Download or read book Active Control Of Fan Noise Feasibility Study Final Report NASA CR 198514 Mar 24 1997 written by and published by . This book was released on 1998 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Active Control Of Fan Noise Feasibility Study Final Report NASA CR 198512 Mar 24 1997 written by and published by . This book was released on 1998 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Active Control Of Fan Noise Feasibility Study Final Report NASA CR 198511 VOL 3 Mar 31 1997 written by and published by . This book was released on 1998 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Active Control of Fan Noise Feasibiity Study Final Report Nasa cr 198513 Mar 24 1997 written by and published by . This book was released on 1998 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Active Control of Fan Noise written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-07-02 with total page 54 pages. Available in PDF, EPUB and Kindle. Book excerpt: This report describes the Active Noise Cancellation (ANC) System designed by General Electric and tested in the NASA Lewis Research Center's (LERC) 48 inch Active Noise Control Fan (ANCF). The goal of this study is to assess the feasibility of using wall mounted secondary acoustic sources and sensors within the duct of a high bypass turbofan aircraft engine for global active noise cancellation of fan tones. The GE ANC system is based on a modal control approach. A known acoustic mode propagating in the fan duct is canceled using an array of flush-mounted compact sound sources. The canceling modal signal is generated by a modal controller. Inputs to the controller are signals from a shaft encoder and from a microphone array which senses the residual acoustic mode in the duct. The key results are that the (6,0) was completely eliminated at the 920 Hz design frequency and substantially reduced elsewhere. The total tone power was reduced 6.8 dB (out of a possible 9.8 dB). Farfield reductions of 15 dB (SPL) were obtained. The (4,0) and (4,1) modes were reduced simultaneously yielding a 15 dB PWL decrease. The results indicate that global attenuation of PWL at the target frequency was obtained in the aft quadrant using an ANC actuator and sensor system totally contained within the duct. The quality of the results depended on precise mode generation. High spillover into spurious modes generated by the ANC actuator array caused less than optimum levels of PWL reduction. The variation in spillover is believed to be due to calibration procedure, but must be confirmed in subsequent tests. Pla, Frederic G. and Hu, Ziqiang and Sutliff, Daniel L. Glenn Research Center...
Download or read book Active Control of Fan Noise Feasibility Study written by and published by . This book was released on 1996 with total page 56 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Active Control of Fan Noise written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-06-28 with total page 48 pages. Available in PDF, EPUB and Kindle. Book excerpt: An extension of a prior study has been completed to examine the potential reduction of aircraft flyover noise by the method of active noise control (ANC). It is assumed that the ANC system will be designed such that it cancels discrete tones radiating from the engine fan inlet or fan exhaust duct, at least to the extent that they no longer protrude above the surrounding broadband noise levels. Thus, without considering the engineering details of the ANC system design, tone levels am arbitrarily removed from the engine component noise spectrum and the flyover noise EPNL levels are compared with and without the presence of tones. The study was conducted for a range of engine cycles, corresponding to fan pressure ratios of 1.3, 1.45, 1.6, and 1.75. This report is an extension of an effort reported previously. The major conclusions drawn from the prior study, which was restricted to fan pressure ratios of 1.45 and 1.75, are that, for a fan pressure ratio of 1.75, ANC of tones gives about the same suppression as acoustic treatment without ANC. For a fan pressure ratio of 1.45, ANC appears to offer less effectiveness from passive treatment. In the present study, the other two fan pressure ratios are included in a more detailed examination of the benefits of the ANC suppression levels. The key results of this extended study are the following observations: (1) The maximum overall benefit obtained from suppression of BPF alone was 2.5 EPNdB at high fan speeds. The suppression benefit increases with increase in fan pressure ratio (FPR), (2) The maximum overall benefit obtained from suppression of the first three harmonics was 3 EPNdB at high speeds. Suppression benefit increases with increase in FPR, (3) At low FPR, only about 1.0 EPNdB maximum reduction was obtained. Suppression is primarily from reduction of BPF at high FPR values and from the combination of tones at low FPR, (4) The benefit from ANC is about the same as the benefit from passive treatment at fan pressure ra...
