Wyniki wyszukiwania - BazTech

1

Effectiveness of the compound helicopter configuration in rotorcraft performance increase

Stanisławski Jarosław

Transactions on Aerospace Research

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2020

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Nr 4 (261)

81--106

EN

The article presents the results of calculations applied to compare flight envelopes of varying helicopter configurations. Performance of conventional helicopter with the main and tail rotors, in the case of compound helicopter, can be improved by applying wings and pusher propellers which generate an additional lift and horizontal thrust. The simplified model of a helicopter structure, consisting of a stiff fuselage and the main rotor treated as a stiff disk, is applied for evaluation of the rotorcraft performance and the required range of control system deflections. The more detailed model of deformable main rotor blades, applying the Galerkin method, is used to calculate rotor loads and blade deformations in defined flight states. The calculations of simulated flight states are performed considering data of a hypothetical medium class helicopter with the take-off mass of 6,000 kg. In the case of both of the helicopter configurations, the articulated main rotor hub is taken under consideration. According to the Galerkin method, the elastic blade model allows to compute blade deformations as a combination of the blade bending and torsional eigen modes. Introduction of additional wing and pusher propellers allows to increase the range of operational speed over 300 km/h. Results of the simulation are presented as timeruns of rotor loads and blade deformations and in a form of disk distribution plots of rotor parameters. The simulation method can be useful in defining requirements for a high speed rotorcraft.

PL

W pracy przedstawiono wyniki obliczeń umożliwiających porównanie obwiedni stanów lotu dla układu konwencjonalnego śmigłowca z wirnikiem głównym i śmigłem ogonowym oraz dla śmigłowca złożonego z dodatkowymi skrzydłami generującymi siłę nośną i śmigłami pozwalającymi zwiększyć poziomą siłę napędową. Uproszczony model struktury śmigłowca obejmujący sztywny kadłub i wirnik nośny traktowany jako sztywny dysk, zastosowano do określenia osiągów wiropłata oraz wymaganego zakresu wychyleń układu sterowania. Bardziej złożony model odkształcalnych łopat wirnika z wykorzystaniem metody Galerkina zastosowano do obliczeń obciążeń wirnika i odkształceń łopat w zadanych stanach lotu obejmujących przedział lotów z dużymi prędkościami. Obliczenia przeprowadzono dla danych dotyczących hipotetycznego śmigłowca średniego o masie 6000 kg i przegubowym połączeniem łopat z głowicą wirnika. Model łopaty odkształcalnej, zgodnie z metodą Galerkina, pozwala wyznaczać odkształcenia łopat jako złożenie składowych pochodzących od uwzględnianych giętnych i skrętnych postaci własnych łopat. wprowadzenie dodatkowych skrzydeł i pchających śmigieł pozwala zwiększyć zakres prędkości lotu powyżej 300 km/h. wyniki obliczeń symulacyjnych przedstawiono w postaci przebiegów czasowych obciążeń wirnika i odkształceń łopat oraz w postaci rozkładów parametrów na dysku wirnika. Metody symulacyjne mogą być zastosowane do zdefiniowania wymagań dotyczących wiropłata dużych prędkości.

2

Simulation investigation of operational conditions of rotor for high-speed compound helicopter

Stanisławski J.

Journal of KONES

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2018

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Vol. 25, No. 1

363--370

EN

The article presents results of simulations concerning possibilities of rotorcraft performance enhancements for compound helicopters with introduced additional wings and propellers. The simple model of helicopter including a point mass of fuselage and a rotor treated as a disk was used for calculations of helicopter flight equilibrium conditions. For the defined flight states, the more detailed model of elastic blade was applied to compute magnitude of rotor loads and level of blade deformations. The model of elastic blade includes out-of-plane bending, in plane bending, and torsion effects due to variable aerodynamic and inertial loads of rotor blades. Equations of motion of rotor blades are solved applying Runge-Kutta method. Taking into account Galerkin method, parameters of blade motion are computed as a combination of assumed torsion and bending Eigen modes of the rotor blade. The six-bladed rotor with stiff connections of blades and hub was applied for comparison of flight envelope for conventional helicopter and versions of compound rotorcraft with additional propellers and with wings and propellers. Simulations indicate that, in the case of compound helicopter configuration, achieving the operational flight conditions at high speed of 400 km/h is possible without generating excessive loads and blade deformations. The results of calculations of rotor loads and generated blade deflections are presented in form of time-run plots and as rotor disk distributions, which depend on radial and azimuthal positions of blade elements. The simulation Keywords: compound helicopter, rotor loads, blade deformation 1.Introduction For classical configuration of helicopter, with main rotor and anti-torque tail rotor, the speed of flight is limited in comparison to fixed wing aircraft. The maximum speed of conventional helicopter is restricted due to high drag associated with compressibility effects for advancing rotor blade and stall phenomenon, which occurs at retreating blade zone. A compound helicopter configuration with added lifting wings and separate source of thrust for propulsion may help to unload main rotor and enhance speed range of rotorcraft. Initial development programs of compound helicopters [6], such as the Bell 533, the Lockheed XH-51A fitted with wings and additional turbojet engines, or the Lockheed AH-56A Cheyenne with wings and pushing propeller and after flight tests were not passed to serial production. Emerging demands for improved performance and progress in composite materials and aerodynamics of rotor blades gave impulse to return to compound helicopter concept. In the last decade, the new experimental compound helicopters with additional propulsion were tested [3]: the American Piasecki X-49 Speedhawk, the Sikorsky X2 and the French Eurocopter X3. It should be mentioned that the Eurocopter X3 achieved speed of 472 km/h setting an unofficial speed record for propeller helicopters. Analytical and experimental researchworks were performed to examine features of compound helicopters, which included effects of varying main rotor tip speed [1], wing-rotor lift share [7, 8] and investigation of dynamic stability characteristics [2]. Basing on collected experiences, the next generation of operational compound helicopter designs are being developed. The American Sikorsky S-97 Raider made the maiden flight in 2015 [4] and the European Airbus Helicopter Racer’s configuration was revealed in 2017 [5]. investigation may help to define demands for rotor of high-speed helicopter.

3

Application of the modified blade element method for propeller blade design on high-speed helicopter X3

Karczewski M., Eglin P.

Zeszyty Naukowe. Cieplne Maszyny Przepływowe - Turbomachinery / Politechnika Łódzka

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2014

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nr 145

63--64

EN

The X3 helicopter is the experimental demonstrator of the H3 compound helicopter concept (High speed Hybrid Helicopter) developed by Airbus Helicopter and intended to operate at cruise speeds of about 113 m/s (220 kt). It is equipped with short fixed wings and two side-mounted propellers. Usually, fixed-wing propellers are sized to optimize the power consumption in cruise flight. In the case of a compound helicopter, some other flight cases such as hover and descent in autorotation also have to be considered. The geometrical criteria to satisfy all flight regimes may be contradicting what implies a compromise and a new approach to the propeller design. This paper presents the different steps of X3 propellers design from novelty theoretical Blade Element Method studies confirmed by CFD, experimental and flight tests.