This paper presents an experimental study on the dynamics of a ducted, conical, laminar premixed flame subjected to low amplitude acoustic excitation from upstream. The heat release response of the flame to velocity disturbances is investigated through measurement of the so called ‘flame transfer function’ for a wide range of forcing frequencies. The results are compared with those predicted by...

Experiments have been carried out with extremely lean, quiescent propane-air mixtures to examine the behavior of irregular flame propagation and to examine the lean limits of flame propagation in a tube under microgravity. The microgravity technique achieved in a freely falling chamber is employed because the realizations of symmetrical flame propagations in a tube are possible. Experimental co...

In most microgravity studies of flame spread, the flame is assumed to be two-dimensional, and twodimensional models are used to aid data interpretation. However, since limited space is available in microgravity facilities, the flames are limited in size. It is important, therefore, to investigate the significance of three-dimensional effects. Three-dimensional and two-dimensional simulations of...

Extinction limits and flame bifurcation of lean premixed dimethyl ether-air flames are investigated numerically using the counterflow flame with a reduced chemistry. Emphasis is paid to the combined effect of radiation and flame stretch on the extinction and flammability limits. A method based on the reaction front is presented to predict the Markstein length. The predicted positive Markstein l...

The flame born in the deep interior of a white dwarf that becomes a Type Ia supernova is subject to several instabilities, the combination of which determines the observational characteristics of the explosion. We briefly review these instabilities and discuss the length scales for which each dominates. Their cumulative effect is to accelerate the speed of the flame beyond its laminar value, bu...

Nonlinear model equation for weakly turbulent premixed flames with realistic fuel expansion is proposed. The equation describes both the hydrodynamic flame instability and flame response to external turbulence in the regime of flamelets. On the basis of the proposed equation the velocity of turbulent flames is investigated for the cases of both weak and relatively strong turbulence. Comparison ...

Combustion instabilities in gas turbine engines often give rise to acoustic resonances. These resonances occur as manifestations of different acoustic modes, of which a single or multiple modes may be present. In this work, the acoustic behavior of a model gas turbine combustor, developed at DLR Stuttgart by Meier, was investigated using both syn(thetic) gas and standard hydrocarbon fuels. Syng...

One of the well-known properties of turbulent, premixed flames is that their speed of propagtion is correlated to the intensity of the turbulence they encounter. A simple consequence is that these types of flames are inherently unstable. Given a source of turbulence, if the flame is propagating faster than the mean flow, it will drift upstream and encounter increased turbulent intensities that ...

Flame propagation along a 1-D array or through a 2D-lattice of fuel droplets has long been suggested to schematize spray-flames spreading in a two-phase premixture. The present numerical work considers the fresh aerosol as a system of individual alkane droplets initially located at the nodes of a face-centred 2D-lattice, surrounded by a variable mixture of alkane and air, in which the droplets ...