Thesis (MEng) -- Stellenbosch University, 2000. / Some digitised pages may appear illegible due to the condition of the original hard copy. / ENGLISH ABSTRACT: This document contains the work done on the bearingless rotor hub for the 24% scale model of the Rooivalk Attack Helicopter situated at the CSIR in Pretoria. This work forms part of the MSc Ing degree of Johannes Steyn. This work was deemed necessary because of a movement away from the fully articulated rotor to one of hingeless and more recently bearingless rotors. The main emphasis of this thesis is to be a technology demonstrator more than the design of a fully working bearingless rotor hub. With this in mind the final design in this report is not an optimal one, but the procedures and methodology in getting to a design are laid out in this document. To verify the design, tests were identified and created. The procedures for these tests are also included in this document. For the fatigue test a test bench had to be designed and built. This document also includes the design of this test bench / AFRIKAANSE OPSOMMING: Die dokument lewer verslag van die aktiwiteite vir die ontwerp van ‘n laerlose rotor van die 24% skaal model van die Rooivalk Helikopter, gelee by die WNNR in Pretoria. Die werk gedoen vorm deel van die MSc Ing graad van Johannes Steyn. Die werk is nodig geag omdat daar ‘n tendens is om weg te beweeg van die volledig geartikuleerde rotor na die van ‘n skanierlose en meer huidig ‘n laerlose rotor. Die hoof klem van die tesis is om as tegnologie demonstrator op te tree, eerder as die daarstel van ‘n werkende laerlose rotor. Na aanleiding van bogenoemde stelling kan die finale ontwerp nie as optimaal beskou word nie. Die prosedures en metodiek wat gevolg is om die ontwerp te kry word uitgele in die dokument. Om die ontwerp te verifieer is toetse gei'dentifiseer. Die prosedures vir elk van die toetse word ook in die dokument ingesluit. Vir die uitputtingstoetse moes ‘n spesiale toetsbank ontwerp en gebou word. Die ontwerp van hierdie toetsbank is ook in die dokument.

No description available.

Thesis (M. App. Sc.)--Carleton University, 2003. / Includes bibliographical references (p. 118-124). Also available in electronic format on the Internet.

Thesis (Ph.D)--Aerospace Engineering, Georgia Institute of Technology, 2009. / Committee Co-Chair: Dr. Dimitri Mavris; Committee Co-Chair: Dr. Lakshmi N. Sankar; Committee Member: Dr. Daniel P. Schrage; Committee Member: Dr. Kenneth S. Brentner; Committee Member: Dr. Mark Costello. Part of the SMARTech Electronic Thesis and Dissertation Collection.

No description available.

BRANCH OF AERONAUTICAL ENGINEERING UNIVERSITY OF THE WITWATERSRAND / An experimental investigation was carried out on a half scale model of a helicopter COmbined Infra-Red Suppression and Tail rotor Elimination (CIRSTEL) system to characterise its performance in terms of power consumption, thrust, pressure drops and temperature reduction. The model consists of a Circulation Control Tail Boom and Thruster (CCTB&T) with the hot engine gasses ducted into the tail boom where they are mixed with ambiant air supplied by a fan situated in the body of the helicopter. The CCTB&T replaces the conventional tail rotor on a helicopter and supplies the torque to counter-act the torque applied to the main rotor. The model was tested using both hot and cold air to simulate the flow of hot engine gasses. The performance is defined in terms of thrust, power, and mass flow coefffcients which were found to be constant for the configuration tested. It was shown that the power requirements of the fan are significantly reduced by introducing the hot engine gasses into the tail Boom. The temperature of the hot engine gasses is also reduced from 450°C to approximately 200°C The surface temperature of the model was found to be less than 55'C of the configuration.

Digitized by Kansas Correctional Industries

Rotordynamics is an important area in mechanical engineering. Many machines contain rotating parts. It is well known that rotating components can develop large amplitude lateral vibrations near certain speeds called critical speeds. This large amplitude vibration is called rotor whirl. This thesis is about rotor whirl. Conventional treatments in rotordynamics use what are called gyroscopic terms and treat the rotor as a one-dimensional structure (Euler-Bernoulli or Timoshenko) with or without rigid masses added to them. Gyroscopic terms are macroscopic inertial terms that arise due to tilting of spinning cross-sections. This approach, while applicable to a large class of industrially important rotors, is not applicable to a general rotor geometry. In this thesis we develop a genuine continuum level three dimensional formulation for rotordynamics that can be used for many arbitrarily shaped rotors. The key insight that guides our formulation is that gyroscopic terms are macroscopic manifestations of the prestress induced due to spin of the rotor. Using this insight, we develop two modal projection techniques for calculating the critical speed of arbitrarily shaped rotors. These techniques along with our prestress based formulation are the primary contributions of the thesis. In addition, we also present two different nonlinear finite element based implementations of our formulation. One is a laborious load-stepping based calculation performed using ANSYS (a commercially available finite element package). The other uses our nonlinear finite element code. The latter two techniques are primarily developed to provide us with an accurate answer for comparison with the results obtained using the modal projection methods. Having developed our formulation and the subsequent modal projection approximations, we proceed to validation. First, we analytically study several examples whose solutions can be easily obtained using routine methods. Second, we consider the problem of a rotating cylinder under axial loads. We use a semi-analytical approach for this problem and offer some insights into the role played by the chosen kinematics for our virtual work calculations. The excellent match with known results obtained using Timoshenko theory validates the accuracy of our formulation. Third, we consider several rotors of arbitrary shape in numerical examples and show that our modal projection methods accurately estimate the critical speeds of these rotors. After validation, we consider efficiency. For axisymmetric rotor geometries, we implement our formulation using harmonic elements. This reduces the dimension of our problem from three to two and considerable savings in time are obtained. Finally, we apply our formulation to describe asynchronous whirl and internal viscous damping phenomena in rotors.

Thèse doctorat : Génie Mécanique : Villeurbanne, INSA : 2004. / Titre provenant de l'écran-titre. Bibliogr. p. 172-175.

Thèse doctorat : Génie Mécanique : Villeurbanne, INSA : 2006. / Titre provenant de l'écran-titre. Bibliogr. p. 148-157.