Abstract

A two-line laser-excited fluorescence technique has been developed to measure the rotational temperature of the OH molecule. This technique eliminates problems encountered in the application of other laser fluorescence methods for measuring the OH temperature in combustion environments, such as fluorescence trapping, nonequilibrium excited state population, spectral bandwidth sensitivity, and quenching. The technique consists of exciting a specific rotational level of the OH molecule in the A2Σ(υ′ = 0) excited state from two different rotational levels in the X2Π(υ″ = 0) ground state using a tunable dye laser and monitoring the broadband fluorescence. An example of the implementation of this technique in an atmospheric pressure methane–air flat flame is included. The possible application of this technique in turbulent combustion is also evaluated.

© 1981 Optical Society of America

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References

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  1. C. C. Wang, L. I. Davis, Appl. Phys. Lett. 25, 34 (1974).
    [CrossRef]
  2. R. J. Cattolica, “OH Rotational Temperature from Laser Induced Fluorescence,” at Spring Meeting, Western States Section/Combustion Institute, Boulder, Colo., 1978, paper 78-18.
  3. J. H. Bechtel, Appl. Opt. 18, 2100 (1979).
    [CrossRef] [PubMed]
  4. K. C. Luck, W. Thielen, J. Quant. Spectrosc. Radiat. Transfer 20, 71 (1978).
    [CrossRef]
  5. R. J. Cattolica, “Laser Absorption Measurements of OH in a Methane–air Flat Flame,” at Fall Meeting, Western States Section/Combustion Institute, Berkeley, Calif., 1979, paper 79-54.
  6. C. Chan, J. W. Daily, Appl. Opt. 19, 1357 (1980).
    [CrossRef] [PubMed]
  7. G. P. Smith, D. R. Crosley, W. L. Davis, “Rotational Population Distributions in Laser Excited OH in an Atmospheric Pressure Flame,” at Fall Meeting, Eastern States Section/Combustion Institute, Atlanta, 1979, paper 2).
  8. R. K. Lengel, D. R. Crosley, J. Chem. Phys. 68, 5309 (1978).
    [CrossRef]
  9. D. R. Crosley, G. P. Smith, Appl. Opt. 19, 517 (1980).
    [CrossRef] [PubMed]
  10. C. Chan, “Laser Induced Fluorescence, Spectroscopy of OH in Flames,” Doctoral Dissertation, U. California, Berkeley (Nov.1979).
  11. R. K. Lengel, D. R. Crosley, J. Chem. Phys. 67, 2085 (1977).
    [CrossRef]
  12. H. Haraguchi, B. Smith, S. Weeks, D. J. Johnson, J. P. Winefordner, Appl. Spectrosc. 31, 156 (1977).
    [CrossRef]
  13. G. H. Dieke, H. M. Crosswhite, J. Quant. Spectrosc. Radiat. Transfer 2, 311 (1962).
    [CrossRef]
  14. I. L. Chidsey, D. R. Crosley, J. Quant. Spectrosc. Radiat. Transfer 23, 187 (1980).
    [CrossRef]
  15. K. R. German, J. Chem. Phys. 62, 2584 (1975).
    [CrossRef]
  16. W. L. Dimpfl, J. L. Kinsey, J. Quant. Spectrosc. Radiat. Transfer 21, 233 (1979).
    [CrossRef]

1980

1979

W. L. Dimpfl, J. L. Kinsey, J. Quant. Spectrosc. Radiat. Transfer 21, 233 (1979).
[CrossRef]

J. H. Bechtel, Appl. Opt. 18, 2100 (1979).
[CrossRef] [PubMed]

1978

K. C. Luck, W. Thielen, J. Quant. Spectrosc. Radiat. Transfer 20, 71 (1978).
[CrossRef]

R. K. Lengel, D. R. Crosley, J. Chem. Phys. 68, 5309 (1978).
[CrossRef]

1977

1975

K. R. German, J. Chem. Phys. 62, 2584 (1975).
[CrossRef]

1974

C. C. Wang, L. I. Davis, Appl. Phys. Lett. 25, 34 (1974).
[CrossRef]

1962

G. H. Dieke, H. M. Crosswhite, J. Quant. Spectrosc. Radiat. Transfer 2, 311 (1962).
[CrossRef]

Bechtel, J. H.

