scholarly journals Unsteady Flow and Whirl-Inducing Forces in Axial-Flow Compressors: Part II—Analysis

2000 ◽  
Vol 123 (3) ◽  
pp. 446-452 ◽  
Author(s):  
F. F. Ehrich ◽  
Z. S. Spakovszky ◽  
M. Martinez-Sanchez ◽  
S. J. Song ◽  
D. C. Wisler ◽  
...  
Keyword(s):  
Unsteady Flow ◽  
Axial Flow ◽  
Turbine Engines ◽  
Jet Engines ◽  
Static Structure ◽  
Static Pressure Distribution ◽  
Eccentric Rotor ◽  
Unsteady Effects ◽  
Analytic Models ◽  
Axial Flow Compressors

An experimental and theoretical investigation was conducted to evaluate the effects seen in axial-flow compressors when the centerline of the rotor becomes displaced from the centerline of the static structure of the engine, thus creating circumferentially nonuniform rotor-tip clearances. This displacement produces unsteady flow and creates a system of destabilizing forces, which contribute significantly to rotor whirl instability in turbomachinery. These forces were first identified by Thomas (1958. Bull. AIM, 71, No. 11/12, pp. 1039–1063.) for turbines and by Alford (1965. J. Eng. Power, Oct., pp. 333–334) for jet engines. In Part I, the results from an experimental investigation of these phenomena were presented. In this Part II, three analytic models were used to predict both the magnitude and direction of the Thomas/Alford force in its normalized form, known as the β coefficient, and the unsteady effects for the compressors tested in Part I. In addition, the effects of a whirling shaft were simulated to evaluate differences between a rotor with static offset and an actual whirling eccentric rotor. The models were also used to assess the influence of the nonaxisymmetric static pressure distribution on the rotor spool, which was not measured in the experiment. The models evaluated were (1) the two-sector parallel compressor (2SPC) model, (2) the infinite-segment-parallel-compressor (ISPC) model, and (3) the two-coupled actuator disk (2CAD) model. The results of these analyses were found to be in agreement with the experimental data in both sign and trend. Thus, the validated models provide a general means to predict the aerodynamic destabilizing forces for axial flow compressors in turbine engines. These tools have the potential to improve the design of rotordynamically stable turbomachinery.

scholarly journals Unsteady Flow and Whirl-Inducing Forces in Axial-Flow Compressors: Part II — Analysis

2000 ◽  
Author(s):  
F. F. Ehrich ◽  
Z. S. Spakovszky ◽  
M. Martinez-Sanchez ◽  
S. J. Song ◽  
D. C. Wisler ◽  
...  
Keyword(s):  
Unsteady Flow ◽  
Axial Flow ◽  
Jet Engines ◽  
Static Structure ◽  
Static Pressure Distribution ◽  
Eccentric Rotor ◽  
Actuator Disc ◽  
Unsteady Effects ◽  
Analytic Models ◽  
Axial Flow Compressors

An experimental and theoretical investigation was conducted to evaluate the effects seen in axial-flow compressors when the centerline of the rotor becomes displaced from the centerline of the static structure of the engine, thus creating circumferentially non-uniform, rotor-tip clearances. This displacement produces unsteady flow and creates a system of destabilizing forces, which contribute significantly to rotor whirl instability in turbomachinery. These forces were first identified by Thomas (1958) for turbines and by Alford (1965) for jet engines. In Part I, the results from an experimental investigation of these phenomena were presented. In this Part II, three analytic models were used to predict both the magnitude and direction of the Thomas/Alford force in its normalized form, known as the β coefficient, and the unsteady effects for the compressors tested in Part I. In addition, the effects of a whirling shaft were simulated to evaluate differences between a rotor with static off-set and an actual whirling eccentric rotor. The models were also used to assess the influence of the non-axisymmetric static pressure distribution on the rotor spool, which was not measured in the experiment. The models evaluated were: (1) the Two-Sector Parallel Compressor (2SPC) model (Ehrich, 1993), (2) the Infinite-Segment-Parallel-Compressor (ISPC) model (Spakovszky, 2000), and (3) the Two-Coupled Actuator Disc (2CAD) model (Song and Cho, 2000). The results of these analyses were found to be in agreement with the experimental data in both sign and trend. Thus, the validated models provide the general means to predict the aerodynamic destabilizing forces for axial flow compressors in turbine engines. These tools have the potential to improve the design of rotordynamically stable turbomachinery.

