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Application of topology optimization technique to size the NGCTR-TD engine mount at high temperature using unconventional materials
No full textWithin the CS2 FRC framework Leonardo Helicopters is leading the team who is going to develop new technologies and solutions for future tiltrotors. The engine mounts turned out to be a design challenge since they have a great impact on the overall weight of the Technological Demonstrator under development and they need to be complaint with very stringent mechanical requirements in a very bad thermal environment (temperatures up to 1100 °C as per certification requirements). The Topology Optimization technique, using Optistruct, was used to investigate a new design of the engine mount of the NGCTR-TD at high temperature. The design guessed was optimized at three different temperatures in the range RT-1000 °C, comparing the use of Stainless steel and Titanium alloy, with the same problem 18 set up to compare the benefits, in terms of mass reduction, of each material. The results demonstrated that, at temperatures under 538 °C, the introduction of the Titanium alloy guarantees a remarkable mass saving for the current design, but at temperatures above 1000 °C, the benefits obtain-able were nullified by the overcoming of the stress constraints, also in areas not subjected to Topology Optimization. In parallel to this work, the possible benefits of introducing a fire tested thermal coating in the design were investigated through thermal analysis with Acusolve, in order to find the most suitable arrangement of layers to protect the structure. The proposed solution proved to protect the engine mount from high temperatures, reaching on the inside a temperature below 250 °C, thus allowing to investigate the use of Aluminum alloy which is an unconventional choice for this type of application. After being Topology Optimized and despite of the contribution introduced by the thermal coating, this solution demonstrated to produce the greatest mass saving compared with the other materials, electing the Aluminum alloy to be used for the next stages of the design of the engine mount
Helicopter drive train failures
No full textThe dangers of using vacuum arc remelted (VAR) steel for the drive trains of helicopters are described. The steel can contain serious cracks, and historical helicopter failures are listed. An equivalent material recommended for use is that produced by the electroslag remelting (ESR) process which is expected to be fundamentally free of major defects
Manoeuvrability investigation for tiltrotor aircraft with an integrated simulation engine
No full textThe tiltrotor aircraft has unique flight dynamics characteristics because of the extensive aerodynamic interference effects present, the possibility of redundant control strategy, and the unique regime occurring during the conversion process, making its controllability more complex during manoeuvres. Also, these tiltrotor configurations are the basis for many Urban-Air-Mobility (UAM) prototypes, in which formation flight features and airworthiness regulation developments for UAM manoeuvring flight in urban areas should be considered. Therefore, this research developed an inverse simulation embedded manoeuvrability method for the tiltrotor aircraft, and this method was incorporated with the existing MAVERIC multi-agent system for the relevant UAM airworthiness investigation. First, the flight simulation model, the inverse simulation algorithm, and the MAVERIC system were introduced. Then, the Pop-up manoeuvre is utilised for the manoeuvrability investigation. The results indicate that the obtained control input is following the understood flight dynamics characteristics of the tiltrotor aircraft. Furthermore, the tiltrotor aircraft model and associated inverse simulation embedded analysis techniques were adapted into the MAVERIC system, which can be utilised to provide an intuitive demonstration of the manoeuvrability of tiltrotor aircraft. They will be an ideal platform for future UAV vehicles and relevant airworthiness investigations
Modal characterisation of a rotor/propeller rig for tip-Mach scaled wind tunnel testing
No full textAn advanced rotor and propeller rig for tip Mach-scaled wind tunnel testing is the subject of dynamic analysis presented in this paper. Experimental modal analysis and finite element method are used to assess the key characteristics such as the modal properties and transfer functions, as well as their changes under varying conditions. This work aims to determine and summarize these characteristics for the purposes of further rig development and its safe operation. The research also includes analysis of the key sources of uncertainty, damping, the effect of unbalanced excitation and model-experiment correlation. The low frequency region is found to be dominated by the three weakly damped global modes whilst the following modes feature increased modal activity of the rotor shaft and the hub. The latter set of modes is also found to be more susceptible to nonlinear effects and associated increased identification and modelling uncertainty
The UK vertical lift network and the mentor project
Get PDFThe UK Vertical Lift Network (UK VLN), founded in 2013, aims at developing synergies between its members and promote collaboration within the UK rotorcraft research community. It is doing so by facilitating the involvement of other members of the network in new research projects. The network is also encouraging cooperation in educational and training activities, through the organisation of yearly events. The VLN collaboration lead to the start of the MENtOR project (Methods and Experiments for NOvel Rotorcraft), which proposes to develop new methods to predict and analyse tiltrotor aircraft, using a multi-disciplinary approach linking aerodynamics, dynamics, control algorithms and flight simulation. The project aims at delivering a set of tools and methods to all members able to perform comprehensive analyses of tiltrotor aircraft
Aerodynamic performance of an arrow airfoil in Mars environment and its optimization
