Download or read book Database of Inlet and Exhaust Noise Shielding for Wedge shaped Airframe written by Carl H. Gerhold and published by . This book was released on 2001 with total page 22 pages. Available in PDF, EPUB and Kindle. Book excerpt: An experiment to measure the noise shielding of the blended wing body design concept was developed using a simplified wedge-shaped airframe. The experimental study was conducted in the Langley Anechoic Noise Research facility. A wideband, omnidirective sound source in a simulated engine nacelle was held at locations representative of a range of engine locations above the wing. The sound field around the model was measured, with the airframe and source in place and with source alone, using an array of microphones on a rotating hoop that is also translated along an axis parallel to the airframe axis. The insertion loss was determined from the difference between the two resulting contours. Although no attempt was made to simulate the noise characteristics of a particular engine, the broadband noise source radiated sound over a range of scaled frequencies encompassing 1 and 2 times the blade passage frequency representative of a large, high-bypass-ratio turbofan engine.

Download or read book Database of Inlet and Exhaust Noise Shielding for Wedge Shaped Airframe written by National Aeronautics and Space Adm Nasa and published by Independently Published. This book was released on 2018-09-27 with total page 36 pages. Available in PDF, EPUB and Kindle. Book excerpt: An experiment to measure the noise shielding of the blended wing body design concept was developed using a simplified wedge-shaped airframe. The experimental study was conducted in the Langley Anechoic Noise Research Facility. A wideband, omnidirective sound source in a simulated engine nacelle was held at locations representative of a range of engine locations above the wing. The sound field around the model was measured with the airframe and source in place and with source alone, using an-array of microphones on a rotating hoop that is also translated along an axis parallel to the airframe axis. The insertion loss was determined from the difference between the two resulting contours. Although no attempt was made to simulate the noise characteristics of a particular engine, the broadband noise source radiated sound over a range of scaled frequencies encompassing 1 and 2 times the blade passage frequency representative of a large, high-bypass-ratio turbofan engine. The measured data show that significant shielding of the inlet-radiated noise is obtained in the area beneath and upstream of the model. The data show the sensitivity of insertion loss to engine location. Gerhold, Carl H. and Clark, Lorenzo R. Langley Research Center NASA/TM-2001-210840, L-18053, NAS 1.15:210840

Download or read book DATABASE OF INLET AND EXHAUST NOISE SHIELDING FOR WEDGE SHAPED AIRFRAME NASA TM 2001 210840 JUN 20 2001 written by and published by . This book was released on 2002 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Jet Noise Shielding from Airframe Surfaces written by Salvador Mayoral and published by . This book was released on 2010 with total page 137 pages. Available in PDF, EPUB and Kindle. Book excerpt: This work investigates the potential suppression of jet noise by airframe surface shielding with application to the Hybrid Wing Body aircraft (HWB). Subscale experiments utilized a bypass-ratio-10 (BPR10) turbofan nozzle that operated at realistic cycle conditions using helium-air mixture jets. The shielding surface was a flat plate shaped in the form of a generic HWB and featured vertical fins and an adjustable elevator. Chevrons and porous wedge fan flow deflectors were incorporated into the baseline nozzle to restructure and alter the jet noise source distribution. Acoustic measurements of the unshielded and shielded jets were conducted inside an anechoic chamber using a 24-microphone apparatus composed of two polar arrays, each consisting of twelve condenser microphones. One polar array was mounted at an azimuth angle [straight phi] = 0° (downward) while the second array was mounted at [straight phi] = 60° (sideline). Noise source distribution measurements were performed by densely grouping twenty-four microphones on a linear array in the downward direction. Surveys of the jet mean flow were conducted with a fully automated three-dimensional Pitot rake traverse. The Pitot rake consists of five high-resolution Pitot probes that measure the local jet total pressure. The potential for noise suppression was quantified in terms of the estimated Effective Perceived Noise Level (EPNL), a noise metric used in aircraft certification. Acoustic results of the baseline BPR10 nozzle with the HWB shield yielded only marginal EPNL reductions, even when the engine was translated two fan diameters upstream of its nominal location. Using the estimated cumulative (downward plus sideline) EPNL reduction as a figure of merit, shielding of the baseline nozzle with the nominal shield configuration yielded a 2.5 dB reduction. Acoustic imaging of the baseline jet noise source revealed that the large fan diameter, inherent to the high bypass ratio, created a long noise source region. The integration of nozzle devices significantly improved EPNL reduction with the engine positioned at its nominal location. Application of the aggressive chevrons increased the reduction to 6.5 dB, while the best wedge configuration improved this value to 6.9 dB. Combination of wedge and aggressive chevrons yielded a benefit of 7.6 dB. Examination of high-definition noise source maps showed a direct link between insertion loss and axial location of the peak noise. Ultimately, the enhanced shielding effect from the nozzle devices resulted from translation of peak intensities upstream closer to the nozzle plug. Thus the compaction and/or redistribution of the noise source via nozzle devices are essential for effective jet noise shielding on the HWB. A proposed correlator for the noise reduction due to shielding is the average illumination angle. The average illumination angle is defined as the average angular sector between noise source and observer not intercepted by the shield. For average illumination angles less than 45 deg, the EPNL reduction exceeds 3 dB. A correlation between the acoustic and mean flow results reveal that the mean velocity field by itself cannot provide useful information for inferring the noise source location.