scholarly journals Unsteady Flow and Whirl-Inducing Forces in Axial-Flow Compressors: Part I — Experiment

2000 ◽  
Author(s):  
A. F. Storace ◽  
D. C. Wisler ◽  
H.-W. Shin ◽  
B. F. Beacher ◽  
F. F. Ehrich ◽  
...  
Keyword(s):  
Unsteady Flow ◽  
Theoretical Investigation ◽  
Computational Models ◽  
Aerodynamic Force ◽  
Axial Flow ◽  
Pressure Rise ◽  
Static Structure ◽  
Stall Margin ◽  
First Time ◽  
Axial Flow Compressors

An experimental and theoretical investigation has been conducted to evaluate the effects seen in axial-flow compressors when the centerline of the rotor is displaced from the centerline of the static structure of the engine. This creates circumferentially non-uniform rotor-tip clearances, unsteady flow, and potentially increased clearances if the rotating and stationary parts come in contact. The result not only adversely affects compressor stall margin, pressure rise capability and efficiency but also generates an unsteady, destabilizing, aerodynamic force, called the Thomas/Alford force, which contributes significantly to rotor whirl instabilities in turbomachinery. Determining both the direction and magnitude of this force in compressors, relative to those in turbines, is especially important for the design of mechanically-stable turbomachinery components. Part I of this two-part paper addresses these issues experimentally and Part II presents analyses from relevant computational models. Our results clearly show that the Thomas/Alford force can promote significant backward rotor whirl over much of the operating range of modern compressors, although some regions of zero and forward whirl were found near the design point. This is the first time that definitive measurements, coupled with compelling analyses, have been reported in the literature to resolve the long-standing disparity in findings concerning the direction and magnitude of whirl-inducing forces important in the design of modern axial-flow compressors.

scholarly journals Unsteady Flow and Whirl-Inducing Forces in Axial-Flow Compressors: Part I—Experiment

2000 ◽  
Vol 123 (3) ◽  
pp. 433-445 ◽  
Author(s):  
A. F. Storace ◽  
D. C. Wisler ◽  
H.-W. Shin ◽  
B. F. Beacher ◽  
F. F. Ehrich ◽  
...  
Keyword(s):  
Unsteady Flow ◽  
Theoretical Investigation ◽  
Computational Models ◽  
Aerodynamic Force ◽  
Axial Flow ◽  
Pressure Rise ◽  
Static Structure ◽  
Stall Margin ◽  
First Time ◽  
Axial Flow Compressors

An experimental and theoretical investigation has been conducted to evaluate the effects seen in axial-flow compressors when the centerline of the rotor is displaced from the centerline of the static structure of the engine. This creates circumferentially nonuniform rotor-tip clearances, unsteady flow, and potentially increased clearances if the rotating and stationary parts come in contact. The result not only adversely affects compressor stall margin, pressure rise capability, and efficiency, but also generates an unsteady, destabilizing, aerodynamic force, called the Thomas/Alford force, which contributes significantly to rotor whirl instabilities in turbomachinery. Determining both the direction and magnitude of this force in compressors, relative to those in turbines, is especially important for the design of mechanically stable turbomachinery components. Part I of this two-part paper addresses these issues experimentally and Part II presents analyses from relevant computational models. Our results clearly show that the Thomas/Alford force can promote significant backward rotor whirl over much of the operating range of modern compressors, although some regions of zero and forward whirl were found near the design point. This is the first time that definitive measurements, coupled with compelling analyses, have been reported in the literature to resolve the long-standing disparity in findings concerning the direction and magnitude of whirl-inducing forces important in the design of modern axial-flow compressors.

