Abstract

A newly developed light scattering device for sizing and velocimetry of large droplets is described. A novel beam shaping technique is employed in conjunction with a laser operating in the circular TEM01 (doughnut) mode as a light source to achieve a ring-shaped source beam. This particular beam geometry allows definition of a sheetlike scattering volume with an approximately constant power density across it resulting in improved sizing and sampling accuracy. The size resolution of the instrument is better than 7%, and the overall sizing accuracy for an input size range of 30 dB (droplets of ∼45–1500 μm in radius) is ∼10%. While the instrument reported in this paper was designed to analyze water droplets entrained in air, it should also be useful in other sizing applications if appropriate modifications are made.

© 1982 Optical Society of America

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References

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  1. D. M. Robinson, W. P. Chu, Appl. Opt. 14, 2177 (1975).
    [Crossref] [PubMed]
  2. D. W. Roberts, Appl. Opt. 16, 1861 (1977).
    [Crossref]
  3. D. W. Roberts, C. W. Brasier, B. W. Bomar, Opt. Eng. 18, 236 (1979).
  4. W. D. Bachalo, C. F. Hess, C. A. Hartwell, “An Instrument for Spray Droplet Size and Velocity Measurements,” presented at the Winter Annual Meeting of ASME, Gas Turbine Division, New York, 2–7 Dec. 1979.
  5. R. G. Knollenberg, J. Appl. Meteorol. 9, 86 (1970).
    [Crossref]
  6. W. G. Eisert, M. Nezel, Rev. Sci. Instrum. 49, 1617 (1978).
    [Crossref] [PubMed]
  7. J. Stapelmann, Dr.-Ing. Dissertation, Universitaet Hannover, West Germany (1979).
  8. J. Cornillault, Appl. Opt. 11, 265 (1972).
    [Crossref] [PubMed]
  9. F. M. Shofner, Y. Watanabe, T. B. Carlson, ISA Trans. 12, 56 (1973).
  10. J. Chan, M. Golay, Atmos. Environ. 2, 775 (1977).
  11. I. Landa, E. S. Tebay, IEEE Trans. Instrum. Meas. IM-21, 56 (1971).
  12. W. J. Glantschnig, S.-H. Chen, Appl. Opt. 20, 2499 (1981).
    [Crossref] [PubMed]
  13. A. Ungut, G. Grehan, G. Gouesbet, Appl. Opt. 20, 2911 (1981).
    [Crossref] [PubMed]
  14. H. W. Kogelnik, T. Li, Appl. Opt. 5, 1550 (1966).
    [Crossref] [PubMed]
  15. B. J. Mason, O. W. Jayaratne, J. W. Woods, J. Sci. Instrum. 40, 247 (1963).
    [Crossref]
  16. S. G. Jennings, “Experiments on Water Drop Interactions,” Phys. Educ. (Sept.1977).
    [Crossref]
  17. T. J. Johnson, M.S. Thesis Department of Nuclear Engineering, MIT, Cambridge, Mass. (1981).
  18. G. Grehan, G. Gouesbet, C. Rabasse, Appl. Opt. 20, 796 (1981).
    [Crossref] [PubMed]
  19. W. Glantschnig, “A Light Scattering Device for Sizing and Velocimetry of Cooling Tower Drift Droplets,” EPRI Report in print;Electric Power Research Institute, Palo Alto, Calif.

1981 (3)

1979 (1)

D. W. Roberts, C. W. Brasier, B. W. Bomar, Opt. Eng. 18, 236 (1979).

1978 (1)

W. G. Eisert, M. Nezel, Rev. Sci. Instrum. 49, 1617 (1978).
[Crossref] [PubMed]

1977 (3)

J. Chan, M. Golay, Atmos. Environ. 2, 775 (1977).

D. W. Roberts, Appl. Opt. 16, 1861 (1977).
[Crossref]

S. G. Jennings, “Experiments on Water Drop Interactions,” Phys. Educ. (Sept.1977).
[Crossref]

1975 (1)

1973 (1)

F. M. Shofner, Y. Watanabe, T. B. Carlson, ISA Trans. 12, 56 (1973).

1972 (1)

1971 (1)

I. Landa, E. S. Tebay, IEEE Trans. Instrum. Meas. IM-21, 56 (1971).

1970 (1)

R. G. Knollenberg, J. Appl. Meteorol. 9, 86 (1970).
[Crossref]

1966 (1)

1963 (1)

B. J. Mason, O. W. Jayaratne, J. W. Woods, J. Sci. Instrum. 40, 247 (1963).
[Crossref]

Bachalo, W. D.

