There is a strong interest in diagnosing engine performance problems and maintenance needs using optical techniques
instead of expensive, time-consuming mechanical inspection. A Telops Hyper-Cam MWIR imaging Fourier-transform
spectrometer collected spectrally-resolved images of jet exhaust from an F109 turbofan engine operating at 53%, 82%,
and 88% of maximum RPM. This work attempts to discern what information content about the turbulent jet flow
field is revealed in the measured spectra. The spectrum is examined and simulated, a radial and axial temperature
mapping of the plume is presented, and a turbulent temporal and spatial analysis method is demonstrated. Spectral
simulation of a pixel centered at nozzle exit finds volume mixing fractions of 3.3% H2O and 2.8% CO2 and an exhaust
temperature of 560K with the engine at 82%. A single, high frequency turbulent feature is mapped and tracked over
several frames. Velocity of this feature, based on the 2.86kHz camera frame rate and 0.067cm2 per pixel spatial
resolution, is approximately 176m/s and compares favorably with an estimate based on the measured mass flow rate.
This effort is a proof of concept and intended to justify qualitative analysis of a more controlled and characterized
turbulent source in future work.
KEYWORDS: Hydrogen fluoride lasers, Chemical species, 3D modeling, Energy transfer, Turbulence, Fluorine, Laser systems engineering, Chemical reactions, Molecules, Laser resonators
The small signal gain of a small-scale HF overtone laser was measured using a sub-Doppler tunable diode laser system. The spatially resolved, two-dimensional small signal gain maps that were generated show a highly inhomogeneous gain medium indicating the dominant role played by mixing of the H2 and F streams in HF laser performance. The measured gain data were analyzed with the aid of a two-dimensional computational fluid dynamics model. The results show that reactant mixing mechanisms have a large effect on the gain averaged over a vertical profile while kinetic rate mechanisms, including reaction rate constants and reactant concentration, have a greater effect on the maximum system gain.
The uncertainty in both the fluorine atom concentration and the gain length has inhibited the development of accurate and device independent models of HF overtone lasers. Furthermore, previous methods of measuring the small signal gain were cumbersome and could not easily generate spatial maps of the gain in the cavity. Experimental techniques have been developed to directly measure the concentration of fluorine atoms, the gain length and the small signal gain in a hydrogen fluoride 5 cm slit nozzle laser. A gas phase titration technique was utilized to measure the fluorine atom concentration using HCl as the titrant. The gain length was measured using a pitot probe to locate the interface of the primary flow with the high Mach number shroud flows. A tunable diode laser was utilized to perform small signal gain measurements on HF overtone (ν=2→0) transitions.
A review of recent advances in chemical laser technology is presented. New technology and concepts related to the Chemical Oxygen Iodine Laser (COIL), All Gas-phase Iodine Laser (AGIL), and HF Overtone Laser are discussed.
KEYWORDS: Hydrogen fluoride lasers, Chemical species, Diffusion, Data modeling, Fluorine, Laser systems engineering, Turbulence, 3D modeling, Chemical reactions, Computer simulations
The small signal gain of a small-scale HF overtone laser was measured using a sub-Doppler tunable diode laser system. Measurements of reactant concentration, flow velocity and gain length were also made. The spatially resolved, two-dimensional small signal gain and temperature maps that were generated show a highly inhomogeneous gain medium indicating the dominant role played by mixing of the H2 and F streams in HF laser performance. The measured gain and temperature data were analyzed with the aid of a two-dimensional computational fluid dynamics model. The results show that reactant mixing mechanisms have a large effect on the gain averaged over a vertical profile while kinetic rate mechanisms, including reaction rate constants and reactant concentration, have a greater effect on the maximum system gain.
Overtone small signal gain data measured while operating a small-scale HF laser saturated on the fundamental transitions are compared with fundamental lasing output spectra and spontaneous overtone emission spectra measured orthogonal to the lasing axis. In all cases, the data are consistent with an equilibrium rotational distribution. These results are discussed in terms of their applicability to the question of rotational nonequilibrium in cw HF lasers.
A tunable diode laser was used to probe the overtone gain medium of a small-scale HF laser. Two-dimensional, spatially resolved small signal gain and temperature maps were generated for the P(3) ro-vibrational transition in the first HF overtone band.
A tunable diode laser was used to probe the overtone gain medium of a small-scale HF laser. 2D, spatially resolved small signal gain and temperature maps were generated for the P(3) ro-vibrational transition in the first HF overtone band.
The chemical oxygen-iodine laser (COIL) has been studied at the Phillips Laboratory since its invention in 1978. One of the most difficult challenges in COIL technology is to produce constant power for more than a few seconds; an essential feature for most applications. The key to developing a laser with these operational characteristics is management of the heat released during the production of singlet delta oxygen. Approximately 10 joules is deposited into the singlet delta oxygen generator (SOG) for every joule extracted as laser power. A recent test series demonstrated run times of 120 seconds at 9 kW by controlling the SOG reaction temperature with a flowing aqueous solution of cold hydroperoxide (BHP). This method of managing the energy released is quite effective but requires a large reservoir of cold BHP.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.