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

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References

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  1. J. Wang, S. T. Sanders, J. B. Jeffries, and R. K. Hanson, �??Oxygen measurements at high pressures using vertical cavity surface-emitting lasers,�?? Appl. Phys. B. 72, 127-135 (2001).
    [CrossRef]
  2. S. T. Sanders, J. Wang, J. B. Jeffries, and R. K. Hanson, �??Diode-laser absorption sensor for line-of-sight gas temperature distributions,�?? Appl. Opt. 40, 4405-4415 (2001).
    [CrossRef]
  3. S. T. Sanders, D. W. Mattison, J. B. Jeffries, and R. K. Hanson, �??Rapid temperature-tuning of a 1.4 m diode laser with application to high pressure H2O absorption spectroscopy,�?? Opt. Lett. 26, 1568-1570 (2001).
    [CrossRef]
  4. S. T. Sanders, �??Diode-laser sensors for harsh environments with application to pulse detonation engines,�?? Ph.D. Thesis, Stanford University, Stanford, CA (2001), <a href="http://vonkarman.stanford.edu/tsd/TSD-142.pdf">http://vonkarman.stanford.edu/tsd/TSD-142.pdf</a>
  5. E. Schlosser, T. Fernholz, H. Teichert, and V. Ebert, �??In-situ detection of potassium atoms in hightemperature coal-combustion systems using near-infrared-diode lasers,�?? Spectrochimica Acta, 2002, (in press).
  6. Z. J. Jabbour, J. Sagle, R. K. Namiotka, and J. Huennekens, �??Measurement of the self-broadening rate coefficients of the cesium resonance lines,�?? J. Quant. Spectrosc. Radiat. Transfer 54, 767-778 (1995)
    [CrossRef]
  7. C. Affolderbach, A. Nagel, S. Knappe, C. Jung, D. Wiedenmann, and R. Wynands, �??Nonlinear spectroscopy with a vertical-cavity surface-emitting laser (VCSEL),�?? Appl. Phys. B. 70, 407-413 (2000).
    [CrossRef]
  8. H. Groll and K. Niemax, �??Multielement diode laser atomic absorption spectrometry in graphite tube furnaces and analytical flames,�?? Spectrochimica Acta 48B, 633-641 (1993).
  9. C. J. Chang-Hasnain, �??Tunable VCSEL,�?? IEEE J. Sel. Top. Quantum Electron. 6, 978-987 (2000).
    [CrossRef]
  10. L. A. Coldren, �??Monolithic Tunable Diode Lasers,�?? IEEE J. Sel. Top. Quantum Electron. 6, 988-999 (2000).
    [CrossRef]
  11. T. Bussing and G. Pappas, �??An introduction to pulse detonation engines,�?? paper 0263 at the 32nd AIAA Aerospace Sciences Meeting, Reno, NV (1994).
  12. J. E. Shepherd, F. Pintgen, J. M. Austin, and C. A. Eckett, �??The structure of the detonation front in gases,�?? paper 0773 at the 40th AIAA Aerospace Sciences Meeting and Exhibit, Reno NV, 14-17 January (2002).
  13. S. T. Sanders, J. A. Baldwin, T. P. Jenkins, D. S. Baer, andR. K. Hanson, �??Diode-Laser Sensor for Monitoring Multiple Combustion Parameters in Pulse Detonation Engines,�?? Proc. Combust. Inst. 28, 587-594 (2000).
    [CrossRef]
  14. S. T. Sanders, D. W. Mattison, J. B. Jeffries, and R. K. Hanson, �??Time-of-flight diode-laser velocimeter using a locally seeded atomic absorber: application in a pulse detonation engine,�?? (submitted to Shock Waves).
  15. B. N. Littleton, A. I. Bishop, T. J. McIntyre, P. F. Barker, H. Rubinsztein-Dunlop, �??Flow tagging velocimetry in a superorbital expansion tube,�?? ShockWaves 10, 225-228 (2000).
    [CrossRef]
  16. S. D. Wehe, �??Development of a tunable diode laser probe for measurements in hypervelocity flows,�?? Ph.D. Thesis, Stanford University, Stanford, CA (2000), <a href="http://vonkarman.stanford.edu/tsd/WeheThesis.pdf">http://vonkarman.stanford.edu/tsd/WeheThesis.pdf</a>
  17. S. T. Sanders, D. W. Mattison, J. B. Jeffries, and R. K. Hanson, �??Sensors for high-pressure, harsh combustion environments using wavlength-agile diode lasers,�?? Proc. Combust. Inst. 29, (in press, 2002).
    [CrossRef]
  18. P. Teulet, J. P. Sarrette, and A. M. Gomes, �??Collisional-radiative modeling of one- and two-temperature air and air-sodium plasmas at atmospheric pressure with temperatures of 2000-12000K,�?? J. Quant. Spectrosc. Radiat. Transfer 70, 159-187 (2000).
    [CrossRef]
  19. I. Glassman, Combustion, (Academic Press, 1996), Chap. 5.
  20. L. Ma, S. T. Sanders, J. B. Jeffries, and R. K. Hanson, �??Monitoring and control of a pulse detonation engine using a diode-laser fuel concentration and temperature sensor,�?? Proc. Combust. Inst. 29, in press (2002).
    [CrossRef]
  21. S. T. Sanders, T. P. Jenkins, and R. K. Hanson, �??Diode laser sensor system for multi-parameter measurements in pulse detonation engine flows,�?? paper #3592 at the 36th Joint Propulsion Conference, July 16-19, Huntsville, AL, (2000).
  22. K. Kailasanath and G. Patnaik, �??Performance estimates of pulsed detonation engines,�?? Proc. Combust. Inst. 28, 595-601 (2000).
    [CrossRef]
  23. A. P. Nefedov, V. A. Sinel�??shchikov, and A. D. Usachev, �??Collisional broadening of the Na-D lines by molecular gases,�?? Physica Scripta 59, 432-442 (1999).
    [CrossRef]

