Experimental Investigation of the Steady and Unsteady Flow Field in a Single Stage Low Pressure Axial Compressor With a Circumferential Groove Casing Treatment

2010 ◽  
Author(s):  
N. Van de Wyer ◽  
B. Farkas ◽  
J. Desset ◽  
J. F. Brouckaert ◽  
J.-F. Thomas ◽  
...  
Keyword(s):  
Experimental Investigation ◽  
Flow Field ◽  
Unsteady Flow ◽  
Axial Compressor ◽  
Low Pressure ◽  
Fast Response ◽  
Single Stage ◽  
Compressor Stage ◽  
Casing Treatment ◽  
Circumferential Groove

This paper deals with the experimental investigation of the influence of a circumferential groove casing treatment on the performance and stability margin of a single stage low pressure axial compressor. The design of the compressor stage is representative of a booster stage for the new counter-rotating turbofan engine architecture and is characterized by unusually high loading and flow coefficients. The choice of the circumferential groove is described on the basis of a numerical parametric study on the number of grooves, the axial position, the depth and width of the groove. The experiments were performed at a Reynolds number corresponding to cruise conditions in the von Karman Institute closed loop high speed compressor test rig R4. The detailed performance characterization of the compressor stage with casing treatment was mapped at four operating points from choke to stall at design speed. The compressor stall limit was determined at several other off-design speeds. Detailed steady and unsteady measurements were performed to determine the flow field characteristics of the rotor and of the complete stage. Conventional pressure, temperature and directional probes were used along with fast response pressure sensors in the rotor casing and in the groove. Simultaneous traverses with a fast response total pressure probe were used to map the unsteady flow field at the rotor exit allowing an experimental capture of the tip leakage vortex path and extension through the rotor passage. A comparison of the flow features with and without casing treatment was performed and the results are discussed against 3D viscous computational predictions. The casing treatment did not present any improvement of the compressor stall margin but no significant performance degradation was observed either. The CFD predictions showed a good agreement with the measurements and their analysis supported the experimental results.

Time-Resolved Measurements of the Unsteady Flow Field in a Single Stage Low Pressure Axial Compressor

2013 ◽  
Author(s):  
J. Sans ◽  
G. Dell’Era ◽  
J. Desset ◽  
J.-F. Brouckaert ◽  
S. Hiernaux
Keyword(s):  
Flow Field ◽  
Unsteady Flow ◽  
Axial Compressor ◽  
Low Pressure ◽  
Fast Response ◽  
Single Stage ◽  
Time Resolved ◽  
Flow Angle ◽  
Aerodynamic Pressure ◽  
Time Resolved Measurements

The experimental investigation of the unsteady flow field in a highly loaded single stage low pressure axial compressor, also called a booster, is presented in this paper. The compressor design is representative of an advanced direct drive turbofan booster. Tests were performed on different speed lines at choke, design, and near stall, in the VKI-R4 closed loop compressor test rig. The rotor casing was instrumented with fast response pressure transducers to perform a detailed survey of the tip flow features. Simultaneous time-resolved measurements with fast response aerodynamic pressure probes were performed by radial and circumferential traverses to map the unsteady flow field at rotor and stator exit. The originality of this paper also resides in the fact that unsteady flow angle data are presented as the probe was used in a virtual 3-hole mode. The casing measurements allow to map the direction and extension of the tip leakage vortex. The flow path measurements show its extension at the exit of the rotor blade passage and its evolution as throttling is increased towards the compressor stability limit. The results are presented in terms of periodic and random fluctuations. These experimental results are combined to provide a three-dimensional view of the experimental flow field. They are discussed and compared to CFD simulations, showing that, in some regions, important features are not captured by the numerical model. In particular, the presence of a second wake has been observed in the unsteady yaw angle map at rotor exit. This uncommon feature is currently under further investigation.

