Unsteady Flames in Gaseous and Spray Turbulent Combustion

Time: Tuesday, February 11, 2014 - 2:00pm - 3:00pm
Type: Seminar Series
Presenter: Yuval Dagan-Department of Aerospace Engineering, Technion, Israel Instiute of Technology, Haifa, Israel
Room/Office:
Location:
Becton Seminar Room 227
15 Prospect Street
New Haven, CT 06510
United States

Yale School of Engineering & Applied Science

Department of Mechanical Engineering

and Materials Science

 

Unsteady Flames in

Gaseous and Spray Turbulent Combustion

Yuval Dagan

Department of Aerospace Engineering

Technion, Israel Institute of Technology, Haifa, Israel

Abstract

Flame instabilities play an important role in combustion. Unsteady flame characteristics in turbulent gaseous and liquid fuel combustion were studied using Large Eddy Simulation (LES). The study focused on the phenomenon of intermittent flame lift-off which was observed both experimentally and computationally.

In the first stage, gaseous fuel combustion was investigated. The mean statistics of the computed flow field were found to be in very good agreement with experimental data. Detailed time-dependent, long duration flame propagation and three-dimensional flame structures were analyzed, utilizing quantification of flame inhomogeneity and dynamics. Two new criteria for the characterization of flame structure were developed in the current study, allowing for the quantification of the overall spatial inhomogeneity in the combustor. Using these criteria, it was possible to characterize the influence of swirl on flame propagation for each swirling case. A significant correlation was found between dominant circumferential and radial fluctuations of the flame.

The research was then extended by introducing a liquid fuel spray into the computation, using a stochastic spray modeling approach. Unsteady turbulent spray-flame propagation was computationally investigated in the current study. Spray-flame propagation was characterized by two repetitive developmental stages, in which the jet spray is either radially diverted or blocked by the recirculation zone. Local statistics of fuel droplet dispersion were investigated by a new approach, revealing low frequencies of the repetitive flame stages, while retaining the turbulent characteristics.