Download or read book Active Control of Fan Noise written by National Aeronautics and Space Adm Nasa and published by . This book was released on 2018-11 with total page 50 pages. Available in PDF, EPUB and Kindle. Book excerpt: The objective of this effort is to develop an analytical model for the coupling of active noise control (ANC) piston-type actuators that are mounted flush to the inner and outer walls of an annular duct to the modes in the duct generated by the actuator motion. The analysis will be used to couple the ANC actuators to the modal analysis propagation computer program for the annular duct, to predict the effects of active suppression of fan-generated engine noise sources. This combined program will then be available to assist in the design or evaluation of ANC systems in fan engine annular exhaust ducts. An analysis has been developed to predict the modes generated in an annular duct due to the coupling of flush-mounted ring actuators on the inner and outer walls of the duct. The analysis has been combined with a previous analysis for the coupling of modes to a cylindrical duct in a FORTRAN computer program to perform the computations. The method includes the effects of uniform mean flow in the duct. The program can be used for design or evaluation purposes for active noise control hardware for turbofan engines. Predictions for some sample cases modeled after the geometry of the NASA Lewis ANC Fan indicate very efficient coupling in both the inlet and exhaust ducts for the m = 6 spinning mode at frequencies where only a single radial mode is cut-on. Radial mode content in higher order cut-off modes at the source plane and the required actuator displacement amplitude to achieve 110 dB SPL levels in the desired mode were predicted. Equivalent cases with and without flow were examined for the cylindrical and annular geometry, and little difference was found for a duct flow Mach number of 0.1. The actuator ring coupling program will be adapted as a subroutine to the cylindrical duct modal analysis and the exhaust duct modal analysis. This will allow the fan source to be defined in terms of characteristic modes at the fan source plane and predict the propagation to the arbit...
Download or read book Active Control of Fan Noise written by National Aeronautics and Space Adm Nasa and published by . This book was released on 2018-10-22 with total page 38 pages. Available in PDF, EPUB and Kindle. Book excerpt: A computational method to predict modal reflection coefficients in cylindrical ducts has been developed based on the work of Homicz, Lordi, and Rehm, which uses the Wiener-Hopf method to account for the boundary conditions at the termination of a thin cylindrical pipe. The purpose of this study is to develop a computational routine to predict the reflection coefficients of higher order acoustic modes impinging on the unflanged termination of a cylindrical duct. This effort was conducted wider Task Order 5 of the NASA Lewis LET Program, Active Noise Control of aircraft Engines: Feasibility Study, and will be used as part of the development of an integrated source noise, acoustic propagation, ANC actuator coupling, and control system algorithm simulation. The reflection coefficient prediction will be incorporated into an existing cylindrical duct modal analysis to account for the reflection of modes from the duct termination. This will provide a more accurate, rapid computation design tool for evaluating the effect of reflected waves on active noise control systems mounted in the duct, as well as providing a tool for the design of acoustic treatment in inlet ducts. As an active noise control system design tool, the method can be used preliminary to more accurate but more numerically intensive acoustic propagation models such as finite element methods. The resulting computer program has been shown to give reasonable results, some examples of which are presented. Reliable data to use for comparison is scarce, so complete checkout is difficult, and further checkout is needed over a wider range of system parameters. In future efforts the method will be adapted as a subroutine to the GEAE segmented cylindrical duct modal analysis program. Kraft, R. E. Unspecified Center NAS3-26617; RTOP 538-03-11...
Download or read book Active Control of Fan Noise written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-06-30 with total page 48 pages. Available in PDF, EPUB and Kindle. Book excerpt: The objective of this effort is to develop an analytical model for the coupling of active noise control (ANC) piston-type actuators that are mounted flush to the inner and outer walls of an annular duct to the modes in the duct generated by the actuator motion. The analysis will be used to couple the ANC actuators to the modal analysis propagation computer program for the annular duct, to predict the effects of active suppression of fan-generated engine noise sources. This combined program will then be available to assist in the design or evaluation of ANC systems in fan engine annular exhaust ducts. An analysis has been developed to predict the modes generated in an annular duct due to the coupling of flush-mounted ring actuators on the inner and outer walls of the duct. The analysis has been combined with a previous analysis for the coupling of modes to a cylindrical duct in a FORTRAN computer program to perform the computations. The method includes the effects of uniform mean flow in the duct. The program can be used for design or evaluation purposes for active noise control hardware for turbofan engines. Predictions for some sample cases modeled after the geometry of the NASA Lewis ANC Fan indicate very efficient coupling in both the inlet and exhaust ducts for the m = 6 spinning mode at frequencies where only a single radial mode is cut-on. Radial mode content in higher order cut-off modes at the source plane and the required actuator displacement amplitude to achieve 110 dB SPL levels in the desired mode were predicted. Equivalent cases with and without flow were examined for the cylindrical and annular geometry, and little difference was found for a duct flow Mach number of 0.1. The actuator ring coupling program will be adapted as a subroutine to the cylindrical duct modal analysis and the exhaust duct modal analysis. This will allow the fan source to be defined in terms of characteristic modes at the fan source plane and predict the propagation to the arbit...
