Abstract

Laser ignition has been discussed widely as a potentially superior ignition source for technical appliances such as internal combustion engines. Ignition strongly affects overall combustion, and its early stages in particular have strong implications on subsequent pollutant formation, flame quenching, and extinction. Our research here is devoted to the experimental investigation of the early stages of laser-induced ignition of CH4/air mixtures up to high pressures. Tests were performed in a 0.9–l combustion cell with initial pressures of up to 25 bar with stoichiometric to fuel-lean mixtures using a 5-ns 50-mJ 1064-nm Nd:YAG laser. Laser-induced fluorescence (LIF) was used to obtain two dimensionally resolved images of the OH radical distribution after the ignition event. These images were used to produce an animation of laser ignition and early flame kernel development. Schlieren photography was used to investigate the laser-induced shock wave, hot core gas, and developing flame ball. We extend existing knowledge to high-pressure regimes relevant for internal combustion engines.

© 2004 Optical Society of America

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References

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  1. H. Kopecek, E. Wintner, H. Pischinger, G. Herdin, and J. Klausner, �??Basics for a future laser ignition system for gas engines,�?? ICE-Vol.35-2, Paper No. 2000-ICE-316, 2000 ICE Fall Technical Conference ASME 2000, Peoria USA (2000).
  2. T. X. Phuoc, �??Single-point versus multi-point laser ignition: experimental measurements of combustion times and pressures,�?? Combustion and Flame 122, 508-510 (2000).
    [CrossRef]
  3. M. H. Morsy, Y. S. Ko, S. H. Chung, and P. Cho, �??Laser-induced two-point ignition of premixture with a single-shot laser,�?? Combust. Flame 125, 724-727 (2001).
    [CrossRef]
  4. J. X. Ma, T. W. R. Ill, and J. P. Buckingham, �??Nd:YAG laser ignition of natural gas,�?? Paper 98-ICE-114, ICE Vol. 30-3, Spring Technical Conference ASME (1998).
  5. J. X. Ma, D. R. Alexander, and D. E. Poulain, �??Laser spark ignition and combustion characteristics of methane-air mixtures,�?? Combust. Flame 112, 492-506 (1998).
    [CrossRef]
  6. H. Kopecek, M. Lackner, E. Wintner, F. Winter, and A. Hultqvist, �??Laser-stimulated ignition in a homogeneous charge compression ignition engine, SAE paper 2004-01-0937, 2004 SAE World Congress, Detroit, USA, March 8�??11 (2004).
  7. J. D. Dale, M. D. Checkel, and P. R. Smy, �??Application of high energy ignition systems to engines,�?? Prog. Energy Combust. Sci. 23, 379-398 (1997).
    [CrossRef]
  8. T. X. Phuoc, �??Laser spark ignition: experimental determination of laser-induced breakdown thresholds of combustion gases,�?? Opt. Commun. 175, 419-423 (2000).
    [CrossRef]
  9. H. Kopecek, M. Lackner, F. Winter, and E. Wintner, �??Laser ignition of methane-air mixtures at pressures up to 4 MPa,�?? J. Laser Phys. 13, 1365 (2003).
  10. T.-W. Lee, V. Jain, and S. Kozola, �??Measurements of minimum ignition energy by using laser sparks for hydrocarbon fuels in air: propane, dodecane, and jet-a fuel,�?? Combust. Flame 125, 1320-1328 (2001).
    [CrossRef]
  11. R. Hickling and W. R. Smith, �??Combustion tests of laser ignition,�?? SAE paper 740114, Society of Automotive Engineers (1974).
  12. J. D. Dale, P. R. Smy, and R. M. Clements, �??Laser ignited internal combustion engine�??an experimental study,�?? SAE paper 780329, Society of Automotive Engineers (1978).
