Comparison Between Complete Hilbert Transform and Simplified Solutions of the Moore Rotating Stall Model

1998 ◽  
Vol 120 (3) ◽  
pp. 446-453
Author(s):  
G. L. Arnulfi ◽  
F. L. Ghiglino ◽  
A. F. Massardo
Keyword(s):  
Hilbert Transform ◽  
Complete Solution ◽  
Axial Compressor ◽  
Axial Flow ◽  
Detailed Comparison ◽  
Rotating Stall ◽  
Flow Coefficient ◽  
Flow Perturbation ◽  
Wide Range ◽  
The Hilbert Transform

The main objective of this work is the analysis and the comparison between different methods utilized to solve the Moore rotating stall model. To date only simplified relations between the axial flow perturbation g and the transverse one h have been utilized and presented in literature, such as h′ = −g or the truncated Fourier series. On the contrary, in this paper the accurate relation given by the Hilbert Transform is utilized, and to improve the numerical stability of the method, a new expression of the first derivative of transverse flow coefficient perturbation is proposed and utilized. A complete and detailed comparison between the results of the simplified methods and the solution proposed here is presented. This comparison is extended to a wide range of geometric and physical compressor parameters, and it allows the accuracy of simplified approaches to be tested. Finally, a correlative approach estimating overall rotating stall effects based on the complete solution proposed here is presented. It allows rotating stall influence to be quickly and easily taken into account in several axial compressor areas (design, optimization, active control, etc.).

scholarly journals Comparison Between Complete Hilbert Transform and Simplified Solutions of the Moore Rotating Stall Model

1996 ◽  
Author(s):  
Gianmario L. Arnulfi ◽  
Fabio L. Ghiglino ◽  
Aristide F. Massardo
Keyword(s):  
Hilbert Transform ◽  
Complete Solution ◽  
Axial Compressor ◽  
Axial Flow ◽  
Detailed Comparison ◽  
Rotating Stall ◽  
Flow Coefficient ◽  
Flow Perturbation ◽  
Wide Range ◽  
The Hilbert Transform

The main objective of this work is the analysis and the comparison between different methods utilised to solve the Moore rotating stall model. To date only simplified relations between the axial flow perturbation g and the transverse one h have been utilised and presented in literature, such as h′ = −g or the truncated Fourier series. On the contrary, in this paper the accurate relation given by the Hilbert Transform is utilised, and to improve the numerical stability of the method a new expression of the first derivative of transverse flow coefficient perturbation is proposed and utilised. A complete and detailed comparison between the results of the simplified methods and the solution proposed here is presented. This comparison is extended to a wide range of geometrical and physical compressor parameters, and it allows the accuracy of simplified approaches to be tested. Finally, a correlative approach estimating overall rotating stall effects based on the complete solution proposed here is presented. It allows rotating stall influence to be quickly and easily taken into account in several axial compressor areas (design, optimisation, active control, etc.).

Parametric Study and Meanline Design of Multistage Axial Flow Compressor for Process Application

2015 ◽  
Author(s):  
Ambrish Singh ◽  
Nand Kumar Singh
Keyword(s):  
Axial Compressor ◽  
Axial Flow ◽  
Flow Coefficient ◽  
Detailed Design ◽  
Axial Flow Compressor ◽  
Wide Range ◽  
Last Stage ◽  
Flow Compressor ◽  
High Level ◽  
Selection Of

An industrial axial compressor has to meet a wide range of operation requirements. These machines have to run continuously for four to five years before going for overhaul. Hence, overall high level of efficiency may be slightly relaxed to meet this requirement. This requires axial flow compressor design to be more conservative and flexible to accommodate changes required for process industry through modern design & development approaches. This paper deals with finding of optimum flow path configuration that will allow a successful detailed design to follow. The effect of various parameters such as hub to tip ratio, proper selection of design rpm, reactions, work coefficient & flow coefficient has been investigated and selected for optimal performance of the machine. Last stage of the compressor is selected as radial stage with the advantage of reduction in axial length and to provide radial outlet, which is more suitable outlet configuration. Meanline design and streamline analysis for each configuration is determined to find out good operating range (stall-free operation) before starting the detailed design.