Aerospace Sciences Meeting (1)

T. Bussing and G. Pappas, �??An introduction to pulse detonation engines,�?? paper 0263 at the 32nd AIAA Aerospace Sciences Meeting, Reno, NV (1994).

Appl. Opt. (1)

S. T. Sanders, J. Wang, J. B. Jeffries, and R. K. Hanson, �??Diode-laser absorption sensor for line-of-sight gas temperature distributions,�?? Appl. Opt. 40, 4405-4415 (2001).
[CrossRef]

Appl. Phys. B (2)

J. Wang, S. T. Sanders, J. B. Jeffries, and R. K. Hanson, �??Oxygen measurements at high pressures using vertical cavity surface-emitting lasers,�?? Appl. Phys. B. 72, 127-135 (2001).
[CrossRef]

C. Affolderbach, A. Nagel, S. Knappe, C. Jung, D. Wiedenmann, and R. Wynands, �??Nonlinear spectroscopy with a vertical-cavity surface-emitting laser (VCSEL),�?? Appl. Phys. B. 70, 407-413 (2000).
[CrossRef]

IEEE J. Sel. Top. Quantum Electron. (2)

C. J. Chang-Hasnain, �??Tunable VCSEL,�?? IEEE J. Sel. Top. Quantum Electron. 6, 978-987 (2000).
[CrossRef]

L. A. Coldren, �??Monolithic Tunable Diode Lasers,�?? IEEE J. Sel. Top. Quantum Electron. 6, 988-999 (2000).
[CrossRef]

J. Quant. Spectrosc. Radiat. Transfer (2)

Z. J. Jabbour, J. Sagle, R. K. Namiotka, and J. Huennekens, �??Measurement of the self-broadening rate coefficients of the cesium resonance lines,�?? J. Quant. Spectrosc. Radiat. Transfer 54, 767-778 (1995)
[CrossRef]

P. Teulet, J. P. Sarrette, and A. M. Gomes, �??Collisional-radiative modeling of one- and two-temperature air and air-sodium plasmas at atmospheric pressure with temperatures of 2000-12000K,�?? J. Quant. Spectrosc. Radiat. Transfer 70, 159-187 (2000).
[CrossRef]