Cattolica, R. J.

R. J. Cattolica, “Laser Absorption Measurements of OH in a Methane–air Flat Flame,” at Fall Meeting, Western States Section/Combustion Institute, Berkeley, Calif., 1979, paper 79-54.

R. J. Cattolica, “OH Rotational Temperature from Laser Induced Fluorescence,” at Spring Meeting, Western States Section/Combustion Institute, Boulder, Colo., 1978, paper 78-18.

Chan, C.

C. Chan, J. W. Daily, Appl. Opt. 19, 1357 (1980).
[CrossRef] [PubMed]

C. Chan, “Laser Induced Fluorescence, Spectroscopy of OH in Flames,” Doctoral Dissertation, U. California, Berkeley (Nov.1979).

Chidsey, I. L.

I. L. Chidsey, D. R. Crosley, J. Quant. Spectrosc. Radiat. Transfer 23, 187 (1980).
[CrossRef]

Crosley, D. R.

I. L. Chidsey, D. R. Crosley, J. Quant. Spectrosc. Radiat. Transfer 23, 187 (1980).
[CrossRef]

D. R. Crosley, G. P. Smith, Appl. Opt. 19, 517 (1980).
[CrossRef] [PubMed]

R. K. Lengel, D. R. Crosley, J. Chem. Phys. 68, 5309 (1978).
[CrossRef]

R. K. Lengel, D. R. Crosley, J. Chem. Phys. 67, 2085 (1977).
[CrossRef]

G. P. Smith, D. R. Crosley, W. L. Davis, “Rotational Population Distributions in Laser Excited OH in an Atmospheric Pressure Flame,” at Fall Meeting, Eastern States Section/Combustion Institute, Atlanta, 1979, paper 2).

Crosswhite, H. M.

G. H. Dieke, H. M. Crosswhite, J. Quant. Spectrosc. Radiat. Transfer 2, 311 (1962).
[CrossRef]

Daily, J. W.

Davis, L. I.

C. C. Wang, L. I. Davis, Appl. Phys. Lett. 25, 34 (1974).
[CrossRef]

Davis, W. L.

G. P. Smith, D. R. Crosley, W. L. Davis, “Rotational Population Distributions in Laser Excited OH in an Atmospheric Pressure Flame,” at Fall Meeting, Eastern States Section/Combustion Institute, Atlanta, 1979, paper 2).

Dieke, G. H.

G. H. Dieke, H. M. Crosswhite, J. Quant. Spectrosc. Radiat. Transfer 2, 311 (1962).
[CrossRef]

Dimpfl, W. L.

W. L. Dimpfl, J. L. Kinsey, J. Quant. Spectrosc. Radiat. Transfer 21, 233 (1979).
[CrossRef]

German, K. R.

K. R. German, J. Chem. Phys. 62, 2584 (1975).
[CrossRef]

Haraguchi, H.

Johnson, D. J.

Kinsey, J. L.

W. L. Dimpfl, J. L. Kinsey, J. Quant. Spectrosc. Radiat. Transfer 21, 233 (1979).
[CrossRef]

Lengel, R. K.

R. K. Lengel, D. R. Crosley, J. Chem. Phys. 68, 5309 (1978).
[CrossRef]

R. K. Lengel, D. R. Crosley, J. Chem. Phys. 67, 2085 (1977).
[CrossRef]

Luck, K. C.

K. C. Luck, W. Thielen, J. Quant. Spectrosc. Radiat. Transfer 20, 71 (1978).
[CrossRef]

Smith, B.

Smith, G. P.

D. R. Crosley, G. P. Smith, Appl. Opt. 19, 517 (1980).
[CrossRef] [PubMed]

G. P. Smith, D. R. Crosley, W. L. Davis, “Rotational Population Distributions in Laser Excited OH in an Atmospheric Pressure Flame,” at Fall Meeting, Eastern States Section/Combustion Institute, Atlanta, 1979, paper 2).