Characteristics of Stable Rotating Stall Cells in an Axial Compressor

2017 ◽  
Author(s):  
Adam R. Hickman ◽  
Scott C. Morris
Keyword(s):  
Flow Field ◽  
High Speed ◽  
Pressure Ratio ◽  
Pressure Sensors ◽  
Axial Compressor ◽  
Field Measurements ◽  
Rotating Stall ◽  
Flow Coefficient ◽  
Stable Operation ◽  
Double Phase

Flow field measurements of a high-speed axial compressor are presented during pre-stall and post-stall conditions. The paper provides an analysis of measurements from a circumferential array of unsteady shroud static pressure sensors during stall cell development. At low-speed, the stall cell approached a stable size in approximately two rotor revolutions. At higher speeds, the stall cell developed within a short amount of time after stall inception, but then fluctuated in circumferential extent as the compressor transiently approached a stable post-stall operating point. The size of the stall cell was found to be related to the annulus average flow coefficient. A discussion of Phase-Locked Average (PLA) statistics on flow field measurements during stable operation is also included. In conditions where rotating stall is present, flow field measurements can be Double Phase-Locked Averaged (DPLA) using a once-per-revolution (1/Rev) pulse and the period of the stall cell. The DPLA method provides greater detail and understanding into the structure of the stall cell. DPLA data indicated that a stalled compressor annulus can be considered to contained three main regions: over-pressurized passages, stalled passages, and recovering passages. Within the over-pressured region, rotor passages exhibited increased blade loading and pressure ratio compared to pre-stall values.

Improved criteria for stall-free preliminary design of axial compressor of aero gas turbine engines

2018 ◽  
Vol 233 (9) ◽  
pp. 3286-3297 ◽  
Author(s):  
MR Aligoodarz ◽  
A Mehrpanahi ◽  
M Moshtaghzadeh ◽  
A Hashiehbaf
Keyword(s):  
Gas Turbine ◽  
Large Scale ◽  
Axial Compressor ◽  
Axial Flow ◽  
Design Criterion ◽  
Flow Coefficient ◽  
Turbine Engines ◽  
Gas Turbine Engines ◽  
Parameter Ranges ◽  
Axial Flow Compressors

A worldwide effort has been devoted to developing highly efficient and reliable gas turbine engines. There exist many prominent factors in the development of these engines. One of the most important features of the optimal design of axial flow compressors is satisfying the allowable range for various parameters such as flow coefficient, stage loading, the degree of reaction, De-Haller number, etc. But, there are some applicable cases that the mentioned criteria are exceeded. One of the most famous parameters is De-Haller number, which according to literature data should not be kept less than 0.72 in any stage of the axial compressor. A deep insight into the current small- or large-scale axial flow compressors shows that a discrepancy will occur among design criterion for De-Haller number and experimental measurements in which the De-Haller number is less than the design limit but no stall or surge is observed. In this paper, an improved formulation is derived based on one-dimensional modeling for predicting the stall-free design parameter ranges especially stage loading, flow coefficient, etc. for various combinations. It was found that the current criterion is much more accurate than the De-Haller criterion for design purposes.

Active Stabilization of Rotating Stall in a Three-Stage Axial Compressor

1993 ◽  
Author(s):  
Joel M. Haynes ◽  
Gavin J. Hendricks ◽  
Alan H. Epstein
Keyword(s):  
High Speed ◽  
Travelling Waves ◽  
Axial Compressor ◽  
Open Loop ◽  
Rotating Stall ◽  
Forced Response ◽  
Flow Coefficient ◽  
Design Parameters ◽  
Time Lags ◽  
Active Stabilization

A three-stage, low speed axial research compressor has been actively stabilized by damping low amplitude circumferentially travelling waves which can grow into rotating stall. Using a circumferential array of hot wire sensors, and an array of high speed individually positioned control vanes as the actuator, the first and second spatial harmonics of the compressor were stabilized down to a characteristic slope of 0.9, yielding an 8% increase in operating flow range. Stabilization of the third spatial harmonic did not alter the stalling flow coefficient. The actuators were also used open loop to determine the forced response behavior of the compressor. A system identification procedure applied to the forced response data then yielded the compressor transfer function. The Moore-Greitzer, 2-D, stability model was modified as suggested by the measurements to include the effect of blade row time lags on the compressor dynamics. This modified Moore-Greitzer model was then used to predict both the open and closed loop dynamic response of the compressor. The model predictions agreed closely with the experimental results. In particular, the model predicted both the mass flow at stall without control and the design parameters needed by, and the range extension realized from, active control.

