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Atomization and Sprays

Journal of the International Institutes for Liquid Atomization and Spray Systems

ISSN for PRINT: 1045-5110

Institutional price:	$787.00
Issues per year:	8

Best Paper Award Selection - Editorial Board Site

2006, Volume16

139 pages

Issue price - $80.00

INFLUENCE OF WATER SPRAYS AND HEAT LOSS ON NEGATIVELY AND POSITIVELY STRETCHED CURVED PREMIXED FLAMES

Jiann-Chang Lin
Department of General Education, Transworld Institute of Technology, Touliu City, Yunlin County 640, Taiwan, R.O.C.

Shuhn-Shyurng Hou
Department of Mechanical Engineering, Kung Shan Institute of Technology, Tainan, Taiwan, Republic of China

ABSTRACT

In the present study, the structure of normal (or inverted) Bunsen flame tips under the influence of a monodisperse dilute water spray and external heat loss is investigated using large activation energy asymptotics. We consider two flame structures: normal and inverted Bunsen flames, and two spray modes: completely and partially prevaporized burnings. In this way, a complete parametric study of flame tip intensification or extinction (opening) can be conducted. Five parameters are used in the analysis. Three are the droplet size, amount of liquid-water loading (which indicates internal heat loss for inert spray), and the external heat loss. The other two are the stretch and Lewis number (Le). Stretch is negative for a normal Bunsen flame but positive for an inverted Bunsen flame. Stretch strengthens (or weakens) the burning intensity of the Le > 1 (or Le < 1) normal Bunsen flame but decreases (or increases) the burning intensity of the Le > 1 (or Le < 1) inverted Bunsen flame. Burning intensity of the flame tip weakens when the water spray has a smaller droplet size or a larger amount of liquid loading, or when the curved flame experiences a larger amount external heat loss. For a rich methane-air normal Bunsen flame with Le > 1 or a lean methane-air inverted Bunsen flame with Le < 1, closed-tip solutions are obtained. Conversely, stretch weakens the burning intensity of a rich methane-air inverted Bunsen flame with Le > 1, or a lean methane-air normal Bunsen flame with Le < 1, eventually leading to tip opening. Moreover, the opening becomes wider when the droplet size decreases, liquid loading increases, or external heat loss enlarges.