Thielen, W.

K. C. Luck, W. Thielen, J. Quant. Spectrosc. Radiat. Transfer 20, 71 (1978).
[CrossRef]

Wang, C. C.

C. C. Wang, L. I. Davis, Appl. Phys. Lett. 25, 34 (1974).
[CrossRef]

Weeks, S.

Winefordner, J. P.

Appl. Opt.

Appl. Phys. Lett.

C. C. Wang, L. I. Davis, Appl. Phys. Lett. 25, 34 (1974).
[CrossRef]

Appl. Spectrosc.

J. Chem. Phys.

R. K. Lengel, D. R. Crosley, J. Chem. Phys. 68, 5309 (1978).
[CrossRef]

R. K. Lengel, D. R. Crosley, J. Chem. Phys. 67, 2085 (1977).
[CrossRef]

K. R. German, J. Chem. Phys. 62, 2584 (1975).
[CrossRef]

J. Quant. Spectrosc. Radiat. Transfer

W. L. Dimpfl, J. L. Kinsey, J. Quant. Spectrosc. Radiat. Transfer 21, 233 (1979).
[CrossRef]

G. H. Dieke, H. M. Crosswhite, J. Quant. Spectrosc. Radiat. Transfer 2, 311 (1962).
[CrossRef]

I. L. Chidsey, D. R. Crosley, J. Quant. Spectrosc. Radiat. Transfer 23, 187 (1980).
[CrossRef]

K. C. Luck, W. Thielen, J. Quant. Spectrosc. Radiat. Transfer 20, 71 (1978).
[CrossRef]

Other

R. J. Cattolica, “Laser Absorption Measurements of OH in a Methane–air Flat Flame,” at Fall Meeting, Western States Section/Combustion Institute, Berkeley, Calif., 1979, paper 79-54.

R. J. Cattolica, “OH Rotational Temperature from Laser Induced Fluorescence,” at Spring Meeting, Western States Section/Combustion Institute, Boulder, Colo., 1978, paper 78-18.

C. Chan, “Laser Induced Fluorescence, Spectroscopy of OH in Flames,” Doctoral Dissertation, U. California, Berkeley (Nov.1979).

G. P. Smith, D. R. Crosley, W. L. Davis, “Rotational Population Distributions in Laser Excited OH in an Atmospheric Pressure Flame,” at Fall Meeting, Eastern States Section/Combustion Institute, Atlanta, 1979, paper 2).

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Figures (13)

Fig. 1
Fig. 1

Four-level model for the OH molecule. Qij is the electronic quenching rate constant. Aij is the spontaneous emission rate constant. Tij is the collisional transfer rate constant, I12 is the laser intensity. b12 is the absorption rate constant including a laser line shape factor q; b12 = qB12. b12 is the stimulated emission rate constant including a laser line shape factor q; b21 = qB21. (Q31 and Q24 have been omitted for clarity.)

Fig. 2
Fig. 2

Rotational energy level differences for ΔN = 2 in the X2Π(υ″ = 0) ground state of the OH molecule.

Fig. 3
Fig. 3

Normalized fluorescence intensity ratio for levels N + 1 and N − 1 in the X2Π(υ″ = 0) state of the OH molecule as a function of temperature.

Fig. 4
Fig. 4

OH concentration in a methane–air mixture with an equivalence ratio ϕ = 1.0.

Fig. 5
Fig. 5

Number of laser shots required for a fluorescence intensity measurement with σfl/Ifl = 0.01 [based on the signal from the S21(7) transition and the laser characteristics given in Table III].

Fig. 6
Fig. 6

Schematic of the experimental setup for simultaneous laser absorption and fluorescence in a methane–air flat flame.

Fig. 7
Fig. 7

Laser fluorescence excitation spectrum of the Q21(9) and Q1(9) transitions in the (υ′ = 0, υ″ = 0) band of OH.

Fig. 8
Fig. 8

Laser absorption spectrum in the (υ′ = 0, υ″ = 0) band of OH.

Fig. 9
Fig. 9

Simultaneous OH absorption and fluorescence for the Q21(9) transition as a function of radial position across a flat-flame burner.