Performance Study of a Mixed Flow Impeller Covering an Unsteady Flow Field

1992 ◽  
Vol 206 (2) ◽  
pp. 83-93 ◽  
Author(s):  
S Sarkar
Keyword(s):  
Axial Flow ◽  
Rotating Stall ◽  
Operating Conditions ◽  
Performance Study ◽  
Mixed Flow ◽  
Pump Impeller ◽  
Wide Range ◽  
Reversal Flow ◽  
Flow Through ◽  
Flow Pump

The results presented here are part of a detailed programme measuring the aerodynamics of a high specific speed mixed flow pump impeller over a wide range of operating conditions, including its behaviour in the unsteady stalled regime. The aim is to elucidate the physics of the flow through such an impeller. The noticeable features are the formation of part-span rotating stall cells having no periodicity and organized structure at reduced flow and also the shifting positions of reversal flow pockets as the flowrate changes. Measurements of loss and its variation with span-wise positions and flowrates enable the variation of local efficiency to be determined. The overall flow picture is similar to that expected in an axial flow impeller, though the present impeller displays a narrow stall hysteresis loop almost right through its operating range.

Prestall Instability in Axial Flow Compressors

2020 ◽  
Vol 142 (7) ◽  
Author(s):  
Mario Eck ◽  
Roland Rückert ◽  
Dieter Peitsch ◽  
Marc Lehmann
Keyword(s):  
Pressure Fluctuations ◽  
Axial Compressor ◽  
Axial Flow ◽  
Leading Edge ◽  
Propagation Speed ◽  
Flow Coefficient ◽  
Spectral Signature ◽  
Time Resolved ◽  
Pressure Transducers ◽  
Flow Disturbances

Abstract The aim of the present paper is to improve the physical understanding of discrete prestall flow disturbances developing in the tip area of the compressor rotor. For this purpose, a complementary instrumentation was used in a single-stage axial compressor. A set of pressure transducers evenly distributed along the circumference surface mounted in the casing near the rotor tip leading edges measures the time-resolved wall pressures simultaneously to an array of transducers recording the chordwise static pressures. The latter allows for plotting quasi-instantaneous casing pressure contours. Any occurring flow disturbances can be properly classified using validated frequency analysis methods applied to the data from the circumferential sensors. While leaving the flow coefficient constant, a continuously changing number of prestall flow disturbances appears to be causing a unique spectral signature, which is known from investigations on rotating instability. Any arising number of disturbances is matching a specific mode order found within this signature. While the flow coefficient is reduced, the propagation speed of prestall disturbances increases linearly, and meanwhile, the speed seems to be independent from the clearance size. Casing contour plots phase-locked to the rotor additionally provide a strong hint on prestall disturbances clearly not to be caused by a leading edge separation. Data taken beyond the stalling limit demonstrate a complex superposition of stall cells and flow disturbances, which the title “prestall disturbance” therefore does not fit to precisely any more. Different convection speeds allow the phenomena to be clearly distinguished from each other. Furthermore, statistical analysis of the pressure fluctuations caused by the prestall disturbances offer the potential to use them as a stall precursor or to quantify the deterioration of the clearance height between the rotor blade tips and the casing wall during the lifetime of an engine.