  13. G. S. Settles, Schlieren and Shadowgraph Techniques (Springer, 2001).
    [CrossRef]
  14. S. Cheskis, �??Quantitative measurements of absolute concentrations of intermediate species in flames,�?? Progress in Energy and Combustion Science 25 (3), 233-252 (1999).
    [CrossRef]
  15. H. �?stmark, M. Carlson, and K. Ekvall, �??Concentration and temperature measurements in a laser-induced high explosive ignition zone. Part I: LIF spectroscopy measurements,�?? Combust. Flame 105 (3), 381-390 (1996).
    [CrossRef]
  16. Y. L. Chen, J. W. L. Lewis, and C. Parigger, �??Probability distribution of laser-induced breakdown and ignition of ammonia,�?? Journal of Quantitative Spectroscopy and Radiative Transfer. 66(1), 41-53 (2000).
    [CrossRef]
  17. M. Villagran-Muniz, H. Sobral, and R. Navarro-Gonzalez, �??Shock and thermal wave study of laser-induced plasmas in air by the probe beam deflection technique,�?? Measurement Science and Technology 14, 614-618 (2003).
    [CrossRef]
  18. Z. Liu, G. J. Steckman, and D. Psaltis, �??Holographic recording of fast phenomena,�?? Appl. Phys. Lett. 80(5), 731-733 (2002).
    [CrossRef]
  19. J.-L. Beduneau, B. Kim, L. Zimmer, and Y. Ikeda, �??Measurements of minimum ignition energy in premixed laminar methane/air flow by using laser induced spark,�?? Combust. Flame 132, 653-665 (2003).
  20. N. Lamoureux, N. Djebaili-Chaumeix, and C.-E. Paillard, �??Laminar flame velocity determination for H2-airHe-CO2 mixtures using spherical bomb method,�?? Experimental Thermal and Fluid Science 27(4), 385-393 (2003).
    [CrossRef]
  21. Y. Ra and W. K. Cheng, �??Laminar flame propagation through a step-stratified charge,�?? The Fifth International Symposium on Diagnostics and Modeling of Combustion in Internal Combustion Engines (COMODIA 2001), Nagoya, Japan (2001).
  22. T. A. Spiglanin, A. Mcilroy, E. W. Fournier, R. B. Cohen, and J. A. Syage, �??Time-resolved imaging of flame kernels: laser spark ignition of H2/O2/Ar mixtures,�?? Combust. Flame 102:310-328 (1995).
    [CrossRef]
  23. R. W. Schmieder, �??Laser spark ignition and extinction of a methane-air diffusion flame,�?? J. Appl. Phys. 52, 3000 (1981).
    [CrossRef]
  24. J. A. Syage, E. W. Fournier, R. Rianda, and R. B. Cohen, �??Dynamics of flame propagation using laserinduced spark initiation: Ignition energy measurements,�?? J. Appl. Phys. 64, 1499 (1988).
    [CrossRef]
  25. W. Gretler and R. Regenfelder, �??Similarity solution for laser-driven shock waves in a particle-laden gas,�?? Fluid Dynamics Research 28, 369-382 (2001).
    [CrossRef]
  26. Q. Qin, and K. Attenborough, �??Characteristics and application of laser-generated acoustic shock waves in air,�?? Appl. Acoust. 65(4), 325-340 (2004).
    [CrossRef]
  27. Y.-L. Chen and J. W. Lewis, �??Visualization of laser-induced breakdown and ignition,�?? Opt. Express 9, 360-371 (2001), <a href="http://www.opticsexpress.org/abstract.cfm?URI=OPEX-9-7-360.">http://www.opticsexpress.org/abstract.cfm?URI=OPEX-9-7-360</a>
    [CrossRef] [PubMed]
  28. H. Malm, G. Sparr, J. Hult, and C. F. Kaminski, �??Nonlinear diffusion filtering of images obtained by planar laser-induced fluorescence spectroscopy,�?? J. Opt. Soc. Am. A 17, 2148-2156 (2000).
    [CrossRef]
  29. R. Navarro-Gonzalez and M. Villagran-Muniz, �??Effect of beam waist on shock properties of laser-induced plasmas in air by the photoacoustic probe beam deflection method,�?? Analytical Sciences 17, 118-121 (2001).