Download or read book NASA Langley Scientific and Technical Information Output 2001 written by and published by . This book was released on 2002 with total page 166 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book AIAA Journal written by American Institute of Aeronautics and Astronautics and published by . This book was released on 2007 with total page 990 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Aeroacoustics of Flight Vehicles written by Harvey H. Hubbard and published by . This book was released on 1991 with total page 620 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book NASA Tech Briefs written by and published by . This book was released on 1990 with total page 526 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Active Radar Cross Section Reduction written by Hema Singh and published by Cambridge University Press. This book was released on 2015-03-02 with total page 354 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book discusses the active and passive radar cross section (RCS) estimation and techniques to examine the low observable aerospace platforms. It begins with the fundamentals of RCS, followed by the dielectric, magnetic and metamaterials parameters of the constituent materials and then explains various methods and the emerging trends followed in this area of study. The RCS estimation of phased array including the mutual coupling effect is also presented in detail in the book. The active RCS reduction is carefully touched upon through the performance of phased arrays, sidelobe cancellers and mitigation of multipath effect. Providing information on various adaptive algorithms like least mean square (LMS), recursive least square (RLS) and weighted least square algorithms, the authors also mention the recent developments in the area of embedded antennas, conformal load bearing antenna, metamaterials and frequency selective surface (FSS) based RCS reduction.

Download or read book Environmental Quality Research and Development a Review and Analysis of Federal Programs written by Federal Council for Science and Technology (U.S.). Ad Hoc Committee on Environmental Quality Research and Development and published by . This book was released on 1972 with total page 152 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Airport Airline Management written by and published by . This book was released on 1960 with total page 410 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Airports and Airport Engineering written by and published by . This book was released on 1960 with total page 498 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Evaluation of a Hydrogen Fuel Cell Powered Blended Wing Body Aircraft Concept for Reduced Noise and Emissions written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-08-20 with total page 46 pages. Available in PDF, EPUB and Kindle. Book excerpt: This report describes the analytical modeling and evaluation of an unconventional commercial transport aircraft concept designed to address aircraft noise and emission issues. A blended-wing-body configuration with advanced technology hydrogen fuel cell electric propulsion is considered. Predicted noise and emission characteristics are compared to a current technology conventional configuration designed for the same mission. The significant technology issues which have to be addressed to make this concept a viable alternative to current aircraft designs are discussed. This concept is one of the "Quiet Green Transport" aircraft concepts studied as part of NASA's Revolutionary Aerospace Systems Concepts (RASC) Program. The RASC Program was initiated to develop revolutionary concepts that address strategic objectives of the NASA Enterprises, such as reducing aircraft noise and emissions, and to identify advanced technology requirements for the concepts.Guynn, Mark D. and Freh, Joshua E. and Olson, Erik D.Glenn Research Center; Langley Research CenterMATHEMATICAL MODELS; EVALUATION; AIRCRAFT DESIGN; AIRCRAFT NOISE; NOISE REDUCTION; AEROSPACE SYSTEMS; BLENDED-WING-BODY CONFIGURATIONS; COMMERCIAL AIRCRAFT; ELECTRIC PROPULSION; FUEL CELLS; NOISE MEASUREMENT

Download or read book Research and Technology 1993 written by and published by . This book was released on 1993 with total page 180 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Airframe and Powerplant Mechanics Airframe Handbook written by United States. Flight Standards Service and published by . This book was released on 1976 with total page 620 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book The Control of Noise written by National Physical Laboratory (Great Britain) and published by . This book was released on 1962 with total page 448 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book From Archangel to Senior Crown written by Peter W. Merlin and published by AIAA (American Institute of Aeronautics & Astronautics). This book was released on 2008 with total page 240 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Lockheed Blackbirds hold a unique place in the development of aeronautics. In their day, the A-12, YF-12, M-21, D-21, and SR-71 variants outperformed all other jet airplanes in terms of altitude and speed. Now retired, they remain the only production aircraft capable of sustained Mach 3 cruise and operational altitudes above 80,000 feet.This is the first book to address the technical aspects of these incredible aircraft. The author describes the design evolution of the Blackbird, from the Archangel to the Senior Crown (the Air Force's SR-71.) He describes in detail the construction and materials challenges faced by Lockheed, as well as the Blackbird's performance characteristics and capabilities.A NASA historian, the author describes NASA's role in using the aircraft as a flying laboratory to collect data on materials, structures, loads, heating, aerodynamics, and performance for high-speed aircraft. The reader will benefit from the technical and programmatic lessons learned.This volume was produced in cooperation with the National Aeronautics and Space Administration.