Expand this Topic clickable element to expand a topic
Skip to content
Optica Publishing Group
Journal Home About Issues in Progress Current Issue All Issues Feature Issues

Wavelength-agile diode-laser sensing strategies for monitoring gas properties in optically harsh flows: application in cesium-seeded pulse detonation engine

Scott T. Sanders, Daniel W. Mattison, Lin Ma, Jay B. Jeffries, and Ronald K. Hanson

Open Access Open Access

Abstract

The rapid, broad wavelength scanning capabilities of advanced diode lasers allow extension of traditional diode-laser absorption techniques to high pressure, transient, and generally hostile environments. Here, we demonstrate this extension by applying a vertical cavity surface-emitting laser (VCSEL) to monitor gas temperature and pressure in a pulse detonation engine (PDE). Using aggressive injection current modulation, the VCSEL is scanned through a 10 cm-1 spectral window at megahertz rates – roughly 10 times the scanning range and 1000 times the scanning rate of a conventional diode laser. The VCSEL probes absorption lineshapes of the ~ 852 nm D2 transition of atomic Cs, seeded at ~ 5 ppm into the feedstock gases of a PDE. Using these lineshapes, detonated-gas temperature and pressure histories, spanning 2000 – 4000 K and 0.5 – 30 atm, respectively, are recorded with microsecond time response. The increasing availability of wavelength-agile diode lasers should support the development of similar sensors for other harsh flows, using other absorbers such as native H2O.

©2002 Optical Society of America

Full Article  |  PDF Article
More Like This
Measurements of multiple gas parameters in a pulsed-detonation combustor using time-division-multiplexed Fourier-domain mode-locked lasers

Andrew W. Caswell, Sukesh Roy, Xinliang An, Scott T. Sanders, Frederick R. Schauer, and James R. Gord
Appl. Opt. 52(12) 2893-2904 (2013)

Quantum cascade laser absorption sensor for carbon monoxide in high-pressure gases using wavelength modulation spectroscopy

R. M. Spearrin, C. S. Goldenstein, J. B. Jeffries, and R. K. Hanson
Appl. Opt. 53(9) 1938-1946 (2014)

Multispecies absorption spectroscopy of detonation events at 100 kHz using a fiber-coupled, time-division-multiplexed quantum-cascade-laser system

Keith D. Rein, Sukesh Roy, Scott T. Sanders, Andrew W. Caswell, Frederick R. Schauer, and James R. Gord
Appl. Opt. 55(23) 6256-6262 (2016)

View More...

Supplementary Material (2)

Media 1: AVI (2369 KB)     
Media 2: AVI (7642 KB)     

Cited By

Optica participates in Crossref's Cited-By Linking service. Citing articles from Optica Publishing Group journals and other participating publishers are listed here.

Alert me when this article is cited.


Figures (10)
Fig. 1.
Fig. 1. Schematic of the Stanford PDE facility, with VCSEL-absorption sensor applied to measure gas temperature and pressure near the exit. Detector 1 monitors Cs absorption lineshapes and detector 2 monitors thermal emission from Cs.

Download Full Size | PDF

Fig. 2.
Fig. 2. Raw transmission data recorded by detector 1 of Fig. 1, with etalon trace overlaid. The first scan is prior to the detonation wave arrival. The detonation arrives during the second scan, and for this scan only the associated beamsteering noise is on the order of the scan repetition rate, thus preventing an accurate absorption measurement. The third scan provides a high-quality absorption feature exhibiting strong collisional broadening. The fourth scan is approximately 4 ms after the detonation wave arrival, and reveals hyperfine splitting.

Download Full Size | PDF

Figure 3.
Figure 3. Raw Cs emission signal recorded by detector 2 of Fig. 1. Emission is in the 852 ± 5 nm spectral region and is proportional to the Cs population in the excited 62P3/2 state. The interfering emission in this band (on the order of 10% of the Cs emission) has been characterized using unseeded detonations and subtracted to obtain this trace.

Download Full Size | PDF

Fig. 4.
Fig. 4. Cesium absorption feature recorded immediately after detonation wave passage. Although the feature contains six hyperfine-split transitions (splittings given in MHz in the diagram at right), a two-line Voigt fit (assuming fixed spacing and fixed relative heights) is sufficiently accurate for extracting total feature area, collisional linewidths (assumed equal), and feature position.

Download Full Size | PDF

Fig. 5.
Fig. 5. History of pertinent lineshape parameters obtained by repeated application (3710 total fits) of the two-line Voigt fit shown in Fig. 4. The integrated Cs absorbance area (right-hand axis) provides the ground state (62S1/2) Cs population, which is used to calculate TCs, electronic (shown in Fig. 6). The collisional linewidth of each component line, Δνc , is used to calculate TCs, kinetic (also shown in Fig. 6).

Download Full Size | PDF

Fig. 6.
Fig. 6. Measured and computed gas temperatures for detonation of stoichiometric C2H4/O2.

Download Full Size | PDF

Fig. 7.
Fig. 7. Calculated equilibrium species concentration histories for detonation of stoichiometric C2H4/O2, obtained using the measured TCs, electronic history shown in Fig. 6 and the measured Pspectroscopic history shown in Fig. 9. The ratio of specific heats, k, is indicated at selected compositions.

Download Full Size | PDF

Fig. 8.
Fig. 8. Determination of the best-fit overall Cs collisional broadening parameter, γCs-detonation products, and its temperature dependence, using the measured Cs electronic temperature as the standard. A linear fit and a gas composition-dependent fit are shown. The composition-dependent fit is used to determine the gas (kinetic) temperature result shown in Fig. 6 from lineshape and pressure measurements. To demonstrate an alternate approach, the same fit is used to find the gas pressure result shown in Fig. 9 from lineshape and (electronic) temperature measurements.

Download Full Size | PDF

Fig. 9.
Fig. 9. Measured and computed pressures for detonation of stoichiometric C2H4/O2.

Download Full Size | PDF

Fig. 10.
Fig. 10. (2.37 MB) Animated summary of the sensor’s results for a single pulse of the PDE. The left panel shows the Cs absorption data (light blue circles) and the 2-line Voigt fit (solid blue fill). A Cs absorption feature is recorded every 2 μs. Each feature produces a TCs, electronic data point (upper right panel) and Pspectroscopic data point (lower right panel). 3710 consecutive scans over the Cs feature are used to obtain the ~ 7ms long temperature and pressure history. Time accelerates during the animation to emphasize the data recorded immediately after detonation passage. (7.64 MB version)

Download Full Size | PDF

Equations (1)

Equations on this page are rendered with MathJax. Learn more.

Δ ν c = 2 γ · P ; γ = γ o ( T Cs,kinetic T o ) n ,
Select as filters
Select Topics Cancel
Top
       
© Copyright 2024 | Optica Publishing Group. All rights reserved, including rights for text and data mining and training of artificial technologies or similar technologies.
Privacy | Terms of Use