ERF European Rotorcraft Forum
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Considerations in building an spr system for rotor blade deformation measurement
No full textA blade deformation measurement system utilizing Stereo Pattern Recognition (SPR) technique has been designed and built. Components of the system were selected considering the size of the model rotor and target accuracy. When considering the 4 m by 3 m measurement area in order to measure the deformation of the 2.5 m diameter rotor blades, the system was designed to have a resolution of the 3D deformation data in the range of 0.1 mm. The azimuthal position of the rotor should be controlled as exactly as 0.01 degree by a time delay control of the trigger signal. The combination of Xenon stroboscope lamps with LEE 799 UV filters, cameras with Edmund 575 nm filters, and rotor blade markers painted with orange/yellow fluorescent paint provided excellent contrast. Image processing and analysis, 3D tracking and reconstruction, and measurement automation functions were validated through initial tests
Wind tunnel investigation of a helicopter model in shipboard operations
No full textThe paper presents the wind tunnel simulation of a helicopter model in shipboard operations. The test rig consists of a scaled helicopter model and a simplified ship model, based on the geometry of the Simple Frigate Shape 1. In the first phase of the experiment, pressure and Particle Image Velocimetry survey of the flow field on the flight deck were performed without the presence of the helicopter, to study the flow features on the ship deck, for several wind conditions obtained modifying the wind speed and direction. The influence of Atmospheric Boundary Layer was investigated as well. Then, the rotorcraft was positioned in a series of points representative of both a typical fore-aft landing trajectory toward the deck, and a vertical descent on the deck. Loads generated by the rotor were monitored by means of a six-axis load cell. Particle Image Velocimetry of the ship wake and of the helicopter inflow were carried out in order to have a better understanding of how the interacting flow fields affected the helicopter performance. The test showed a significant effect of the mutual aerodynamic influence between the helicopter and the ship model and a limited effect of the Atmospheric Boundary Layer
A comparision study of rotorcraft with Hybrid Electric Propulsion System
No full textHybrid Electric Propulsion System (HEPS) is being developed as a novel propulsion system not only for the reduction of carbon emission but also for significant design freedom. However, the inevitable disadvantages of additional weight penalty and efficiency lost were induced by the electrification. Despite this, various aero-propulsive interactions enabled by the design freedom were proposed to overcome these impediments for enhanced performance of the aerial vehicle. Therefore, this study presents a comparative study of winged helicopter and fan-in-body, the two exemplary hybrid concepts of rotorcraft and fixed-wing, utilizing HEPS to investigate novel rotorcraft concepts capable of maximizing advantageous characteristics of the electrification. To this end, HEPS rotorcraft design framework was proposed, integrating the sizing of electrical devices and the aero-propulsive interaction. With the HEPS rotorcraft design framework, the design optimizations were carried out for two different mission profiles; resupply mission dominated by high-speed maneuver and reconnaissance mission dominated by the hovering and loitering missions. The success of this study presents that hybridization of the propulsion system incurs notable performance refinements for the mission requiring the maximum power with short operating time, mainly due to the inherent technological limitation of the battery
Multi-objective industrial optimization of high-speed helicopter main rotor blades with dynamically-adapted structural properties
Get PDFA multidisciplinary multi-objective optimization tool chain developed for designing main-rotor blades of high-speed helicopters is presented. Objectives focus on the dynamic loads in high-speed level flight, along with rotor power in hover. The tool chain relies on a genetic algorithm coupled to loads and performance simulation tools. In order to fulfill potentially strong industrial constraints, low-cost models are used in the comprehensive rotor simulation code HOST. Dynamic control loads may become critical in high speed and accurately representing both inertial and elastic responses of the blade to aerodynamic excitations is essential in the blade-design process. A new methodology is proposed in this work for the modelling of the blade structural properties. The strategy adopted is as follows: the design space is first sampled with a fixed number of donor-blade designs which cover most of the foreseen realistic planforms. The internal structure of each donor blade is tailored so that the blade eigenfrequencies placement is optimal with respect to the rotor harmonics, together with a mitigation of the blade-to-cabin modal transmissibility. Then, for each design candidate in the optimization process, a relevant donor blade is selected amongst the donor pool based on geometric similarities. The candidate structural properties are finally obtained by correcting the donor structural description with empirical functions based on the geometric discrepancies, assuming a similar structural technology. Twist, chord, and offset spanwise distributions are parameterized with Bézier curves and an optimization procedure is conducted so as to minimize the required power for hovering as well as to minimize the dynamic control loads in highspeed cruise conditions. A Pareto optimal solution is chosen and a more detailed analysis is achieved using higher-fidelity tools. The inclusion of the automatic structural update provides more realistic blade designs. The analysis of the updated structural properties indicates that the hypothesis assuming that the donor and the candidate blade have very similar eigenmodes is not entirely verified. Nevertheless, the method yields promising candidates and demonstrates the challenge of integrating the blade internal properties into the global industrial design process