Opt. Lett. (1)

Physica Scripta (1)

A. P. Nefedov, V. A. Sinel�??shchikov, and A. D. Usachev, �??Collisional broadening of the Na-D lines by molecular gases,�?? Physica Scripta 59, 432-442 (1999).
[CrossRef]

Proc. Combust. Inst. (4)

K. Kailasanath and G. Patnaik, �??Performance estimates of pulsed detonation engines,�?? Proc. Combust. Inst. 28, 595-601 (2000).
[CrossRef]

L. Ma, S. T. Sanders, J. B. Jeffries, and R. K. Hanson, �??Monitoring and control of a pulse detonation engine using a diode-laser fuel concentration and temperature sensor,�?? Proc. Combust. Inst. 29, in press (2002).
[CrossRef]

S. T. Sanders, D. W. Mattison, J. B. Jeffries, and R. K. Hanson, �??Sensors for high-pressure, harsh combustion environments using wavlength-agile diode lasers,�?? Proc. Combust. Inst. 29, (in press, 2002).
[CrossRef]

S. T. Sanders, J. A. Baldwin, T. P. Jenkins, D. S. Baer, andR. K. Hanson, �??Diode-Laser Sensor for Monitoring Multiple Combustion Parameters in Pulse Detonation Engines,�?? Proc. Combust. Inst. 28, 587-594 (2000).
[CrossRef]

ShockWaves (1)

B. N. Littleton, A. I. Bishop, T. J. McIntyre, P. F. Barker, H. Rubinsztein-Dunlop, �??Flow tagging velocimetry in a superorbital expansion tube,�?? ShockWaves 10, 225-228 (2000).
[CrossRef]

Spectrochimica Acta (2)

E. Schlosser, T. Fernholz, H. Teichert, and V. Ebert, �??In-situ detection of potassium atoms in hightemperature coal-combustion systems using near-infrared-diode lasers,�?? Spectrochimica Acta, 2002, (in press).

H. Groll and K. Niemax, �??Multielement diode laser atomic absorption spectrometry in graphite tube furnaces and analytical flames,�?? Spectrochimica Acta 48B, 633-641 (1993).

Other (6)

S. T. Sanders, �??Diode-laser sensors for harsh environments with application to pulse detonation engines,�?? Ph.D. Thesis, Stanford University, Stanford, CA (2001), <a href="http://vonkarman.stanford.edu/tsd/TSD-142.pdf">http://vonkarman.stanford.edu/tsd/TSD-142.pdf</a>

S. D. Wehe, �??Development of a tunable diode laser probe for measurements in hypervelocity flows,�?? Ph.D. Thesis, Stanford University, Stanford, CA (2000), <a href="http://vonkarman.stanford.edu/tsd/WeheThesis.pdf">http://vonkarman.stanford.edu/tsd/WeheThesis.pdf</a>

S. T. Sanders, D. W. Mattison, J. B. Jeffries, and R. K. Hanson, �??Time-of-flight diode-laser velocimeter using a locally seeded atomic absorber: application in a pulse detonation engine,�?? (submitted to Shock Waves).

J. E. Shepherd, F. Pintgen, J. M. Austin, and C. A. Eckett, �??The structure of the detonation front in gases,�?? paper 0773 at the 40th AIAA Aerospace Sciences Meeting and Exhibit, Reno NV, 14-17 January (2002).

S. T. Sanders, T. P. Jenkins, and R. K. Hanson, �??Diode laser sensor system for multi-parameter measurements in pulse detonation engine flows,�?? paper #3592 at the 36th Joint Propulsion Conference, July 16-19, Huntsville, AL, (2000).

I. Glassman, Combustion, (Academic Press, 1996), Chap. 5.

Supplementary Material (2)

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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.

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.

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.

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.

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).

Fig. 6.
Fig. 6.

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

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.

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.

Fig. 9.
Fig. 9.

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

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)

Equations (1)

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Δ ν c = 2 γ · P ; γ = γ o ( T Cs,kinetic T o ) n ,

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