The Potential of Rotor and Stator Clocking in a 2.5-Stage Low-Speed Axial Compressor

2012 ◽  
Author(s):  
J. Städing ◽  
J. Friedrichs ◽  
T. Waitz ◽  
C. Dobriloff ◽  
B. Becker ◽  
...  
Keyword(s):  
Axial Compressor ◽  
Axial Flow ◽  
Pressure Rise ◽  
Boundary Layer Transition ◽  
Experimental Investigations ◽  
Layer Transition ◽  
Low Speed ◽  
Beneficial Effects ◽  
Pass Through ◽  
Flow Compressor

Detailed experimental investigations have been conducted to gain profound knowledge of airfoil clocking mechanisms in axial compressors. Clocking, the circumferential indexing of adjacent rotor or stator rows with equal blade counts, is known as a potential means to modify the flow field in multistage turbo-machinery and increase overall efficiencies of both turbines and compressors. These beneficial effects on turbomachine performance are due to wake-airfoil interactions and primarily depend on the alignment of a downstream blade or vane row with upstream wake trajectories that are generated in the same frame of reference. The present survey describes and discusses the experimental research on Rotor and Stator Clocking effects in a low-speed 2.5-stage axial flow compressor. For both Rotor and Stator Clocking, variations of Stage 2 performance have been found that are sinusoidal in trend over the clocking angle and originate from a significant change in static pressure rise across the clocked blade rows. Time-averaged measurements basically suggest the highest pressure gain, if the upstream wakes pass through mid-passage of the downstream blade row. In case of Rotor Clocking, this may even lead to a variation in compressor operating range. The fundamental aerodynamic mechanism responsible for the clocking effect can be attributed to a shift of the suction-sided boundary layer transition over the clocking angle. Regarding overall Stage 2 performance, the investigations show that Full Clocking, i.e. the combination of Rotor and Stator Clocking, nearly doubles the potential of single row indexing.

Combined Effects of Forward Sweep and Tip Clearance on the Performance of Axial Flow Compressor Stage

2009 ◽  
Author(s):  
P. V. Ramakrishna ◽  
M. Govardhan
Keyword(s):  
Total Pressure ◽  
Axial Compressor ◽  
Axial Flow ◽  
Pressure Rise ◽  
Tip Clearance ◽  
Numerical Work ◽  
Low Speed ◽  
Operating Range ◽  
Axial Flow Compressor ◽  
Flow Compressor

There are a number of performance indices for a turbomachine on the basis of which its strength is evaluated. In the case of axial compressors, pressure ratio, efficiency and stall margin are few such indices which are of major concern in the design phase as well as in the evaluation of performance of the machine. In the process of improving the blade design, 3D blade stacking, where the aerofoil sections constituting the blade are moved in relation to the flow. Tilting the blade sections to the flow direction (blade sweep) would increase the operating range of an axial compressor due to modifications in the pressure and velocity fields on the suction surface. On the other hand, blade tip gap, though finite, has great influence on the performance of a turbomachine. The present work investigates the combined effect of these two factors on various flow characteristics in a low speed axial flow compressor. The objective of the present paper is thereby confined to study the collective effects of sweep and tip clearance without attempting to suggest an outright new design. In the present numerical work, the performance of Tip Chordline Sweeping (TCS) and Axial Sweeping (AXS) of low speed axial compressor rotor blades are studied. For this, 15 computational domains were modeled for five rotor sweep configurations and three different clearance levels for each rotor. Through the results, 20°AXS rotor is found to be distinctive among all the rotors with highest pressure rise, higher operating range and less tip clearance loss characteristics. TCS rotors produced improved total pressure rise at the low flow coefficients when the tip gap is increased. Hence there is a chance that an “optimum” tip gap exists for the TCS rotors in terms of total pressure coefficient and operating range, while AXS rotors are at their best with the minimum possible clearance.

Flow Fields in an Axial Flow Compressor During Four-Quadrant Operation

2013 ◽  
Author(s):  
Andrew Gill ◽  
Theodor W. von Backström ◽  
Thomas M. Harms ◽  
Dwain Dunn
Keyword(s):  
Flow Direction ◽  
Tangential Velocity ◽  
Axial Compressor ◽  
Axial Flow ◽  
Pressure Rise ◽  
Flow Fields ◽  
Time Dependent ◽  
Axial Flow Compressor ◽  
Compressor Rotor ◽  
Flow Compressor

It has been shown in previous investigations that when all combinations of both positive and negative direction of rotation and flow direction are allowed in operating a multistage axial flow compressor, the operating point may be in any of the four quadrants of the pressure rise versus flow characteristic. The present paper is the first discussion of the flow field of all possible modes of operation of an axial flow compressor. During the present study interstage time dependent hot film velocity measurements and five hole pneumatic probe measurements were combined with steady and time dependent CFD solutions to investigate the flow fields in the three-stage axial compressor. Results are presented in terms of mean-line velocity triangles, mean stream surface plots, mid-span radial velocity contours right through the compressor, rotor-downstream radial distributions of axial and tangential velocity, stator-downstream axial velocity contours and mid-span entropy contours through the compressor. Main flow features are pointed out and discussed. The study was instigated in an effort to understand possible accident scenarios in a three-shaft closed cycle nuclear powered helium gas turbine.

