Achievements obtained on Aero-Thermal Loaded Materials for High-Speed Atmospheric Vehicles within ATLLAS

Abstract

The project ATLLAS (Aerodynamic and Thermal Load Interactions with Lightweight Advanced Materials for High Speed Flight) kicked off in October 2006. Its main objective is to evaluate and assess potential high-temperature resistant materials for sustained superand hypersonic flight. This covers both materials for the external geometry as well as for the internal combustor geometries. The project, led by ESA-ESTEC, is co-funded by the European Commission under the 6 th Framework Program and a consortium of 13 partners from industry, research institutions and universities.The objective is to identify and assess lightweight advanced materials which can withstand ultra high temperatures and heat fluxes enabling high-speed flight above Mach 3. At these high speeds, classical materials used for airframes and propulsion units are not longer feasible and need to be replaced preferably by high-temperature, lightweight materials and if required, some parts with active cooling. Both metallic and non-metallic materials are tested extensively including Ni-based Hollow Sphere Packings, Ultra High Temperature Composites and several (non)-oxide Ceramic Matrix Composites. Envisaged cooling techniques for CMC based combustion liners are film, effusion, transpiration and regenerative cooling.

High temperature and pressure reactive flows through porous media

“…The right term of the Eq. 1 is composed of two parts, one related to the Darcy's law for low velocity regime filtration (first right term) and the other quadratic one related to the Stokes's law to ensure the continuity of velocity and stress at the solid-fluid frontier (second right term) (Steelant 2009). The gravity term is neglected in numerous studies (but not all, for example in case of vertical flows (Zhao 2003)).…”

“…For high-speed applications, the material withstanding and the cooling management are the key issues which limit the flight Mach number to about 3 (Steelant 2008;Steelant 2009). The hypersonic flight can be achieved in the future only if a strong development of light-weight and high-temperature composite materials are proposed.…”

Novel viscosity determination method: Validation and application to fuel flow

“…The regenerative cooling technique consists in using hydrocarbon fuel as coolant for the thermal management of hypersonic structures and to take benefits from the endothermicity of its pyrolysis [1], [3]. The complex and coupled phenomena need to be studied together to ensure the correct understanding of their relationship [4] even if specific studies dedicated to single phenomena are also required [5].…”

Determination of Darcian permeability of porous material by infrared spectrometry

“…Third, global laws instead of inapplicable 3-D ones (supplementary source of uncertainty due to this simplification) are used with intermediate coefficients and properties such as the dynamic viscosity and density. The variation of these latest through the porous media due to pressure drop and to the thermal gradient are very difficult to consider despite some work to improve this point [5]. Consequently, numerical simulations should be preferred to investigate multi-physics reacting flow in permeable materials, particularly to manage a full 3-D case.…”

“…No method currently exists to determine the permeability of a structure, especially under high speed flight conditions. For example, the combustion chamber of SCRamjet engine is expected to be cooled directly by the fuel which filtrates through the porous wall (internal convection, film cooling and endothermic pyrolysis) [1][2][3][4][5]. Due to reacting process (pyrolysis coupled to heat and mass transfer), to coke formation and to degradation of the composite structure itself, the permeability is expected to change strongly (several orders of magnitude) [6].…”