Laser System for Multiplexed Time-Resolved Measurements in High-Speed Flows and Combustion
Abstract
Georgia Tech is investigating several topics of interest to the ONR that involve a complex interplay of unsteady fluid mechanics and, combustion processes. These topics include the canonical jet in crossflow (on-going ONR program), augmentor screech phenomenon (wor,king with Pax River team on alternative fuel effects on augmentors), spray and breakup of liquid fuels, film cooling, swirl flow dyn,amics, combustion noise, detonation and shock wave dynamics, and advanced optical and embedded sensors. These research projects are,sponsored and/or performed in collaboration with a range of other DOD sponsors, including AFRL, AFOSR, DTRA and have strong overlaps, with the ONRs Power, Propulsion and Thermal Management programs.To understand complex unsteady fluid mechanics and combustion pr,ocesses, it is critical to simultaneously image multiple quantities with sufficient repetition-rate to resolve dynamics of interest., While the past two decades have seen the rapid proliferation of laser diagnostics using diode-pumped solid-state (DPSS) technology,, such systems are limited to repetition-rates on the order of 10 kHz and pulse energies on the order of 10 mJ at 532 nm. However, th,is rate often is insufficient for practical navy warfighter applications (including jets in crossflows, screeching instabilities in,augmentors, detonations, super/hypersonic flows) and this pulse energy is insufficient for many important measurement techniques (mo,lecular tagging velocimetry, Rayleigh scattering, Raman scattering, etc.). The relatively recent advent of commercial pulse-burst, lasers has helped overcome the limitations of DPSS systems. Instead of a continuous train of 10 mJ pulses at around 10 kHz, these s,ystems provide bursts of high-energy (ca. 1 J) pulses at rates of 0.1-1 MHz. The combustion lab at Georgia Tech, which operates as s,hared facility amongst all the combustion/propulsion faculty, has a pulse-burst laser system. However, this single leg system can,only produce one output laser beam at a time; it cannot be used for simultaneous measurement of multiple quantities that require dif,ferent wavelengths, laser pulse timing, etc. Anticipating the need for multiplexed measurements, the current laser system was built,on an upgradable platform that allows additional legs to be installed in a relatively economical manner (approximately 60% the cost,of a separate laser with similar specifications). The proposed DURIP will add a second-leg to the system, allowing for two laser bea,ms with independent wavelengths and pulse timing. Moreover, this second leg will have higher pulse energy than the previous leg, ena,bling a wider suite of measurements. Key simultaneous measurements that would be enabled by this two-leg system include (but are not, limited to) particle image velocimetry (PIV) and particle tracking velocimetry (PTV), species tagging velocimetry (STV), planar las,er induced fluorescence (PLIF), Raman scattering, Rayleigh scattering (including filtered and interferometric Rayleigh scattering),,coherent anti-Stokes Raman scattering (CARS), laser induced incandescence (LII), laser Thomson scattering (LTS), phosphorescence the,rmometry, laser induced breakdown spectroscopy (LIBS), and various spray diagnostics.In addition to enhancing the diagnostics for va,rious collaborative experiments, the next generation of engineers graduating from the Combustion Lab are exposed to high-speed advan,ced laser diagnostics capabilities applied to practical combustion devices, which they then bring into real world experience at vari,ous OEMs and government labs.APPROVED FOR PUBLIC RELEASE
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Apr 01, 2022
- Source ID
- N000142212259
Entities
People
- Tim Lieuwen
Organizations
- Georgia Tech Research Corporation
- Office of Naval Research
- United States Navy