Abstract

UV absorption in the combustion phase of spark-ignition engines strongly influences laser-induced-fluorescence measurements and flame-emission techniques because of the attenuation of a laser and/or signal light. This absorption was assessed with spatial, spectral, and temporal resolutions in an optically accessible research engine. Absorption was measured along a line for different crank-angle positions throughout the combustion phase of the engine by use of spectrally resolved transmittance measurements of both broadband illumination from a deuterium lamp and emission of laser-excited hot oxygen. Evaluating the spatial patterns of absorptivity revealed that no increased absorption can be attributed to the flame-front region and that homogeneous absorption cross sections for the whole burned-gas region can be assumed. The temporal change of absorption was shown to depend on the pressure effect with only negligible changes in absorption cross sections. Results obtained from the absorption measurements are applied for spatially resolved corrections of two-dimensional laser-induced-fluorescence measurements of NO concentration fields obtained under different operating conditions.

© 1999 Optical Society of America

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References

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  1. A. C. Eckbreth, Laser Diagnostics for Combustion, Temperature and Species (Gordon & Breach, Amsterdam, 1996).
  2. K. Kohse-Höinghaus, “Laser techniques for the quantitative detection of reactive intermediates in combustion systems,” Prog. Energ. Combust. Sci. 20, 203–247 (1994).
    [CrossRef]
  3. E. W. Rothe, P. Andresen, “Application of tunable excimer lasers to combustion diagnostics: a review,” Appl. Opt. 36, 3971–4033 (1997).
    [CrossRef] [PubMed]
  4. H. Zhao, N. Ladommatos, “Optical diagnostics for in-cylinder mixture formation measurements in IC engines,” Prog. Energ. Combust. Sci. 24, 297–336 (1998).
    [CrossRef]
  5. C. Schulz, V. Sick, J. Wolfrum, V. Drewes, M. Zahn, R. Maly “Quantitative 2D single-shot imaging of NO concentrations and temperatures in a transparent SI engine,” in Proceedings of the Twenty-Sixth International Symposium on Combustion (The Combustion Institute, Pittsburgh, Pa., 1996), pp. 2597–2604.
  6. M. Knapp, A. Luczak, H. Schlüter, V. Beushausen, W. Hentschel, P. Andresen, “Crank-angle-resolved laser-induced fluorescence imaging of NO in a spark-ignition engine at 248 nm and correlations to flame front propagation and pressure release,” Appl. Opt. 35, 4009–4017 (1996).
    [CrossRef] [PubMed]
  7. A. Bräumer, V. Sick, J. Wolfrum, V. Drewes, R. R. Maly, M. Zahn, “Quantitative two-dimensional measurements of nitric oxide and temperature in a transparent SI engine,” in 1995 SAE Fuels and Lubricants Meeting (Society of Automotive Engineers, Warrendale, Pa., 1995), paper 952462.
  8. W. Stolz, J. Köhler, W. Lawrenz, F. Meier, W. H. Bloss, R. R. Maly, R. Herweg, M. Zahn, “Cycle-resolved flow field measurements using a PIV movie technique in an SI engine,” in 1992 SAE Congress and Exposition (Society of Automotive Engineers, Warrendale, Pa., 1992), paper 922354.
  9. R. R. Maly, M. Zahn, “Engine and fuel interactions,” (The Comission of the European Communities, Brussels, Belgium, 1995).
  10. C. Schulz, J. Wolfrum, V. Sick, “Comparative study of experimental and numerical NO profiles in SI combustion,” in Proceedings of the Twenty-Seventh International Symposium on Combustion (The Combustion Institute, Pittsburgh, Pa., 1998).
  11. R. J. Jensen, R. D. Guettler, J. L. Lyman, “The ultraviolet absorption spectrum of hot carbon dioxide,” Chem. Phys. Lett. 277, 356–360 (1997).
    [CrossRef]
  12. C. Schulz, V. Sick, J. Heinze, W. Stricker, “Laser-induced fluorescence detection of nitric oxide in high-pressure flames with A–X(0,2) excitation,” Appl. Opt. 36, 3227–3232 (1997).
    [CrossRef] [PubMed]
  13. V. Sick, M. Decker, J. Heinze, W. Stricker, “Collisional processes in the B state of O2,” Chem. Phys. Lett. 249, 335–340 (1996).
    [CrossRef]
  14. C. Schulz, V. Sick, U. Meier, “Quantification of NO A–X(0,2) laser-induced fluorescence: investigation of calibration and collisional influences in high-pressure flames,” Submitted to Appl. Opt. (1998).
  15. P. Witze, “In-cylinder diagnostics for production spark ignition engines,” in Unsteady Combustion, F. Culick, M. V. Heitor, J. H. Whitelaw, eds., Vol. 306 of NATO ASI Series (Kluwer, Dordrecht, The Netherlands, 1996).
    [CrossRef]
  16. F. Hildenbrand, C. Schulz, V. Sick, G. Josefsson, I. Magnusson, Ö. Andersson, M. Aldén, “Laser spectroscopic investigation of flow fields and NO-formation in a realistic SI engine,” in 1998 SAE Congress and Exposition (Society of Automotive Engineers, Warrendale, Pa., 1998), paper 980148.
  17. J. E. Dec, R. E. Canaan, “PLIF imaging of NO formation in a DI diesel engine,” in 1998 SAE Congress and Exposition (Society of Automotive Engineers, Warrendale, Pa., 1998), paper 980147.

