FLOW PHYSICS DURING SURGE AND RECOVERY OF A MULTI-STAGE HIGH-SPEED COMPRESSOR

2021 ◽  
pp. 1-29
Author(s):  
Fanzhou Zhao ◽  
John Dodds ◽  
Mehdi Vahdati
Keyword(s):  
High Speed ◽  
Transient Flow ◽  
Rotating Stall ◽  
Blade Loading ◽  
Acoustic Reflection ◽  
Hot Air ◽  
Multi Stage ◽  
Strong Shear ◽  
Flow Features ◽  
Urans Cfd

Abstract Stall followed by surge in a high-speed compressor can lead to violent disruption of the flow, damage to the blade structures and eventually engine shutdown. Knowledge of unsteady blade loading during surge is crucial for compressor design such as axial gap optimisation. The aim of this paper is to demonstrate the feasibility of using 3D full assembly URANS CFD for modelling surge cycles of an 8-stage high-speed compressor rig. Results from this work show stalling of the mid-stages is the surge trigger. During the flow reversal, a strong acoustic reflection occurs when the convected entropy perturbations reach the intake opening, which increase the blade loading significantly. During recovery, a hysteresis loop was recorded due to hot air reingestion, which led to a strong shear at mid-span of the IGV/R1 domain and the formation of rotating helical flow structures. The final phase of recovery was accompanied by a 4-cell multi-row tip rotating stall, which was cleared as the compressor recovered to the forward flow characteristic. It was also shown that the single passage model, despite its limitations and shortcomings in modelling recovery, can provide reasonably accurate transient flow features during surge and thus considerable insight to the flow behaviour, which can be used to obtain a first approximation of casing and blade loading.

Flow Physics During Surge and Recovery of a Multi-Stage High-Speed Compressor

2020 ◽  
Author(s):  
Fanzhou Zhao ◽  
John Dodds ◽  
Mehdi Vahdati
Keyword(s):  
High Speed ◽  
Transient Flow ◽  
Rotating Stall ◽  
Blade Loading ◽  
Acoustic Reflection ◽  
Hot Air ◽  
Multi Stage ◽  
Strong Shear ◽  
Flow Features ◽  
Urans Cfd

Abstract Stall followed by surge in a high-speed compressor can lead to violent disruption of the flow, damage to the blade structures and eventually engine shutdown. Knowledge of unsteady blade loading during surge is crucial for compressor design such as axial gap optimisation. The aim of this paper is to demonstrate the feasibility of using 3D full assembly URANS CFD for modelling surge cycles of an 8-stage high-speed compressor rig. Results from this work show stalling of the mid-stages is the surge trigger. During the flow reversal, a strong acoustic reflection occurs when the convected entropy perturbations reach the intake opening, which increase the blade loading significantly. During recovery, a hysteresis loop was recorded due to hot air reingestion, which led to a strong shear at mid-span of the IGV/R1 domain and the formation of rotating helical flow structures. The final phase of recovery was accompanied by a 4-cell multi-row tip rotating stall, which was cleared as the compressor recovered to the forward flow characteristic. It was also shown that the single passage model, despite its limitations and shortcomings in modelling recovery, can provide reasonably accurate transient flow features during surge and thus considerable insight to the flow behaviour, which can be used to obtain a first approximation of casing and blade loading.

Post-Stall Behaviour of a Multi-Stage High Speed Compressor at Off-Design Conditions

2018 ◽  
Author(s):  
Fanzhou Zhao ◽  
John Dodds ◽  
Mehdi Vahdati
Keyword(s):  
High Speed ◽  
Transient Flow ◽  
Axisymmetric Flow ◽  
Axial Compressor ◽  
Rotating Stall ◽  
Experimental Measurements ◽  
Cfd Simulations ◽  
Blade Loading ◽  
Transient Behaviour ◽  
Multi Stage

