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Design of a Transpiration Cooled Sharp Leading Edge for SHEFEX III Christian Dittert, Hannah Böhrk and Henning Elsässer 8th European Conference on Aerothermodynamics for Space Vehicles, Lisbon

> 8th European Conference on Aerothermodynamics for Space Vehicles> Christian Dittert> 05.03.2015 www.DLR.de • Chart 1

Outline

- SHEFEX III geometry and mission profile

- Nose Design

- Boundary Conditions

- FEM Results - Conclusion

- Outlook

> 8th European Conference on Aerothermodynamics for Space Vehicles> Christian Dittert> 05.03.2015 www.DLR.de • Folie 2

SHEFEX-III

• lifted- body concept

• active flight control

• two flight condition (max. lift, max. L/D)

• facetted thermal protection system

• transpiration cooled leading edge

• maximum weight ~ 500kg

• length ~2.1m

• maximum Mach number ~17


Nose design

• porous C/C ceramic • C/C-SiC TPS ceramic • tungsten sealing plate • Laval nozzle with sensor transducers

• secondary gas system • pressure reducer • supperalloy frame and cover plate


Nose design - supply route

200x105 Pa

consumer 200x105 Pa

RCS 30x105 Pa

pressure reducer solenoid valve Laval-nozzle

200x105 Pa


Boundary conditions thermal loads • due to the angle of attack, different flow conditions for top and bottom

side

• two approaches to determine the heat flux density

• during detached shock phase an estimation from Tauber and Mendes* is used

• for oblique shock condition a model from van Driest§ for a flat plate is

taken

• transpiration cooling is taken into account with 35 % of the uncooled

heat flux density

*Tauber, M.E. , G.P., Meneses, \Aerothermodynamics of Transatmospheric Vehicles., AIAA, 1986 §E.R. van Driest, {The Problem of Aerodynamic Heating, Aeronautical Engineering Review, 1956,


Boundary conditions thermal loads

• uncooled heat fluxes

• bottom side much higher than top side

• heat fluxes at the tip higher than at rear

• at top side two solutions during detached shock

• first solution after Tauber and Mendes

• second solution, 1% of Tauber solution

this is necessary, because the Tauber model is only valid for the windward side


Boundary conditions aerodynamic loads • bow shock

• oblique shock


Results- transient thermal simulation

• results after 57s (max. heat peak from trajectory) • uncooled stagnation temperature above 4000K • temperatures simulated with reduced heat flux, still

higher than max. material temperature but only at the very tip

uncooled transpiration cooled



• results after 57s (max. heat peak from trajectory) • uncooled stagnation temperature above 4000K • behind stagnation point temperatures significantly

lower

uncooled uncooled version B



• results after 250s • temperatures in both cases are under max.

material temperature • uncooled temperatures still higher than

transpiration cooled temperatures

uncooled transpiration cooled



• results after 250s • temperatures in both cases are under max.

material temperature • during oblique shock phase, temperatures are

similar

uncooled uncooled version B



• both cases, cooled and uncooled have equal solutions for the tungsten plate, because the plate is far behind the cooled region

• max. temperatures at both time steps are under the max. material temperature


uncooled/transpiration cooled uncooled/transpiration cooled version B

Results- thermo-mechanical simulation

• input pressure and temperature distribution for both time steps • max. tension after 250s at the front surface, which is attached to the

tungsten plate • max. tension probably to high, due to wrong constraints for the

contacts

simulation time 57s simulation time 250s


Conclusion

• temperatures are too high, transpiration cooling is necessary

• detached shock heat fluxes, not have an impact on the stagnation point temperature but for the area behind

• thermo-mechanical results are not reliable at the moment

• design is working with some updates


Outlook

• more accurate determination of the loads for the top side, especially for the bow shock condition

• refinement of the simulation, particularly the constraints of the contacts

• development of a model to predict wall temperatures of a transpiration cooled leading edge


Thank you for your attention !

The work was partly supported by the Helmholtz Alliance as the Helmholtz Young Investigator’s Group VH-NG-909 Temperature Management in Hypersonic Flight. Special thanks to Malte Wagenknecht, who has greatly contributed to this work.

Acknowledgement



• both cases, cooled and uncooled have equal solutions for the tungsten plate, because the plate is to far away from cooled region

• high temperature gradients in the structure

uncooled/transpiration cooled uncooled/transpiration cooled version B


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