Get PDFA novel arrow airfoil is proposed in the Mars atmospheric condition for high L/D, and the flow characteristics around the airfoil are investigated through numerical analysis. Since the bubble on the upper surface of the airfoil by the arrow, the lift increased and the frictional drag decreased, in turn, L/D increases. The optimized arrow airfoil that maximizes the maximum L/D over angle of attack 0 to 10° is obtained under the operating condition of NASA Mars Helicopter Technology Demonstrator(MHTD), based on 5% cambered flat plate airfoil. There is an increase in maximum L/D of 10.51% and 7.05% in the first and second flow conditions, respectively, and no design is derived that satisfies the constraints in the third flow condition. In addition, off-design analysis of optimum arrow airfoil is conducted to investigate the effect of Mach number, and it is confirmed that arrow airfoil is effective at M = 0.5 or less
Analysis of eVTOL multicopter weight and power budget as a function of the number of rotors
Get PDFIn this work, we focused on predicting the power budget and weight variation of an electric, wingless multicopter operating in a typical UAM mission as a function of the total number of rotors in the propulsion group. The aerodynamic performance was obtained using the actuator disk inflow model, and weights were estimated based on semi-empirical scaling laws of the electrical components in the power train. The key aspect of this analysis procedure is that it accounted for the potential failure events that reflected on the power budget and weight of the rotorcraft. Results describe the weights of the propulsion system components, power requirements, and energy budget of the rotorcraft as a function of the total number of rotors. The main conclusion is that a larger number of rotors is beneficial for the rotorcraft’s weight and power budget, for a number of rotors within the practical range, i.e. ???? ? [6, 20]. A global minimum exists for both energy budget requirements and MTOW if the efficiency of the power train degrades with an increasing number of rotors. Optimising multicopter for minimum weight can be misleading as it does not result in the most efficient configuration energy budget-wise
Numerical investigation of the rotor-rotor aerodynamic interaction of eVTOL configurations by a mid-fidelity approach
Get PDFThe rotor-rotor aerodynamic interaction is one of the characteristic phenomena that influence both flow physics and performance of most of the new electric vehicles for urban air mobility (eVTOLs) widely investigated in recent years. The present article describes a numerical activity aimed to the systematic study of the rotor-rotor aerodynamic interaction with application to eVTOLs cruise flight condition. The activity considers numerical simulations performed with DUST, a novel mid-fidelity aerodynamic solver based on vortex particle method. In particular, the test case considered consists of two propellers both in side-by-side and tandem configuration. Simulations results highlighted quantitatively the loss of propellers performance by varying separations distance between them and provided a detailed insight about flow physics involved in such aerodynamic interactions
Flight trial demonstration of increased general aviation and rotorcraft operations supported by GNSS solutions
No full textThe project GRADE has received funding from the SESAR Joint Undertaking under grant agreement No 783170 under European Union’s Horizon 2020 research and innovation program. The operational scope of one of the project’s exercises was to demonstrate the feasibility and benefits of executing SESAR 1 solution Sol#113, which covered the demonstration of Standard Point In Space (PinS) helicopter procedures as well as low level IFR routes for helicopters. In addition, it was demonstrated that the PinS procedure can be conducted independently from approaching fixed wing traffic, resulting in a Simultaneous Non-Interfering (SNI) operation. For guiding the pilot along the planned flight route, different display formats of a primary flight display, navigation display, and tunnel-in-the-sky guidance display were customized and finally tested on a head-down display on DLR’s HubSim simulator in the scope of a real-time simulation. The results of this campaign were already presented on 45th European Rotorcraft Conference in Warsaw. Following up on the outlook given at that conference, this subsequent paper describes the results of the flight tests that were carried out from 20th August until 18th September 201
Rotor blade tip sweep effect on lead-lag damping in hover and forward flight
Get PDFRotor blade geometry (tip sweep, planform taper and anhedral) significantly influences the aerodynamic efficiency, vibratory loads and aeroacoustic behavior of the helicopter rotor. In this paper, the focus is on analyzing the effect of blade tip sweep on the structural dynamic, aeroelastic loads and blade lead-lag damping in hover and forward flight for an isolated rotor. For carrying out this analysis, a comprehensive analytical model is developed. In the structural model blade undergoes coupled flap, lag, torsion and axial deformations. Tip sweep, pretwist, precone, predroop, torque offset and root offset are included in the model. Aerodynamic model includes 3-state Peters-He dynamic wake theory for inflow and the modified ONERA dynamic stall theory for airloads calculations. The comprehensive model is first validated by comparing the predicted results with experimental data. The predicted results of blade root loads and lag damping for a straight blade in hover, over the collective angle settings of -2 to 6 degrees, are in a very good agreement with the measured whirl tower test data. In hover and forward speeds, the lag damping values of swept tip blade are less compared to the straight blade for various collective angle settings. For a straight blade, lag damping values show slight increase and decrease with the increase in advance ratio, whereas for the swept tip blade, lag damping shows a marginal increase at lower advance ratio up to 0.1 and then a decrease in the range of advance ratios 0.1 to 0.2 and thereafter it shows an increasing trend. This kind of variation in damping trends for straight and swept blades with forward speed qualitatively agrees with experimental observations available in the literature