Unsteady Pressure Measurements in a Single Stage Low Pressure Axial Compressor: Tip Vortex Flow and Stall Inception

2009 ◽  
Author(s):  
J. F. Brouckaert ◽  
N. Van de Wyer ◽  
B. Farkas ◽  
F. Ullmann ◽  
J. Desset ◽  
...  
Keyword(s):  
Flow Field ◽  
Axial Compressor ◽  
Low Pressure ◽  
Fast Response ◽  
Single Stage ◽  
Pressure Probe ◽  
Pressure Measurements ◽  
Stall Inception ◽  
Unsteady Pressure ◽  
Unsteady Pressure Measurements

The experimental investigation of the unsteady flow field in a single stage low pressure axial compressor designed for a counter-rotating turbofan engine architecture is presented in this paper. The rotor casing was instrumented with fast response pressure transducers to perform a detailed survey of the tip flow features during stable operation, near stall and during stall. Tests were performed at two different Reynolds numbers representative of cruise and take-off conditions in the VKI-R4 closed loop compressor test rig. Simultaneous time-resolved measurements with a miniature fast response total pressure probe were performed by radial traverses at the rotor exit to support the tip flow field investigation. The casing measurements allow to map the direction and extension of the tip leakage vortex. The flow path measurements show its extension at the exit of the rotor blade passage and its evolution as throttling is increased towards the compressor stability limit. These experimental results are discussed and compared to CFD simulations, showing good agreement. Stall inception and rotating stall patterns are investigated as well and described in this paper. They are based both on hot wire measurements and on the casing unsteady pressure measurements.

Computational Analysis of Effect of Circumferential Groove Casing Treatment With Different Axial Coverage Over Rotor Blade Tip Chord on the Performance of a Transonic Axial Compressor Stage

2015 ◽  
Author(s):  
Nishit J. Mehta ◽  
Dilipkumar Bhanudasji Alone ◽  
Harish S. Choksi
Keyword(s):  
Flow Field ◽  
Rotor Blade ◽  
Stokes Equations ◽  
Flow Behavior ◽  
Base Line ◽  
Compressor Stage ◽  
Casing Treatment ◽  
Transonic Compressor ◽  
Circumferential Groove ◽  
Blade Tip

Previous studies on circumferential groove casing treatments have shown that the effectiveness of casing Grooves highly depends on their axial location over blade tip. The present work aims to study the flow behavior and its impact on the performance of the compressor stage when the casing treatment grooves are placed to provide different axial coverage over rotor chord in each case. Geometry of a transonic compressor stage was modeled for this study. Flow field solutions for this model with smooth casing wall were obtained by solving steady state 3-D Reynolds-Averaged Navier-Stokes equations for three different grids to prove the grid independence of the solutions. Results obtained with the intermediate grid density were used as the baseline results to compare with results of casing treatment geometries. The basic casing treatment geometry has 10 circumferential groves of width 4mm, depth 16mm and axial spacing of 2mm between each groove. This casing treatment geometry was superimposed over the rotor domain with the grooves extending axially over the entire axial chord (58mm) of rotor blade tip and flow field solutions were again obtained. After that, for each case the grooves are removed from the rear side and axial coverage is shortened. Flow solutions for various axial coverage and hence for various number of grooves are thus obtained and compared. These results depict improvement in the operating range when compared to the Base-line results. Results also exhibit that as the grooves from the rear end are removed gradually, recovery in the overall efficiency is seen in compressor performance. Post processing of the flow solutions confirms the trend and shows that the grooves in the rear of the chord are almost idle not providing sufficient flow to pass over from pressure surface to suction surface of the blade and hence contributing very less towards performance enhancement.

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

2017 ◽  
Vol 139 (12) ◽  
Author(s):  
Matthias Rolfes ◽  
Martin Lange ◽  
Konrad Vogeler ◽  
Ronald Mailach
Keyword(s):  
Total Pressure ◽  
Solid Wall ◽  
Pressure Ratio ◽  
Axial Compressor ◽  
Chord Length ◽  
Single Stage ◽  
Low Speed ◽  
Casing Treatment ◽  
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 (TC) cannot be reduced to any amount and minimum values might be necessary for safety reasons, the TC 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 the authors' previous paper, 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 TC (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 TC sizes of 1.2% and 5% of tip chord length were investigated. At the small TC, 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 TC, 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 TC sizes will be discussed.