1998 (1)

H. Zhao, N. Ladommatos, “Optical diagnostics for in-cylinder mixture formation measurements in IC engines,” Prog. Energ. Combust. Sci. 24, 297–336 (1998).
[CrossRef]

1997 (3)

1996 (2)

1994 (1)

K. Kohse-Höinghaus, “Laser techniques for the quantitative detection of reactive intermediates in combustion systems,” Prog. Energ. Combust. Sci. 20, 203–247 (1994).
[CrossRef]

Aldén, M.

F. Hildenbrand, C. Schulz, V. Sick, G. Josefsson, I. Magnusson, Ö. Andersson, M. Aldén, “Laser spectroscopic investigation of flow fields and NO-formation in a realistic SI engine,” in 1998 SAE Congress and Exposition (Society of Automotive Engineers, Warrendale, Pa., 1998), paper 980148.

Andersson, Ö.

F. Hildenbrand, C. Schulz, V. Sick, G. Josefsson, I. Magnusson, Ö. Andersson, M. Aldén, “Laser spectroscopic investigation of flow fields and NO-formation in a realistic SI engine,” in 1998 SAE Congress and Exposition (Society of Automotive Engineers, Warrendale, Pa., 1998), paper 980148.

Andresen, P.

Beushausen, V.

Bloss, W. H.

W. Stolz, J. Köhler, W. Lawrenz, F. Meier, W. H. Bloss, R. R. Maly, R. Herweg, M. Zahn, “Cycle-resolved flow field measurements using a PIV movie technique in an SI engine,” in 1992 SAE Congress and Exposition (Society of Automotive Engineers, Warrendale, Pa., 1992), paper 922354.

Bräumer, A.

A. Bräumer, V. Sick, J. Wolfrum, V. Drewes, R. R. Maly, M. Zahn, “Quantitative two-dimensional measurements of nitric oxide and temperature in a transparent SI engine,” in 1995 SAE Fuels and Lubricants Meeting (Society of Automotive Engineers, Warrendale, Pa., 1995), paper 952462.

Canaan, R. E.

J. E. Dec, R. E. Canaan, “PLIF imaging of NO formation in a DI diesel engine,” in 1998 SAE Congress and Exposition (Society of Automotive Engineers, Warrendale, Pa., 1998), paper 980147.

Dec, J. E.

J. E. Dec, R. E. Canaan, “PLIF imaging of NO formation in a DI diesel engine,” in 1998 SAE Congress and Exposition (Society of Automotive Engineers, Warrendale, Pa., 1998), paper 980147.

