Download or read book Vital Role of Shock cell and Mach disk in Noise Production of Jet Engines written by Gibin Raju and published by GRIN Verlag. This book was released on 2018-07-30 with total page 95 pages. Available in PDF, EPUB and Kindle. Book excerpt: Master's Thesis from the year 2018 in the subject Engineering - Aerospace Technology, grade: 3.64, University of Cincinnati, language: English, abstract: The aim of this thesis is to discuss the vital role of shock-cell and Mach disk in noise production of jet engines. This study focuses on calculation of shock-cell spacing and Mach disk from various configuration of C-D Nozzles using Shadowgraph technique and detailing on how it varies with the test conditions. In the past three decades, the air traffic has nearly increased by about 40% and have always called for alternative propulsion techniques to replace or support the current traditional propulsion methodology in order to travel longer distances in shorter frame of time. In the light of current demand, the thesis draws motivation from increase in noise levels due to technological advancements of meeting higher specific thrust thus, achieving higher efficiency. The thesis emphasizes on the study of shock-cell noise by developing a complete view of the shock-cell structure and associated parameters with an imperfectly expanded supersonic jet on CD Nozzles over range of under-expanded, design and over-expanded operating conditions. In the entire thesis study, the heated jets from the different C-D Nozzle are analyzed for proper visualization for the shock-cell structure. Shadowgraph is used in current study as it offers very high flexibility and acts as an excellent technique for visualizing the shock diamond exhaust structure and turbulent eddies. A systematic analysis has been performed to quantify the shadowgraph data through semantic video analysis and measured the shock-cell spacing over different temperature ratios (TR) and nozzle pressure ratios (NPR). Circular, rectangular and method of characteristics (MOC) convergent-divergent nozzles of 1.5 design Mach number with and without plates were tested to interpret the results. The data recorded during the experiment was processed to obtain an averaged image. Further, the averaged images were utilized to compute the shock-cell spacing of each nozzle. The computed shock-cell spacing is compared over the theoretical shock-cell length using empirical formula to validate the results. A good match has been established between theoretical and experimental results for the tested nozzles expect for over-expanded operating conditions.

Download or read book The Generation and Radiation of Supersonic Jet Noise Append 2 Shock associated noise data written by and published by . This book was released on 1972 with total page 176 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book The Near Noise Field of Static Jets and Some Model Studies of Devices for Noise Reduction written by Leslie W. Lassiter and published by . This book was released on 1954 with total page 46 pages. Available in PDF, EPUB and Kindle. Book excerpt: Choked operation of model jets with unheated air indicates the appearence of a discrete-frequency component of very large magnitude. Shadowgraph records of the flow show that this condtion is associated with the appearance of flow formations suggestive of partly formed toroidal vortices in the vicinity of the shocks. Elimination of these formations is found to eliminate the discrete component and thereby to reduce the overall noise level.

Download or read book Effect of Forward Velocity on Sound pressure Level in the Near Noise Field of a Moving Jet written by John C. Fakan and published by . This book was released on 1959 with total page 20 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book The Generation and Radiation of Supersonic Jet Noise Future studies for definition of supersonic jet noise generation and reduction mechanisms written by and published by . This book was released on 1972 with total page 52 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 Aerospace and Associated Technology written by Anup Ghosh and published by Taylor & Francis. This book was released on 2022-09-24 with total page 607 pages. Available in PDF, EPUB and Kindle. Book excerpt: The International Conference on Theoretical Applied Computational and Experimental Mechanics is organized every three years by the Department of Aerospace Engineering IIT Kharagpur. The conference is devoted to providing a platform for scientists and engineers to exchange their views on the latest developments in Mechanics since 1998. ICTACEM Conference is aimed at bringing together academics and researchers working in various disciplines of mechanics to exchange views as well as to share knowledge between people from different parts of the globe. The 8th ICTACEM was held from December 20-22, 2021, at the Indian Institute of Technology, Kharagpur.

Download or read book Fundamental Study of Jet Noise Generation and Suppression written by W. C. Sperry and published by . This book was released on 1961 with total page 150 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Some Open Questions on the Jet Noise Problem written by J. E. Ffowcs Williams and published by . This book was released on 1968 with total page 24 pages. Available in PDF, EPUB and Kindle. Book excerpt: The paper starts with a description of the possible sources of sound that can be met in low Mach number jet flows, and their strength is given in terms of the flow parameters. The arguments are of order of magnitude only and the precise value of the coefficients accompanying these formulae are some of the details which wait to be resolved. The initial section deals with the issue of jet noise at very low speed where nozzle exit turbulence may be a major contributor. Lighthill's theory is then briefly summarized and used to estimate the sound of jets at moderate speeds. The object of this step is to show that very reasonable estimates of the field can be achieved from a very crude description of the turbulent flow without recourse to any of the more involved aspects of the quadrupole theory. Then the question of noise produced by combustion of excess fuel in the exhaust is examined according to Lighthill's theory. It is argued that this is unlikely to be a significant source of noise unless very large proportions of the fuel are burned in the exhaust. The theory is then applied to high Mach number situations where it is argued that the role of both Mach waves and shock waves needs further study. Finally, estimates of the sources to be expected in a moderate speed jet issuring from a multitube suppressor are made and a question is raised regarding the possible significance to the noise from the fully developed jet flow. (Author).

Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1991 with total page 1102 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Shock associated noise reduction from inverted velocity profile coannular jets written by H. K. Tanna and published by . This book was released on 1981 with total page 194 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Shock Associated Noise Reduction from Inverted velocity profile Coannular Jets written by H. K. Tanna and published by . This book was released on 1981 with total page 160 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Jet Engine Test Cell Noise Reduction written by C. A. Kodres and published by . This book was released on 2000-08-01 with total page 77 pages. Available in PDF, EPUB and Kindle. Book excerpt: Passive methods for decreasing jet engine test cell noise emissions are evaluated and compared. Such methods have the dual advantages of low cost and simplicity. In addition, the effect on the aerothermal performance of the test cell is minimal. Sound pressure levels were measured in and around test facilities equipped with various devices to further reduce noise. The data were supplemented with parametric studies of noise reduction techniques conducted using a 1/20th scale physical model of the Navy's standard T-10 jet engine test cell. Methods that attack the noise problem from outside and methods that attack the problem from inside the test cell are assessed, including trees and other vegetation, acoustic walls, core busters, and modifications to the exhaust stack. Mounting screens in the path of the jet and increasing the height of the exhaust stack are found to be the most effective.

Download or read book Predictions of Supersonic Jet Mixing and Shock Associated Noise Compared with Measured Far Field Data written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-05-22 with total page 78 pages. Available in PDF, EPUB and Kindle. Book excerpt: Codes for predicting supersonic jet mixing and broadband shock-associated noise were assessed using a database containing noise measurements of a jet issuing from a convergent nozzle. Two types of codes were used to make predictions. Fast running codes containing empirical models were used to compute both the mixing noise component and the shock-associated noise component of the jet noise spectrum. One Reynolds-averaged, Navier-Stokes-based code was used to compute only the shock-associated noise. To enable the comparisons of the predicted component spectra with data, the measured total jet noise spectra were separated into mixing noise and shock-associated noise components. Comparisons were made for 1/3-octave spectra and some power spectral densities using data from jets operating at 24 conditions covering essentially 6 fully expanded Mach numbers with 4 total temperature ratios. Dahl, Milo D. Glenn Research Center JET MIXING FLOW; JET AIRCRAFT NOISE; SUPERSONIC JET FLOW; AERODYNAMIC NOISE; NOISE MEASUREMENT; NOISE SPECTRA; FLUID JETS; MACH NUMBER; PREDICTIONS; SHOCK WAVES; TEMPERATURE RATIO

Download or read book Noise Generation by Shock turbulence Interaction written by Massachusetts Institute of Technology. Gas Turbine Laboratory and published by . This book was released on 1970 with total page 18 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book STAR written by and published by . This book was released on 1966 with total page 1230 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Experimental Investigation of the Noise Reduction of Supersonic Exhaust Jets with Fluidic Inserts written by Russell Powers and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The noise produced by the supersonic, high temperature jets that exhaust from military aircraft is becoming a hazard to naval personnel and a disturbance to communities near military bases. Methods to reduce the noise produced from these jets in a practical full-scale environment are difficult. The development and analysis of distributed nozzle blowing for the reduction of radiated noise from supersonic jets is described. Model scale experiments of jets that simulate the exhaust jets from typical low-bypass ratio military jet aircraft engines during takeoff are performed. Fluidic inserts are created that use distributed blowing in the divergent section of the nozzle to simulate mechanical, hardwall corrugations, while having the advantage of being an active control method. This research focuses on model scale experiments to better understand the fluidic insert noise reduction method. Distributed blowing within the divergent section of the military-style convergent divergent nozzle alters the shock structure of the jet in addition to creating streamwise vorticity for the reduction of mixing noise. Enhancements to the fluidic insert design have been performed along with experiments over a large number of injection parameters and core jet conditions. Primarily military-style round nozzles have been used, with preliminary measurements of hardwall corrugations and fluidic inserts in rectangular nozzle geometries also performed. It has been shown that the noise reduction of the fluidic inserts is most heavily dependent upon the momentum flux ratio between the injector and core jet. Maximum reductions of approximately 5.5 dB OASPL have been observed with practical mass flow rates and injection pressures. The first measurements with fluidic inserts in the presence of a forward flight stream have been performed. Optimal noise reduction occurs at similar injector parameters in the presence of forward flight. Fluidic inserts in the presence of a forward flight stream were observed to reduce the peak mixing noise below the already reduced levels by nearly 4 dB OASPL and the broadband shock-associated noise by nearly 3 dB OASPL. Unsteady velocity measurements are used to complement acoustic results of jets with fluidic inserts. Measured axial turbulence intensities and mean axial velocity are examined to illuminate the differences in the flow field from jets with fluidic inserts. Comparisons of laser Doppler measurements with RANS CFD simulations are shown with good agreement. Analysis of the effect of spatial turbulence on the measured quantities is performed. Experimental model scale measurements of jets with and without fluidic inserts over a simulated carrier deck are presented. The model carrier environment consists of a ground plane of adjustable distance below the jet, and a simulated jet blast deflector similar to those found in practice. Measurements are performed with far-field microphones, near-field microphones, and unsteady pressure sensors. The constructive and destructive interference that results from the interaction of the direct and reflected sound waves is observed and compared with results from free jets. The noise reduction of fluidic inserts in a realistic carrier deck environment with steering of the ``quiet planes'' is examined. The overall sound pressure level in heat-simulated jets is reduced by 3-5 dB depending on the specific angle and ground plane height. Jets impinging upon a modeled jet blast deflector are tested in addition to jets solely in the presence of the carrier deck. Observed modifications to the acoustic field from the presence of the jet blast deflector include downstream acoustic shielding and low frequency augmentation. The region of maximum noise radiation for heat-simulated jets from nozzles with fluidic inserts impinging on the jet blast deflector is reduced in overall sound pressure level by 4-7 dB. This region includes areas where aircraft carrier personnel are located.