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.

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.

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.

Three Dimensional Clocking Effects in a One and a Half Stage Transonic Turbine

2009 ◽  
Vol 132 (1) ◽  
Author(s):  
O. Schennach ◽  
J. Woisetschläger ◽  
B. Paradiso ◽  
G. Persico ◽  
P. Gaetani
Keyword(s):  
Flow Field ◽  
Three Dimensional ◽  
Fast Response ◽  
Secondary Flows ◽  
Pressure Probe ◽  
Time Resolved ◽  
Flow Angle ◽  
Aerodynamic Pressure ◽  
Velocity Flow ◽  
Transonic Turbine

This paper presents an experimental investigation of the flow field in a high-pressure transonic turbine with a downstream vane row (1.5 stage machine) concerning the airfoil indexing. The objective is a detailed analysis of the three-dimensional aerodynamics of the second vane for different clocking positions. To give an overview of the time-averaged flow field, five-hole probe measurements were performed upstream and downstream of the second stator. Furthermore in these planes additional unsteady measurements were carried out with laser Doppler velocimetry in order to record rotor phase-resolved velocity, flow angle, and turbulence distributions at two different clocking positions. In the planes upstream of the second vane, the time-resolved pressure field has been measured by means of a fast response aerodynamic pressure probe. This paper shows that the secondary flows of the second vane are significantly modified by the different clocking positions, in connection with the first vane modulation of the rotor secondary flows. An analysis of the performance of the second vane is also carried out, and a 0.6% variation in the second vane loss coefficient has been recorded among the different clocking positions.

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.

Identification of Spinning Mode in the Unsteady Flow Field of a Low Pressure Turbine

2012 ◽  
Vol 134 (5) ◽  
Author(s):  
Davide Lengani ◽  
Berardo Paradiso ◽  
Andreas Marn ◽  
Emil Göttlich
Keyword(s):  
Flow Field ◽  
Guide Vane ◽  
Low Pressure ◽  
Fast Response ◽  
Turbine Rotor ◽  
Pressure Probe ◽  
Model Parameters ◽  
Time Resolved ◽  
Flow Angle ◽  
Lp Turbine

This paper presents an experimental investigation of the vane-blade unsteady interaction in an unshrouded low pressure (LP) turbine research rig with uneven blade/vane count (72 blades and 96 vanes). The rig was designed in cooperation with MTU Aero Engines and considerable efforts were put on the adjustment of all relevant model parameters. In particular blade count ratio, airfoil aspect ratio, reduced mass flow, reduced speed, and Mach and Reynolds numbers were chosen to reproduce the full scale LP turbine at take off condition. Measurements by means of a fast-response pressure probe were performed adopting a phase-locked acquisition technique in order to provide the time resolved flow field downstream of the turbine rotor. The probe has been fully traversed both in circumferential and radial traverses. The rotor exit is characterized by strong perturbations due to the tip leakage vortex and the rotor blade wake. Circumferential nonuniformities due to the upstream vane wake and to the downstream exit guide vane potential effects are also identified. Furthermore, in the present configuration with an uneven blade/vane count the nonuniformities due to the stator and rotor row are misaligned along the whole turbine circumference and create a spinning mode that rotates in direction opposite to the rotor at a high frequency. The aeroacoustic theory is employed to explain such further unsteady pattern. The variations of the exit flow angle within a cycle of such pattern are not negligible and almost comparable to the ones within the blade passing period.

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.

Experimental Investigations of Clocking in a One and a Half Stage Transonic Turbine Using Laser-Doppler-Velocimetry and a Fast Response Aerodynamic Pressure Probe

2006 ◽  
Author(s):  
O. Schennach ◽  
J. Woisetschla¨ger ◽  
A. Fuchs ◽  
E. Go¨ttlich ◽  
A. Marn ◽  
...  
Keyword(s):  
Flow Field ◽  
Laser Doppler Velocimetry ◽  
Fast Response ◽  
Laser Doppler ◽  
Experimental Investigations ◽  
Pressure Probe ◽  
Doppler Velocimetry ◽  
Flow Angle ◽  
Aerodynamic Pressure ◽  
Transonic Turbine

The current paper presents experimental clocking investigations of the flow field in midspan in a high-pressure transonic turbine with a downstream vane row (1.5 stage machine). Laser-Doppler-Velocimetry measurements were carried out in order to record rotor phase resolved velocity, flow angle and turbulence distributions upstream and downstream of the second vane row at several different vane-vane positions. Additionally, a fast response aerodynamic pressure probe was used to get the total pressure distribution downstream of the second vane row for the same positions. Altogether, the measurements were performed for ten different 1st vane to 2nd vane positions (clocking positions) for measurements downstream of the 2nd vane row and two different clocking positions for measurements upstream of the 2nd vane row. The paper shows that different clocking positions have a significant influence on the flow field downstream of the 2nd vane row. Furthermore different measurement lines upstream of the 2nd vane row indicate that clocking has nearly no influence on the flow field close to the rotor exit.

