Investigations on axial compressor cascades with aspiration hub Thierry Obrecht Michel Dumas Elia Colombo - Cécile Deslot Snecma (Groupe Safran) Peter Ott Villaroche, France Laboratoire de Thermique Appliquée et de Turbomachines Lionel Castillon Ecole Polytechnique Fédérale de Lausanne ONERA Switzerl Meudon, France François Bario Laboratoire de Mécanique des Fluides et d'acoustique Ecole Centrale de Lyon France
Structure of the presentation Introduction Test case design Experimental setup Experimental results CFD results comparisons Conclusions 2
Introduction Axial compressor Fluid extraction is done for turbine cooling => can extract up to at no cost Use extraction for performance increase Increase load Reduce compressor mass Increase effectiveness L. Prtl, O. Tietjens, Hydro- und Aeromechanik nach Vorlesungen von L. Prtl, Berlin 1929 3
Test case: axial compressor geometry More hub conicity Inlet Mach numbers: 0.7-0.8 Inlet Flow angles: 61 67 4
Separation /blade corner Blade Hub α1=63 α1=64 α1=65 Aerodynamic blockage Pressure raise limitation Deflection reduction Stagnation pressure losses Stability limitations 5
Design of the hub aspiration slot 6
Design of the blade aspiration slot 7
First test cascade 8
Non rotating annular cascade wind tunnel air outlet non rotating cascade swirled streamtube radial-axial nozzle 9
Instrumentation Aerodynamic 5-hole probes (2.5mm diameter) 0.6 chords upstream of leading edge 0.3 chords downstream of trailing edge Laser Doppler Anemometry (from LMFA Lyon) In the same planes as the 5-hole probes Pressure taps casing walls Outlet plane Pressure taps on the blades On the midspan of pressure side suction side Interblade plane Inlet plane 10
Performed investigations High load Med dium load blades 14 blades 14 No aspiration Ma1=0.8: α1=61, 63, 65 Ma1=0.8: α1=61, 63, 65, 67 Hub aspiration: 0%,, 4% Ma1=0.8: α1=63, 65 Ma1=0.7: α1=61, 63, 65 Hub aspiration: Blade aspiration: 0%, 1%, Ma1=0.8: α1=63, 65 Ma1=0.7: α1=61, 63, 65 Hub aspiration: Blade aspiration: 0%, 1%, Campaign 1 Campaign 2 Campaign 3 11
Performed investigations Red: With LDA High load Med dium load blades 14 blades 14 No aspiration Ma1=0.8: α1=61, 63, 65 Ma1=0.8: α1=61, 63, 65, 67 Hub aspiration: 0%,, 4% Ma1=0.8: α1=63, 65 Ma1=0.7: α1=61, 63, 65 Hub aspiration: Blade aspiration: 0%, 1%, Ma1=0.8: α1=63, 65 Ma1=0.7: α1=61, 63, 65 Hub aspiration: Blade aspiration: 0%, 1%, Campaign 1 Campaign 2 Campaign 3 12
Outlet plane results (5-hole probe) 13
Probe results for cases with Ma1=0.8 α1=63 No aspiration 0 0 0 0 4% 0 0 pt/pt1ave: 0.75 0.78 0.81 0.84 0.87 0.9 0.93 0.96 0.99 1.02 1.05 Alpha: 15 21 24 27 30 33 36 39 42 45
Probe results for cases with Ma1=0.8 α1=63 0 0 pt/pt1ave: 0.75 0.78 0.81 0.84 0.87 0.9 0.93 0.96 0.99 1.02 1.05 Alpha: 15 21 24 27 30 33 36 39 42 45
Probe results for cases with Ma1=0.8 α1=63 0 0 1% 0 0 0 0 pt/pt1ave: 0.75 0.78 0.81 0.84 0.87 0.9 0.93 0.96 0.99 1.02 1.05 Alpha: 15 21 24 27 30 33 36 39 42 45
Probe results for cases with Ma1=0.8 α1=63 1% 0 0 0 0 pt/pt1ave: 0.75 0.78 0.81 0.84 0.87 0.9 0.93 0.96 0.99 1.02 1.05 Alpha: 15 21 24 27 30 33 36 39 42 45
Probe results for cases with Ma1=0.8 α1=63 1% 0 0 0 172 272 267 0 172 272 267 14 0 172 299 294 289 304 284 279 0 172 299 294 289 304 284 279 pt/pt1ave: 0.75 0.78 0.81 0.84 0.87 0.9 0.93 0.96 0.99 1.02 1.05 Alpha: 15 21 24 27 30 33 36 39 42 45
Average performance for cases with Ma1 = 0.8 0. 0.0 0.160 0.140 0.120 0.100 0.080 0.060 0.040 0.020 0.000 63 63 65 Bl. -Hub: No slots -Blades: No slots Losses Bl. -Hub: 0% -Blades: No slots Bl. -Hub: -Blades: No slots Bl. -Hub: 4% -Blades: No slots pˆ pˆ CD = p p % Bl. -Hub: -Blades: t,1 0% t,2 Bl. -Hub: -Blades: 0.75% ˆt,1 s,1 Bl. -Hub: -Blades: 1.5% 14Bl. -Hub: -Blades: 0% 14Bl. -Hub: -Blades: 0.75% 14 Bl. -Hub: -Blades: 1.5% No aspiration 14
Average performance for cases with Ma1 = 0.8 0. 0.0 0.160 0.140 0.120 0.100 0.080 0.060 0.040 0.020 0.000 63 65 63 65 Bl. -Hub: No slots -Blades: No slots Losses Bl. -Hub: 0% -Blades: No slots Bl. -Hub: -Blades: No slots Bl. -Hub: 4% -Blades: No slots pˆ pˆ CD = p p % Bl. -Hub: -Blades: t,1 0% t,2 Bl. -Hub: -Blades: 0.75% ˆt,1 s,1 Bl. -Hub: -Blades: 1.5% 14Bl. -Hub: -Blades: 0% 14Bl. -Hub: -Blades: 0.75% 14 Bl. -Hub: -Blades: 1.5% No aspiration 14