CFD-based blade shape optimization of MGT-70(3)axial flow compressor

2019 ◽  
Vol 30 (6) ◽  
pp. 3307-3321 ◽  
Author(s):  
Mohammad Reza Pakatchian ◽  
Hossein Saeidi ◽  
Alireza Ziamolki
Keyword(s):  
Neural Network ◽  
Artificial Neural Network ◽  
Shape Optimization ◽  
Fluid Dynamic ◽  
Axial Compressor ◽  
Axial Flow ◽  
Design Parameters ◽  
Content Type ◽  
Wide Range ◽  
Artificial Neural

Purpose This study aims at enhancing the performance of a 16-stage axial compressor and improving the operating stability. The adopted approaches for upgrading the compressor are artificial neural network, optimization algorithms and computational fluid dynamics. Design/methodology/approach The process starts with developing several data sets for certain 2D sections by means of training several artificial neural networks (ANNs) as surrogate models. Afterward, the trained ANNs are applied to the 3D shape optimization along with parametrization of the blade stacking line. Specifying the significant design parameters, a wide range of geometrical variations are considered by implementation of appropriate number of design variables. The optimized shapes are analyzed by applying computational fluid dynamic to obtain the best geometry. Findings 3D optimal results show improvements, especially in the case of decreasing or elimination of near walls corner separations. In addition, in comparison with the base geometry, numerical optimization shows an increase of 1.15 per cent in total isentropic efficiency in the first four stages, which results in 0.6 per cent improvement for the whole compressor, even while keeping the rest of the stages unchanged. To evaluate the numerical results, experimental data are compared with obtained data from simulation. Based on the results, the highest absolute relative deviation between experimental and numerical static pressure is approximately 7.5 per cent. Originality/value The blades geometry of an axial compressor used in a heavy-duty gas turbine is optimized by applying artificial neural network, and the results are compared with the base geometry numerically and experimentally.

Surge and Rotating Stall in Axial Flow Compressors—Part II: Experimental Results and Comparison With Theory

1976 ◽  
Vol 98 (2) ◽  
pp. 199-211 ◽  
Author(s):  
E. M. Greitzer
Keyword(s):  
Quantitative Description ◽  
Axial Compressor ◽  
Axial Flow ◽  
Rotating Stall ◽  
Experimental Results ◽  
System Response ◽  
Physical Parameters ◽  
Geometrical Parameters ◽  
Compression System ◽  
Transient System

This paper reports an experimental study of axial compressor surge and rotating stall. The experiments were carried out using a three stage axial flow compressor. With the experimental facility the physical parameters of the compression system could be independently varied so that their influence on the transient system behavior can be clearly seen. In addition, a new data analysis procedure has been developed, using a plenum mass balance, which enables the instantaneous compressor mass flow to be accurately calculated. This information is coupled to the unsteady pressure measurements to provide the first detailed quantitative picture of instantaneous compressor operation during both surge and rotating stall transients. The experimental results are compared to a theoretical model of the transient system response. The theoretical criterion for predicting which mode of compression system instability, rotating stall or surge, will occur is in good accord with the data. The basic scaling concepts that have been developed for relating transient data at different corrected speeds and geometrical parameters are also verified. Finally, the model is shown to provide an adequate quantitative description of the motion of the compression system operating point during the transients that occur subsequent to the onset of axial compressor stall.

The Measurement and Interpretation of Flow within Rotating Stall Cells in Axial Compressors

1978 ◽  
Vol 20 (2) ◽  
pp. 101-114 ◽  
Author(s):  
I. J. Day ◽  
N.A. Cumpsty
Keyword(s):  
Flow Direction ◽  
Axial Flow ◽  
Tangential Direction ◽  
Rotating Stall ◽  
Design Flow ◽  
Flow Measurements ◽  
Axial Compressors ◽  
Multi Stage ◽  
Wide Range ◽  
Flow Compressor

Detailed flow measurements obtained by a new measuring technique are presented for the flow in a stalled axial-flow compressor. Results were obtained from a wide range of compressor builds, including multi-stage and single-stage configurations of various design flow rates and degrees of reaction. Instantaneous recordings of absolute velocity, flow direction and total and static pressures have been included for both full-span and part-span stall. With the aid of these results, it has been shown that the conventional model of the flow in a stall cell is erroneous. An alternative model is proposed, based on the observation that the fluid must cross from one side of the cell to the other in order to preserve continuity in the tangential direction. An investigation of the experimental results also reveals the finer details of the flow in the cell and shows how these details are related to the design flow rate of the compressor. The influence of these cell details on the power absorbed by a stalled compressor are investigated, and consideration is given to the complex pressure patterns encountered in the compressor.

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