Modelling and simulation of sprays in laminar flames
- 77 Downloads
- 7 Citations
Abstract
In the present paper we model and numerically simulate steady, laminar, premixed spray flames. The gasphase is described in Eulerian form by the equations governing the conservation of overall mass, momentum, energy and species mass. The liquid phase is described in Lagrangian form by the overall continuity equation, which reduces to an equation for the droplet size, the equations of motion, the energy equation and a droplet density function transport equation. The latter is the so-called ‘spray equation’, which, at any position in the chemically reacting flowfield, describes the joint distribution of droplet size, droplet velocity and droplet temperature. Herein the spray equation is solved using a Monte Carlo method. Detailed models of the exchange of mass, momentum and energy between the gaseous and the liquid phase are taken into account. The results presented in this paper are for an octane-air flame, where small amounts of liquid octane in form of a liquid spray are added to a fresh, unburnt gaseous octane-air mixture.
Key words
Droplet size distribution Spray Laminar flame CombustionSommario
Nel presente lavoro vengono modellate e simulate numericamente fiamme a spruzzo premescolate, stazionarie e laminari. La fase gassosa viene descritta in forma euleriana dalle equazioni che governano la conservazione della massa totale, della quantità di moto, dell'energia e della massa delle singole specie. La fase liquida viene descritta in forma lagrangiana dall'equazione di continuità globale che si riduce and una equazione per la dimensione della goccia, le equazioni del moto, l'equazione dell'energia e una equazione di trasporto della funzione densità di goccia. L'ultima è la cosiddetta ‘equazione dello spruzzo’, che, ad ogni posizione nel campo di flusso chimicamente reagente, descrive la distribuzione congiunta della dimensione, della velocità e della temperatura della goccia. Nel presente lavoro l'equazione dello spruzzo viene risolta usando un metodo Monte Carlo. Vengono considerati modelli dettagliati dello scambio di massa, quantità di moto ed energia tra la fase liquida e quella gassosa. I risultati presentati in questo lavoro sono riferiti ad una fiamma aria-ottano, dove piccole quantità di ottano liquido in forma di spruzzo liquido vengono aggiunte ad una miscela di aria e ottano gassosa non bruciata e pura.
Preview
Unable to display preview. Download preview PDF.
References
- 1.Williams, F.A., ‘Progress in spray-combustion analysis’. In Eighth Symposium on Combustion, The Combustion Institute, 1962, pp. 50–69.Google Scholar
- 2.Lin, T.H., Law, C.K. and Chung, S.H., ‘Theory of laminar flame propergation in off-stoichiometric dilute sprays’, Int. J. Heat Mass Transfer, 31 (1988) 1023–1034.Google Scholar
- 3.Lin, T.H. and Sheu, Y.Y., ‘Theory of laminar flame propergation in near-stoichiometric dilute sprays’, Combust. and Flame, 84 (1991) 333–342.Google Scholar
- 4.Polymeropoulos, C.E., ‘Flame propagation in a one-dimensional liquid fuel spray’, Combust. Sci. and Tech., 9 (1974) 197–207.Google Scholar
- 5.Burgoyne, J.H. and Cohen, L., ‘The effect of drop size on flame propagation in liquid aerosol’, Proc. Royal Society, A 225 (1954) 375–392.Google Scholar
- 6.Hayashi, S., Kumagai, S. and Sakai, T., ‘Propagation velocity and structure of flames in droplet-vapor-air mixtures’, Combust. Sci. and Tech., 15 (1976) 169–177.Google Scholar
- 7.Silverman, I., Greenberg, J.B. and Tambour, Y., ‘Asymptotic analysis of a premixed polydisperse spray flame’, SIAM J. Appl. Math, 50, (5) (1991) 1284–1303.Google Scholar
- 8.Silverman, I., Greenberg, J.B. and Tambour, Y., ‘Stoichiometry and polydisperse effects in premixed spray flames’, Combust. and Flame, 93 (1993) 97–118.Google Scholar
- 9.Westbrook, C.K. and Dryer, F.L., ‘Simplified reaction mechanisms for the oxidation of hydrocarbon fuels in flames’, Combust. Sci. and Tech., 27 (1981) 31–43.Google Scholar
- 10.Williams, F.A., Combustion Theory, Benjamin/Cummings, Menlo Park, 2nd edition, 1985.Google Scholar
- 11.Crowe, C.T., Sharma, M.P. and Stock, D.E., ‘The Particle-source-in-cell (PSI-CELL) model for gas-droplet flows’, Transactions of the ASME, Journal of Fluids Engineering, June 1977, 325–332.Google Scholar
- 12.Abramzon, B. and Sirignano, W.A., ‘Droplet vaporization model for spray combustion calculation’, Int. J. Heat Mass Transfer, 32 (9) (1989) 1605–1618.Google Scholar
- 13.Faeth, G.M., ‘Current status of droplet and liquid combustion’, Prog. Energy Combust. Sci., 3 (1977) 191–224.Google Scholar
- 14.Adeniji-Fashola, A. and Chen, C.P., ‘Modelling of confined turbulent fluid-particle flows using Eulerian and Lagrangian schemes’, Int. J. Heat Mass Transfer, 33 (4) (1990) 691–701.Google Scholar
- 15.Rogg, B., RUN-1DL: A Computer Program for the Simulation of One-Dimensional Chemically Reacting Flows, Technical Report CUED/A-THERMO/TR39, University of Cambridge, Department of Engineering, April 1991.Google Scholar
- 16.Rogg, B., RUN-1DL: ‘The Cambridge universal laminar flamelet computer code’. In: Peters, N. and Rogg, B. (editors) Reduced Kinetic Mechanisms for Applications in Combustion Systems, Appendix C. Springer-Verlag, Berlin, Heidelberg, 1993.Google Scholar
- 17.Rogg, B., RUN-1DL: The Universal Laminar Flame and Flamelet Code, Technical report, 1994.Google Scholar
- 18.Reid, R.C., Prausnitz, J.M. and Poling, B.E., The Properties of Gases and Liquids, McGraw-Hill, New York, 4th edition, 1987.Google Scholar