Burning rate extinction behavior

With the small mean particle sizes (>— 15and less), it was found for underoxidized propellants that pressure increase would cause the burning rate to increase, reach a plateau, decrease, and then possibly extinguish at some critical pressure. Where extinction did not occur, the burning rate would continue to decrease after the plateau, reach a minimum and then again increase monotonically. Further reduction of oxidizer content accentuated the tendency toward plateau behavior. The... 

Low pressure burning behavior gives information concerning the detailed structure of the flame zone. It is known that the fuel-oxidant reaction zone becomes very weak at very low pressures. Thus, the nature of any remaining exothermic reactions occurring at or near the propellant surface is more obvious in the over-all propellant burning behavior. Burning rates and extinction behavior have been measured for a number of propellant systems and are reported below. These results are then interpreted in terms of the theoretical predictions made previously. 

In addition to the low-strain limit, which can be used to determine laminar burning velocities, the opposed-flow configuration can also be used to determine high-strain-rate extinction limits. As the inlet velocities increase, the flame is pushed closer to the symmetry plane and the maximum flame temperature decreases. There is a flow rate beyond which a flame can no longer be sustained (i.e., it is extinguished). Figure 17.11 illustrates extinction behavior for premixed methane-air flames of varying stoichiometries. 

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