Simultaneous CH Research Articles

Simultaneous CH planar laser-induced fluorescence and particle imaging velocimetry in turbulent nonpremixed flames

=18600). Here, PLIF images reveal a CH layer of thickness typically <1 mm from flame base to tip. Furthermore, in these permanently blue flames, we observe instantaneous flamefront strain rates – derived from the PIV data – in excess of ±104 s-1 without flame extinction.

SnO 2 multilayered gas sensor with high selectivity prepared by an aerosol electrostatic process

A SnO 2 multilayered gas sensor was prepared by using electrostatic agglomeration and electrostatic adhesion of aerosol particles, in order to develop a new system which enables simultaneous CH 4 and CO sensing. The multilayer consists of an initial subsensor layer for CH 4 detection and a second subsensor layer for CO detection coated on the initial layer. The initial subsensor uses a membrane prepared by electrostatic adhesion of SnO 2 whisker particles. The interior SnO 2 whisker subsensor layer has a lot of pores, which consist of several sizes distributed from 100 μm to 100 nm in diameter. The second subsensor comprises a membrane prepared by electrostatic adhesion of SnO 2-Pd composite particles. Electrostatic agglomeration enables composite particle preparation where Pd particles agglomerate onto a SnO 2 particle. The exterior subsensor layer ensures a dendrite microstructure of the SnO 2-Pd composite particles with a three-dimensional network and a uniform Pd distribution on the surface of SnO 2 core particles over the whole film. The SnO 2 multilayered sensor reveals a high selectivity to CH 4 and CO gases, which means high sensitivity to CH 4 and no response to CO of the interior subsensor, and, in turn, no response to CH 4 and high sensitivity to CO of the exterior subsensor.

Near-field instantaneous flame and fuel concentration structures

Simultaneous two-dimensional CH 4 and CH imaging data are obtained and analyzed in the near field of nonpremixed jet and bluff-body stabilized flames. CH is used as an indicator of the reaction zone. Both flames are found to have similar CH/CH 4 structures located in the vicinity of the 0.1 CH 4 concentration contour. In both cases, the flame zone consists of a narrow envelope that follows the fuel structure movements. Large-scale fuel structure protrusions are shown to produce gaps in the reaction zone. The data, combined with mixing time estimates for eddies smaller than the experimental resolution, support the concept that the fuel and air are premixed at the flame initiation point. Fuel concentrations in the reaction zone are substantial and range approximately within the flammability limits of the fuel at ambient temperature. The data are consistent with a dissipative eddy model, where reaction is limited to small isolated premixed structures within the flow, reaction occurs over a region several times thicker than the laminar flame thickness and the reaction is bounded by a fuel concentration range similar to the flammability range of the fuel.