2000 ICE Fall Technical Conference ASME (1)

H. Kopecek, E. Wintner, H. Pischinger, G. Herdin, and J. Klausner, �??Basics for a future laser ignition system for gas engines,�?? ICE-Vol.35-2, Paper No. 2000-ICE-316, 2000 ICE Fall Technical Conference ASME 2000, Peoria USA (2000).

2004 SAE World Congress (1)

H. Kopecek, M. Lackner, E. Wintner, F. Winter, and A. Hultqvist, �??Laser-stimulated ignition in a homogeneous charge compression ignition engine, SAE paper 2004-01-0937, 2004 SAE World Congress, Detroit, USA, March 8�??11 (2004).

Analytical Sciences (1)

R. Navarro-Gonzalez and M. Villagran-Muniz, �??Effect of beam waist on shock properties of laser-induced plasmas in air by the photoacoustic probe beam deflection method,�?? Analytical Sciences 17, 118-121 (2001).

Appl. Acoust. (1)

Q. Qin, and K. Attenborough, �??Characteristics and application of laser-generated acoustic shock waves in air,�?? Appl. Acoust. 65(4), 325-340 (2004).
[CrossRef]

Appl. Phys. Lett. (1)

Z. Liu, G. J. Steckman, and D. Psaltis, �??Holographic recording of fast phenomena,�?? Appl. Phys. Lett. 80(5), 731-733 (2002).
[CrossRef]

Combust. Flame (6)

J.-L. Beduneau, B. Kim, L. Zimmer, and Y. Ikeda, �??Measurements of minimum ignition energy in premixed laminar methane/air flow by using laser induced spark,�?? Combust. Flame 132, 653-665 (2003).

H. �?stmark, M. Carlson, and K. Ekvall, �??Concentration and temperature measurements in a laser-induced high explosive ignition zone. Part I: LIF spectroscopy measurements,�?? Combust. Flame 105 (3), 381-390 (1996).
[CrossRef]

T.-W. Lee, V. Jain, and S. Kozola, �??Measurements of minimum ignition energy by using laser sparks for hydrocarbon fuels in air: propane, dodecane, and jet-a fuel,�?? Combust. Flame 125, 1320-1328 (2001).
[CrossRef]

J. X. Ma, D. R. Alexander, and D. E. Poulain, �??Laser spark ignition and combustion characteristics of methane-air mixtures,�?? Combust. Flame 112, 492-506 (1998).
[CrossRef]

M. H. Morsy, Y. S. Ko, S. H. Chung, and P. Cho, �??Laser-induced two-point ignition of premixture with a single-shot laser,�?? Combust. Flame 125, 724-727 (2001).
[CrossRef]

T. A. Spiglanin, A. Mcilroy, E. W. Fournier, R. B. Cohen, and J. A. Syage, �??Time-resolved imaging of flame kernels: laser spark ignition of H2/O2/Ar mixtures,�?? Combust. Flame 102:310-328 (1995).
[CrossRef]

Combust. Sci. (1)

J. D. Dale, M. D. Checkel, and P. R. Smy, �??Application of high energy ignition systems to engines,�?? Prog. Energy Combust. Sci. 23, 379-398 (1997).
[CrossRef]

Combustion and Flame (1)

T. X. Phuoc, �??Single-point versus multi-point laser ignition: experimental measurements of combustion times and pressures,�?? Combustion and Flame 122, 508-510 (2000).
[CrossRef]

COMODIA 2001 (1)

Y. Ra and W. K. Cheng, �??Laminar flame propagation through a step-stratified charge,�?? The Fifth International Symposium on Diagnostics and Modeling of Combustion in Internal Combustion Engines (COMODIA 2001), Nagoya, Japan (2001).