Download or read book Active Control of Fan Noise written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-06-30 with total page 36 pages. Available in PDF, EPUB and Kindle. Book excerpt: A computational method to predict modal reflection coefficients in cylindrical ducts has been developed based on the work of Homicz, Lordi, and Rehm, which uses the Wiener-Hopf method to account for the boundary conditions at the termination of a thin cylindrical pipe. The purpose of this study is to develop a computational routine to predict the reflection coefficients of higher order acoustic modes impinging on the unflanged termination of a cylindrical duct. This effort was conducted wider Task Order 5 of the NASA Lewis LET Program, Active Noise Control of aircraft Engines: Feasibility Study, and will be used as part of the development of an integrated source noise, acoustic propagation, ANC actuator coupling, and control system algorithm simulation. The reflection coefficient prediction will be incorporated into an existing cylindrical duct modal analysis to account for the reflection of modes from the duct termination. This will provide a more accurate, rapid computation design tool for evaluating the effect of reflected waves on active noise control systems mounted in the duct, as well as providing a tool for the design of acoustic treatment in inlet ducts. As an active noise control system design tool, the method can be used preliminary to more accurate but more numerically intensive acoustic propagation models such as finite element methods. The resulting computer program has been shown to give reasonable results, some examples of which are presented. Reliable data to use for comparison is scarce, so complete checkout is difficult, and further checkout is needed over a wider range of system parameters. In future efforts the method will be adapted as a subroutine to the GEAE segmented cylindrical duct modal analysis program. Kraft, R. E. Unspecified Center NAS3-26617; RTOP 538-03-11...
Download or read book Active Control of Fan Noise Feasibility Study Volume 2 written by and published by . This book was released on with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Active Control of Fan Noise Feasibility Study Volume 2 Canceling Noise Source Design F G Pla Et Al Ge March 1995 written by and published by . This book was released on with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Nucleus written by F.D. Smit and published by Springer Science & Business Media. This book was released on 1999 with total page 540 pages. Available in PDF, EPUB and Kindle. Book excerpt: Proceedings of the International Conference on The Nucleus: New Physics for the New Millennium, held January 18-22, 1999, at the National Accelerator Centre, Faure, South Africa
Download or read book The History of Medical Informatics in the United States written by Morris F. Collen and published by Springer. This book was released on 2015-10-08 with total page 769 pages. Available in PDF, EPUB and Kindle. Book excerpt: This is a meticulously detailed chronological record of significant events in the history of medical informatics and their impact on direct patient care and clinical research, offering a representative sampling of published contributions to the field. The History of Medical Informatics in the United States has been restructured within this new edition, reflecting the transformation medical informatics has undergone in the years since 1990. The systems that were once exclusively institutionally driven – hospital, multihospital, and outpatient information systems – are today joined by systems that are driven by clinical subspecialties, nursing, pathology, clinical laboratory, pharmacy, imaging, and more. At the core is the person – not the clinician, not the institution – whose health all these systems are designed to serve. A group of world-renowned authors have joined forces with Dr Marion Ball to bring Dr Collen’s incredible work to press. These recognized leaders in medical informatics, many of whom are recipients of the Morris F. Collen Award in Medical Informatics and were friends of or mentored by Dr Collen, carefully reviewed, editing and updating his draft chapters. This has resulted in the most thorough history of the subject imaginable, and also provides readers with a roadmap for the subject well into later in the century.
Download or read book Guide to Industrial Assessments for Pollution Prevention and Energy Efficiency written by and published by DIANE Publishing. This book was released on 2001 with total page 486 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Complications in Maxillofacial Cosmetic Surgery written by Elie M. Ferneini and published by Springer. This book was released on 2017-12-28 with total page 249 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book is designed to offer practitioners clear, up-to-date guidance on the management of complications associated with maxillofacial cosmetic surgery. The first section provides a detailed overview of general topics relating to cosmetic surgery patients, including assessment, anesthesia and medical complications, wound healing, postoperative infection, pain management, and medicolegal issues. The second section then discusses the nature and management of the complications associated with each maxillofacial cosmetic surgery procedure, from laser treatment and use of neuromodulators and soft tissue fillers to orthognathic surgery, rhinoplasty, neck procedures, rhytidectomy, genioplasty, and facial implants. Complications in Maxillofacial Cosmetic Surgery is multi-authored, multi-institutional, and multi-specialty based. It will be of value for a range of health care providers who practice in the head and neck area, including oral and maxillofacial surgeons, otolaryngologists, plastic and reconstructive surgeons, dermatologists, and cosmetic surgeons.
