Effect of Quarl on N2- and CO2-Diluted Methane Oxy-Flames Stabilized by an Axial-Plus-Tangential Swirler

Abstract

Stabilization of nearly stoichiometric CO2- and N2-diluted premixed methane/oxygen swirling flames is investigated in an atmospheric test rig equipped with an axial-plus-tangential swirler exhausting in a cylindrical injection tube eventually ended by a diverging quarl. The investigated flames are stabilized aerodynamically away from the solid elements of the combustor without the help of any central bluff body in the injector. The flowrates through the axial and tangential slits of the swirler can be adjusted separately. Effects of swirl and quarl angle on the flowfield and flame shape are analyzed. Laser tomography on small oil particles reveals that fuel, oxidizer and diluents injected in separated channels are well mixed at the injector outlet. Velocimetry measurements and flame images show that the axial-plus-tangential swirler allows a flexible control of the flame leading edge position with respect to the injector outlet. For a fixed injector geometry with a given quarl angle and swirl number, it is found that N2- and CO2-diluted flames feature the same topology if the injected combustible mixtures feature the same adiabatic flame temperature, while they may feature different bulk injection velocities and laminar burning velocities. The operability range of well stabilized CO2-diluted flames is however reduced.

Effects of a Diverging Cup on Swirl Number, Flow Pattern and Topology of Premixed Flames

“…. This setup was also used to compare the stabilization of CO 2 -and N 2 -diluted oxy-methane flames and examine rules for switching between air-to oxy-combustion operating mode with the same injector [17,23]. Only the main elements of the test rig are briefly described below.…”

“…Heat losses to the chamber walls are also known to alter the structure of the reacting flow [11,12]. A central bluff-body [2,13,14] and a diffuser [2,4,13,[15][16][17] constitute other widely used elements to enhance the stabilization of swirling flames. In high power systems, it is however more suitable to operate without any central insert to reduce the thermal stress on the solid components of the injector.…”

Stabilization Mechanisms of Swirling Premixed Flames With an Axial-Plus-Tangential Swirler

“…Mixing of these streams was studied in [25]. Tests were made with small light oil particles (2 micrometers) injected in the different streams and the homogeneity of the flow seeding at the burner outlet was analyzed by laser tomography in axial and transverse planes.…”

Desenvolvimento De Um Queimador Para O Estudo De Chamas Turbulentas Pré-Misturadas Com Swirl

“…Esse fenômeno foi estudado por Galley et al [11], Nogenmyr et al [12], Giuberti et al [13], Khalil et al [14] e Jourdaine et al [15]. Na verdade, esses estudos indicam que uma forte interação da chama com as paredes leva a um pré-aquecimento da mistura fresca e à recirculação de produtos quentes da combustão.…”