Decker, M.

V. Sick, M. Decker, J. Heinze, W. Stricker, “Collisional processes in the B state of O2,” Chem. Phys. Lett. 249, 335–340 (1996).
[CrossRef]

Drewes, V.

C. Schulz, V. Sick, J. Wolfrum, V. Drewes, M. Zahn, R. Maly “Quantitative 2D single-shot imaging of NO concentrations and temperatures in a transparent SI engine,” in Proceedings of the Twenty-Sixth International Symposium on Combustion (The Combustion Institute, Pittsburgh, Pa., 1996), pp. 2597–2604.

A. Bräumer, V. Sick, J. Wolfrum, V. Drewes, R. R. Maly, M. Zahn, “Quantitative two-dimensional measurements of nitric oxide and temperature in a transparent SI engine,” in 1995 SAE Fuels and Lubricants Meeting (Society of Automotive Engineers, Warrendale, Pa., 1995), paper 952462.

Eckbreth, A. C.

A. C. Eckbreth, Laser Diagnostics for Combustion, Temperature and Species (Gordon & Breach, Amsterdam, 1996).

Guettler, R. D.

R. J. Jensen, R. D. Guettler, J. L. Lyman, “The ultraviolet absorption spectrum of hot carbon dioxide,” Chem. Phys. Lett. 277, 356–360 (1997).
[CrossRef]

Heinze, J.

Hentschel, W.

Herweg, R.

W. Stolz, J. Köhler, W. Lawrenz, F. Meier, W. H. Bloss, R. R. Maly, R. Herweg, M. Zahn, “Cycle-resolved flow field measurements using a PIV movie technique in an SI engine,” in 1992 SAE Congress and Exposition (Society of Automotive Engineers, Warrendale, Pa., 1992), paper 922354.

Hildenbrand, F.

F. Hildenbrand, C. Schulz, V. Sick, G. Josefsson, I. Magnusson, Ö. Andersson, M. Aldén, “Laser spectroscopic investigation of flow fields and NO-formation in a realistic SI engine,” in 1998 SAE Congress and Exposition (Society of Automotive Engineers, Warrendale, Pa., 1998), paper 980148.

Jensen, R. J.

R. J. Jensen, R. D. Guettler, J. L. Lyman, “The ultraviolet absorption spectrum of hot carbon dioxide,” Chem. Phys. Lett. 277, 356–360 (1997).
[CrossRef]

Josefsson, G.

F. Hildenbrand, C. Schulz, V. Sick, G. Josefsson, I. Magnusson, Ö. Andersson, M. Aldén, “Laser spectroscopic investigation of flow fields and NO-formation in a realistic SI engine,” in 1998 SAE Congress and Exposition (Society of Automotive Engineers, Warrendale, Pa., 1998), paper 980148.

Knapp, M.

Köhler, J.

W. Stolz, J. Köhler, W. Lawrenz, F. Meier, W. H. Bloss, R. R. Maly, R. Herweg, M. Zahn, “Cycle-resolved flow field measurements using a PIV movie technique in an SI engine,” in 1992 SAE Congress and Exposition (Society of Automotive Engineers, Warrendale, Pa., 1992), paper 922354.

Kohse-Höinghaus, K.

K. Kohse-Höinghaus, “Laser techniques for the quantitative detection of reactive intermediates in combustion systems,” Prog. Energ. Combust. Sci. 20, 203–247 (1994).
[CrossRef]

Ladommatos, N.

H. Zhao, N. Ladommatos, “Optical diagnostics for in-cylinder mixture formation measurements in IC engines,” Prog. Energ. Combust. Sci. 24, 297–336 (1998).
[CrossRef]

Lawrenz, W.

W. Stolz, J. Köhler, W. Lawrenz, F. Meier, W. H. Bloss, R. R. Maly, R. Herweg, M. Zahn, “Cycle-resolved flow field measurements using a PIV movie technique in an SI engine,” in 1992 SAE Congress and Exposition (Society of Automotive Engineers, Warrendale, Pa., 1992), paper 922354.