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.

A New Approach to the Experimental Study of Turbomachinery Flow Phenomena

1977 ◽  
Vol 99 (1) ◽  
pp. 97-105 ◽  
Author(s):  
J. P. Gostelow
Keyword(s):  
Flow Field ◽  
Unsteady Flow ◽  
Axial Flow ◽  
Centrifugal Pumps ◽  
New Approach ◽  
Static Pressure Distribution ◽  
Compressor Rotor ◽  
Flow Phenomena ◽  
On Line ◽  
Flow Compressor

Measurements of the unsteady flow field over a rotor and within its wake are needed in the development of most turbomachines. The technique advocated is that of data acquisition by on-line computer, using the periodic passing of a blade as a phase reference. The phase-lock averaging process is described as is its use in reducing the noise of raw data traces. Measurements of the unsteady flow over a cascade and of the resulting boundary layer behavior are presented. The approach was used in interpreting the unsteady flow field of an axial-flow compressor rotor and the static pressure distribution over the rotor tip. Finally the application to centrifugal pumps is discussed, enabling the designer to obtain information on the suction pressures and the extent of any separated region.

Compressibility Effects on the Two Generations of Unsteady Flow Types in Axial Flow Compressors

2005 ◽  
Author(s):  
Xinqian Zhen ◽  
Sheng Zhou ◽  
Anping Hou ◽  
Jinsong Xiong
Keyword(s):  
Unsteady Flow ◽  
Axial Flow ◽  
Separated Flows ◽  
Design System ◽  
Relative Reduction ◽  
Positive Effects ◽  
Flow Type ◽  
Wide Range ◽  
Two Generations ◽  
Axial Flow Compressors

There occurred unsteady separated flows inside axial flow compressors, which was however not taken into consideration in the present aerodynamic design system. This discrepancy indicates that the potential underlying unsteady separated flows is yet to be explored, hence the present research team proposes the concept of two generations of unsteady flow types, i.e. Unsteady Natural Flow Type (UNFT) and Unsteady Cooperative Flow Type (UCFT). Numerical simulations are carried out in the present paper to study the compressibility effect on the unsteady cooperative flow type in axial flow compressors. The studies show that aerodynamic performances are remarkably enhanced by means of transforming the flow type from UNFT into UCFT by imposing unsteady excitations. In the case of 2D subsonic cascade, performances are greatly improved in a wide range of Ma number (Ma < 0.8) and the maximum relative reduction of the loss coefficient reaches 40.2%. In the case of 2D trans-supersonic cascade, positive effects can’t be captured. However, in the case of a 3D trans-supersonic single rotor, the adiabatic efficiency is increased from 87.0% to 90.2%.

Highly Loaded Axial Flow Compressors: History and Current Developments

1990 ◽  
Vol 112 (4) ◽  
pp. 567-578 ◽  
Author(s):  
A. J. Wennerstrom
Keyword(s):  
Mach Number ◽  
Axial Flow ◽  
Turbine Engines ◽  
Development Programs ◽  
Future Developments ◽  
1960S And 1970S ◽  
The 1960S ◽  
Very High ◽  
Made In ◽  
Axial Flow Compressors

This paper discusses approaches taken over many years to achieve very high loading levels in axial-flow compressors. These efforts have been associated predominantly with aircraft turbine engines. The objective has been to reduce the size and weight of the powerplant, to increase its simplicity and ruggedness, and, whenever possible, to reduce cost. In the introduction, some fundamentals are reviewed that indicate that increased work per stage can only be obtained at a cost of increased Mach number, increased diffusion, or both. The earliest examples cited are some ambitious development programs of the 1950s and 1960s. Some innovative schemes to increase diffusion limits are described that took place in the 1960s and 1970s. Major advancements in dealing with higher Mach number were made in the 1980s. Finally, a few thoughts directed toward potential future developments are presented.

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