Endoscopic Stereoscopic PIV for Turbomachinery Applications 25 Years of Particle Image Velocimetry in Aerodynamics Sept. 23 – 25, 2009, DLR Center Göttingen, Germany Michael Bartelt, Arman Mohseni, Victor Opilat, Jörg R. Seume ( ) Leibniz Universität Hannover Institute of Turbomachinery and Fluid Dynamics (TFD) Appelstr. 9, De-30167 Hannover Email: [email protected] Tel +49 (0)511 762-2732 www.tfd.uni-hannover.de Headline For several years, Particle Image Velocimetry (PIV) has been success- fully used for the determination of planar velocity fields. With the intro- duction of the Stereoscopic PIV (SPIV) all components of internal velocity fields can be captured in enclosed spaces. This method has proved to be particularly suitable for the investigation of strongly unsteady, turbulent flow structures in turbomachines. However, compared to conventional applications, PIV measurements in turbomachines are more challenging. Limited access to measurement section, light reflections, camera calibration, and machine vibration must be taken into account, to name but a few. The implementation of endoscopic PIV in turbomachines gives an advantage for investigating more complex measurement setups and even real machines. Fig.: ESPIV measurement between IGV and impeller. (a) assembly of PIV system, (b) ESPIV setup, (c) a typical single exposure double image, (d) and (e) three-component velocity field. Axial Exhaust Diffuser SPIV on Centrifugal Compressor 7-Stage Air Turbine The centrifugal compressor test faci- lity at the institute of turbomachinery and fluid dynamics consists of a one-stage centrifugal air compressor with inlet guide vanes (IGV), capable of operating in open and closed-loop modes. During successive projects, the compressor has been equipped with new and optimized IGV and impeller. Current research activities involve the use of endoscopic stereo- scopic particle image velocimetry (ESPIV) in order to investigate the flow phenomena at compressor inlet, including flow interaction between IGV and impeller. The design of PIV setup pro-vides the ability to capture spatial steady state phase-resolved three-component velocity fields between IGV and impeller by section−wise PIV measurements. The axial exhaust diffuser test facility at the institute of turbomachinery and fluid dynamics is a 1:10 scaled model of a heavy duty gas turbine exhaust diffuser with a last turbine stage simulation in form of a rotating spoke wheel. The variable inlet velocity can reach up to Mach 0.15. The purpose of the PIV application is to capture unsteady structures in the diffuser flow and to find information about their influence on the flow separation. The velocity distribution is measured 15 mm downstream of the blade passage. An external trigger synchronizes PIV images and the rotor position. For seeding very lightweight hollow glass particles are used, which are brought into inlet by a powder dispersion generator. In the present work a method is developed to realize SPIV measure- ments only by means of endoscopic entrances (both camera and light sheet). Using the endoscope techno- logy a low interference into the existing system is ensured, since only three entrance drillings in the machine casing are needed. How- ever, this requires a camera calib- ration outside of the machine. The endoscopic SPIV system is em- ployed to a complex test facility of a 700 kW 7-stage thermal working air turbine to study the wake structures behind the last stage. It is shown that a precise detection of the 3−component velocity field can be achieved with this kind of SPIV application (at medium loading of 40% mass flow and 83% of design speed). In comparison with a 1-dimensional calculation and con- ventional 5-hole probe measure- ments the results of velocity mag- nitude and flow angles are in range. Fig.: PIV in exhaust diffuser. (a) SPIV setup, (b) diffuser test facility, (c) evaluated image, (d) velocity distribution. Fig.: (a) ESPIV setup on air turbine, (b) measurement principle, (c) velocity distribution and vector field of turbine outlet flow. a b c Fig.:Typical endoscopic stereoscopic PIV setup in an axial machine
Welcome message from author
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
Endoscopic Stereoscopic PIV for Turbomachinery Applications25 Years of Particle Image Velocimetry in AerodynamicsSept. 23 – 25, 2009, DLR Center Göttingen, Germany
Michael Bartelt, Arman Mohseni, Victor Opilat, Jörg R. Seume ( )Leibniz Universität HannoverInstitute of Turbomachinery and Fluid Dynamics (TFD)Appelstr. 9, De-30167 Hannover Email: [email protected] +49 (0)511 762-2732www.tfd.uni-hannover.de
Headline For several years, Particle Image Velocimetry (PIV) has been success-fully used for the determination of planar velocity fields. With the intro-duction of the Stereoscopic PIV (SPIV) all components of internal velocity fields can be captured in enclosed spaces. This method has proved to be particularly suitable for the investigation of strongly unsteady, turbulent flow structures in turbomachines.
However, compared to conventional applications, PIV measurements in turbomachines are more challenging. Limited access to measurement section, light reflections, camera calibration, and machine vibration must be taken into account, to name but a few. The implementation of endoscopic PIV in turbomachines gives an advantage for investigating more complex measurement setups and even real machines.
Fig.: ESPIV measurement between IGV and impeller. (a) assembly of PIV system, (b) ESPIV setup, (c) a typical single exposure double image, (d) and (e) three-component velocity field.
Axial Exhaust Diffuser
SPIV onCentrifugalCompressor
7-Stage Air Turbine
The centrifugal compressor test faci-lity at the institute of turbomachineryand fluid dynamics consists of a one−stage centrifugal air compressor with inlet guide vanes (IGV), capable of operating in open and closed-loop modes. During successive projects, the compressor has been equipped with new and optimized IGV and impeller. Current research activities involve the use of endoscopic stereo-scopic particle image velocimetry
(ESPIV) in order to investigate the flow phenomena at compressor inlet, including flow interaction between IGV and impeller. The design of PIV setup pro-vides the ability to capture spatial steady state phase-resolved three-component velocity fields between IGV and impeller by section−wise PIV measurements.
The axial exhaust diffuser test facility at the institute of turbomachinery and fluid dynamics is a 1:10 scaled model of a heavy duty gas turbine exhaust diffuser with a last turbine stage simulation in form of a rotating spoke wheel. The variable inlet velocity can reach up to Mach 0.15.The purpose of the PIV application is to capture unsteady structures in the diffuser flow and to find information
about their influence on the flow separation. The velocity distribution is measured 15 mm downstream of the blade passage. An external trigger synchronizes PIV images and the rotor position. For seeding very lightweight hollow glass particles are used, which are brought into inlet by a powder dispersion generator.
In the present work a method is developed to realize SPIV measure-ments only by means of endoscopicentrances (both camera and light sheet). Using the endoscope techno-logy a low interference into the existing system is ensured, since only three entrance drillings in the machine casing are needed. How-ever, this requires a camera calib-ration outside of the machine. The endoscopic SPIV system is em-ployed to a complex test facility of a
700 kW 7-stage thermal working air turbine to study the wake structures behind the last stage. It is shown that a precise detection of the 3−component velocity field can be achieved with this kind of SPIV application (at medium loading of 40% mass flow and 83% of design speed). In comparison with a 1−dimensional calculation and con-ventional 5-hole probe measure-ments the results of velocity mag-nitude and flow angles are in range.
Fig.: PIV in exhaust diffuser. (a) SPIV setup, (b) diffuser test facility, (c) evaluated image, (d) velocity distribution.
Fig.: (a) ESPIV setup on air turbine, (b) measurement principle,(c) velocity distribution and vector field of turbine outlet flow.
a
b
c
Fig.:Typical endoscopic stereoscopic PIV setup in an axial machine