DESIGN PARAMETERS OF A VORTICAL(SWIRLER), RADIAL AND AXIAL FLAME HOLDER Heraldo da Silva Couto NTC/CCT - Universidade de Fortaleza,– Av. Washington Soares, 1321, B. Edson Queiroz – 60811-905 - Fortaleza - Ce couto@unifor.br João Batista Furlan Duarte NTC/CCT - Universidade de Fortaleza,– Av. Washington Soares, 1321, B. Edson Queiroz – 60811-905 - Fortaleza - Ce furlan@unifor.br Lutero Carmo de Lima NTC/CCT - Universidade de Fortaleza,– Av. Washington Soares, 1321, B. Edson Queiroz – 60811-905 - Fortaleza - Ce luterocl@unifor.br Antônio Roberto Lins de Macêdo NTC/CCT - Universidade de Fortaleza,– Av. Washington Soares, 1321, B. Edson Queiroz – 60811-905 - Fortaleza - Ce boblmacedo@edu.unifor.br Abstract. This work deals with the main parameters of two types of aerodynamic flame holders, presently employed in industrial plants: swirler of axial and radial types. In the aerodynamics of combustion one of the fundamental problems is the holding and anchoring of flame. The increase in the efficiency of combustion points that the flames must be turbulent and the more the turbulence the better the efficiency since the turbulence promotes a better mixture of oxydizer and fuel. However on the other hand the increase at the level of turbulence of a flame might cause its lifting due to the excessive velocity and eventually its blow out of the burner causing consequently its extintion. In order to avoid this kind of undesirable phenomenon it is a common practice to use bluff bodies as flame holding devices which usually are conical or circular disk and frequently have holes and slots in its surface permitting by this way the direct flow of air for preventing overheating and the formation of scars on the front surface. By this way, in order to avoid overheating and surface scars and also due to the fact that the admission of air close to the base of the flame contributes to the increase in the efficiency of the combustion. All this aspects led to the development of aerodynamic flame anchoring device of vortical type (swirlers). These devices are usually employed in the design of modern burners. Keywords. Combustion, Swirler, Flame holding, bluff body. 1. Introduction There are basically two kinds of aerodynamic flame holders: axial and radial swirlers. The axial one usually employs inclined vanes located at the extremity of the hub, attached to the fuel ejector and may have length smaller or equal to the distance between the ejector and the wall of the air out let duct. The one of radial type normally has fixed and inclined blades and a moveable part responsible for the continued narrowing of the air entrance area that in its turn is responsible for the flame anchoring. When constructed with the purpose of finding experimental data it has moveable blades that make it easy the variation of the swirl number, parameter very important for the performance of the device. The flame holder of the radial type frequently uses the decreasing of the air admitting area as a way of varying the swirl number. Such a device uses a set of fixed and inclined blades and a set of moveable blades which are responsible for the variation of the area of air entrance, varying by this way its velocity and blockage coefficient and at the same time maintaining the air mass flow, or in other words, varying the swirl number through the increase in the Reynolds number. Swirlers nowadays have a great number of applications such as flame holders, in the modern industries plants, in turbines and in every burner in which flame anchoring is necessary. They are designed and constructed in substitution to the bluff bodies and screens devices since the employment of such swirlers does not result in great pressure losses as the imposed by the bluff bodies and neither suffer the imposition of elevated temperatures, and at same time show excellent performance to the stabilization of flame and proportionate fast transfer of energy (Syred, 1972 and Beér and Chigier, 1974). The utilization of swirlers in the industry is the result of three decades of intense research in the field of swirling flows since the very first work of Chigier and Béer (1964) who introduced the concept of number of swirl and created the base for future works (Lilley, 1977). More recently, Weber and Dugué (1992) proposed the so called effective swirl number for the well mixtured flames for taking into account the effect of combustion in turbulent fluxes. They also have shown how the inner recirculation zone can be correlated to the swirl number. In the article of Weber and Dugué it was proposed an easy control of the level of swirl by the division of the entrance air in lines of tangential and axial fluxes, varying then the ratio of the tangential flow with the entrance of air. A swirler with moveable blades was introduced and used for the same objective, that is, to perform a control of level of swirl (Weber and Dugué, 1992, Wall, 1987, Heap et all, 1973). Both the axial and radial swirler are broadly used in the industry for the control of flame (anchoring and size of flame). Here in this article it is described the performance of such systems, varying the angle of the blades in the axial type swirler and varying the entrance area of air in the radial type swirler.