Unsteady Flow Interactions Between a High- and Low-Pressure Turbine: Part 2 — Rotor-Synchronic Averaging and Proper Orthogonal Decomposition of the Unsteady Flow Fields

2019 ◽  
Author(s):  
M. Dellacasagrande ◽  
P. Z. Sterzinger ◽  
S. Zerobin ◽  
F. Merli ◽  
L. Wiesinger ◽  
...  
Keyword(s):  
Flow Field ◽  
Unsteady Flow ◽  
Proper Orthogonal Decomposition ◽  
Low Pressure ◽  
Fast Response ◽  
Orthogonal Decomposition ◽  
Pressure Probe ◽  
Low Pressure Turbine ◽  
Aerodynamic Pressure ◽  
Proper Orthogonal

Abstract This paper, the second of two parts, presents an experimental investigation of the unsteady flow field evolving in a two-stage two-spool test turbine facility. The experimental setup, which was designed to reproduce the operating condition of modern commercial aero-engines, consists of a high-pressure turbine (HPT) stage followed by a turbine center frame (TCF) with non-turning struts, and a co-rotating low-pressure turbine (LPT) stage. Measurements carried out with a fast-response aerodynamic pressure probe (FRAPP) were post-processed to describe the unsteady evolution of the flow downstream of the HPT rotor, through the TCF duct, and at the exit of the LPT stage. The time-resolved results presented in the first part of this paper show that deterministic fluctuations due to both rotors characterize the flow field downstream of the LPT. In order to characterize the deterministic unsteadiness induced by all the components constituting the turbine facility (HPT, TCF and LPT) and their interactions, measurements were carried out in three different planes located downstream of the HPT, at the exit of the TCF and downstream of the LPT stage. The unsteady results obtained in the plane located at the exit of the LPT are discussed in more details in this second part of this paper, providing information about the interactions between the two rotors. A proper phase-average procedure, known as rotor synchronic averaging (RSA), which takes into account the rotorrotor interaction, was adopted to capture the unsteadiness due to both rotors. Proper Orthogonal Decomposition (POD) was also applied to provide a characterization of the major contributors in terms of energy to the deterministic unsteadiness occurring in the test turbine facility. At the exit of the LPT rotor, the perturbations induced by the HPT stage and the interactions between the two rotors were found to dominate over the unsteadiness due to the LPT only.

Numerical Investigation on Effect of Aspect Ratio of Axisymmetric Circumferential Groove Casing Treatment Coupled to a Transonic Axial Flow Compressor Stage

2015 ◽  
Author(s):  
Nishit J. Mehta ◽  
Dilipkumar Bhanudasji Alone ◽  
Harish S. Choksi
Keyword(s):  
Aspect Ratio ◽  
Flow Field ◽  
Flow Behavior ◽  
Geometrical Parameters ◽  
Compressor Stage ◽  
Casing Treatment ◽  
Transonic Compressor ◽  
Circumferential Groove ◽  
Aspect Ratios ◽  
The Impact

While the effects of axisymmetric casing treatment on performance of an axial compressor stage have been extensively studied numerically as well as experimentally, the major geometrical parameters which govern these effects have been identified. Studies are now focused on understanding how each of these parameters individually impacts the performance of a casing treatment. The present work aims to study the impact on performance of casing treatment geometry when aspect ratio of the grooves is varied in a circumferential groove casing treatment. The compressor geometry chosen for this study has design characteristics of a transonic compressor stage. Flow field solutions were derived for baseline model by solving steady state 3-D Reynolds-Averaged Navier-Stokes (RANS) equations for three grid densities and the grid independence was proved. The basic casing treatment geometry has 10 circumferential grooves of width 4mm and axial spacing of 2mm between each groove. The aspect ratio was varied by changing the depth of the grooves in each case. These casing treatment geometries were superimposed over the rotor domain with the grooves extending over the entire blade tip chord and flow field solutions were again obtained for various aspect ratios of grooves. These results depict improvement in the range of operation in terms of mass flow rate. Results also show that the aspect ratio of the grooves significantly influences the overall effectiveness of casing treatment on the performance of compressor stage. Improvement in overall compressor efficiency is noted with lower aspect ratio casing treatments when compared to those with higher aspect ratios, however, the range improvement is higher with higher aspect ratios. It is also observed that, after a certain depth of grooves is reached, there is no significant improvement in performance on further increasing the depth and hence the aspect ratio. Post processing results of the flow solutions are presented which confirm the trends and show that the flow behavior near rotor tip governs this effect.

