An Experimental Investigation on Multiflame Burning Structure in Conserved Systems

Abstract

The characteristics of multiflame burnings are investigated through modification of the boundary conditions in conserved systems. The experiments measure the maximum temperature and the thickness of the high-temperature zone in counterflows. To provide a conserved system, the total volume flow rate of mixtures through each burner and the total volume flow rates of methane, oxygen, and nitrogen flowing out of both burners are kept constant The possible burning structures are observed to be single-flame, double-flame and triple-flame burnings in which the individual flame can be burned independently. or burned beyond the fiammability limit by the support of another stronger flame. Results show that an optimum burning identified by the highest values of the maximum temperature and the thickness of the high-temperature zone is achieved under the condition of a triple-flame burning which has a closer approach to the equilibrium combusiton state. However, the enrichment of nitrogen in the flow will produce a double-flame burning which has a highest value of maximum temperature but a smaller high-temperature zone. The local minima of the maximum temperature and the thickness of the high-temperature zone are obtained under the critical condition of the lean or rich premixed flame being ready to propagate away from the diffusion flame. Finally, a complete process of flame transition is addressed.