Jet propulsion

About: Jet propulsion is a research topic. Over the lifetime, 1867 publications have been published within this topic receiving 19668 citations.

Hypersonic Airbreathing Propulsion

Abstract: The next great leap for jet propulsion will be to power-sustained, efficient flight through the atmosphere "Hypersonic Airbreathing Propulsion presents the first comprehensive, unified introduction to all elements of the scramjet engine that will make this feat possible The text emphasizes fundamental principles, guiding concepts, analytical derivations, and numerical examples having clear, useful, insightful results

Elements of Gas Turbine Propulsion

Abstract: This text provides an introduction to gas turbine engines and jet propulsion for aerospace or mechanical engineers The text is divided into four parts: introduction to aircraft propulsion; basic concepts and one-dimensional/gas dynamics; parametric (design point) and performance (off-design) analysis of air breathing propulsion systems; and analysis and design of major gas turbine engine components (fans, compressors, turbines, inlets, nozzles, main burners, and afterburners) Design concepts are introduced early (aircraft performance in introductory chapter) and integrated throughout Written with extensive student input on the design of the book, the book builds upon definitions and gradually develops the thermodynamics, gas dynamics, and gas turbine engine principles

Jet Mixing Noise from Fine-Scale Turbulence

Abstract: It is known that turhulent mixing noise from high-speed jets consists of two components. They are the noise from large turbulent structures in the form of Mach wave radiation and the less directional fine-scale turbulence noise. The Mach wave radiation dominates in the downstream direction. The fine-scale turbulence noise dominates in the sideline and upstream directions. A semiempirical theory is developed for the prediction of the spectrum, intensity, and directivity of the fine-scale turhulence noise. The prediction method is self-contained. The turbulence information is supplied by the k-e turhulence model. The theory contains three empirical constants beyond those of the k-e model. These constants are determined by best fit of the calculated noise spectra to experimental measurements. Extensive comparisons between calculated and measured noise spectra over a wide range of directions of radiation,jet velocities, and temperatures have heen carried out. Excellent agreements are found. It is believed that the present theory offers significant improvements over current empirical or semiempirical jet noise prediction methods in use. There is no first principle jet noise theory at the present time.

Aeroacoustics of hot jets

Abstract: A systematic study has been undertaken to quantify the effect of jet temperature on the noise radiated by subsonic jets. Nozzles of different diameters were tested to uncover the effects of Reynolds number. All the tests were carried out at Boeing's Low Speed Aeroacoustic Facility, with simultaneous measurement of thrust and noise. It is concluded that the change in spectral shape at high jet temperatures, normally attributed to the contribution from dipoles, is due to Reynolds number effects and not dipoles. This effect has not been identified before. A critical value of the Reynolds number that would need to be maintained to avoid the effects associated with low Reynolds number has been estimated to be 400 000. It is well-known that large-scale structures are the dominant generators of noise in the peak radiation direction for high-speed jets. Experimental evidence is presented that shows the spectral shape at angles close to the jet axis from unheated low subsonic jets to be the same as from heated supersonic jets. A possible mechanism for the observed trend is proposed. When a subsonic jet is heated with the Mach number held constant, there is a broadening of the angular sector in which peak radiation occurs. Furthermore, there is a broadening of the spectral peak. Similar trends have been observed at supersonic Mach numbers. The spectral shapes in the forward quadrant and in the near-normal angles from unheated and heated subsonic jets also conform to the universal shape obtained from supersonic jet data. Just as for unheated jets, the peak frequency at angles close to the jet axis is independent of jet velocity as long as the acoustic Mach number is less than unity. The extensive database generated in the current test programme is intended to provide test cases with high-quality data that could be used for the evaluation of theoretical/semi-theoretical jet noise prediction methodologies.

The mass and size distribution of planetesimals formed by the streaming instability. i. the role of self-gravity

Abstract: NASA [NNX13AI58G, NNX16AB42G, NAS 5-26555]; NSF [AST 1313021]; Space Telescope Science Institute [HST-AR-12814]; XSEDE grant [TG-AST120062]; California Institute of Technology (Caltech); Jet Propulsion Laboratory (JPL) - NASA