ENHANCEMENT OF BLOWOUT LIMIT BY THE INTERACTION OF MULTIPLE NONPREMIXED JET FLAMES

Abstract

The effects of interaction between nonpremixed flames on the enlargement of blowout velocity are experimentally investigated. Nozzle separation distances, fuel flow rates, number of nozzles, and array shapes are considered to make flame interaction. Four types of nozzle arrays, which are arranged in diamond, cross, matrix, and circle shapes, are used. Interacting flame has two distinct characteristics compared with a single jet flame—higher blowout velocity and constant turbulent liftoff heights. There are optimum nozzle separation distances for the augmentation of blowout limit. Blowout velocities for the small-diameter multiple jets are higher than a single large-diameter nozzle with the same area. The flames are not extinguished even in choking conditions at the nozzle exit when there is not a nozzle at the center of optimally spaced matrix- or circle-shaped configurations. Flow visualization shows that the enhanced stability in the case without a center nozzle is due to recirculation within the fuel jet arrays.

Keywords:

• flame interaction
• liftoff
• nonpremixed flam

This work was supported by the Korea Science and Engineering Foundation through the Combustion Engineering Research Center.