Luczak, A.

Lyman, J. L.

R. J. Jensen, R. D. Guettler, J. L. Lyman, “The ultraviolet absorption spectrum of hot carbon dioxide,” Chem. Phys. Lett. 277, 356–360 (1997).
[CrossRef]

Magnusson, I.

F. Hildenbrand, C. Schulz, V. Sick, G. Josefsson, I. Magnusson, Ö. Andersson, M. Aldén, “Laser spectroscopic investigation of flow fields and NO-formation in a realistic SI engine,” in 1998 SAE Congress and Exposition (Society of Automotive Engineers, Warrendale, Pa., 1998), paper 980148.

Maly, R.

C. Schulz, V. Sick, J. Wolfrum, V. Drewes, M. Zahn, R. Maly “Quantitative 2D single-shot imaging of NO concentrations and temperatures in a transparent SI engine,” in Proceedings of the Twenty-Sixth International Symposium on Combustion (The Combustion Institute, Pittsburgh, Pa., 1996), pp. 2597–2604.

Maly, R. R.

A. Bräumer, V. Sick, J. Wolfrum, V. Drewes, R. R. Maly, M. Zahn, “Quantitative two-dimensional measurements of nitric oxide and temperature in a transparent SI engine,” in 1995 SAE Fuels and Lubricants Meeting (Society of Automotive Engineers, Warrendale, Pa., 1995), paper 952462.

W. Stolz, J. Köhler, W. Lawrenz, F. Meier, W. H. Bloss, R. R. Maly, R. Herweg, M. Zahn, “Cycle-resolved flow field measurements using a PIV movie technique in an SI engine,” in 1992 SAE Congress and Exposition (Society of Automotive Engineers, Warrendale, Pa., 1992), paper 922354.

R. R. Maly, M. Zahn, “Engine and fuel interactions,” (The Comission of the European Communities, Brussels, Belgium, 1995).

Meier, F.

W. Stolz, J. Köhler, W. Lawrenz, F. Meier, W. H. Bloss, R. R. Maly, R. Herweg, M. Zahn, “Cycle-resolved flow field measurements using a PIV movie technique in an SI engine,” in 1992 SAE Congress and Exposition (Society of Automotive Engineers, Warrendale, Pa., 1992), paper 922354.

Meier, U.

C. Schulz, V. Sick, U. Meier, “Quantification of NO A–X(0,2) laser-induced fluorescence: investigation of calibration and collisional influences in high-pressure flames,” Submitted to Appl. Opt. (1998).

Rothe, E. W.

Schlüter, H.

Schulz, C.

C. Schulz, V. Sick, J. Heinze, W. Stricker, “Laser-induced fluorescence detection of nitric oxide in high-pressure flames with A–X(0,2) excitation,” Appl. Opt. 36, 3227–3232 (1997).
[CrossRef] [PubMed]

F. Hildenbrand, C. Schulz, V. Sick, G. Josefsson, I. Magnusson, Ö. Andersson, M. Aldén, “Laser spectroscopic investigation of flow fields and NO-formation in a realistic SI engine,” in 1998 SAE Congress and Exposition (Society of Automotive Engineers, Warrendale, Pa., 1998), paper 980148.

C. Schulz, V. Sick, U. Meier, “Quantification of NO A–X(0,2) laser-induced fluorescence: investigation of calibration and collisional influences in high-pressure flames,” Submitted to Appl. Opt. (1998).

C. Schulz, V. Sick, J. Wolfrum, V. Drewes, M. Zahn, R. Maly “Quantitative 2D single-shot imaging of NO concentrations and temperatures in a transparent SI engine,” in Proceedings of the Twenty-Sixth International Symposium on Combustion (The Combustion Institute, Pittsburgh, Pa., 1996), pp. 2597–2604.

