2013 1(12)

INFLUENCE OF ACOUSTIC OSCILLATIONS ON THE DIFFUSION COMBUSTION OF PROPANE IN THE MICRO-JET

Litvinenko Yu.A.¹, Kozlov V.V.¹, Grek G.R.¹, Katasonov M.M.¹, Shmakov A.G.², Korobeynichev O.P.²

¹ Khristianovich Institute Of Theoretical And Applied Mechanics SB RAS, Novosibirsk, Russia
² Voevodsky Institute of Chemical Kinetics and Combustion SB RAS, Novosibirsk, Russia

Introduction

Organization of the mixing process is the important factor determinant of the nature of the diffusion flame combustion. A typical example of diffusion combustion is the ignition the fuel gas jet flowing from a long tube with small diameter into the atmosphere. At low velocity the flow corresponds to a laminar regime and the flame is characterized by a high even torch. At high velocity separation of flame from the jet nozzle takes place and turbulent regime of combustion is realized. The turbulent regime of combustion is of considerable interest due to widely practice application and include many fundamental mechanisms which are responsible for the development and stabilization of the flame.

Purpose

The purpose of this work is the experimental study of the influence of the initial conditions at the nozzle exit of micro-jet and the influence of acoustic oscillations on the structure and characteristics of laminar and turbulent round micro-jet with and without combustion.

Method

In the current experiments development of micro-jet instability under the acoustic oscillations and convective forces is investigated. Two experimental facility for realization of the round and plane micro-jet, which have a possibility of the flow stability control in the velocity range from 0,5m/s to 30m/s, were used. By means of a loudspeaker positioned in close surroundings of the jet outlet the acoustic oscillations were generated and the maximum power was 90dB. The laser-smoke visualization and hot-wire measurements were used for the flow investigation.

Results

It was found that the diffusion combustion of propane in a round laminar micro - jet with a "top-hat" and parabolic velocity profiles at the nozzle exit is characterized by attached to the outlet nozzle flame without any oscillations. For the case of a turbulent round micro-jet the diffusion combustion goes with flame separation from the nozzle. The combustion process occurs only in the jet shear layer, with shape a hollow cylinder, because it has a maximum perturbation level and consequently more intensive gas and air mixing. The acoustic oscillations have a clear influence on the flame at diffusion combustion of the round jet with its flattening and separation on two jets. These phenomena associated with development of oscillation process in the jet. Without acoustic forcing the combustion process is returned to the original conditions of combustion.

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