Experimental Thermal and Fluid Science (1)

N. Lamoureux, N. Djebaili-Chaumeix, and C.-E. Paillard, �??Laminar flame velocity determination for H2-airHe-CO2 mixtures using spherical bomb method,�?? Experimental Thermal and Fluid Science 27(4), 385-393 (2003).
[CrossRef]

Fluid Dynamics Research (1)

W. Gretler and R. Regenfelder, �??Similarity solution for laser-driven shock waves in a particle-laden gas,�?? Fluid Dynamics Research 28, 369-382 (2001).
[CrossRef]

J. Appl. Phys. (2)

R. W. Schmieder, �??Laser spark ignition and extinction of a methane-air diffusion flame,�?? J. Appl. Phys. 52, 3000 (1981).
[CrossRef]

J. A. Syage, E. W. Fournier, R. Rianda, and R. B. Cohen, �??Dynamics of flame propagation using laserinduced spark initiation: Ignition energy measurements,�?? J. Appl. Phys. 64, 1499 (1988).
[CrossRef]

J. Laser Phys. (1)

H. Kopecek, M. Lackner, F. Winter, and E. Wintner, �??Laser ignition of methane-air mixtures at pressures up to 4 MPa,�?? J. Laser Phys. 13, 1365 (2003).

J. Opt. Soc. Am. A. (1)

H. Malm, G. Sparr, J. Hult, and C. F. Kaminski, �??Nonlinear diffusion filtering of images obtained by planar laser-induced fluorescence spectroscopy,�?? J. Opt. Soc. Am. A 17, 2148-2156 (2000).
[CrossRef]

Journal of Quantitative Spectroscopy and (1)

Y. L. Chen, J. W. L. Lewis, and C. Parigger, �??Probability distribution of laser-induced breakdown and ignition of ammonia,�?? Journal of Quantitative Spectroscopy and Radiative Transfer. 66(1), 41-53 (2000).
[CrossRef]

Measurement Science and Technology (1)

M. Villagran-Muniz, H. Sobral, and R. Navarro-Gonzalez, �??Shock and thermal wave study of laser-induced plasmas in air by the probe beam deflection technique,�?? Measurement Science and Technology 14, 614-618 (2003).
[CrossRef]

Opt. Commun. (1)

T. X. Phuoc, �??Laser spark ignition: experimental determination of laser-induced breakdown thresholds of combustion gases,�?? Opt. Commun. 175, 419-423 (2000).
[CrossRef]

Opt. Express (1)

Progress in Energy and Combustion Scienc (1)

S. Cheskis, �??Quantitative measurements of absolute concentrations of intermediate species in flames,�?? Progress in Energy and Combustion Science 25 (3), 233-252 (1999).
[CrossRef]

Society of Automotive Engineers (2)

R. Hickling and W. R. Smith, �??Combustion tests of laser ignition,�?? SAE paper 740114, Society of Automotive Engineers (1974).

J. D. Dale, P. R. Smy, and R. M. Clements, �??Laser ignited internal combustion engine�??an experimental study,�?? SAE paper 780329, Society of Automotive Engineers (1978).

Sprint Technical Conference ASME (1)

J. X. Ma, T. W. R. Ill, and J. P. Buckingham, �??Nd:YAG laser ignition of natural gas,�?? Paper 98-ICE-114, ICE Vol. 30-3, Spring Technical Conference ASME (1998).

Other (1)

G. S. Settles, Schlieren and Shadowgraph Techniques (Springer, 2001).
[CrossRef]

Supplementary Material (1)

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Figures (12)

Fig. 1.
Fig. 1.

Experimental setup for Schlieren photography; 1: pulsed Nd:YAG laser for ignition; 2: flash lamp; 3: combustion chamber; 4: CCD camera; 5: focus of the Nd:YAG laser beam; 6: spherical mirror (f = 660 mm); 7: knife edge or aperture; M: mirror.

