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.

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.

Experimental and Numerical Investigation of a Circumferential Groove Casing Treatment in a Low Speed Axial Research Compressor at Different Tip Clearances

2017 ◽  
Author(s):  
Matthias Rolfes ◽  
Martin Lange ◽  
Konrad Vogeler ◽  
Ronald Mailach
Keyword(s):  
Total Pressure ◽  
Solid Wall ◽  
Pressure Ratio ◽  
Axial Compressor ◽  
Chord Length ◽  
Single Stage ◽  
Tip Clearance ◽  
Low Speed ◽  
Operating Range ◽  
Circumferential Groove

The demand of increasing pressure ratios for modern high pressure compressors leads to decreasing blade heights in the last stages. As tip clearances cannot be reduced to any amount and minimum values might be necessary for safety reasons, the tip clearance ratios of the last stages can reach values notably higher than current norms. This can be intensified by a compressor running in transient operations where thermal differences can lead to further growing clearances. For decades, the detrimental effects of large clearances on an axial compressor’s operating range and efficiency are known and investigated. The ability of circumferential casing grooves in the rotor casing to improve the compressor’s operating range has also been in the focus of research for many years. Their simplicity and ease of installation are one reason for their continuing popularity nowadays, where advanced methods to increase the operating range of an axial compressor are known. In a previous paper [1], three different circumferential groove casing treatments were investigated in a single stage environment in the Low Speed Axial Research Compressor at TU Dresden. One of these grooves was able to notably improve the operating range and the efficiency of the single stage compressor at very large rotor tip clearances (5% of chord length). In this paper, the results of tests with this particular groove type in a three stage environment in the Low Speed Axial Research Compressor are presented. Two different rotor tip clearance sizes of 1.2% and 5% of tip chord length were investigated. At the small tip clearance, the grooves are almost neutral. Only small reductions in total pressure ratio and efficiency compared to the solid wall can be observed. If the compressor runs with large tip clearances it notably benefits from the casing grooves. Both, total pressure and efficiency can be improved by the grooves in a similar extent as in single stage tests. Five-hole probe measurements and unsteady wall pressure measurements show the influence of the groove on the flow field. With the help of numerical investigations the different behavior of the grooves at the two tip clearance sizes will be discussed.

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.

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.

End-Wall and Profile Losses in a Low-Speed Axial Flow Compressor Rotor

1986 ◽  
Vol 108 (1) ◽  
pp. 22-31 ◽  
Author(s):  
B. Lakshminarayana ◽  
N. Sitaram ◽  
J. Zhang
Keyword(s):  
Axial Flow ◽  
Pressure Rise ◽  
Tip Clearance ◽  
Blade Loading ◽  
Pressure Losses ◽  
Axial Flow Compressor ◽  
Compressor Rotor ◽  
Profile Losses ◽  
Flow Compressor ◽  
End Wall

The blade-to-blade variation of relative stagnation pressure losses in the tip region inside the rotor of a single-stage, axial-flow compressor is presented and interpreted in this paper. The losses are measured at two flow coefficients (one at the design point and the other at the near peak pressure rise point) to discern the effect of blade loading on the end-wall losses. The tip clearance losses are found to increase with an increase in the pressure rise coefficient. The losses away from the tip region and near the hub regions are measured downstream. The losses are integrated and interpreted in this paper.

scholarly journals Experimental Study and Theoretical Prediction of Secondary Flows in a Transonic Axial Flow Compressor

1982 ◽  
Author(s):  
F. Leboeuf ◽  
F. Bario ◽  
G. Boris ◽  
K. D. Papailiou
Keyword(s):  
Secondary Flow ◽  
Vortex Motion ◽  
Axial Compressor ◽  
Axial Flow ◽  
Inviscid Flow ◽  
Secondary Flows ◽  
Tip Clearance ◽  
Axial Distance ◽  
Axial Flow Compressor ◽  
Flow Compressor

Detailed time-mean measurements have been realized on a transonic axial flow compressor. Flow quantities in the secondary flow regions have been obtained. The purpose of this paper is to present some essential features which drive the secondary following development in axial compressor among others, the strong influence of secondary vortex motion on the energy transfer between the flow and the blading is displayed. Also, we study the effect of tip clearance and axial distance between blade row. A secondary flow model is used for comparisons with theoretical computations. Very good comparisons have been obtained which show the validity of the theoretical model, in particular, the decomposition of the secondary flow into a viscous part and a vortical part, using an inviscid flow as a basis.