W. D. Bachalo, C. F. Hess, C. A. Hartwell, “An Instrument for Spray Droplet Size and Velocity Measurements,” presented at the Winter Annual Meeting of ASME, Gas Turbine Division, New York, 2–7 Dec. 1979.

Bomar, B. W.

D. W. Roberts, C. W. Brasier, B. W. Bomar, Opt. Eng. 18, 236 (1979).

Brasier, C. W.

D. W. Roberts, C. W. Brasier, B. W. Bomar, Opt. Eng. 18, 236 (1979).

Carlson, T. B.

F. M. Shofner, Y. Watanabe, T. B. Carlson, ISA Trans. 12, 56 (1973).

Chan, J.

J. Chan, M. Golay, Atmos. Environ. 2, 775 (1977).

Chen, S.-H.

Chu, W. P.

Cornillault, J.

Eisert, W. G.

W. G. Eisert, M. Nezel, Rev. Sci. Instrum. 49, 1617 (1978).
[Crossref] [PubMed]

Glantschnig, W.

W. Glantschnig, “A Light Scattering Device for Sizing and Velocimetry of Cooling Tower Drift Droplets,” EPRI Report in print;Electric Power Research Institute, Palo Alto, Calif.

Glantschnig, W. J.

Golay, M.

J. Chan, M. Golay, Atmos. Environ. 2, 775 (1977).

Gouesbet, G.

Grehan, G.

Hartwell, C. A.

W. D. Bachalo, C. F. Hess, C. A. Hartwell, “An Instrument for Spray Droplet Size and Velocity Measurements,” presented at the Winter Annual Meeting of ASME, Gas Turbine Division, New York, 2–7 Dec. 1979.

Hess, C. F.

W. D. Bachalo, C. F. Hess, C. A. Hartwell, “An Instrument for Spray Droplet Size and Velocity Measurements,” presented at the Winter Annual Meeting of ASME, Gas Turbine Division, New York, 2–7 Dec. 1979.

Jayaratne, O. W.

B. J. Mason, O. W. Jayaratne, J. W. Woods, J. Sci. Instrum. 40, 247 (1963).
[Crossref]

Jennings, S. G.

S. G. Jennings, “Experiments on Water Drop Interactions,” Phys. Educ. (Sept.1977).
[Crossref]

Johnson, T. J.

T. J. Johnson, M.S. Thesis Department of Nuclear Engineering, MIT, Cambridge, Mass. (1981).

Knollenberg, R. G.

R. G. Knollenberg, J. Appl. Meteorol. 9, 86 (1970).
[Crossref]

Kogelnik, H. W.

Landa, I.

I. Landa, E. S. Tebay, IEEE Trans. Instrum. Meas. IM-21, 56 (1971).

Li, T.

Mason, B. J.

B. J. Mason, O. W. Jayaratne, J. W. Woods, J. Sci. Instrum. 40, 247 (1963).
[Crossref]

Nezel, M.

W. G. Eisert, M. Nezel, Rev. Sci. Instrum. 49, 1617 (1978).
[Crossref] [PubMed]

Rabasse, C.

Roberts, D. W.

D. W. Roberts, C. W. Brasier, B. W. Bomar, Opt. Eng. 18, 236 (1979).

D. W. Roberts, Appl. Opt. 16, 1861 (1977).
[Crossref]

Robinson, D. M.

Shofner, F. M.

F. M. Shofner, Y. Watanabe, T. B. Carlson, ISA Trans. 12, 56 (1973).

Stapelmann, J.

J. Stapelmann, Dr.-Ing. Dissertation, Universitaet Hannover, West Germany (1979).

Tebay, E. S.

I. Landa, E. S. Tebay, IEEE Trans. Instrum. Meas. IM-21, 56 (1971).

Ungut, A.

Watanabe, Y.

F. M. Shofner, Y. Watanabe, T. B. Carlson, ISA Trans. 12, 56 (1973).

Woods, J. W.