Experimental evaluation on a Mach-scaled SNUF blade for active vibration control
Get PDFSeoul National University Flap (SNUF) blade equipped with an active trailing-edge flap is fabricated and tested under static conditions. Bench tests on the flap mechanism reveal the control authority and endurance of the devised flap actuation mechanism while centrifugal load acts on the flap. Also, the frequency response of the flap mechanism is identified where the static load is imposed on the flap. Blade tensile tests are performed for each root and flap component separately. Each specimen shows greater than 40% of safety margin compared with the expected maximum centrifugal load from comprehensive rotor analysis. The axial stiffness estimated from the measured skin strain is in good agreement with the cross-sectional analysis. Basic properties tests on the fabricated blade are carried out. Both sectional strain measurements and the identified modal frequencies show similar discrepancies in the flapping and torsional directions, which are 4% and 20% differences with design analysis, respectively. Finally, estimated MAC values for the first three fundamental modes satisfy the rejection criteria of 0.9
Assessment of the harmonic balance method for rotor blade performance predictions
Get PDFThis paper presents an assessment of the harmonic balance method for rotor blade performance predictions. The harmonic balance method within the HMB3 solver of Glasgow University has been extended to include overset grids, and results are presented for the PSP and AH-64A rotor blades in hover and forward flight. The predictions are compared with results from steady-state and time marching simulations. In particular, the harmonic balance method is assessed for capturing key flow features, such as the strength of the advancing blade shockwave and retreating side blade dynamic stall. The limitations of the method are also discussed. The findings show that the harmonic balance method is a promising alternative to time-marching simulations due to a significant reduction in computational costs, leading to the potential use of high-fidelity Navier-Stokes methods in optimisation studies
Helicopter gearbox periodic strut with geometrical discontinuity for vibration and noise reduction
Get PDFA novel periodic strut for helicopter cabin noise reduction is presented in this paper. The strut uses monomaterial with periodical changing geometry in the longitudinal direction. To design the strut, a theoretical model is built based on the lumped-mass method. On this basis, a parametric analysis is carried out. The results showed that if the static stiffness and the weight are constants, the stop band of the strut is mainly determined by the periodic number and the cell stiffness ratio. The strut can be quickly designed through reducing the periodic number and increasing the cell stiffness ratio to obtain a lower stop band. Subsequently, a sample strut is designed. Its translational and rotational transmissibility are simulated. It is found that except for the designed longitudinal direction, the strut has broadband vibration attenuation characteristics in the lateral direction. However, resonances appear in some frequencies due to the small damping, which would cause noise amplification. In spite of this, with the novel periodic struts, nearly 20dB noise attenuation appears in the cabin of the helicopter model between 500-2000 Hz
Ferrium steels and other high performance materials for next generation rotorcraft transmissions and applications
Get PDFIntegrated Computational Materials Engineering (ICME) technologies are effective tools to accelerate implementation of new higher performance alloys, shortening design time and reducing cost compared to empirical methods. Using these technologies and their Materials by Design® approach, QuesTek Innovations LLC has designed, commercialized and deployed a class of high-performance Ferrium steels specifically addressing demanding and critical transmission applications for the global rotorcraft industry. Furthermore, these ICME technologies have been expanded to the field of Additive Manufacturing (AM) to adapt the Ferrium steels and design new alloys specifically tailored to the unique processing conditions to bring advanced capability to the rotorcraft and aerospace industries
Numerical investigation of aerodynamics and acoustics of rigid main rotor in forward flight
No full textThe paper is devoted to the numerical simulation of the flow near the rigid helicopter rotor in the forward flight mode using the Reynolds-averaged Navier-Stokes equations in the rotating non-inertial reference frame. The numerical method is based on the vertex-centered EBR scheme for unstructured hybrid meshes. The computations are performed using the in-house code NOISEtte and the software package ANSYS CFX. The numerically obtained aerodynamic characteristics of the rotor are comparatively analysed against the results of full-scale experiments
The final phase of a helicopter automatic landing on a vessel’s deck
No full textThe paper presents part of the results obtained in the HELIMARIS project (”Modification of an optionally piloted helicopter for maritime mission performance”) led by PZL Swidnik in cooperation with Warsaw University of Technology and CTO. In the paper, way of integration of light helicopter dynamic model, automatic control and prediction algorithm for landing on the moving vessel at different sea states is presented. For the purpose of the landing task a Linear Quadratic Regulator (helicopter control) and autoregressive method with parameters calculated using Burg’s method (vessel movement prediction) are used. The model of the helicopter is developed and evaluated in FLIGHTLAB software using flight test data for validation. Developed system for landing of the helicopter on the vessel is presented, results are shown and discussed