SHEFEX III - Assessment of Cooling Concepts for Sharp Leading Edges

Transcription

1 Chart 1 > SHEFEX III - Assessment of Cooling Concepts for Sharp Leading Edges >C. Dittert, H. Böhrk > SHEFEX III - Assessment of Cooling Concepts for Sharp Leading Edges C. Dittert H. Böhrk German Aerospace Center Stuttgart

2 Chart 2 > SHEFEX III - Assessment of Cooling Concepts for Sharp Leading Edges >C. Dittert, H. Böhrk > Outline - SHEFEX III geometry and mission profile - HEATS - Investigated cooling concepts Radiation cooled leading edge (C/C-SiC) Radiation cooled leading edge (pitch fiber) Transpiration cooled leading edge (C/C) - Assessment - Next steps

3 Chart 3 > SHEFEX III - Assessment of Cooling Concepts for Sharp Leading Edges >C. Dittert, H. Böhrk >

4 Chart 4 > SHEFEX III - Assessment of Cooling Concepts for Sharp Leading Edges >C. Dittert, H. Böhrk > SHEFEX III dimensions length: 1500mm witdh: max. 1040mm height: max. 470mm mass: complete ~500kg

5 Ma dynamic pressure [kpa] velocity [m/s] altitude [km] Chart 5 > SHEFEX III - Assessment of Cooling Concepts for Sharp Leading Edges >C. Dittert, H. Böhrk > SHEFEX III a possible trajectory Velocity Mach number Altitude Dynamic pressure source: Astrium

6 temperature [K] h [W/m 2 K ] Chart 6 > SHEFEX III - Assessment of Cooling Concepts for Sharp Leading Edges >C. Dittert, H. Böhrk > Heat transfer - determine conditions behind oblique shock - determine heat transfer coefficient h = Stρuc p - Stanton number is calculated according to van Driest for laminar and turbulent flow conditions - ρ, u, c p and T r are given behind the shock - calculated h and T r define the heat transfer between flow and wall q conv = h(t r T wall ) M θ = 32 recovery temperature M 1 β heat transfer coefficient

7 Chart 7 > SHEFEX III - Assessment of Cooling Concepts for Sharp Leading Edges >C. Dittert, H. Böhrk > HEATS* - developed for the layout of transpiration cooled systems - determines transient wall temperatures for transpiration-cooled, film-cooled, uncooled surface conditions - different models are used: Van Driest: arodynamic heating Goldstein: film-cooling Florio, Henderson: transpiration cooling *Journal of Thermophysics and Heat Transfer; Heat Balance of a Transpiration-Cooled Heat Shield; H.Böhrk et. al

8 wall temperature [K] wall temperature [K] Chart 8 > SHEFEX III - Assessment of Cooling Concepts for Sharp Leading Edges >C. Dittert, H. Böhrk > HEATS numerical model and setup HEATS is validated by ANSYS - constraint: mean instead of local heat transfer coefficient is used reference points.. 150mm Reference points are: - MP1: at the tip - MP2, 3, 4 are 2mm below the surface in a distance of 20mm, 50mm and 100mm from the tip HEATS MP:1 HEATS MP:2 MP:1 MP: HEATS MP:1 local h HEATS MP:1 mean h. 32. HEATS MP:4 local h HEATS MP:4 mean h

9 wall temperature [K] Chart 9 > SHEFEX III - Assessment of Cooling Concepts for Sharp Leading Edges >C. Dittert, H. Böhrk > Radiation cooled leading edge: C/C-SiC MP:1 MP:2 MP:3 2 λ = 17 W mk λ = 8 W mk 1 - standard material at DLR Stuttgart - already used in flight as heatshield (TPS) on SHEFEX II Boundary conditions are: - convection, mean h and T r - radiation, ε = 0, 85

10 wall temperature [K] Chart 10 > SHEFEX III - Assessment of Cooling Concepts for Sharp Leading Edges >C. Dittert, H. Böhrk > Radiation cooled leading edge: pitch fiber 2 MP:1 Pitch fiber MP:2 Pitch fiber MP:3 Pitch fiber λ = 150 W mk λ = 50 W mk 1 Idea: transport the heat away from the tip using the very high thermal conductivity Boundary conditions are: - convection, mean h and T r - radiation, ε = 0, 85