Fig. 10
Fig. 10

Simultaneous OH absorption and fluorescence for the S21(7) transition as a function of radial position across a flat-flame burner.

Fig. 11
Fig. 11

Radial profiles of laser fluorescence signals, fluorescence ratio, and temperature distribution across a methane–air flat-flame burner ϕ = 1.0.

Fig. 12
Fig. 12

Temperature measurements along the center line of a methane–air flat-flame burner ϕ = 1.0.

Fig. 13
Fig. 13

Laser energy/bandwidth required to obtain a fluorescence intensity measurement with 1% standard deviation [three commercial lasers: (a) 1.66 × 10−3 J/cm−1; (b) 5.83 × 10−3 J/cm−1; and (c) 5.83 × 10−2 J/cm−1].

Tables (4)

Tables Icon

Table I Errors in Temperature Produced by a 1% Error in Measured Fluorescence Intensity Ratios for Selected Rotational Levels and Flame Temperatures

Tables Icon

Table II Two-Line LEF Transition Pairs for N = 0 and N = 7

Tables Icon

Table III Experimental Parameters and Laser Characteristics for Two-Line LEF Technique

Tables Icon

Table IV Minimum Allowable Laser Beam Diameter (mm) to Eliminate Saturation Effects

Equations (18)

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d n 1 d t = n 1 ( b 12 I 12 + T 14 ) + n 2 ( b 21 I 12 + Q 21 + A 21 ) + n 3 ( Q 31 + A 31 ) + n 4 T 41 ,
d n 2 d t = n 1 b 12 I 12 n 2 ( b 21 I 12 + Q 21 + A 21 + Q 24 + A 24 + T 23 ) + n 3 T 32 ,
d n 3 d t = n 2 T 23 n 3 ( Q 31 + A 31 + Q 34 + A 34 + T 32 ) ,
n T = n 1 0 + n 4 0 = n 1 + n 2 + n 3 + n 4 .
n 1 b 12 I 12 = n 2 ( Q 21 + A 21 + Q 24 + A 24 + T 23 ) n 3 T 32 ,
n 3 T 32 = n 2 T 23 + n 3 ( Q 31 + A 31 + Q 34 + A 34 ) .
n 1 b 12 I 12 = n 2 ( A 21 + A 24 + Q 21 + Q 24 ) + n 3 ( A 31 + A 34 + Q 31 + Q 34 ) .
n 1 o b 12 I 12 = n 2 [ ( A 21 + A 24 + Q 21 + Q 24 ) + n 3 n 2 ( A 31 + A 34 + Q 31 + Q 34 ) ] .
I fl = C 1 n 2 [ ( A 21 + A 24 ) + n 3 n 2 ( A 31 + A 34 ) ] ,
n 1 o b 12 I 12 = I fl C 1 × [ ( A 21 + A 24 + Q 21 + Q 24 ) + n 3 n 2 ( A 31 + A 34 + Q 31 + Q 34 ) ] [ ( A 21 + A 24 ) + n 3 n 2 ( A 31 + A 34 ) ] .
n 1 o b 1 2 I 1 2 = I fl C 1 × [ ( A 2 1 + A 2 4 + Q 2 1 + Q 2 4 ) + n 3 n 2 ( A 3 1 + A 3 4 + Q 3 1 + Q 3 4 ) ] [ ( A 2 1 + A 2 4 ) + n 3 n 2 ( A 3 1 + A 3 4 ) ] .
I fl I f l = n 1 o b 12 I 12 n 1 o b 1 2 I 1 2 .
R = I fl / I 12 I f l / I 1 2 = B 12 B 1 2 g 1 g 1 exp [ ( E 1 E 1 ) / k T r ] .
σ ( T r ) T r = k T r h c Δ E σ ( R ) R ,
n 2 = n 1 o B 12 q I 12 Q 21 + A 21 + B 21 I 12 .
n 2 = B 12 q I 12 Q 21 n 1 o .
n 1 o = n tot ( g i Z int ) exp [ ( E i / k T r ) ] .
I fl = η Ω A L n 2 A 21 4 π ,

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