Passive Tip Clearance Control Dr Nick Atkins, University of Sussex
Introduction Radial inflow offers significant potential to reduce drum time constant by removing existing buoyancy driven regime 2D axi-sym. scoping study, and 3D CFD proof of concept done in Y3 Test rig has been design, manufactured and assembled. Testing underway Radial inflow bleed b ω s a r s Bore flow
Effect of Drum Response on Clearance 0 2x reduction in time constant Clousure behaviour - Stage 3 5x reduction in time constant Lumped model SC03 CBC Tightest closure point Worst case accel. FHRS -0.5 Normalised Closure -1-1.5 0 1000 2000 3000 4000 5000 6000 7000 8000 Time (s) IDLE MTO IDLE
Pre-test CFD Parametric study at IDLE and MTO conditions ~ x10 htc increase for radial bleed from ~ 6% bore flow 250 Area weighted average htc versus radial inflow mass flow rate Upstream Disc ω r V θ Area weighted average htc (Wm -2 K -1 ) 200 150 100 50 MTO Downstream Disc ICAS-GT2 MTO ICAS-GT2 IDLE IDLE Swirl ratio, V θ /rω 0 0 5 10 15 Radial inflow mass flow rate (% of total bore mass flow)
Pre-test CFD non-axisymmetry due to vortex breakdown A 2 Swirl ratio 0 Section A-A A 10,000 rpm
Pre-test CFD htc prediction
Test Rig Design Full non-dimensional scaling to engine conditions Transient test to measure time constant direct Approx. 1:1 size Full 2D thermo-mechanical analysis to check integrity at 8,000 rpm, 110 C Sign off with R-R April 2009 Build complete testing started
Test Rig Design Speed, T in, mass flow Radiant heaters Inserts t 1 2 3 4 5 Low High Low Bore flow 8,000 rpm @ High power 82 Rotating thermocouples
Test Rig Design
Test Rig Design Plasma coated abradable lining Bore flow inlet ~0.1 mm clearance on each seal Blown seal supply Pressure balance tap Oil fed roller bearing to allow axial expansion
Test Rig Design Plasma coated abradable lining ~0.1 mm clearance on each seal Radial inflow supply Blown seal supply Silicon Nitride bearing Pressure balance tap
Rotor Instrumentation Air TCs 82 TCs Metal TCs Rotor assy.
Test Rig Build and Assy. 20 kw radiant heaters Test cell installation Final Assembly
Control system - IDLE conditions Rig inlet, 4.5 bar, 110 C
Control system - MTO conditions Rig inlet, 4.5 bar, 110 C
Preliminary Baseline Results 1 Baseline Square Cycle Test - no radial in-flow 0.9 0.8 Normalised Metal Temperature 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 0 20 40 60 80 100 120 140 160 180 200 Time (minutes)
Preliminary Radial-Inflow Results 1 Square Cycle Test - 6% radial inflwo 0.9 0.8 Normalised Metal Temperature 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 0 20 40 60 80 100 120 140 160 180 200 Time (minutes)
Conclusions Theoretical lumped mass analysis shows great potential to reduce mismatch between rotor and casing to low levels Full 2D axi-symmetric thermo-mechanical modelling has shown that the benefits may saturate due to heat pickup Disc region htc increase by a factor of 8 could give: Improvements in cruise clearance of 15% of nominal gap Improvement in worst case acceleration clearance of 27% of nominal gap Radial in-flow test facility has been designed, manufactured and installed Early results show:.