An Experimental Study of the Inception of Rotating Stall in a Single-Stage Low-Speed Axial Compressor

2007 ◽  
Author(s):  
Alexander K. Simpson ◽  
John P. Longley
Keyword(s):  
Axial Compressor ◽  
Axial Flow ◽  
Rotating Stall ◽  
Single Stage ◽  
Predictive Tool ◽  
Stall Inception ◽  
Low Speed ◽  
Blade Row ◽  
Flow Compressor ◽  
Critical Incidence

There are two established mechanisms, spike and modal inception, by which rotating stall is initiated in an axial flow compressor. Whilst the “Critical incidence hypothesis” and the “Zero slope criterion” are useful ideas in explaining the different stability boundaries for spikes and modes they do not provide the designer with a predictive tool. A detailed experimental investigation utilising a single-stage low-speed compressor is presented in which the aerodynamic environment of a rotor blade row is changed (rotor geometry is held fixed) so that it exhibited both spike and modal inception upon throttling into stall. The dominant mechanism of stall inception was found to be dependent on both the inlet flowfield and the downstream stator. The measurements are analysed and show that the meridional acceleration across the tip region of the rotor influences the mechanism by which rotating stall is incepted. This research is presented as a contribution towards the prediction of the stall inception mechanism.

Stalling Pressure Rise Capability of Axial Flow Compressor Stages

1981 ◽  
Vol 103 (4) ◽  
pp. 645-656 ◽  
Author(s):  
C. C. Koch
Keyword(s):  
Experimental Data ◽  
Reynolds Number ◽  
Axial Flow ◽  
Pressure Rise ◽  
Tip Clearance ◽  
Flow Coefficient ◽  
Low Speed ◽  
Axial Flow Compressor ◽  
Wide Range ◽  
Flow Compressor

A procedure for estimating the maximum pressure rise potential of axial flow compressor stages is presented. A simplified stage average pitchline approach is employed so that the procedure can be used during a preliminary design effort before detailed radial distributions of blading geometry and fluid parameters are established. Semi-empirical correlations of low speed experimental data are presented that relate the stalling static-pressure-rise coefficient of a compressor stage to cascade passage geometry, tip clearance, bladerow axial spacing and Reynolds number. Blading aspect ratio is accounted for through its effect on normalized clearances, Reynolds number and wall boundary layer blockage. An unexpectedly strong effect of airfoil stagger and of the resulting flow coefficient of the stage’s vector triangle is observed in the experimental data. This is shown to be caused by the differing ability of different types of stage vector triangles to re-energize incoming low-momentum fluid. Use of a suitable “effective” dynamic head in the pressure rise coefficient gives a good correlation of this effect. Stalling pressure rise data from a wide range of both low speed and high speed compressor stages are shown to be in good agreement with these correlations.

Flow Fields in an Axial Flow Compressor During Four-Quadrant Operation

2013 ◽  
Vol 136 (6) ◽  
Author(s):  
Andrew Gill ◽  
Theodor W. Von Backström ◽  
Thomas M. Harms
Keyword(s):  
Flow Direction ◽  
Tangential Velocity ◽  
Axial Compressor ◽  
Axial Flow ◽  
Pressure Rise ◽  
Flow Fields ◽  
Time Dependent ◽  
Axial Flow Compressor ◽  
Compressor Rotor ◽  
Flow Compressor

It has been shown in previous investigations that when all combinations of both positive and negative direction of rotation and flow direction are allowed in operating a multistage axial flow compressor, the operating point may be in any of the four quadrants of the pressure rise versus flow characteristic. The present paper is the first discussion of the flow field of all possible modes of operation of an axial flow compressor. During the present study interstage time dependent hot film velocity measurements and five hole pneumatic probe measurements were combined with steady and time dependent CFD solutions to investigate the flow fields in the three-stage axial compressor. Results are presented in terms of mean-line velocity triangles, mean stream surface plots, midspan radial velocity contours right through the compressor, rotor-downstream radial distributions of axial and tangential velocity, stator-downstream axial velocity contours and midspan entropy contours through the compressor. Main flow features are pointed out and discussed. The study was instigated in an effort to understand possible accident scenarios in a three-shaft closed cycle nuclear powered helium gas turbine.

