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Author: Publisher: ISBN: Category : Languages : en Pages : 126
Book Description
Three separate sections are included. The first is a brief review of the work done on active control of rotating stall under this contract. The second is a paper on the existence of precursor travelling waves in compressor annuli and on some of the signal processing techniques used to examine such waves. The third section is a paper describing first-of-a-kind (as far as we are aware) experiments in which tailored system structural properties have been used to suppress compression system aerodynamic instability (surge). (jhd).
Author: Publisher: ISBN: Category : Languages : en Pages : 126
Book Description
Three separate sections are included. The first is a brief review of the work done on active control of rotating stall under this contract. The second is a paper on the existence of precursor travelling waves in compressor annuli and on some of the signal processing techniques used to examine such waves. The third section is a paper describing first-of-a-kind (as far as we are aware) experiments in which tailored system structural properties have been used to suppress compression system aerodynamic instability (surge). (jhd).
Author: Louis Jezequel Publisher: CRC Press ISBN: 1000443744 Category : Technology & Engineering Languages : en Pages : 372
Book Description
The introduction of active control in structural dynamics has led to a number of developments over wide-ranging industrial domains. This work investigates this area and examines a number of topics including: smart materials and structures; new strategies of active control and its applications.
Author: Sandeep Agarwal Publisher: ISBN: Category : Actuators Languages : en Pages :
Book Description
Lead-lag dampers are present in most rotors to provide the required level of damping in all flight conditions. These dampers are a critical component of the rotor system, but they also represent a major source of maintenance cost. In present rotor systems, both hydraulic and elastomeric lead-lag dampers have been used. Hydraulic dampers are complex mechanical components that require hydraulic fluids and have high associated maintenance costs. Elastomeric dampers are conceptually simpler and provide a "dry" rotor, but are rather costly. Furthermore, their damping characteristics can degrade with time without showing external signs of failure. Hence, the dampers must be replaced on a regular basis. A semi-active friction based lead-lag damper is proposed as a replacement for hydraulic and elastomeric dampers. Damping is provided by optimized energy dissipation due to frictional forces in semi-active joints. An actuator in the joint modulates the normal force that controls energy dissipation at the frictional interfaces, resulting in large hysteretic loops. Various selective damping strategies are developed and tested for a simple system containing two different frequency modes in its response, one of which needs to be damped out. The system reflects the situation encountered in rotor response where 1P excitation is present along with the potentially unstable regressive lag motion. Simulation of the system response is obtained to compare their effectiveness. Next, a control law governing the actuation in the lag damper is designed to generate the desired level of damping for performing adaptive selective damping of individual blade lag motion. Further, conceptual design of a piezoelectric friction based lag damper for a full-scale rotor is presented and various factors affecting size, design and maintenance cost, damping capacity, and power requirements of the damper are discussed. The selective semi-active damping strategy is then studied in the context of classical ground resonance problem. In view of the inherent nonlinearity in the system due to friction phenomena, multiblade transformation from rotating frame to nonrotating frame is not useful. Stability analysis of the system is performed in the rotating frame to gain an understanding of the dynamic characteristics of rotor system with attached semi-active friction based lag dampers. This investigation is extended to the ground resonance stability analysis of a comprehensive UH-60 model within the framework of finite element based multibody dynamics formulations. Simulations are conducted to study the performance of several integrated lag dampers ranging from passive to semi-active ones with varying levels of selectivity. Stability analysis is performed for a nominal range of rotor speeds using Prony's method.
Author: Publisher: ISBN: Category : Research Languages : en Pages : 1794
Book Description
Sections 1-2. Keyword Index.--Section 3. Personal author index.--Section 4. Corporate author index.-- Section 5. Contract/grant number index, NTIS order/report number index 1-E.--Section 6. NTIS order/report number index F-Z.
Author: North Atlantic Treaty Organization. Advisory Group for Aerospace Research and Development. Flight Vehicle Integration Panel. Symposium Publisher: ISBN: Category : Helicopters Languages : en Pages : 402
Author: Publisher: ISBN: Category : Aeronautics Languages : en Pages : 932
Book Description
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).
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Author: Louis Jezequel
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Author: Sandeep Agarwal
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Author: North Atlantic Treaty Organization. Advisory Group for Aerospace Research and Development. Flight Vehicle Integration Panel. Symposium
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