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Experimental evaluation of flow distortion at tilt-rotor full-scale model air intake wind tunnel test
Get PDFWithin the Clean Sky 2 Fast Rotorcraft platform, a Next Generation Civil Tilt-Rotor demonstrator is being developed. Within the related TRINIDAT project the key driving aerodynamic choices of the engine air intake configuration are being investigated. A wind tunnel model has been successfully designed and manufactured for full-scale intake testing of the basic intake configuration. The model is comprised of a nacelle, modular intake duct, rotatable spinner hub (rotor head) and wing part including deflectable aileron. In order to assess the flow quality at the Air Inlet Plane (AIP), a novel highly instrumented rotary rake has been designed. The model also includes a large amount of static pressure taps on wing and intake duct surfaces. A wind tunnel test in the DNW-LLF has been successfully performed, simulating the full flight envelope and parameter variations. The adopted scaling methodology is explained. The 6 x 6 m2 test section allowed to test the full scale model at Ma = 0.40 which is nearly cruise Mach number. The test program included a wide range of variations in angle of attack, sideslip angle, aileron deflection and suction mass-flow rate. Post-processing of the test data yielded a large database including flow distortion parameters based on the total pressure field and the velocity field in the AIP. The sensitivity of key distortion parameters to variation of model attitude, aileron deflection and mass-flow rate has been obtained for a selected set of conditions. The development of unsteady pressures along the intake duct including AIP has been characterized as well
Evaluation of functionality and mass of two IVT-drives in helicopter-compound split drivetrains
No full textThe research described in this paper is part of the international research project VARI-SPEED. The aim of this project is to enable main rotor speed variation of rotorcraft in order to reduce the required propulsion power, which enables modern and ecologically efficient aviation. Application of an infinitely variable transmission, capable of speed ratios from ?? to 0, inside the helicopters compound-split module allows for seamless change of rotor speed within a ratio spread of 1.5. This study investigates whether two continuously variable transmission concepts based on the principle of the freewheel and the NuVinci traction drive satisfy the boundary conditions with regard to speed ratio range, mass and power transmission capability for a helicopter of the CS29 class. The general functionality is described for both transmission concepts and kinematic as well as force models are given in order to allow for a rough design, which acts as a base for the mass calculation. Validation for the freewheel gearbox is performed via multi-body dynamics simulation in SIMPACK and gear design in KISSsoft. The design of the traction drive is accomplished by implementation of a parametric model in MATLAB and fully automatic optimization by genetic algorithm. Although the freewheel gearbox allows a transmission ratio of ?? to ?1, the necessary speed ratio of ?? to 0 could not be achieved. The traction drive concept, although capable of the required transmission ratio, is impaired significantly by recirculating power and much greater mass than the reference hydraulic variator unit utilized in previous publications. These findings are important for choosing the best infinitely variable transmission for application in the compound split drivetrain investigated in VARI-SPEE
Large Eddy Simulation of parallel blade-vortex interaction on low Reynolds airfoil
No full textIn the present work the Large Eddy Simulation approach has been used to investigate the parallel interaction between a vortex and a SD7003 airfoil at angle of attack equal to 8_ and Reynolds number 60000. The numerical code is based on the Local Discontinuous Galerkin finite element method associated with sophisticated anisotropic subgrid scale model. During the simulation, the polynomial degree has been adapted locally in space and dynamically in time on the base of the structure function indicator suitable for LES. The simulation shows the interaction with the vortex which stronghly affects the transitional separation on the airfoil and the force coefficients
Tiltrotor whirl flutter analysis in support of NGCTR aeroelastic wind tunnel model design
Get PDFThis work presents the modeling and preliminary whirl-flutter stability results achieved within the Advanced Testbed for TILtrotor Aeroelastics (ATTILA) CleanSky2 project. ATTILA entails the design, manufacturing and testing of a semi-span wind tunnel model of the Next Generation Civil TiltRotor. A description of the preliminary MBDyn and FLIGHTLAB multibody models is presented. The modelling technique of each subcomponent of the model, namely the wing, the rotor, the blades and the yoke is briefly illustrated. The predicted dynamic characteristics of the wing-pylon system and the rotor are then compared. Finally, some preliminary whirl-flutter stability predictions are presented, along with the techniques that will also be used in the wind tunnel tests to identify the aeroelastic modes of the model
Aerodynamic design modification of the Kopter AW09 helicopter
