Counterflow diffusion flame
For safety reasons diffusion flames – where fuel and air are introduced separately into the combustion chamber and form an ignitable mixture by diffusion – are widely used in practical combustion systems. Additionally, measurements in diffusion flames provide valuable data with respect to optimizing combustion processes and experimental data for validation of flame modelling.
We perform optical diagnostic measurements within diffusion flames at atmospheric pressure where fuel and air impinge on each other in a counterflow geometry. Aa laminar flame can be stabilized in the stagnation region of both gas flows in an optically accessible combustion chamber of rectangular cross section. Using laser-spectroscopic techniques and conventional emission spectroscopy spatially resolved temperatures concentration values of minority species as well as spectrally resolved chemiluminescence within these flames can be determined.
The burner consists of a 1 m long air flow channel with a converging nozzle on which the combustion chamber is attached (internal squared cross section of 10 × 10 cm2). Four fans at the bottom of the channel deliver an air flow with a top hat velocity profile in the optically accessible combustion chamber where it hits the fuel flow emanating through a 1 cm wide sinter plate as part of a cylindrically shaped burner head. The water cooled burner head can be translated in vertical direction using a motor driven translation stage. Fuel (CH4, H2) and an additional coflow (N2) are metered with mass flow controllers.
Temperatures are determined by fitting simulated to measured NO laser-induced fluorescence (LIF) excitation spectra of NO, which is added to the air flow in small amounts (100–500 ppm). Fluorescence is detected with intensified CCD cameras. Formaldehyde and OH radicals are also detected using LIF, while spatially resolved chemiluminescence spectra are obtained with a spectrograph/CCD camera setup.
Dr. T. Dreier, Thomas Dreier, Tel: +49 (0)203 379 8072, IVG