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1 Advance Publication by J-STAGE 日本機械学会論文集 Transactions of the JSME (in Japanese) DOI:.299/transjsme.6-23 Received date : 8 May, 26 Accepted date : 5 July, 26 J-STAGE Advance Publication date : 22 July, 26

2 2 Simultaneous measurement of concentration fluctuations of two species using pulsed laser diodes in light absorption spectrometric method Takashi KUBO, Hiroki TOYODA 2 and Hiroyuki FURUKAWA, 2 Department of Mechanical Engineering, Meijo University -5 Shiogamaguchi, Tempaku-ku, Nagoya-shi, Aichi , Japan Abstract In this study, we developed a simultaneous measurement system for measuring the concentration fluctuations of two species using pulsed laser diodes in the light absorption spectrometric method. Conventional methods utilize halogen lamps or continuous laser diodes as light sources for concentration measurements. These light sources require multimonochrometers or dichroic mirrors, which makes these methods rather expensive. However, using pulsed laser diodes as the light sources eliminates the need for additional multi-monochrometers and dichroic mirrors. A diffusion field consisting of two dye species in an axisymmetric turbulent jet was measured using the developed concentration measurement system. To ascertain the validity of our concentration measurements, we compared the present measurement results with those of a single dye species and previous studies. It was observed that the concentrations of the two dye species were measured accurately by the present measuring system. Therefore, such low-cost concentration measurement systems can be developed and applied in various simultaneous measurements of concentration fluctuations of multiple species such as in turbulent reactive flows. Key words : Concentration measurement, Light absorption spectrometric method, Laser diode, Turbulent jet, Diffusion. Bilger (Bilger et al., 99) (Brown and Bilger, 996) (Li and Bilger, 996) NO + O 3 NO 2 + O 2 NO NO 2 Komori (Komori et al., 994) No.6-23 [DOI:.299/transjsme.6-23] of corresponding author: tkubo@meijo-u.ac.jp

3 99 998; 2 29a, 29b , 998 λ Beer-Lambert ln I(λ) I (λ) = α(λ)lγ I l I Γ α λ 2 () P(λ) = k(λ)γ (2) P(λ) = ln I(λ) I (λ) k(λ) = α(λ)l (3) (4) P(λ) k(λ) λ Γ B Γ Y Beer-Lambert λ λ 2

4 2 B (Acid Blue 9) Y (Sunset Yellow FCF) Absorbance Wavelength [nm] Fig. Absorbance of dye species B (Acid Blue 9) and Y (Sunset Yellow FCF). The wavelength of maximum absorbance is observed near λ 2 = 635 nm and λ = 488 nm for species B and Y, respectively. P (λ ) = ln I (λ ) I (λ ) = k BΓ B + k Y Γ Y P 2 (λ 2 ) = ln I 2(λ 2 ) I 2 (λ 2 ) = k B2Γ B + k Y 2 Γ Y (5a) (5b) 2 λ λ 2 k β j β λ j P P 2 (5) 635 nm 488 nm. 635 nm Acid Blue 9 (C.I. 429) nm 488 nm Sunset Yellow FCF (C.I. 5985) Acid Blue 9 Sunset Yellow FCF B Y B Y. g/l l = mm (3) (Absorbance) UV FOLS-7, 635 nm FOLS-7, 488nm.5 mm.7 mm.4 mm 3

5 Pulse generator Red laser diode (635 nm). ms Optical fiber I t Blue laser diode (488 nm) Photomultiplier Tube Incident light I (λ) Fiber bundle φ.5 mm l =.7 mm Diffusing matter (Two species) Transmitted light I (λ) Sampling volume Data acquisition system Personal computer Fig. 2 Schematic of the concentration measurement system. In this measurement system, two pulsed laser diodes, which emit lights alternatively, are used as the light source; thus, the absorption values (Eq. (5)) can be measured using only one photomultiplier tube (5) B Y B.3,.6,.9,.2,.5,.8 g/l Y.6,.2,.8,.24,.3,.36 g/l 3 B Y B Y Beer-Lambert B Y :2 B Y.3 g/l.7 g/l 2.7 g/l

6 4 4 ln(i /I ) 3 2 = 488 nm 2 = 635 nm k B2 = 2.54 ln(i /I ) 3 2 = 488 nm 2 = 635 nm k Y = 7.25 k B =.8..2 B [g/l] k Y2 = Y [g/l] Fig. 3 Calibration results for dye B (left) and Y (right). It is found that the absorption values increase linearly with increasing concentrations for both B and Y, thus satisfying the Beer Lambert law. 3. B Y 3 4 d = 4 mm U = 3.5 m/s Reynolds Re = U d/ν = 3 Γ B.3 g/l Y.6 g/l 4 mm 4 mm 2 mm x r. ms Taylor.7 mm x/d = 2 8 U c =..3 m/s ms 7 khz I TSI, 2-2W Model (x) 5 U c b U x/d = 2 8 Gauss U c

r O x Round jet Diameter, d =4mm Velocity, U =3.5m/s Concentration, Γ =.3 g/l (dye B) and.6 g/l (dye Y) Fig. 4 Sketch of the turbulent diffusion jet. In this experiment, d = 4 mm and U = 3.