Stall followed by surge in a high speed compressor can lead to violent disruption of flow, damage to the blade structures and, eventually, engine shutdown. A knowledge of unsteady blade loading during such events is crucial in determining the aeroelastic stability of blade structures, experimental test of such events is however significantly limited by the potential risk and cost associated. Numerical modelling, such as unsteady CFD simulations, can provide a more informative understanding of the flow field and blade forcing during post-stall events, however very limited publications, particularly concerning multi-stage high speed compressors, can be found. The aim of this paper is to demonstrate the possibility of using CFD for modelling full-span rotating stall and surge in a multi-stage high speed compressor, and, where possible, validate the results against experimental measurements. The paper presents an investigation into the onset and transient behaviour of rotating stall and surge in an 8-stage high speed axial compressor at off-design conditions, based on 3D URANS computations, with the ultimate future goal being aeroelastic modelling of blade forcing and response during such events. By assembling the compressor with a small and a large exit plenum volume respectively, a full-span rotating stall and a deep surge were modelled. Transient flow solutions obtained from numerical simulations showed trends matching with experimental measurements. Some insights are gained as to the onset, propagation and merging of stall cells during the development of compressor stall and surge. It is shown that surge is initiated as a result of an increase in the size of the rotating stall disturbance, which grows circumferentially to occupy the full circumference resulting in an axisymmetric flow reversal.

Numerical Investigation of VSVs Mal-Schedule Effects in a Three-Stage Axial Compressor

2014 ◽  
Author(s):  
Yan-Ling Li ◽  
Abdulnaser Sayma
Keyword(s):  
High Speed ◽  
High Performance ◽  
Numerical Study ◽  
Axial Compressor ◽  
Rotating Stall ◽  
Multi Stage ◽  
Flow Features ◽  
Grid Points ◽  
Stage Matching ◽  
Outflow Boundary

Variable Stator Vanes (VSVs) are commonly used in multi-stage axial compressors for stage matching at part load operations and during start up. Improper VSVs settings or malfunction of the controlling actuator system can lead to compressor instabilities including rotating stall and surge. It is important to be able to predict the aerodynamic behaviour of compressors in such events to either produce tolerant designs or incorporate diagnosis and recovery systems. This paper presents a numerical study of a compressor operating near the stall boundary for a mal-scheduled VSVs case. A high-speed three-stage axial compressor with Inlet Guide Vanes (IGV) is used in the investigation because of its relative simplicity and availability of geometry and aerodynamic data. A 3D RANS viscous unsteady time-accurate flow solver was used to perform the full annulus simulation with a downstream variable nozzle to control outflow boundary conditions. The unstructured mesh contained about 25 million grid points and the simulation was performed on a high performance computing cluster for many engine rotations. Rotating stall with one single cell covering several passages in all three rotors was predicted which propagated at approximately half of the shaft speed. Full analysis of the flow features is presented in the paper.

scholarly journals An Investigation of Surge in a High-Speed Centrifugal Compressor Using Digital PIV

2000 ◽  
Vol 123 (2) ◽  
pp. 418-428 ◽  
Author(s):  
Mark P. Wernet ◽  
Michelle M. Bright ◽  
Gary J. Skoch
Keyword(s):  
Flow Field ◽  
Centrifugal Compressor ◽  
High Speed ◽  
Transient Flow ◽  
Dynamic Pressure ◽  
Rotating Stall ◽  
Transient Pressure ◽  
Pressure Transducers ◽  
Stable Operating ◽  
Particle Imaging

Compressor stall is a catastrophic breakdown of the flow in a compressor, which can lead to a loss of engine power, large pressure transients in the inlet/nacelle, and engine flameout. The implementation of active or passive strategies for controlling rotating stall and surge can significantly extend the stable operating range of a compressor without substantially sacrificing performance. It is crucial to identify the dynamic changes occurring in the flow field prior to rotating stall and surge in order to control these events successfully. Generally, pressure transducer measurements are made to capture the transient response of a compressor prior to rotating stall. In this investigation, Digital Particle Imaging Velocimetry (DPIV) is used in conjunction with dynamic pressure transducers to capture transient velocity and pressure measurements simultaneously in the nonstationary flow field during compressor surge. DPIV is an instantaneous, planar measurement technique that is ideally suited for studying transient flow phenomena in high-speed turbomachinery and has been used previously to map the stable operating point flow field in the diffuser of a high-speed centrifugal compressor. Through the acquisition of both DPIV images and transient pressure data, the time evolution of the unsteady flow during surge is revealed.