B. J. Mason, O. W. Jayaratne, J. W. Woods, J. Sci. Instrum. 40, 247 (1963).
[Crossref]

Appl. Opt. (7)

Atmos. Environ. (1)

J. Chan, M. Golay, Atmos. Environ. 2, 775 (1977).

IEEE Trans. Instrum. Meas. (1)

I. Landa, E. S. Tebay, IEEE Trans. Instrum. Meas. IM-21, 56 (1971).

ISA Trans. (1)

F. M. Shofner, Y. Watanabe, T. B. Carlson, ISA Trans. 12, 56 (1973).

J. Appl. Meteorol. (1)

R. G. Knollenberg, J. Appl. Meteorol. 9, 86 (1970).
[Crossref]

J. Sci. Instrum. (1)

B. J. Mason, O. W. Jayaratne, J. W. Woods, J. Sci. Instrum. 40, 247 (1963).
[Crossref]

Opt. Eng. (1)

D. W. Roberts, C. W. Brasier, B. W. Bomar, Opt. Eng. 18, 236 (1979).

Phys. Educ. (1)

S. G. Jennings, “Experiments on Water Drop Interactions,” Phys. Educ. (Sept.1977).
[Crossref]

Rev. Sci. Instrum. (1)

W. G. Eisert, M. Nezel, Rev. Sci. Instrum. 49, 1617 (1978).
[Crossref] [PubMed]

Other (4)

J. Stapelmann, Dr.-Ing. Dissertation, Universitaet Hannover, West Germany (1979).

W. D. Bachalo, C. F. Hess, C. A. Hartwell, “An Instrument for Spray Droplet Size and Velocity Measurements,” presented at the Winter Annual Meeting of ASME, Gas Turbine Division, New York, 2–7 Dec. 1979.

T. J. Johnson, M.S. Thesis Department of Nuclear Engineering, MIT, Cambridge, Mass. (1981).

W. Glantschnig, “A Light Scattering Device for Sizing and Velocimetry of Cooling Tower Drift Droplets,” EPRI Report in print;Electric Power Research Institute, Palo Alto, Calif.

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Figures (9)

Fig. 1
Fig. 1

Schematic diagram of the optical subsystem: BE, beam expander; M, mirror; A, ring-shaped aperture; V, scattering volume; C, collimator; PMT, photomultiplier tube.

Fig. 2
Fig. 2

Radial light intensity distribution of the expanded laser beam above and below the ring-shaped aperture.

Fig. 3
Fig. 3

(a) Schematic representation of laser beam in the center of the wind-tunnel test section. The beam has the appearance of a slowly expanding conical shell. (b) Definition of the scattering volume by means of two collimators, one in front of each photomultiplier tube. Only that part of the light wall indicated comprises the scattering volume.

Fig. 4
Fig. 4

Block diagram of the electronic system: PMT, photomultiplier tube; PREA, preamplifier; AMP, amplifier and signal processing unit; ADC, analog-to-digital converter; SCA, single channel analyzer; TAC, time-to-amplitude converter; DIV, divider; COINC, coincidence channel amplifier and signal processing unit; DPU, dual parameter unit; PHA, pulse height analyzer.

Fig. 5
Fig. 5

Calibration droplet peak obtained with the instrument analyzing droplets produced with a monodisperse droplet generator. Since each PHA size group corresponds to a particular voltage υ(R), the proportionality constant k in Eq. (4) can be determined knowing the size of the calibration droplets.

Fig. 6
Fig. 6

Instrument reponse (calibration) curve obtained by combining the results of many calibration runs in which monodisperse droplets of different sizes were analyzed.

Fig. 7
Fig. 7

Variation of the true droplet velocity υd as a function of droplet size. For all but the smallest droplets the measured velocity as given by the height υmes of the velocity pulse underestimates the real droplet velocity.

Fig. 8
Fig. 8

Variation of the effective beamwidth as a function of droplet size. The effective beamwidth is seen to increase as the droplet size increases.

Fig. 9
Fig. 9

Droplet distribution as a function of droplet size and velocity as displayed on the CRT of the pulse height analyzer. Each horizontal line represents a velocity group consisting of 256 size groups.

Equations (4)

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Ī Ω ( I 0 , R , m , r ) = I 0 K ( m , r ) R 2 ,
Ī Ω [ I 0 ( ρ ) , R , M , r ] = I 0 ( ρ ) K ( m , r ) R 2 .
V T = A V ̅ BA T ,
υ ( R ) = k R 2 .

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