7 r O x Round jet Diameter, d =4mm Velocity, U =3.5m/s Concentration, Γ =.3 g/l (dye B) and.6 g/l (dye Y) Fig. 4 Sketch of the turbulent diffusion jet. In this experiment, d = 4 mm and U = 3.5 m/s; therefore, the jet Reynolds number, Re = U d/ν = 3. The concentrations at the exit of the jet are Γ =.3 g/l for dye B and Γ =.6 g/l for dye Y. U/U c.2.8 Present exp. x/d = 2 x/d = 4 x/d = 6 x/d = 8 Present exp. x/d = 2 x/d = 4 x/d = 6 x/d = 8 u'/u' c.5 Panchapakesan and Lumley (993a).6 Gaussian r/b U Fig. 5 Radial profiles of mean velocity at different x/d (Kubo et al., 26). The mean velocity profiles exhibit good self-similarity in the present measurement region (x/d = 2 8) and can be well approximated by a Gaussian profile. Fig r/b U Radial profiles of velocity fluctuation r.m.s. values (Kubo et al., 26). The velocity fluctuations exhibit good self-similarity, which are in agreement with the results obtained by Panchapakesan and Lumley (Panchapakesan and Lumley, 993a). b U U ( x ) =.35 U c d b ( U x ) d =.96 d +.38 (6) (7) r.m.s. 6 r.m.s. u c b U x/d = 2 8 r.m.s. Panchapakesan (Panchapakesan and Lumley, 993a) r.m.s. u c U ( x ) u C =.66 d (8) B Y x/d = 2 x/d = 6 Γ

8 .6 /.4.2 x/d = 2 /.4.2 x/d = 6 B Y (+.) t [s] Fig. 7 Two typical concentration fluctuations on the jet axis using our measuring system for x/d =2 and 6. This shows that the concentrations of the two species are in agreement with each other and can be measured accurately. Y. B Y 8 Γ c Γ d x B Γ ( x ) =.2 Γ c d B Y LIF Papanicolaou (Papanicolaou and List, 988) Birch (Birch et al., 978) B Y 3.3 % x/d = 2, Γ c b Γ Gauss B Y Gauss b Γ d =.9 ( x d ) γ c/γ c B x/d > 5 Papanicolaou (Papanicolaou and List, 988) Birch (Birch et al., 978) x/d = 2, 4 6 r.m.s. γ c b Γ (9) ()

9 / c Present exp. B, Y B (single species) Papanicolaou and List (988) Birch et al. (978) x/d = 2 x/d = 4 x/d = 6 B Y / c.5 Gaussian Fig x/d Downstream variations of mean concentration on the jet axis. The mean concentrations of the dye species B and Y are in agreement with the measurements performed on the single species B using continuous laser diode. Fig r/b Radial profiles of mean concentration. Similar to the case of mean velocity, it is found that the profiles of mean concentrations exhibit good self-similarity in the present measurement region and agree well with the Gaussian profile. ' c / c Present exp. B, Y B (single species) x/d = 2 x/d = 4 x/d = 6 B Y ' / ' c 2.5 B (single species) Birch et al. (978) Panchapakesan and Lumley (993b). Papanicolaou and List (988) Birch et al. (978) x/d r/b Fig. Downstream variations of relative intensity of concentration on the jet axis. The relative intensities are in good agreement with the measurement of the single species B using continuous laser diode. Fig. Radial profiles of the concentration fluctuation r.m.s. values. It can be observed that the profiles exhibit self-similarity and are in good agreement with the data obtained in previous studies. Panchapakesan (Panchapakesan and Lumley, 993b) Birch (Birch et al., 978) r.m.s. B Y 4.2 % 2 r.m.s. B Y B 5/3

10 - E( f )/ ' x/d = 2 x/d = 4 x/d = 6 5/ f [Hz] Fig. 2 Power spectrum densities of concentration fluctuation on the jet axis. The power spectrum density becomes larger in the low frequency region, while it becomes smaller in the high frequency region because the scale of concentration fluctuation becomes larger in the downstream direction. 998 B Y 4. JSPS 5K582, 5K Bilger, R. W., Saetran, L. R. and Krishnamoorthy, L. V., Reaction in a scalar mixing layer, Journal of Fluid Mechanics, Vol. 233 (99), pp Birch, A. D., Brown, D. R., Dodson, M. G. and Thomas, J. R., The turbulent concentration field of a methane jet, Journal of Fluid Mechanics, Vol. 88, part 3 (978), pp Brown, R. J. and Bilger, R. W., An experimental study of a reactive plume in grid turbulence, Journal of Fluid Mechanics, Vol. 32 (996), pp Komori, S., Kanzaki, T. and Murakami, Y., Concentration correlation in a turbulent mixing layer with chemical reaction, Journal of Chemical Engineering of Japan, Vol. 27, No. 6 (994), pp B Vo. 66, No. 648 (2), pp