Blade Row Interaction in a One and a Half Stage Transonic Turbine Focusing on Three Dimensional Effects: Part II—Clocking Effects

2008 ◽  
Author(s):  
O. Schennach ◽  
B. Paradiso ◽  
G. Persico ◽  
P. Gaetani ◽  
J. Woisetschla¨ger
Keyword(s):  
High Pressure ◽  
Flow Field ◽  
Three Dimensional ◽  
Field Measurements ◽  
Fast Response ◽  
Secondary Flows ◽  
Pressure Probe ◽  
Flow Angle ◽  
Aerodynamic Pressure ◽  
Transonic Turbine

The paper presents an experimental investigation of the flow field in a high-pressure transonic turbine with a downstream vane row (1.5 stage machine) concerning the airfoil indexing. The objective is a detailed analysis of the three dimensional flow field downstream of the high pressure turbine for different vane clocking positions. To give an overview of the time averaged flow field, measurements by means of a pneumatic five hole probe were performed upstream and downstream of the second stator. Furthermore in this planes additional unsteady measurements were carried out with Laser Doppler Velocimetry in order to record rotor phase resolved velocity, flow angle and turbulence distributions at two different clocking positions. In the measurement plane upstream the second vane the time resolved pressure field has been analyzed by means of a Fast Response Aerodynamic Pressure Probe. The paper shows that the secondary flows of the second vane are significantly modified for different clocking positions, in connection with the first vane modulation of the rotor secondary flows. An analysis of the performance of the second vane is also carried out.

Unsteady Flow Interactions Between a High- and Low-Pressure Turbine: Part 1 — Time-Resolved Flow

2019 ◽  
Author(s):  
P. Z. Sterzinger ◽  
S. Zerobin ◽  
F. Merli ◽  
L. Wiesinger ◽  
M. Dellacasagrande ◽  
...  
Keyword(s):  
Unsteady Flow ◽  
Low Pressure ◽  
Flow Fields ◽  
System Level ◽  
Flow Structures ◽  
Pressure Probe ◽  
Time Resolved ◽  
Low Pressure Turbine ◽  
Aerodynamic Pressure ◽  
Flow Interactions

Abstract This two-part paper presents the unsteady flow interactions between an engine-representative high-pressure turbine (HPT) and low-pressure turbine (LPT) stage, connected by a turbine center frame (TCF) duct with non-turning struts. The setup was tested at the high-speed two-spool test turbine facility at the Institute for Thermal Turbomachinery and Machine Dynamics at Graz University of Technology and includes relevant purge and turbine rotor tip leakage flows. Due to the complexity of such a test, the unsteady component interactions in an HPT-TCF-LPT module have not received much attention in the past and require additional analysis to determine new approaches for further performance improvements on the system level. The flow downstream of an HPT is highly unsteady and dominated by statorrotor interactions, which affect the flow behavior through the downstream TCF and LPT. To capture the unsteady flow structures, time-resolved aerodynamic measurements were carried out with a fast-response aerodynamic pressure probe (FRAPP) at three different measurement planes. In this first part of the paper, the time-resolved and phase-averaged flow fields with respect to the HPT and LPT trigger are studied. Since the two rotors are uncorrelated, the applied method allows the identification of the flow structures induced by either of them. Upstream of the LPT stage, the HPT flow structures evolving through the TCF duct dominate the flow fields. Downstream of the LPT stage, the flow is affected by both the HPT and the LPT secondary flow structures. The interactions between the various stator rows and the two rotors are detected by means of time-space plots and modal decomposition. To describe the fluctuations induced by both rotors, particularly the rotor-rotor interaction, the Rotor Synchronic Averaging (RSA) is used to analyze the flow field downstream of the LPT. The second part of the paper decomposes the flow fields to gain additional insight into the rotor-rotor interactions using the Proper Orthogonal Decomposition (POD) and RSA methods. The paper highlights the need to account for the HPT-induced unsteady mechanisms in addition to the LPT flow structures and the interaction of both to arrive at improved LPT designs.

On the Influence of an Acoustically Optimized Turbine Exit Casing Onto the Unsteady Flow Field Downstream of a Low Pressure Turbine Rotor

2018 ◽  
Author(s):  
L. Simonassi ◽  
M. Zenz ◽  
S. Zerobin ◽  
F. Heitmeir ◽  
A. Marn ◽  
...  
Keyword(s):  
Flow Field ◽  
Unsteady Flow ◽  
Low Pressure ◽  
Turbine Rotor ◽  
Low Noise ◽  
Test Facility ◽  
Pressure Probe ◽  
Guide Vanes ◽  
Low Pressure Turbine ◽  
Aerodynamic Pressure

Modern low pressure turbines (LPT) are designed in order to fulfil a various number of requirements such as high endurance, low noise, high efficiency, low weight and low fuel consumption. Regarding the reduction of the emitted noise, different designs of low pressure turbine exit guide vanes (aerodynamically and/or acoustically optimized) of the turbine exit casing (TEC) were tested and their noise reduction capabilities and aerodynamic performance were evaluated. In particular, measurements of TEC-losses were performed and differences in the losses were reported. Measurements were carried out in a one and a half stage subsonic turbine test facility at the engine relevant operating point approach. This work focuses on the study of the unsteady flow field downstream of an unshrouded low pressure turbine rotor. The influence on the upstream flow field of a TEC design including acoustically optimized vanes (Inverse cut-off TEC) is investigated and compared with a second TEC configuration without vanes (Vaneless TEC), by means of fast response aerodynamic pressure probe measurements. The second configuration served as a reference concerning the influence of TEGVs onto the upstream located LPT rotor. The interactions between the stator and rotor wakes, secondary flows and the turbine exit guide vanes potential effect are identified via modal decomposition according to the theory of Tyler and Sofrin. The main structures constituting the unsteady flow field are detected and the role of the major interaction effects in the loss generation mechanism and in the acoustic emission is analysed. This study based on the modal analysis of the unsteady flow field offers new insight into the main interaction mechanisms and their importance in the assessment of the aerodynamic and aeroelastic performance of modern low pressure turbine exit casings.

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