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Show PresenJed at: the Fifth InJernaJional Symposium on the Applications of Laser Techniques to Fluid Mechanics, Lisbon, Portugal, July 1990 CONCLUSIONS: Data were reported which characterize the gas and condensed phases of a swirl-stabilized kerosene spray flame in a research furnace. These data were generated as part of a database to be used in validation of numerical models. From these data the following conclusions may be drawn: (1) Probing of the flow in the region closest to the nozzle proved to be difficult. Not until -2(3 of the spray had already evaporated could a complete set of reliable information be obtained. (2) Near the nozzle. the axial component of velocity is independent of droplet size. but the radial and tangential components show strong correlation. The radial velocity data show that the small droplets are preferentially carried towards the centerline of the spray, while larger droplets fly outward in a ballistic fashion. The tangential velocity data suggest that the gas-phase tangential velocity exceeds the condensed-phase component and that the lag in picking up this component is dependent upon droplet inertia (diameter). (3) Both the radial and tangential components of velocity exhibited a decrease in RMS with-droplet size. This implies thaL the larger droplets accelerate the gas-phase locally (thus broadening the gas-phase and small droplet distributions). bUL that by virtue of their inertia they experience little. if any, broadening in the flow. (4) In the upper regions of the flow, intermittency between the spray and gas flows causes the small droplet PDPA signals to deviate from the gas-phase velocity. Although it is possible that these intermittent packets of spray droplets are locally equilibrated with the gas-phase (no-slip), the spray density is so low that this seems doubtful. (5) Mean droplet diameter data (as well as radial velocity data) show that small droplets are convected towards the centerline while larger droplets move radially outwards. However. as the flow proceeds downstream, this trend (small droplets in the center and larger outside) reverses due LO the presence of a hot internal recirculation ZDne along the centerline of the flow. This reversal is attributed to the combined effect of d2-law evaporation and a radially decreasing temperature field. £xhaus l Porl ---r--,-... furnace/Exhausl Porl Tra nsiUon Fused Silica 1 Windows -r--~ 11+----+----+---1 0.93 i~n:,ary f1_am_e_ lII III.~ .:. .t :1 1:1=: \1:-jIIi~r--.'Y.. .. -tilll '8' Alomizmg Alomizing Air r(mm) (6) Mean droplet diameter increases along the centerline of the spray sheath (nominal 30· half-angle). This is due to both the d2-law evaporation process and the ability of larger droplets to retain their velocity (momentum) farther into the flow . REFERENCES Marx, K. D. and Edwards, C. F.: Numerical Investigation of Spray Phenomena in a Swirl-Stabilized Kerosene Spray Flame. accepted for presentation at the Fourth Annual Conference on Liquid Atomization and Spray Systems. ILASS-Americas. 1990. Mao, c., Wang. G. and Chigier. N.: Twenty-First Symposium (InlernaJional) on Combustion, p. 665. The Combustion Institute, 1986. McDonell. V. G., Wood, C. P. and Samuelson. G. S .: Twenty-First Symposium (Inlernational) on Combustion. p. 685, The Combustion Instinlte, 1986. McDonell, V. G. and Samuelson, G. S.: Twenty-Second Symposium (International) on Combustion, p. 1961, The Combustion Institute, 1988. McDonell, V. G. and Samuelson, G. S.: Optical Measuremenls of the Behavior of a Poly dispersed Spray Under Reacting and Non-Reacting Conditions, Paper 89-59 presented at the 1989 Fall Meeting of the Western States Section/The Combustion Institute, Livermore, California. October 1989. Cameron, C. D., Brouwer, 1. and Samuelson, G. S.: A Comparison of Spray CharacterizaJion in an Isothermal Chamber and in a Model Gas Turbine Combustor, 4th International Conference on Liquid Atomization and Spray Systems, p. 145, 1988. Rudoff, R. C., Brena de la Rosa. A., Sankar, S. V. and Bachalo. W. D.: Time Analysis of Poly disperse Sprays in Complex Turbulenl Environments, Paper AIAA-89-0052 presented at the AIAA 27th Aerospace Sciences Meeting, Reno. Nev .. January 1989. Hardalupas, Y., Taylor. A. M. K. P. and Whitelaw. 1. H.: Velocity and Size Characteristics of Liquid-Fuelled Flames Stabilized by a Swirl Burner, accepted for publication in the Proceedings of the Royal Society, March 1989. Edwards, C. F.: InvestigaJion of Spray Flame Structure in a NearAxisymmetric, Optical Access Research Furnace. in Collected Papers in Heat Transfer 1988 (K. T. Yang. Ed.), HTD-Vol. 104, p. 99. ASME. 1988. Bachalo, W. D. and Houser, M. 1.: Op. Engr., 23, 583, (1984). Edwards, C. F., and Rudoff, R. C.: Structure of a Swirl-Stabilized Spray Flame by Imaging, Laser Doppler Velocimetry, and Phase Doppler Anemometry, accepted for presentation at the Twenty-Third Symposiwn (International) on Combustion. The Combustion Institute, 1990. 2.0 ISO 12~ ~ 100 .!t !I 7~ I J G: SO .. ~ ~ 2~ '0 > 100 z(mm) Fig. I Schematic of the Optical Access Research Furnace. Fig. 2. Summary diagram of the internal structure of a swirl-stabilized spray flame (Edwards and Rudoff, 1990). Fig. 3. Liquid volume flowrate as a function of axial position in the spray flame. |
