Diffusion flame

About: Diffusion flame is a research topic. Over the lifetime, 9266 publications have been published within this topic receiving 233522 citations.

Method and apparatus for characterizing a combustion flame

Abstract: Characteristics of a flame within a turbine or burner are determined based upon ultraviolet, visible, and infrared measurements of the flame. The measurements include a measurement of the amplitute of frequency bands that are indicative of an efficient combustion process, such as those that increase when the flame temperature increases. The measurements also include of the amplitude of frequency bands that are indicative of an inefficient combustion process, such as those that do not vary, increase a relatively small amount, or decrease when the flame temperature increases. The temperature of the flame may therefore be determined accurately, to facilitate efficient operation of the turbine or burner while minimizing polluting emissions. A fiber structure, suitable for remote location of sensors and processing equipment passes energy for several spectra by providing a hollow core that passes infrared energy, in combination with a core of visible-transmissive material that passes visible or ultraviolet energy. Contaminants in the turbine or burner are detected, and a degree of contamination measured, by detection of energy levels for particular wavelengths associated with a respective contaminant.

Direct ignition and S-curve transition by in situ nano-second pulsed discharge in methane/oxygen/helium counterflow flame

Abstract: A well-defined plasma assisted combustion system with novel in situ discharge in a counterflow diffusion flame was developed to study the direct coupling kinetic effect of non-equilibrium plasma on flame ignition and extinction. A uniform discharge was generated between the burner nozzles by placing porous metal electrodes at the nozzle exits. The ignition and extinction characteristics of CH4/O2/He diffusion flames were investigated by measuring excited OH∗ and OH PLIF, at constant strain rates and O2 mole fraction on the oxidizer side while changing the fuel mole fraction. It was found that ignition and extinction occurred with an abrupt change of OH∗ emission intensity at lower O2 mole fraction, indicating the existence of the conventional ignition-extinction S-curve. However, at a higher O2 mole fraction, it was found that the in situ discharge could significantly modify the characteristics of ignition and extinction and create a new monotonic and fully stretched ignition S-curve. The transition from the conventional S-curves to a new stretched ignition curve indicated clearly that the active species generated by the plasma could change the chemical kinetic pathways of fuel oxidation at low temperature, thus resulting in the transition of flame stabilization mechanism from extinction-controlled to ignition-controlled regimes. The temperature and OH radical distributions were measured experimentally by the Rayleigh scattering technique and PLIF technique, respectively, and were compared with modeling. The results showed that the local maximum temperature in the reaction zone, where the ignition occurred, could be as low as 900 K. The chemical kinetic model for the plasma–flame interaction has been developed based on the assumption of constant electric field strength in the bulk plasma region. The reaction pathways analysis further revealed that atomic oxygen generated by the discharge was critical to controlling the radical production and promoting the chain branching effect in the reaction zone for low temperature ignition enhancement.