Effect of Secondary Air Inlet Ports Arrangement on N.G. Flame Combustion Characteristics

The aim of the present work is to investigate theoretically the secondary air ports arrangement on the NG flame
combustion characteristics. The normal secondary air was introduced into the combustion chamber through its first half
length. Nine different port arrangements are discussed. There are three levels (vertical heights) groups. They are four, eigh t
and sixteen levels so that first level of each group starts at 100 mm that equals 10% of the combustor len gth. Each group
level has four, eight and sixteen ports. Therefore the number of total ports per level is varied from 16 (four levels with fo ur
ports) to 256 (16 levels with sixteen ports) ports. A theoretical model was used to study the different arrangements. The
model consists of a vertical combustor with an air swirler, primary air line, and secondary air and fuel lines. The air swirler
number and the primary air to fuel rat io are kept constant for all running conditions and they are 0.87 and 50, respec tively.
A three dimensional model was used to simulate the turbulent reacting flow using computational fluid dynamics package
(Fluent 6.3). For validation, the comparison between the measured and calculated axial temperature distribution was made
and shows a good agreement. A remarkable effect of using the secondary air on temperature maps was found. For any value
of SPAR > 0.0, the flame became wider in diameter and longer in length. The flame length increased by about 58, 100 and
125 % when the SPAR increased from 0 to 90% for the ports arrangement of 4x4, 8x8 and 16x16 level groups, respectively