11 , B Vol. 75, No. 749 (29a), pp , 2 B Vol. 75, No. 749 (29b), pp Vol. 6, No. (26) pp Li, J. D. and Bilger, R. W., The diffusion of conserved and reactive scalars behind line sources in homogeneous turbulence, Journal of Fluid Mechanics, Vol. 38 (996), pp Panchapakesan, N. R. and Lumley, J. L., Turbulence measurements in axisymmetric jets of air and helium. part. air jet, Journal of Fluid Mechanics, Vo., 246 (993a), pp Panchapakesan, N. R. and Lumley, J. L., Turbulence measurements in axisymmetric jets of air and helium. part 2. helium jet, Journal of Fluid Mechanics, Vol. 246 (993b), pp Papanicolaou, P. N. and List, E. J., Investigations of round vertical turbulent buoyant jets, Journal of Fluid Mechanics, Vol. 95 (988), pp B Vol. 56, No. 522 (99), pp B Vol. 64, No. 628 (998), pp References Bilger, R. W., Saetran, L. R. and Krishnamoorthy, L. V., Reaction in a scalar mixing layer, Journal of Fluid Mechanics, Vol. 233 (99), pp Birch, A. D., Brown, D. R., Dodson, M. G. and Thomas, J. R., The turbulent concentration field of a methane jet, Journal of Fluid Mechanics, Vol. 88, part 3 (978), pp Brown, R. J. and Bilger, R. W., An experimental study of a reactive plume in grid turbulence, Journal of Fluid Mechanics, Vol. 32 (996), pp Komori, S., Kanzaki, T. and Murakami, Y., Concentration correlation in a turbulent mixing layer with chemical reaction, Journal of Chemical Engineering of Japan, Vol. 27, No. 6 (994), pp Kubo, T., Sakai, Y., Ohta, I. and Nakamura, I., A study of turbulent jet diffusion with competitive-consecutive reaction (st report, effectuality of simultaneous measurement of concentration fluctuations of three species), Transactions of the Japan Society of Mechanical Engineers, Series B, Vo. 66, No. 648 (2), pp (in Japanese). Kubo, T., Sakai, Y. and Honda, S., Reactive scalar diffusion in liquid grid-turbulence (st report, one-step reaction case), Transactions of the Japan Society of Mechanical Engineers, Series B, Vol. 75, No. 749 (29a), pp (in Japanese). Kubo, T., Sakai, Y. and Honda, S., Reactive scalar diffusion in liquid grid-turbulence (2nd report, competitive-consecutive reaction case), Transactions of the Japan Society of Mechanical Engineers, Series B, Vol. 75, No. 749 (29b), pp (in Japanese). Kubo, T., Takemura, M. and Furukawa, H., Development of a simultaneous measurement system for concentration fluctuations of multiple species by light absorption spectrometric method (Concentration measurement of three species by using laser diodes), Journal of the Japanese Society for Experimental Mechanics, Vol. 6, No. (26), pp (in Japanese). Li, J. D. and Bilger, R. W., The diffusion of conserved and reactive scalars behind line sources in homogeneous turbulence, Journal of Fluid Mechanics, Vol. 38 (996), pp Panchapakesan, N. R. and Lumley, J. L., Turbulence measurements in axisymmetric jets of air and helium. part. air jet, Journal of Fluid Mechanics, Vo., 246 (993a), pp Panchapakesan, N. R. and Lumley, J. L., Turbulence measurements in axisymmetric jets of air and helium. part 2. helium jet, Journal of Fluid Mechanics, Vol. 246 (993b), pp

12 Papanicolaou, P. N. and List, E. J., Investigations of round vertical turbulent buoyant jets, Journal of Fluid Mechanics, Vol. 95 (988), pp Sakai, Y., Nakamura, I., Tsunoda, H. and Kushida, T., Development of an optical fiber type of fluctuation concentration measuring system of multiple species by the light absorption spectrometric method, Transactions of the Japan Society of Mechanical Engineers, Series B, Vol. 56, No. 522 (99), pp (in Japanese). Sakai, Y., Kubo, T. and Nakamura, I., A study of the turbulent jet diffusion with chemical reaction (st report, validity of a concentration fluctuation measuring system of multiple species), Transactions of the Japan Society of Mechanical Engineers, Series B, Vol. 64, No. 628 (998), pp (in Japanese).

液相化学反応を伴う乱流拡散の研究名城大学理工学部研究報告 No.5 21 R 6 R S 1) B 6 2 M =1 Nozzle ID =1.2 OD = x mm 6 mm 6 mm 2 mm M = 1 mm mm 1.5 mm x 1 x = 1 m

液相化学反応を伴う乱流拡散の研究名城大学理工学部研究報告 No.5 21 R 6 R S 1) B 6 2 M =1 Nozzle ID =1.2 OD = x mm 6 mm 6 mm 2 mm M = 1 mm mm 1.5 mm x 1 x = 1 m 1) A Study on Turbulent Diffusion with Chemical Reaction in Liquid Takashi KUBO 1) Abstract Turbulent diffusion with chemical reactions is of practical importance in many engineering and environmental