Download or read book Optimizing Tuning Masses for Helicopter Rotor Blade Vibration Reduction Including Computed Airloads and Comparison with Test Data written by and published by . This book was released on 1992 with total page 14 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Optimal Placement of Tuning Masses for Vibration Reduction in Helicopter Rotor Blades written by and published by . This book was released on 1988 with total page 20 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1972 with total page 1070 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Aerospace America written by and published by . This book was released on 1992 with total page 662 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Monthly Catalogue United States Public Documents written by and published by . This book was released on 1993-03 with total page 1482 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Monthly Catalog of United States Government Publications written by United States. Superintendent of Documents and published by . This book was released on 1993 with total page 804 pages. Available in PDF, EPUB and Kindle. Book excerpt: February issue includes Appendix entitled Directory of United States Government periodicals and subscription publications; September issue includes List of depository libraries; June and December issues include semiannual index
Download or read book Structural Dynamics Division Research and Technology Accomplishments for FY 1992 and Plans for FY 1993 written by Eleanor C. Wynne and published by . This book was released on 1993 with total page 232 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book An Initiative in Multidisciplinary Optimization of Rotorcraft written by and published by . This book was released on 1988 with total page 46 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book NASA SP written by and published by . This book was released on 1992 with total page 548 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Aeronautical Engineering written by and published by . This book was released on 1993 with total page 712 pages. Available in PDF, EPUB and Kindle. Book excerpt: A selection of annotated references to unclassified reports and journal articles that were introduced into the NASA scientific and technical information system and announced in Scientific and technical aerospace reports (STAR) and International aerospace abstracts (IAA)
Download or read book Helicopter Rotor Smoothing with a Continuous Trailing Edge Flap written by Lan Ding and published by . This book was released on 2020 with total page 172 pages. Available in PDF, EPUB and Kindle. Book excerpt: Helicopters are prone to high vibration with its elastic blades whirling in a turbulent aerodynamic environment. The high vibration leads to discomfort of crew and passengers and shortens service life of on-board avionics, structures, and mechanical parts. The primary source of helicopter vibration is the main rotor. Since rotor hub loads are the summation of loads on each blade, the vibratory loads, for a rotor with identical blades, consist of harmonics of integer multiples of the rotational speed. A conventional vibration reduction process (only handles blade-number related harmonics) can be implemented. For a rotor with dissimilar blades, either in terms of inertia or aerodynamics, the vibratory rotor hub loads consist of a full spectrum of harmonics related to the rotor speed. In order to reduce the vibration in such a large range of frequency content, a novel approach named rotor smoothing is needed. This dissertation investigates a helicopter rotor smoothing process with a continuous trailing-edge flap (CTEF). The CTEF is a monolithic active blade control design with no mechanical linkages compared to the conventional discrete trailing-edge flap (DTEF). In this design, micro fiber composite (MFC) layers are embedded inside the airfoil to deform the trailing-edge when voltages are applied to the MFC. The CTEF airfoil sectional analysis and design optimization are iipresented in the first part of this dissertation. Several steps are conducted to perform this sectional analysis. First, a computational fluid dynamics (CFD) analysis is developed using OpenFOAM to study the aerodynamics of the CTEF airfoil. Next, a reduced-order structural analysis is used to predict the deflection of the actuated CTEF airfoil. Then, an aero-structural coupling procedure is developed to calculate the CTEF airfoil deflection under both actuation and aerodynamic loads. Finally, the coupling procedure is validated using the static structural bench test and wind tunnel test data from previous studies. The CTEF airfoil displacements are calculated for three different actuation voltages - 0 and ℗ł750 V at different far-field velocities. Predicted deformation as well as aerodynamic coefficients of the baseline and actuated CTEF airfoil are calculated and compared well with the test data. To obtain the optimal CTEF airfoil layouts to maximize its actuation output, a gradient-based optimization procedure is developed. The MFC ply parameters are set as the optimization process variables with