C. Schulz, J. Wolfrum, V. Sick, “Comparative study of experimental and numerical NO profiles in SI combustion,” in Proceedings of the Twenty-Seventh International Symposium on Combustion (The Combustion Institute, Pittsburgh, Pa., 1998).

Sick, V.

C. Schulz, V. Sick, J. Heinze, W. Stricker, “Laser-induced fluorescence detection of nitric oxide in high-pressure flames with A–X(0,2) excitation,” Appl. Opt. 36, 3227–3232 (1997).
[CrossRef] [PubMed]

V. Sick, M. Decker, J. Heinze, W. Stricker, “Collisional processes in the B state of O2,” Chem. Phys. Lett. 249, 335–340 (1996).
[CrossRef]

C. Schulz, J. Wolfrum, V. Sick, “Comparative study of experimental and numerical NO profiles in SI combustion,” in Proceedings of the Twenty-Seventh International Symposium on Combustion (The Combustion Institute, Pittsburgh, Pa., 1998).

C. Schulz, V. Sick, U. Meier, “Quantification of NO A–X(0,2) laser-induced fluorescence: investigation of calibration and collisional influences in high-pressure flames,” Submitted to Appl. Opt. (1998).

F. Hildenbrand, C. Schulz, V. Sick, G. Josefsson, I. Magnusson, Ö. Andersson, M. Aldén, “Laser spectroscopic investigation of flow fields and NO-formation in a realistic SI engine,” in 1998 SAE Congress and Exposition (Society of Automotive Engineers, Warrendale, Pa., 1998), paper 980148.

C. Schulz, V. Sick, J. Wolfrum, V. Drewes, M. Zahn, R. Maly “Quantitative 2D single-shot imaging of NO concentrations and temperatures in a transparent SI engine,” in Proceedings of the Twenty-Sixth International Symposium on Combustion (The Combustion Institute, Pittsburgh, Pa., 1996), pp. 2597–2604.

A. Bräumer, V. Sick, J. Wolfrum, V. Drewes, R. R. Maly, M. Zahn, “Quantitative two-dimensional measurements of nitric oxide and temperature in a transparent SI engine,” in 1995 SAE Fuels and Lubricants Meeting (Society of Automotive Engineers, Warrendale, Pa., 1995), paper 952462.

Stolz, W.

W. Stolz, J. Köhler, W. Lawrenz, F. Meier, W. H. Bloss, R. R. Maly, R. Herweg, M. Zahn, “Cycle-resolved flow field measurements using a PIV movie technique in an SI engine,” in 1992 SAE Congress and Exposition (Society of Automotive Engineers, Warrendale, Pa., 1992), paper 922354.

Stricker, W.

Witze, P.

P. Witze, “In-cylinder diagnostics for production spark ignition engines,” in Unsteady Combustion, F. Culick, M. V. Heitor, J. H. Whitelaw, eds., Vol. 306 of NATO ASI Series (Kluwer, Dordrecht, The Netherlands, 1996).
[CrossRef]

Wolfrum, J.

C. Schulz, J. Wolfrum, V. Sick, “Comparative study of experimental and numerical NO profiles in SI combustion,” in Proceedings of the Twenty-Seventh International Symposium on Combustion (The Combustion Institute, Pittsburgh, Pa., 1998).

A. Bräumer, V. Sick, J. Wolfrum, V. Drewes, R. R. Maly, M. Zahn, “Quantitative two-dimensional measurements of nitric oxide and temperature in a transparent SI engine,” in 1995 SAE Fuels and Lubricants Meeting (Society of Automotive Engineers, Warrendale, Pa., 1995), paper 952462.

C. Schulz, V. Sick, J. Wolfrum, V. Drewes, M. Zahn, R. Maly “Quantitative 2D single-shot imaging of NO concentrations and temperatures in a transparent SI engine,” in Proceedings of the Twenty-Sixth International Symposium on Combustion (The Combustion Institute, Pittsburgh, Pa., 1996), pp. 2597–2604.

Zahn, M.