11 wall temperature [K] Chart 11 > SHEFEX III - Assessment of Cooling Concepts for Sharp Leading Edges >C. Dittert, H. Böhrk > Radiation cooled leading edge: pitch carbon fiber 2 1 MP:1 PF + const. wall MP:2 PF + const. wall MP:3PF + const. wall λ = 150 W mk λ = 50 W mk T wall = 480K Idea: transport the heat away from the tip using the very high thermal conductivity Boundary conditions are: - convection, mean h and T r - radiation, ε = 0, 85

12 wall temperature [K] temperature [K] h [W/m 2 K ] Chart 12 > SHEFEX III - Assessment of Cooling Concepts for Sharp Leading Edges >C. Dittert, H. Böhrk > Radiation cooled leading edge: comparison 2 1 MP:1 PF + const. wall MP:1 Pitch fiber MP:1 C/C-SiC recovery temperature heat transfer coefficient time 400 [sec] no effect between 180s-400s - heat loads during this time dictate the temperature - material properties show their effect after 400s

13 wall temperature [K] Chart 13 > SHEFEX III - Assessment of Cooling Concepts for Sharp Leading Edges >C. Dittert, H. Böhrk > Transpiration cooled leading edge: C/C 156mm - transpiration cooling already tested in arc jet facilities - AKTIV experiment: a transpiration cooled C/C tile flown on SHEFEX 2 10mm C/C C/C-SiC W λ = 14 mk W λ = 2 mk λ = 17 W mk W λ = 8 mk - model simplified to a flat plate - max. temperatures are the same Boundary conditions are: - convection, mean h and T r - radiation, ε = 0, MP:1 flat plate MP:1 C/C-SiC

14 temperature [K] Chart 14 > SHEFEX III - Assessment of Cooling Concepts for Sharp Leading Edges >C. Dittert, H. Böhrk > Transpiration cooled leading edge: C/C 156mm 10mm C/C C/C-SiC - cooling from 120s-s - cooling gas is nitrogen with 4g/s - wall temperatures determined with local heat transfer coefficient 3 MP1: no cooling MP2: no cooling 2 MP:1;ṁ=4g/s MP:2;ṁ=4g/s transpiration cooling reduce the wall temperature immediately

15 temperature [K] temperature [K] Chart 15 > SHEFEX III - Assessment of Cooling Concepts for Sharp Leading Edges >C. Dittert, H. Böhrk > Transpiration cooled leading edge: C/C 156mm 10mm C/C C/C-SiC - cooling effect can be controlled by different parameters e.g. mass flow, or cooling time 3 MP:1;ṁ=0.4g/s MP:2;ṁ=0.4g/s 3 MP:1;ṁ=4g/s MP:2;ṁ=4g/s 2 1 MP:1;ṁ=4g/s MP:2;ṁ=4g/s 2 1 MP:1;ṁ=4g/s MP:2;ṁ=4g/s

16 Chart 16 > SHEFEX III - Assessment of Cooling Concepts for Sharp Leading Edges >C. Dittert, H. Böhrk > Assessment and Problems Radiation cooled leading edge: C/C-SiC - pro: material investigated, already used as TPS - contra: heat loads might be to high Radiation cooled leading edge: pitch fiber - pro: effect to transport the heat is clearly visible for constant wall temperature - contra: heat loads might be to high, and material development just started Transpiration cooled leading edge: C/C - pro: has the ability to face these high heat loads - pro: material and concept investigated and tested in flight - contra: cooling system more complex, higher failure risk Source: Dr. Jens Schmidt DLR, 2010

17 Chart 17 > SHEFEX III - Assessment of Cooling Concepts for Sharp Leading Edges >C. Dittert, H. Böhrk > Next steps - HEATS transpiration code should be expanded for wedge geometry - more calculations with variation of parameters - design update - material and cooling concept test in arc jet facilities

18 Chart 18 > SHEFEX III - Assessment of Cooling Concepts for Sharp Leading Edges >C. Dittert, H. Böhrk > Thank you for listening! Do you have any questions?