aerodynamic coefficients as the object function. The MFC parameters include bender lengths, ply numbers, and core area materials, which are filled in between upper and lower MFC stacks. The optimization with and without aerodynamic loads is conducted and analyzed. Core area shapes designed with second-order and third-order polynomial curvatures are studied. Once the optimal sectional design is obtained, the variational-asymptotical beam sectional analysis (VABS) is used to calculate the beam sectional properties for applying the CTEF airfoil to helicopter blades. To study a helicopter rotor with the CTEF airfoil on the blade, an aeromechanics (elasticity) analysis is developed in the second part of this dissertation. A 4-bladed baseline helicopter rotor model is developed using a multibody dynamics code Dymore. To validate the Dymore rotor models, flight test data are compared with the Dymore predictions. A CTEF airfoil embedded rotor model is then developed using Dymore. A numerical wind tunnel trim is conducted by prescribing a total lift and zero blade flapping. The variation of vibratory rotor loads with different CTEF inputs are presented, and the control authority of the CTEF airfoil is tested. The application of the CTEF airfoil to the rotor smoothing process is promising. To reduce vibration and smooth rotor in operation, a helicopter rotor smoothing process using the CTEF is developed at the last step. Two dissimilar rotor models with unbalanced inertial force and unbalanced aerodynamics are developed. A dissimilar rotor harmonics analysis is conducted and unbalance harmonics introduced by the dissimilarity are identified. A closed-loop regulator is applied to target the identified unbalance harmonics and conventional vibratory harmonics on both dissimilar rotor models. The smoothing processes are shown to be successful for the complete speed range, and the harmonics are compared before and after the smoothing process. The maximum harmonics reduction of the vertical hub force is 60%. To manage more hub loads harmonics with less flap motion inputs, a higher-harmonic-control (HHC) controller is developed and applied to the rotor smoothing. A rotor with identical blades open-loop flap motion sweep is conducted to validate the HHC controller. A rotor smoothing, targeting the full spectrum harmonics on the unbalanced inertia model, is conducted. The reduction rate reaches 40%.
Download or read book A Collection of Technical Papers written by and published by . This book was released on 1992 with total page 878 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Shock and Vibration Digest written by and published by . This book was released on 1994 with total page 640 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Recent Advances in Multidisciplinary Optimization of Rotorcraft written by and published by . This book was released on 1992 with total page 18 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book International Aerospace Abstracts written by and published by . This book was released on 1997 with total page 702 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Integrated Aerodynamic Dynamic Optimization of Helicopter Rotor Blades written by National Aeronautics and Space Adm Nasa and published by Independently Published. This book was released on 2018-12-29 with total page 32 pages. Available in PDF, EPUB and Kindle. Book excerpt: An integrated aerodynamic/dynamic optimization procedure is used to minimize blade weight and 4 per rev vertical hub shear for a rotor blade in forward flight. The coupling of aerodynamics and dynamics is accomplished through the inclusion of airloads which vary with the design variables during the optimization process. Both single and multiple objective functions are used in the optimization formulation. The Global Criteria Approach is used to formulate the multiple objective optimization and results are compared with those obtained by using single objective function formulations. Constraints are imposed on natural frequencies, autorotational inertia, and centrifugal stress. The program CAMRAD is used for the blade aerodynamic and dynamic analyses, and the program CONMIN is used for the optimization. Since the spanwise and the azimuthal variations of loading are responsible for most rotor vibration and noise, the vertical airload distributions on the blade, before and after optimization, are compared. The total power required by the rotor to produce the same amount of thrust for a given area is also calculated before and after optimization. Results indicate that integrated optimization can significantly reduce the blade weight, the hub shear and the amplitude of the vertical airload distributions on the blade and the total power required by the rotor. Chattopadhyay, Aditi and Walsh, Joanne L. and Riley, Michael F. Langley Research Center NASA-TM-101553, NAS 1.15:101553, AIAA PAPER 89-1269 RTOP 505-61-51-10...
Download or read book Integrated Multidisciplinary Design Optimization of Rotorcraft written by Howard M. Adelman and published by . This book was released on 1989 with total page 16 pages. Available in PDF, EPUB and Kindle. Book excerpt:
