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Megahertz rate schlieren visualization of underexpanded, impinging jet using pulsed high power LED

Willert, Christian and Mitchell, Daniel and Soria, Julio (2010) Megahertz rate schlieren visualization of underexpanded, impinging jet using pulsed high power LED. 63rd Annual Meeting, American Physical Society, Division of Fluid Dynamics (DFD), 21.-23. Nov. 2010, Long Beach (CA), USA.

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Official URL: http://meetings.aps.org/Meeting/DFD10/Event/133971

Abstract

Recent advances in light emitting diode (LED) technology has resulted in high power, single chip devices that provide luminous radiant fluxes exceeding several watts. Operated in pulsed current mode the instantaneous light emission of an LED can be further increased to levels comparable to that of photographic (xenon) flash units making it a suitable light source for Schlieren imaging. Compared to the commonly used xenon flash units an LED can be triggered within tens of nanoseconds at rise times on the order of 100 ns thereby enabling stroboscopic illumination at megahertz rates. In the present application the LED's driving electronics were synchronized to a high speed camera to provide time-resolved schlieren images of an underexpanded free jet impinging on a flat plate (nozzle pressure ratio 2.0 to 5.2). The LED was pulsed in burst mode for 102 images at currents of up to 120 A at 500 ns per pulse. Compared to images obtained with a xenon white light flash the nearly monochromatic green light of the LED results in much crisper flow features with superior repeatability in intensity without any speckle artifacts commonly found with laser illumination.

Document Type:Conference or Workshop Item (Speech)
Title:Megahertz rate schlieren visualization of underexpanded, impinging jet using pulsed high power LED
Authors:
AuthorsInstitution or Email of Authors
Willert, Christianchris.willert@dlr.de
Mitchell, DanielMonash University
Soria, JulioMonash University
Date:November 2010
Refereed publication:No
In SCOPUS:No
In ISI Web of Science:No
Status:Published
Keywords:flow visualization, high speed imaging, supersonic flow, light emitting diode, overdriven LED, pulsed illumination
Event Title:63rd Annual Meeting, American Physical Society, Division of Fluid Dynamics (DFD)
Event Location:Long Beach (CA), USA
Event Type:international Conference
Event Dates:21.-23. Nov. 2010
Organizer:University of Southern California, California State University Long Beach, California Institute of Technology, University of California Los Angeles
HGF - Research field:Aeronautics, Space and Transport (old)
HGF - Program:Aeronautics
HGF - Program Themes:Propulsion Systems
DLR - Research area:Aeronautics
DLR - Program:L ER - Engine Research
DLR - Research theme (Project):L - Virtual Engine and Validation Methods
Location: Köln-Porz
Institutes and Institutions:Institute of Propulsion Technology > Engine Measurement Systems
Deposited By: Dr.phil. Christian Willert
Deposited On:16 Dec 2010 14:29
Last Modified:16 Dec 2010 14:29

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