C. Schulz, V. Sick, J. Wolfrum, V. Drewes, M. Zahn, R. Maly “Quantitative 2D single-shot imaging of NO concentrations and temperatures in a transparent SI engine,” in Proceedings of the Twenty-Sixth International Symposium on Combustion (The Combustion Institute, Pittsburgh, Pa., 1996), pp. 2597–2604.

R. R. Maly, M. Zahn, “Engine and fuel interactions,” (The Comission of the European Communities, Brussels, Belgium, 1995).

W. Stolz, J. Köhler, W. Lawrenz, F. Meier, W. H. Bloss, R. R. Maly, R. Herweg, M. Zahn, “Cycle-resolved flow field measurements using a PIV movie technique in an SI engine,” in 1992 SAE Congress and Exposition (Society of Automotive Engineers, Warrendale, Pa., 1992), paper 922354.

A. Bräumer, V. Sick, J. Wolfrum, V. Drewes, R. R. Maly, M. Zahn, “Quantitative two-dimensional measurements of nitric oxide and temperature in a transparent SI engine,” in 1995 SAE Fuels and Lubricants Meeting (Society of Automotive Engineers, Warrendale, Pa., 1995), paper 952462.

Zhao, H.

H. Zhao, N. Ladommatos, “Optical diagnostics for in-cylinder mixture formation measurements in IC engines,” Prog. Energ. Combust. Sci. 24, 297–336 (1998).
[CrossRef]

Appl. Opt. (3)

Chem. Phys. Lett. (2)

V. Sick, M. Decker, J. Heinze, W. Stricker, “Collisional processes in the B state of O2,” Chem. Phys. Lett. 249, 335–340 (1996).
[CrossRef]

R. J. Jensen, R. D. Guettler, J. L. Lyman, “The ultraviolet absorption spectrum of hot carbon dioxide,” Chem. Phys. Lett. 277, 356–360 (1997).
[CrossRef]

Prog. Energ. Combust. Sci. (2)

H. Zhao, N. Ladommatos, “Optical diagnostics for in-cylinder mixture formation measurements in IC engines,” Prog. Energ. Combust. Sci. 24, 297–336 (1998).
[CrossRef]

K. Kohse-Höinghaus, “Laser techniques for the quantitative detection of reactive intermediates in combustion systems,” Prog. Energ. Combust. Sci. 20, 203–247 (1994).
[CrossRef]

Other (10)

A. C. Eckbreth, Laser Diagnostics for Combustion, Temperature and Species (Gordon & Breach, Amsterdam, 1996).

C. Schulz, V. Sick, J. Wolfrum, V. Drewes, M. Zahn, R. Maly “Quantitative 2D single-shot imaging of NO concentrations and temperatures in a transparent SI engine,” in Proceedings of the Twenty-Sixth International Symposium on Combustion (The Combustion Institute, Pittsburgh, Pa., 1996), pp. 2597–2604.

A. Bräumer, V. Sick, J. Wolfrum, V. Drewes, R. R. Maly, M. Zahn, “Quantitative two-dimensional measurements of nitric oxide and temperature in a transparent SI engine,” in 1995 SAE Fuels and Lubricants Meeting (Society of Automotive Engineers, Warrendale, Pa., 1995), paper 952462.

W. Stolz, J. Köhler, W. Lawrenz, F. Meier, W. H. Bloss, R. R. Maly, R. Herweg, M. Zahn, “Cycle-resolved flow field measurements using a PIV movie technique in an SI engine,” in 1992 SAE Congress and Exposition (Society of Automotive Engineers, Warrendale, Pa., 1992), paper 922354.

R. R. Maly, M. Zahn, “Engine and fuel interactions,” (The Comission of the European Communities, Brussels, Belgium, 1995).

C. Schulz, J. Wolfrum, V. Sick, “Comparative study of experimental and numerical NO profiles in SI combustion,” in Proceedings of the Twenty-Seventh International Symposium on Combustion (The Combustion Institute, Pittsburgh, Pa., 1998).

