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Analysis of gas-particle nozzle flow is carried out with attention to the effect of dust particles on the vibrational relaxation phenomena and consequent effects on the gain of a gasdynamic laser. The phase nonequilibrium between the gas mixture and the particles during the nozzle expansion process is taken into account simultaneously. The governing equations of the two-phase nozzle flow have been transformed into similar form, and general correlating parameters have been obtained. It is shown from the present analysis that the particles present in the mixture affect the optimum gain obtainable from a gasdynamic laser adversely, and the effect depends on the size and loading of the particles in the mixture.

The governing equations for gas flows in 16-^m CO2-N2-H2 gasdynamic lasers using conical or hyperbolic nozzles have been presented in universal form so that for a given gas composition the solutions depend on a single parameter that combines all other parameters of the laser system. The solutions of these equations are used to compute the optimum values of small signal optical gain, and the corresponding optimum values of the area ratio, the reservoir temperature T'0 and the binary scaling parameter p'0L', which is a product of reservoir pressure p'0 and nozzle shape factor L', for a wide range of gas mixture compositions. The results are presented in graph form. An optimum value of 2.06% cm'1 gain has been calculated for the gas composition of C02:N2:H2 = 15:65:20.

A theoretical analysis of a 16-\mu m $CO_2-N_2-H_2$ downstream-mixing gasdynamic laser, where a cold $CO_2$, $H_2$ stream is mixed with a vibrationally excited $N_2$ stream, tangentially downstream of the nozzle exit, is presented. The flowfield is analyzed numerically using 2-dimensional, unsteady, laminar, and viscous flow modeling, including the appropriate finite-rate vibrational kinetic equations. The effect of variation of different flowfield parameters on 16-mm small-signal gain is studied, and results are discussed in detail. The anal. shows that the presence of $H_2$ gas is detrimental to small-signal gain. The velocity ratio 1:1 between the $CO_2$, $H_2$, and $N_2$ mixing streams is the best choice rendering local small-signal gain as high as 21.75 $m^-1$ and corresponding av. small-signal gain of 16.7 $m^-1$ for $N_2$ reservoir temp. of 2000 K. These high values of small-signal gain clearly underscore the high potential which a downstream-mixing scheme has over the conventional methods for a 16-\mu m laser source.

Reynolds number, viscosity and atom concentration in hypervelocity nozzles measured using stagnation point heat transfer

In an earlier publication,1 we reported the theoretical gain optimiation studies of a 16-\mu m $CO_2-N_2-H_2$ gasdynamic laser (GDL) in which it was showed that the optimum value of a 2.06% $cm^{-1}$ gain could be obtained with conical or hyperbolic nozzles. In this Note, we report the results of optimization studies with a 16\mu m $CO_2-N_2-H_2$ GDL using twodimensional wedge nozzles. We have found that the optimum value of the gain that can be achieved is as high as 12.7% $cm^{-1}$ on the P(15) line of the $(02^00)$\rightarrow $(01^10)$ transition of $CO_2$ for a gas mixture composition of $CO_2:N_2:H_2$ =30:50:20%. The corresponding optimum values for the reservoir pressure and area ratio are computed as functions of the resevoir temperature and presented graphically. Results are presented for a range of gas mixture compositions.

Modified model for vibration-dissociation relaxation coupling phenomena in nonequilibrium high temperature gas flow, discussing parameter U variation with kinetic temperature