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.

Studies on Downstream Stator With Rotor Re-Staggering and Forward Sweeping in a Subsonic Axial Compressor Stage

2011 ◽  
Author(s):  
P. V. Ramakrishna ◽  
M. Govardhan
Keyword(s):  
Flow Field ◽  
Computational Model ◽  
Flow Rate ◽  
Total Pressure ◽  
Axial Compressor ◽  
Pressure Rise ◽  
Axial Distance ◽  
Compressor Stage ◽  
Numerical Work ◽  
Stagger Angle

The present numerical work studies the flow field in subsonic axial compressor stator passages for: (a) preceding rotor sweep (b) preceding rotor re-staggering (three stagger angle changes: 0°, +3° and +5°); and (c) stator sweeping (two 20° forward sweep schemes). The following are the motives for the study: at the off-design conditions, compressor rotors are re-staggered to alleviate the stage mismatching by adjusting the rows to the operating flow incidence. Fundamental to this is the understanding of the effects of rotor re-staggering on the downstream component. Secondly, sweeping the rotor stages alters the axial distance between the successive rotor-stator stages and necessitates that the stator vanes must also be swept. To the best of the author’s knowledge, stator sweeping to suit such scenarios has not been reported. The computational model for the study utilizes well resolved hexahedral grids. A commercial CFD package ANSYS® CFX 11.0 was used with standard k-ω turbulence model for the simulations. CFD results were well validated with experiments. The following observations were made: (1) When the rotor passage is closed by re-staggering, with the same mass flow rate and the same stator passage area, stators were subjected to negative incidences. (2) Effect of stator sweeping on the upstream rotor flow field is insignificant. Comparison of total pressure rise carried by the downstream stators suggests that an appropriate redesign of stator is essential to match with the swept rotors. (3) While sweeping the stator is not recommended, axial sweeping is preferable over true sweeping when it is necessary.

scholarly journals Effect of Circumferential Single Casing Groove Location on the Flow Stability under Tip-Clearance Effect in a Transonic Axial Flow Compressor Rotor

Energies ◽  
2021 ◽  
Vol 14 (19) ◽  
pp. 6143
Author(s):  
Xiaoxiong Wu ◽  
Bo Liu ◽  
Botao Zhang ◽  
Xiaochen Mao
Keyword(s):  
Control Mechanism ◽  
Incidence Angle ◽  
Axial Flow ◽  
Flow Stability ◽  
Tip Clearance ◽  
Tip Leakage Flow ◽  
Flow Angle ◽  
Axial Flow Compressor ◽  
Compressor Rotor ◽  
Flow Compressor

Numerical simulations have been performed to study the effect of the circumferential single-grooved casing treatment (CT) at multiple locations on the tip-flow stability and the corresponding control mechanism at three tip-clearance-size (TCS) schemes in a transonic axial flow compressor rotor. The results show that the CT is more efficient when its groove is located from 10% to 40% tip axial chord, and G2 (located at near 20% tip axial chord) is the best CT scheme in terms of stall-margin improvement for the three TCS schemes. For effective CTs, the tip-leakage-flow (TLF) intensity, entropy generation and tip-flow blockage are reduced, which makes the interface between TLF and mainstream move downstream. A quantitative analysis of the relative inlet flow angle indicates that the reduction of flow incidence angle is not necessary to improve the flow stability for this transonic rotor. The control mechanism may be different for different TCS schemes due to the distinction of the stall inception process. For a better application of CT, the blade tip profile should be further modified by using an optimization method to adjust the shock position and strength during the design of a more efficient CT.

Sign in / Sign up

Export Citation Format

Share Document