C. Schulz, V. Sick, U. Meier, “Quantification of NO A–X(0,2) laser-induced fluorescence: investigation of calibration and collisional influences in high-pressure flames,” Submitted to Appl. Opt. (1998).

P. Witze, “In-cylinder diagnostics for production spark ignition engines,” in Unsteady Combustion, F. Culick, M. V. Heitor, J. H. Whitelaw, eds., Vol. 306 of NATO ASI Series (Kluwer, Dordrecht, The Netherlands, 1996).
[CrossRef]

F. Hildenbrand, C. Schulz, V. Sick, G. Josefsson, I. Magnusson, Ö. Andersson, M. Aldén, “Laser spectroscopic investigation of flow fields and NO-formation in a realistic SI engine,” in 1998 SAE Congress and Exposition (Society of Automotive Engineers, Warrendale, Pa., 1998), paper 980148.

J. E. Dec, R. E. Canaan, “PLIF imaging of NO formation in a DI diesel engine,” in 1998 SAE Congress and Exposition (Society of Automotive Engineers, Warrendale, Pa., 1998), paper 980147.

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Figures (9)

Fig. 1
Fig. 1

Experimental setup for absorption measurements in the research engine. Two series of experiments with either a broadband D2 lamp or O2 LIF excited by a tunable KrF excimer laser were carried out to assess light absorption in the cylinder with spatial and spectral resolution.

Fig. 2
Fig. 2

Measured pressure trace from the research engine fueled with stoichiometric propane/air mixtures in the skip-fired mode (ignition every tenth engine cycle) at 0.4-bar intake pressure. Ignition was set to 340° ca.

Fig. 3
Fig. 3

Single-shot transmission spectrum obtained at 361° ca at an equivalence ratio of ϕ = 1.0. The horizontal axis gives the wavelength λ whereas the vertical axis shows the spatial position x (x = 0 is the location of the spark plug). Dark horizontal lines at approximately x = 1.4 cm are due to the deflection of transmitted light close to the outer limit of the flame. Light at λ = 320 nm exhibits negligible absorption. Therefore spatial profiles at λ = 320 nm were used to correct for the deflection effects. Note that the look-up table is compressed to enhance contrast.

Fig. 4
Fig. 4

Averaged, corrected transmission spectrum for the same conditions as those shown in Fig. 3.

Fig. 5
Fig. 5

Transmissions at 226 and 235 nm as functions of the distance to the spark plug. A comparison of measured data (as obtained from the single-shot spectra presented in Fig. 3) and simulation calculations is shown. The size of the flame was extracted from the measurements, and the absorption coefficients ε (one constant value for each wavelength) were fitted to the spatially resolved transmission data.

Fig. 6
Fig. 6

Absorption coefficient ε versus wavelength for the same conditions as those shown in Fig. 3. The three peaks at 261, 281 and 308 nm are caused by absorption due to OH radicals in their (2,0), (1,0), and (0,0) vibrational bands, respectively.

Fig. 7
Fig. 7

Absorption coefficients ε for the burned gases versus crank angle for three wavelengths relevant for NO detection. Data for different equivalence ratios ϕ are included.

Fig. 8
Fig. 8

Transmissions versus crank angle for 231 and 239 nm as obtained from the O2 LIF measurements relative to transmission at 358° ca. Fluorescence intensities obtained from the O2 BX(2,6) and (2,5) bands are divided by the intensities from the (2,8) band at 257 nm to correct for O2 concentration and temperature effects.

Fig. 9
Fig. 9

Averaged NO concentration fields obtained from two-dimensional LIF measurements5 with and without corrections for absorption of the signal light. Profiles along the lines indicated in the images are given in the graph at the bottom.

Equations (5)

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

A=1-I/I0=1-10-N/Vεd.
d=crt2-x2  for xrt.
I02,5=Iref2,15A2,5/A2,15.
T231=I2,5/I02,5.
logT231T239=-NV dε231-ε239.

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