Advanced Design Methods for Engine/Airframe Integration

The use of new available engines by aircraft producers is limited by absence of appropriate design know-how and by several technological challenges one needs to overcome once decided to install a new type of engine into the aircraft.  Engine - aircraft integration is traditionally underresearched area, with practically no FP projects in this field. A new corroborative approach between EU airframes and EU turbine engine makers in the GA sector is planned in ESPOSA.

The project will search for multidisciplinary solutions for issues connected to engine mechanical integration, aerodynamic drag aspects and nacelle thermal management. Novel approaches to airframe and engine integration are needed for optimized nacelle design including latest technology applications. The innovative solutions will also cover the “white spots” of engine-aircraft integration, namely inertial separation of solid particles inside engine inlet duct, use of vortex generators to optimize internal duct flow paths,  whirl flutter phenomena, thermal assessment and heat composite structures for nacelle design with respect to weight and manufacture costs.

The ambition is to reduce the time and development costs connected with engine installation. The new or improved simulation tools and design methodologies gathered together as a kind of a design guide can make any new engine installation more effective and pave the way for increased use of GTE engines on small aircraft.


Complex design methodology for engine mechanical integration (WP6.1)

The engine mechanical integration is a complex design work. Engine nacelle is a relatively small place where all demands of aircraft itself, power units and systems - inner and outer aerodynamic, stress, weight, maintenance, controls, heat management, fuel system, and electric power system meet together. Designers must find out the best trade-off among all these requirements. Typically it is done by means of iterative process when all necessary information is collected, detailed, evaluated (trade-off) and finally processed into the power unit installation.

The main objective of the work is to increase ability of GA airframes to install power units in optimal way allowing utilization of advanced tools even in the environment of small development teams. The work will generate new knowledge and design methodologies for improved processes of power unit integration.

In order to find out the general methodology for all current Aircraft Configurations (ACC), the work will be focused on four basic types of propulsion unit installations to the airframe:

  • Tractor configuration with the engine in the fuselage - TR1
  • Tractor configuration with the engine on the wing - TR2
  • Pusher configuration with the engine on the wing - PU2
  • Helicopter configuration - HE1

These configurations will be investigated up to the stage of DMU (Digital MockUp).  Some design methodologies and procedures will be proved by validation on real engine installations of older version of BE1 platform, together with newly developed engine systems installed on that engine. The outcome of the work will be a design methodology (guide for designers) for optimal GTE unit installation respecting very complex requirements.

 

Reliable design technology for aerodynamic engine/airframe integration (WP6.2)

The RTD work will be oriented on the aerodynamic engine/airframe integration. Even if technologies for aerodynamic engine integration are quite assessed for large commercial aircraft, these are not simply scalable for small aircraft. Furthermore, for this class of aircraft industrial  requirements related to low development costs and time can be translated into the need for numerical methodologies and procedures characterized as follows; small man-power effort for setting-up the simulation model and analyzing the results; not CPU intensive; low overall turnaround time for multidisciplinary simulation and optimization; high level of accuracy.

A specific problem to be addressed for general aviation related to airframe integration studies is the propeller slipstream effect.  The work will cover three important areas:

  • Configuration impact on propulsion performances
  • Innovative technologies and aerodynamic design methodology for air inlet and internal nacelle duct
  • Aerodynamic design methodology of nacelle external shape

Outcomes of this work will be improved methods and design procedures for each specific propeller configuration, for external nacelle shape, inlet and internal nacelle air ducts including solid particle separators studies and study on potential of vortex generators employment in internal ducts. The work will also comprise upgrades/validation of surrogate methods and methods based on short turnaround time mesh generation.

 

Engine and nacelle aeroelastic integration – “Whirl Flutter” (WP6.3)

The standard whirl flutter analysis is based on the NASTRAN solver supported by the auxiliary SW tools for the propeller aerodynamic matrices calculation as well as for the results postprocessing. In the frame of the 6th FP project "CESAR", the optimization based analysis procedure was formed and the program tool for the propeller aerodynamics calculation was created. However, there are still technical limitations in the whole technique. Objective of the work is a development of improved and more reliable tools used for the whirl flutter analysis to improve the accuracy of the results and to reduce the development and certification time. The work will be focused on the following topics:

  • Increasing the limit number of rotors included to the analysis
  • Improvement of the propeller aerodynamics (lift force distribution, unsteady aerodynamic theory)
  • Improvement of the residual structure aerodynamics and effect of the propeller / nacelle / wing interference, including the effect of the fatigue
  • Improvement of the results postprocessing tools

 

Reliable simulation tools for engine thermal integration (WP6.4)

During the development of a new aircraft, one of the tasks performed by the aircraft manufacturer is to ensure that temperatures of the engine, aircraft equipments and the nacelle remain under their allowable temperature throughout the whole aircraft’s flight envelope. Therefore aircraft manufacturers meet design challenges regarding the thermal integration of the power plant, even for severe thermal (convective and irradiative) operational conditions.

For the aircraft manufacturer the integration of a new power plant into a new airframe, made largely of composite materials, presents challenges in the thermal and ventilation design of the engine nacelle. At present this phenomena is usually “checked” and measured during the flight test phase, because no complex affordable methodology for heat load prediction exists.  This approach leads to modifications and changes in later stages of development process resulting in extra time, extra cost and not optimum technical solution – just troubles are cured.

Following topics in the engine thermal integration will be addressed:

  • Heat exchanger (Engine Oil Cooler Generator Cooler) system design;
  • Nacelle case ventilation;
  • Exhaust plume design optimization

The main outputs of the RTD work will be novel models, tools, and optimizations methods that will allow more efficient and accurate aero-thermal design and assessments with respect to the engine thermal integration and nacelle design.


New design and manufacturing approaches for "hot" composite nacelles (WP6.5)

Development of new design approaches aimed at the realization of advanced, higher temperature capability composite nacelle structures for small aircraft and leads to a cost effective manufacturing solution suitable for this class of aircraft. The advanced composites are to be used for nacelle components which traditionally could only be made using metals requiring significant thermal insulation resulting in a weight and cost penalty. To achieve this goal several composite technologies will be investigated in order to exploit the potential expressed by the most promising emerging materials and processes such as Liquid Moulding (infusion), Quick-Step and Out-of-autoclave prepregs. Work will result in design knowledge and complex design methodology for heat resistance composites and their application on nacelles and demonstrated in real aircraft installations.

The work will comprise investigation of optimal materials and processes for hot composite nacelle structures and their associated properties, design allowable and processing parameters and development of design methodology for hot composite nacelle structures satisfying design requirements and manufacturing constraints.