scholarly journals Influence of blade vibration on part-span rotating stall

2020 ◽  
Vol 4 ◽  
pp. 285-295
Author(s):  
Fanzhou Zhao ◽  
John Dodds ◽  
Mehdi Vahdati
Keyword(s):  
High Speed ◽  
Rotating Stall ◽  
Tip Clearance ◽  
Blade Vibration ◽  
Natural Form ◽  
Multi Stage ◽  
Sensitivity Studies ◽  
Aeroelastic Simulations ◽  
Pattern Sensitivity ◽  
Lock In

This paper presents the interaction between blade vibration and part-span rotating stall in a multi-stage high speed compressor. Unsteady aerodynamic and aeroelastic simulations were conducted using URANS CFD. Steady state computations showed short length scale disturbances formed local to the tip of a front stage rotor. Using a full annulus model, these disturbances were shown to coalesce into flow structures rotating around the annulus at approximately 76% of the shaft rotational speed. Natural evolution of the rotating stall did not result in a coherent spatial pattern. Sensitivity studies showed that operating point and tip clearance have significant impact on the developed state of rotating stall. Subsequent analyses carried out with prescribed rotor blade vibration showed a spatial ‘lock-in’ event where the circumferential order of the part-span rotating stall shifted to match that induced by the vibration mode. Moreover, in contrast to its natural form in the absence of vibration, the fully developed rotating stall showed a coherent stall signal. More importantly, it was found that numerical boundary conditions such as mixing plane and sliding planes can significantly influence the outcome of prediction.

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.

Integrated Control of Rotating Stall and Surge in High-Speed Multi-Stage Compression Systems

1997 ◽  
Author(s):  
K. M. Eveker ◽  
D. L. Gysling ◽  
C. N. Nett ◽  
O. P. Sharma
Keyword(s):  
Active Control ◽  
Control Strategy ◽  
High Speed ◽  
Control Strategies ◽  
Integrated Control ◽  
Axial Flow ◽  
Rotating Stall ◽  
Low Flow ◽  
Multi Stage ◽  
Simultaneous Control

Aeroengines operate in regimes for which both rotating stall and surge impose low flow operability limits. Thus, active control strategies designed to enhance operability of aeroengines must address both rotating stall and surge as well as their interaction. In this paper, a previously developed nonlinear control strategy that achieves simultaneous active control of rotating stall and surge is applied to a high-speed 3-stage axial flow compression system with operating parameters representative of modern aeroengines. The controller is experimentally validated for 2 compressor builds and its robustness to radial distortion assessed. For actuation, the control strategy utilizes an annulus-averaged bleed valve with bandwidth on the order of the rotor frequency. For sensing, measurements of the circumferential asymmetry and annulus-averaged unsteadiness of the flow through the compressor are used. Experimental validation of simultaneous control of rotating stall and surge in a high-speed environment with minimal sensing and actuation requirements is viewed as another important step towards applying active control to enhance operability of compression systems in modem aeroengines.

Comparisons Between Measured and Calculated Stall Development in Four High-Speed Multi-Stage Compressors

1997 ◽  
Author(s):  
A. A. J. Demargne ◽  
J. P. Longley
Keyword(s):  
Numerical Simulation ◽  
High Speed ◽  
Development Process ◽  
Rotating Stall ◽  
Two Dimensional ◽  
Stall Inception ◽  
Mass Injection ◽  
Multi Stage ◽  
Design Speed

In this paper the development of rotating stall in four different high-speed multi-stage compressors is investigated using a numerical simulation. Below 90 per cent of design speed the model calculates well the two-dimensional moderate to long lengthscale development of rotating stall, irrespective of the lengthscale and form of the stall inception mechanism. At higher operating speeds the model is less reliable, providing better comparisons for those compressors which exhibited modal rather than spike stall inception. The model is also used to investigate the feasibility of actively controlling the stall development process in a compressor. The conclusions reached are that mass injection and removal is far more effective than varying the blade stagger angles and that sensors must be upstream of actuators.