Three-Dimensional Flows and Loss Reduction in Axial Compressors

1987 ◽  
Vol 109 (3) ◽  
pp. 354-361 ◽  
Author(s):  
Y. Dong ◽  
S. J. Gallimore ◽  
H. P. Hodson
Keyword(s):  
Three Dimensional ◽  
Axial Compressor ◽  
Axial Flow ◽  
Tracer Gas ◽  
Suction Surface ◽  
Axial Compressors ◽  
Small Clearance ◽  
Oil Flow ◽  
Stator Blade ◽  
Flow Compressor

Measurements have been performed in a low-speed high-reaction single-stage axial compressor. Data obtained within and downstream of the rotor, when correlated with the results of other investigations, provide a link between the existence of suction surface–hub corner separations, their associated loss mechanisms, and blade loading. Within the stator, it has been shown that introducing a small clearance between the stator blade and the stationary hub increases the efficiency of the stator compared to the case with no clearance. Oil flow visualizaton indicated that the leakage reduced the extensive suction surface–hub corner separation that would otherwise exist. A tracer gas experiment showed that the large radial shifts of the surface streamlines indicated by the oil flow technique were only present close to the blade. The investigation demonstrates the possible advantages of including hub clearance in axial flow compressor stator blade rows.

Numerical Efforts of Aerodynamic Re-Design in a Single-Stage Transonic Axial Compressor: Part 1 — Stator Design

2017 ◽  
Author(s):  
Justin (Jongsik) Oh
Keyword(s):  
Pressure Ratio ◽  
Axial Compressor ◽  
Axial Flow ◽  
Single Stage ◽  
Design Flow ◽  
Design Parameters ◽  
Original Design ◽  
Circular Arc ◽  
Surge Margin ◽  
Flow Compressor

In many aerodynamic design parameters for the axial-flow compressor, three variables of tailored blading, blade lean and sweep were considered in the re-design efforts of a transonic single stage which had been designed in 1960’s NASA public domains. As Part 1, the re-design was limited to the stator vane only. For the original MCA (Multiple Circular Arc) blading, which had been applied at all radii, the CDA (Controlled Diffusion Airfoil) blading was introduced at midspan as the first variant, and the endwalls of hub and casing (or tip) were replaced with the DCA (Double Circular Arc) blading for the second variant. Aerodynamic performance was predicted through a series of CFD analysis at design speed, and the best aerodynamic improvement, in terms of pressure ratio/efficiency and operability, was found in the first variant of tailored blading. It was selected as a baseline for the next design efforts with blade lean, sweep and both combined. Among 12 variants, a case of positively and mildly leaned blades was found the most attractive one, relative to the original design, providing benefits of an 1.0% increase of pressure ratio at design flow, an 1.7% increase of efficiency at design flow, a 10.5% increase of the surge margin and a 32.3% increase of the choke margin.

Effects of inlet radial distortion on the type of stall precursor in low-speed axial compressor

2016 ◽  
Vol 232 (1) ◽  
pp. 55-67 ◽  
Author(s):  
Ali Arshad ◽  
Qiushi Li ◽  
Simin Li ◽  
Tianyu Pan
Keyword(s):  
Pressure Fluctuations ◽  
Axial Compressor ◽  
Rotating Stall ◽  
Experimental Investigations ◽  
Inlet Flow ◽  
Blade Loading ◽  
Stall Inception ◽  
Low Speed ◽  
Modal Type ◽  
Stall Precursor

Experimental investigations of the effect of inlet blade loading on the rotating stall inception process are carried out on a single-stage low-speed axial compressor. Temporal pressure signals from the six high response pressure transducers are used for the analysis. Pressure variations at the hub are especially recorded during the stall inception process. Inlet blade loading is altered by installing metallic meshed distortion screens at the rotor upstream. Three sets of experiments are performed for the comparison of results, i.e. uniform inlet flow, tip, and hub distortions, respectively. Regardless of the type of distortion introduced to the inflow, the compressor undergoes a performance drop, which is more severe in the hub distortion case. Under the uniform inlet flow condition, stall inception is caused by the modal type disturbance while the stall precursor switched to spike type due to the highly loaded blade tip. In the presence of high blade loading at the hub, spike disappeared and the compressor once again witnessed a modal type disturbance. Hub pressure fluctuations are observed throughout the process when the stall is caused by a modal wave while no disturbance is noticed at the hub in spike type stall inception. It is believed that the hub flow separation contributes to the modal type of stall inception phenomenon. Results are also supported by the recently developed signal processing techniques for the stall inception study.

Optimized Preliminary Design of a Multistage Low-Speed Axial FLow Compressor

2021 ◽  
Author(s):  
AbdelRahman Ahmed Kamal ◽  
Alyaa Abdelnaby Thabet ◽  
Mohamed M. A. Elnabawy
Keyword(s):  
Axial Flow ◽  
Preliminary Design ◽  
Low Speed ◽  
Axial Flow Compressor ◽  
Flow Compressor
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