Fig. 2.
Fig. 2.

Schematic setup for planar laser-induced fluorescence imaging.

Fig. 3.
Fig. 3.

Image of the emission 200 ns after breakdown in air. The ignition laser is entering from the left side. The asymmetric intensity results from the increased absorption of laser radiation by the generated plasma in the later stages of the pulse and has considerable effect on the ignition and flame propagation characteristics of laser-ignited gas mixtures. Experimental conditions: Pressure: 1 bar, medium: air, temperature: 300 K, exposure time: 3 ns, laser energy: 230 mJ.

Fig. 4
Fig. 4

Breakdown occurred at two locations simultaneously; therefore two shock waves can be observed. In the middle of these, one can see the hot core air. Less energy was deposited in the left region, so the resulting shock wave is smaller. Experimental conditions: Pressure: 25 bar, medium: air, temperature: 373 K, light source: flash lamp, exposure time: 30 ns, laser energy: 50 mJ, time: 8 μs after ignition; image dimensions: 11.6 mm × 9.15 mm.

Fig. 5.
Fig. 5.

Multiexposure image of the shock wave in air at 10 bar in 500-ns steps after ignition. The distance between the first two shock front structures outside the hot core gas is visibly larger than between the subsequent exposures. The imaging rate of the camera was at its fastest, so no exact shock-wave speed variation could be deduced from these multiexposure images.

Fig. 6.
Fig. 6.

Left: Dimensions of the shock wave and the hot core gas in 1 bar CO2. Right: dimensions of the flame kernel in a stoichiometric CH4/air mixture at 10 bar. ∥: parallel direction to the igniting laser; └: perpendicular to it.

Fig. 7.
Fig. 7.

Velocities of the shock waves in (a) air, (b) CO2, and (c) H2 at pressures between 1 and 25 bar. Note the same scales for all subfigures. The velocities were determined in the transverse direction to the igniting laser (torus).

Fig. 8.
Fig. 8.

Schlieren image of a stoichiometric CH4/air mixture at 10 bar, 500 μs after ignition (left) and the corresponding image of the hot gas core in air (right) at identical conditions. The shock wave is far outside the region of observation; only the hot core of the gas mixture in the beginning stages of combustion is visible. The difference in size is not typical but can be attributed to variations of laser energy deposition. The structures in the combustible mixture are much sharper owing to the beginning of heat release and subsequent higher-density gradients in the flame front. Comparison with the corresponding image top right in Fig. 7 shows the OH-fluorescence signal in the same characteristical geometry.

Fig. 9.
Fig. 9.

Flame kernel in laser-ignited CH4/air mixtures at 10 bar. (a) Temporal evolution of the hot core in air, (b) that of the flame kernel in a stoichiometric and fuel-lean CH4/air mixture. Note that combustion is faster at λ = 1.

Fig. 10.
Fig. 10.

Planar laser-induced fluorescence images of the OH radical, ignition laser entering from the right side. λ = 1.0; CH4/air, 25 bar. Image diameter is 18 mm. From left to right: 0.2 , 0.5, 1.5, and 2.5 ms after ignition

Fig. 11.
Fig. 11.

Planar laser-induced fluorescence images of the OH radical, ignition laser entering from the right side. λ =1.3, CH4/air 4.3 bar. Top row: 0.5 ms after ignition, from left to right: 50 mJ, 140 mJ ignition laser energy. Bottom row: 2.5 ms after ignition, from left to right: 50 mJ, 140 mJ ignition laser energy. Despite the difference in the first 500 μs after ignition the flame kernel geometry appears similar after 2.5 ms, showing the transition from turbulent to laminar flame front propagation. Observation of the full scale image was restricted by the window diameter.

Fig. 12.
Fig. 12.

(1.100 kB): Three-dimensional visualization of the flame front after laser ignition in a fuel-lean CH4/air mixture.

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