Effect of reactant-surface stretching on chemical laser performance

It is noted that the laser cavity reactant mixing rate in high-pressure DF chemical lasers is increased with the aid of gas trip jets. In comparison with the laminar mixing value, the trip jets can improve the laser efficiency by about 100 percent. It is postulated that the trip jets give rise to a secondary flow that increases the mixing rate by stretching the contact surface between the reactant streams. A strain rate can be used to describe the surface stretching rate. The performance characteristics of trip-nozzle lasers are explained qualitatively by developing flow and laser models that can define the effect of strain on the reactant burning rate and laser efficiency. Strain affects the performance of the laser through a single parameter gamma, equal to twice the characteristic constant linear strain rate divided by the characteristic collisional deactivation rate for the lasing specie. Strain levels where gamma = 2-3 are seen as consistent with trip nozzle data. The model also reveals that the efficiency of low-pressure laminar mixing (gamma = 0) lasers could be increased significantly for strain rate levels where gamma is 3-5.