Density Measurement of Three-Phase Flows Inside of Vertical Piping Using Planar Laser Induced Fluorescence PLIF

2021 ◽  
Author(s):  
Amy Brooke McCleney ◽  
Kevin Robert Supak
Keyword(s):  
High Speed ◽  
Gas Flow ◽  
Transient Flow ◽  
Two Phase ◽  
Mixture Density ◽  
Three Phase ◽  
Planar Laser ◽  
Flow Features ◽  
Oil Water ◽  
Oil Gas

Abstract Planar laser induced fluorescence (PLIF) is a measurement technique that can be used to provide a laboratory reference for validating the performance of field instrumentation that either directly measures mixture density or infers it from a combination of ancillary techniques. PLIF density measurements offer high-speed response and the ability to resolve minute flow features in transient flow patterns. Fundamentally, PLIF can also be used to verify multiphase flow models and predictive tools that are used for designing production piping. The use of PLIF to determine an instantaneous mixture density of two-phase flows has been successfully accomplished in previous fundamental laboratory studies found in literature. However, the use of this technique to determine the mixture density of three-phase flows for field-related scenarios has not been previously evaluated. To assess PLIF as a potential reference measurement system, a testing effort was undertaken to measure the instantaneous mixture density from a comingled oil-gas, water-oil, and oil-water-gas flow that was subjected to slug, churn, and bubble transient flow conditions inside of vertical piping. The objective of this work was to compare and validate the results obtained using the PLIF measurement approach against a commercially available gamma densitometer and tomography system for a variety of flowing conditions. The PLIF technique was able to resolve transient flow features and density values for both two-phase and three-phase flows through the piping. Distinct slug flow features such as the slug head, gas pocket, pocket collapse, and the tail were captured by PLIF and were observable in the raw image sequence captured by a high-speed camera. Additionally, the results for a variety of water-oil-gas flowing conditions were within 3% difference of a mixture density model that was calculated from liquid and gas flow measurements utilized in the test facility. The comparison of the PLIF results to the reference instrumentation indicates that this technique is successful at obtaining a mixture density for steady and transient oil, water, and gas comingled flows.

A Method for Evaluating the Effect of Circumferential Inlet Distortion on the Aerodynamic Stability of Multi-Stage Axial-Flow Compressors

2010 ◽  
Author(s):  
Tsuguji Nakano ◽  
Andy Breeze-Stringfellow
Keyword(s):  
Steady State ◽  
High Speed ◽  
Axial Flow ◽  
Pressure Rise ◽  
Stability Limit ◽  
Rotating Stall ◽  
Classical Dynamic ◽  
Inlet Flow ◽  
Inlet Distortion ◽  
Multi Stage

A simple engineering parameter to evaluate the stability of high-speed multi-stage compressors with distorted inlet flow has been derived based on a simplified semi-compressible linear stability model. The parameter consists of steady-state flow quantities and geometric parameters of the compressor and it indicates that the circumferential integral of the slope of the steady-state individual blade row static pressure rise characteristics is important in the determination of the compressor stability limit in the presence of distortion. The parameter reduces to the author’s rotating stall inception parameter in the limit of non-distorted inlet flow. Since the model includes a downstream plenum and throttle, a condition for pure surge inception with undistorted inlet flow has been deduced. The pure surge conditions can be reduced to the classical dynamic and static instability conditions in the limit of a constant annulus area incompressible compressor. The results indicate that rotating stall always precedes surge instability, as many engineers and researchers would expect from experience. The parameter for instability with inlet distortion was calculated using test data measured in a high-speed 5-stage compressor with two different types of circumferential inlet distortion, and the results show that the parameter has a strong correlation with the data and is an improvement over the classical incompressible stability parameter. The results demonstrate that the parameter captures much of the physics important during the instability inception in a high-speed multi-stage compressor subjected to circumferential inlet distortion. The parameter clearly shows how each compressor component’s characteristics contribute to the overall stability in a high speed axial multi-stage compressor, therefore, it will aid engineers and designers in their understanding and prediction of the aerodynamic instability inception phenomena.

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