Average performance for cases with Ma1 = 0.8 1.300 1.250 1. 1.150 1.100 Bl. -Hub: No slots -Blades: No slots Pressure Raise Bl. -Hub: 0% -Blades: No slots Bl. -Hub: -Blades: No slots Bl. -Hub: 4% -Blades: No slots p% / p% Bl. -Hub: -Blades: 0% s,2 s,1 Bl. -Hub: -Blades: 0.75% Bl. -Hub: -Blades: 1.5% 1.050 1.000 63 65 63 65 14Bl. -Hub: -Blades: 0% 14Bl. -Hub: -Blades: 0.75% 14 Bl. -Hub: -Blades: 1.5% No aspiration 14
Average performance for cases with Ma1 = 0.8 32.000 31.000 30.000 29.000 28.000 Bl. -Hub: No slots -Blades: No slots Deflection Bl. -Hub: 0% -Blades: No slots Bl. -Hub: -Blades: No slots Bl. -Hub: 4% -Blades: No slots ˆ α ˆ α Bl. -Hub: 1-Blades: 20% Bl. -Hub: -Blades: 0.75% Bl. -Hub: -Blades: 1.5% 27.000 26.000 63 65 63 65 14Bl. -Hub: -Blades: 0% 14Bl. -Hub: -Blades: 0.75% 14 Bl. -Hub: -Blades: 1.5% No aspiration 14
Observations on experimental results Hub blade aspiration influence mainly hub/blade separation Blockage decreased, diffusion improved Reduced losses, better pressure raise deflection also increase tip leakage vortex (negative) Hub aspiration very effective Blade aspiration effective for the low inlet flow angles High inlet flow angles aspiration dispositive ineffective Circumferential separation elongation for highly loaded cases Less guidance less deflection Highly loaded similar to medium loaded thanks to aspiration 23
Numerical simulations Numerical domain: 4.4 E 6 nodes Structured mesh Tip gap, blade aspiration coincident y+ 1.0 K-ε turbulence modelling RANS, elsa v3.3.03 24
Comparison of simulation probe results Outlet Mach number: Ma1=0.7, α1=63 14 Outlet flow angle: 25
Comparison of simulation LDA results Outlet Mach number: Ma1=0.7, α1=63 14 Outlet flow angle: 26
Variation of blade slot aspiration over height (CFD) Ma1=0.7, α1=63 H/Ho 14 0 27
influence on separation tip leakage (CFD) 14 1% 14 28
Comparison of CFD Exp. averages for Ma1 = 0.8 Losses: pˆ pˆ CD = p ˆ p % t,1 t,2 t,1 s,1 Pressure raise: p% / p% s,2 s,1 Deflection: ˆ α ˆ α 1 2 0.060 1.300 32.000 0.050 1.250 31.000 0.040 1. 30.000 0.030 1.150 29.000 0.020 1.100 28.000 0.010 1.050 27.000 0.000 63 65 1.000 63 65 26.000 63 65 No aspiration 14 29
Observations on CFD results Similar trends as experimental results Losses over predicted by CFD Flow mechanisms identified in experiment recognised Significant support to interpretation understing Deeper insight to aspiration influence on flow features 30
Conclusions (1/2) Extensive investigation on aspiration for chosen geometry Probe, LDA measurements CFD completed each other showed positive influence on separated region Hub aspiration more effective / aspiration rate Improvement of diffusion, flow extraction pressure raise Reduction of stagnation pressure losses Improvements limited by enlargement of tip leakage vortex effective for lower tested inlet flow angles 61 63 Highly loaded cascade (less blades) Deflection lower than for medium loaded Performance close to medium loaded cascade thanks asp. 31
Conclusions (2/2) Lessons learned aspiration technique, measurement technique CFD influence could be improved if tip leakage reduced e.g. casing treatment, tip gap reduction Blade design could be adapted to determine location where aspiration needed Improve results for higher inlet flow angles Still some detailed analysis ongoing (e.g. leakage jet, boundary layer close to aspiration slots) 32
Results dissemination (extract) A. Sachdeva, A. Touyeras, T. Obrecht, F. Leboeuf (AAAF conf. paper), 8 Control of Hub Corner Separation on a Stator Blade with Boundary Layer E. Colombo, F. Bario, P. Ott (Euroturbo conference paper), 9 Experimental Investigations on Active Flow Control by slots on the Hub of an Axial Compressor Rotor Geometry A. Sachdeva (PhD thesis), 2010 _ongoing_ Study control of 3D flow separations in a high pressure compressor stator blade row with boundary layer aspiration E. Colombo (PhD thesis), 2010 _ongoing_ Investigations on an axial compressor geometry with aspiration & hub E. Colombo, L. Castillon, P. Ott (Euroturbo conference paper), 2011 _ongoing_ Influence of blade spiration on the flow quality of an annular axial compressor cascade 33
Thanks European Union Project partners (LMFA, Snecma, Onera, MTU) Arttic EPFL Consulting experts (academic, industry) 34