines with air injection actuation is also presented. The compressible rotating stall inception model is a two-dimensional linearized stability model and pre-stall dynamics measurements from a single stage transonic compressor were used to validate the model. The compressible rotating stall inception model is an important tool that can be used for studying the effects of compressor design parameters on stability during compressor redesign, and for designing and evaluating feedback controllers.

Effects of Rotating Inlet Distortion on a 5-Stage HP-Compressor

2001 ◽  
Author(s):  
Thomas Peters ◽  
Thomas Bürgener ◽  
Leonhard Fottner
Keyword(s):  
Pressure Sensors ◽  
Rotating Stall ◽  
Stall Inception ◽  
Inlet Distortion ◽  
Compressor Rotor ◽  
Surge Margin ◽  
Compressor Design ◽  
High Rotation Speed ◽  
Design Speed ◽  
Compressor Map

In a twin-spool jet engine the HP-compressor experiences a rotating inlet distortion if rotating stall in the upstream LP-compressor occurs. This destabilizing effect on the compressor operating behavior may lead to HP-compressor instabilities like rotating stall or surge. In order to investigate this specific type of unsteady inlet distortion a 5-stage HP-compressor is operated with a newly developed high rotation speed distortion generator in the inlet duct. It produces a rotating inlet distortion with up to 65% of the compressor design speed rotating clockwise or counterclockwise with the compressor rotor. Kulite pressure sensors as well as hot-wire probes are installed to resolve the unsteady character of the inlet distortion, to define the compressor map and to analyse the stall inception process. Describing the rotating inlet distortion and its influence on the compressor operating behavior will be the major objective of this paper. In the experiment the distortion speed of an inlet distortion rotating clockwise with the compressor rotor is varied at different compressor speeds and the effects on the surge margin are analysed.

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