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ATLLAS
Aerodynamic and Thermal Load Interactions with Lightweight Advanced Materials for High-speed Flight

Tags: Air

Background

One option for a future air transport system is the use of supersonic vehicles allowing to reach the antipodes in a few hours. In Europe, very limited research has been carried out in the field of supersonic transport vehicles above Mach 3. Concorde and other studies on supersonic transport in America and Japan limit the flight speed to Mach 2 to 2.4, which still allows the use of classical aluminium alloys.

For high-speed aircraft, the lift to drag ratio of the vehicle and the material and cooling issues for both airframe and engine are some of the key elements which force the designer to limit the flight Mach number.

A wide range of heat-resistant and lightweight materials is available nowadays but their definition and implementation requires the availability of vehicle system conditions and constraints.

Indeed, the expected benefits of economical, high-performance and high-speed civil-aircraft designs that are being considered for the future will be realised only through the development of lightweight, high-temperature composite materials for structure and engine applications to reduce weight, fuel consumption and direct operating costs.

While the LAPCAT project investigates propulsion systems for flight Mach number ranging between 3 and 8, this ATTLAS project looks into the vehicle aerodynamics and the testing of potential materials that can withstand the high heat loads encountered at these very high velocities.

Objectives

The objectives of ATTLAS are:

  • to evaluate two innovative supersonic aicraft concepts that will be able to provide acceptable levels of lift to drag ratios for flight Mach numbers ranging between 3 and 6,
  • to identify and assess lightweight advanced materials that can withstand ultra high temperatures and heat fluxes enabling flights above Mach 3. At these high speeds, the classical materials used for airframes and propulsion units are no longer feasible and need to be replaced by high-temperature, lightweight materials, with an active cooling of some parts.
Creep test facility
Creep test facility
DLR

Description of work

First of all, the overall design for high-speed transports will be revisited to increase the lift/drag ratio and volumetric efficiency through the ‘compression lift’ and ‘waverider’ principles, taking into account sonic boom reduction. This should allow vehicle definitions for Mach 3 and Mach 6 cruise flights.

Second, materials and cooling techniques, and their interaction with the aero-thermal loads will be addressed for both the airframe and propulsion components. The former will focus on sharp leading edges, intakes and skin materials coping with different aerothermal loads, the latter on combustion chamber liners.

After carrying out material characterisation and shape definition at specific aerothermal loadings, dedicated on-ground experiments will be conducted. Both ceramic matrix composites (CMC) and heat-resistant metals will be tested to evaluate their thermal and oxidiser resistance. In parallel, novel cooling techniques based on transpiration and electro-aerodynamics principles will be investigated.

Combined aerothermal experiments will test various material specimens with a realistic shape at extreme aerothermal conditions for elevated flight Mach numbers. Dedicated combustion experiments on CMC combustion chambers will allow the reduction of combustion liner cooling resulting in a NOx-reduction and overall thermal efficiency increase.

Finally, a particular aerothermal-material interaction will strongly influence the aerothermal loadings. Conjugate heat transfer, transpiration cooling and compressible transition phenomena are investigated and modelled.

Results

The project will result in:

  • the definition of the requirements and operational conditions at system level,
  • the assesment of the performance of two supersonic vehicles,
  • dedicated and thorough in-depth experiments performed on material characterisation in combination with aerothermal loads and combustion processes,
  • setting-up and validating physical models integrated into numerical simulation tools.
PATH Structure
PATH Structure

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