No full textWind tunnel testing and accompanying numerical analyses are the basic methods applied to improve and optimize the aerodynamic design of the Kopter AW09, a 2.8 ton-class single engine utility helicopter. In order to ensure good handling qualities and performance, modifications of the upper fuselage are tested and evaluated by means of force and moment measurements, particle image velocimetry, and CFD analysis. Based on particular examples, these methods are presented
Optimisation of the structure of a helicopter blade in view of reducing cabin vibration
Get PDFThe study presented in this paper aims at bringing the blade internal structure into a global multi-physics optimization of the helicopter rotor. The optimization is applied to vibration reduction in forward flight with aeroelastic and multidisciplinary constraints. The objective function consists of the dynamic hub loads, and behaviour constraints are imposed on dynamics, performance and manufacturability criteria. A genetic algorithm is used to conduct a global search of the design space among numerous combinations of blade physical parameters with discrete values (positioning of tuning masses, composite skin layers, counterweight materials…). The novelty brought by this study includes simulations integrated in a tool-chain based on physical parameters with manufacturability constraint
Mid-fidelity numerical approach to tiltrotor aerodynamics
Get PDFThe study of complex aerodynamics that characterise tiltrotors represents a challenge for computational fluid dynamics tools. URANS numerical solvers are typically used to explore the aerodynamic features that characterise the different flight conditions of these aircraft, but their computational cost limits their applications to a few vehicle configurations. The present work explores the capabilities of the new mid-fidelity aerodynamic code DUST, based on vortex particle method for wake modelling, to investigate the performance and flow physics of tiltrotors. A thorough assessment of the code capabilities was performed by comparison of numerical results with high-fidelity Computational Fluid Dynamics (CFD) data. This thorough comparison showed that the mid-fidelity numerical approach implemented in DUST is suitable for capturing flow physics related to the complex aerodynamic interactions between the proprotors and the wing along with the entire flight envelope of a tiltrotor
In-plane vortex-rotor interaction and its impact on rotor trim: an analytic solution for arbitrary vortex orientation and position
Get PDFThe general aerodynamic problem of arbitrary oriented in-plane vortex-rotor interaction was investigated in the past only by numerical simulation. Just one special case of in-plane vortex-rotor interaction with the vortex axis in flight direction was recently solved analytically. In this paper the analytical solution for arbitrary in-plane vortex orientation and position relative to the rotor on thrust and hub moments is given that was published for the first time just before. Results provide the vortex impact on rotor trim (thrust, aerodynamic rolling and pitching moments about the hub) and the rotor controls required to mitigate these disturbances. In this paper the sensitivity of these results with respect to the main parameters will be given: the vortex core radius, its distance to the rotor center and its orientation angle relative to the rotor longitudinal axis, the rotor blade begin and end of the airfoiled section, and the advance ratio
Helicopter hover ceiling improvement possibilities and its limits with an electric tail-rotor
No full textFor conventional helicopters with single main-rotor and fixed-speed tail-rotor whose hover ceiling is limited by the tail-rotor thrust, variable speed electric tail-rotors could potentially improve hover ceiling by operating at higher rotor speed. On the basis of a 2D-panel method code and transonic small disturbance theory for airfoil section coefficients, and blade-element and momentum (BEM) theory model, the tail-rotor performance is analysed for higher rotor speeds compared to base configuration. Results are presented for an example existing helicopter for hover out-of-ground effect (OGE) with maximum take-off weight (MTOW) conditions. The results confirm that compressibility effects at the tip-section is the major limitation for operating at higher rotor speeds. Combined with the thrust and power balance for the tail-rotor and helicopter powerplant respectively, hover ceiling improvement is quantified. In spite of the limited speed increase possibility due to compressibility effects a noticeable improvement to hover ceiling is made possible with the variable speed electric tail-rotor configuration
Ground-based tests of a digital displacement hydraulic transmission for distributed propulsion
Get PDFThis paper progresses the concept of the Digital Displacement hydrostatic transmission as applied to hybrid multirotor UAVs and other applications of distributed propulsion. A summary of the concept is made and the simulation work done to date is described on the H380 UAV concept. A ground based test facility is described, and results are shown for steady state and transient rotor performance, with validation of the simulation model. Thermal performance is shown. An outlook for development towards flight testing is made