Experimental Investigation of the Unsteady Flow Field Downstream of a Counter-Rotating Two-Spool Turbine Rig

2012 ◽  
Author(s):  
Davide Lengani ◽  
Cornelia Santner ◽  
Rosario Spataro ◽  
Berardo Paradiso ◽  
Emil Göttlich
Keyword(s):  
Experimental Investigation ◽  
Flow Field ◽  
Unsteady Flow ◽  
Fast Response ◽  
Secondary Flows ◽  
Operating Conditions ◽  
Pressure Probe ◽  
Time Resolved ◽  
Flow Angle ◽  
Aerodynamic Pressure

The paper presents an experimental investigation of the unsteady flow field in the two-spool counter-rotating transonic turbine at Graz University of Technology. The test setup consists of a high pressure (HP) stage, a diffusing mid turbine frame with turning struts (TMTF) and a shrouded low pressure (LP) rotor. The two rotors are mounted on mechanically independent shafts in order to provide engine-representative operating conditions. The rig was designed in cooperation with MTU Aero Engines and Volvo Aero within the EU project DREAM (ValiDation of Radical Engine Architecture SysteMs). A two-sensor fast response aerodynamic pressure probe (2S-FRAP) has been employed to provide time-resolved aerodynamic area traverses downstream of the LP turbine. Such measurement allows estimating the total deterministic unsteadiness transported through the duct. In particular, it has been possible to isolate the structures induced by each rotor by means of the encoders mounted on the two shafts. A global ensemble averaged field, which takes into account the rotor-rotor interactions, is also provided. The time resolved distributions of the flow quantities are then discussed in details. The perturbations due to the HP rotor in terms of velocity and flow angle are negligible in this downstream plane. Indeed, the largest fluctuations of velocity are due to the TMTF-LP rotor interaction, they occur in the wake and secondary flows of the TMTF. Large fluctuations of static and total pressure are instead due to both rotors to the same extent.

scholarly journals Investigation of Performance and Rotor Tip Flow Field in a Low Speed Research Compressor with Circumferential Groove Casing Treatment at Varying Tip Clearance

2017 ◽  
Vol 2017 ◽  
pp. 1-14 ◽  
Author(s):  
Matthias Rolfes ◽  
Martin Lange ◽  
Ronald Mailach
Keyword(s):  
Flow Field ◽  
Operating Conditions ◽  
Single Stage ◽  
Tip Clearance ◽  
Experimental Investigations ◽  
Low Speed ◽  
Pressure Transducers ◽  
Casing Treatment ◽  
Operating Range ◽  
Circumferential Groove

Experimental investigations in a single-stage low speed axial research compressor are presented. The influence of four different rotor tip clearances on the overall compressor performance and on the rotor tip flow field is investigated in configurations with and without circumferential groove casing treatments. Piezo-resistive pressure transducers are used to capture the unsteady flow field in the rotor tip region. The investigated casing groove is effectively working at the three largest investigated tip clearance sizes. The largest achieved operating range increase by the groove is 6.9%. The groove can delay the upstream movement of the flow interface between leakage flow and main flow and thus increase the stable operating range. Rotating instabilities are shown to exist at large tip clearance sizes in throttled operating conditions. Their amplitudes can be damped by the casing groove. No modal activities could be detected in the current single-stage compressor build.

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.

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