Application of the DSMC Method for Design of a Coaxial Microthruster Nozzle
The Direct Simulation Monte Carlo (DSMC) method is used to numerically simulate and design a micronozzle with improved performance. Thrust calculations using the DSMC method demonstrate that the coaxial micronozzles can achieve milli-Newton thrust levels with specific impulses on the order of 45 s using argon in a cold gas expansion. Improved micronozzle designs of coaxial microthrusters are also proposed. Coaxial micronozzles utilizing center-body geometries to exploit pressure thrust show about 140% increase in specific impulse at low Reynolds numbers compared to a traditional converging nozzle.
Calculation of three-dimensional inviscid flowfields in propulsive nozzles with centerbodies
A numerical procedure for calculating three-dimensional inviscid subsonic/transonic/supersonic (i.e., trisonic) flowfields in propulsive nozzles with centerbodies is presented. The procedure can be used to investigate advanced propulsive nozzle concepts for improved engine-airframe integration. The interior point unit process is based on the MacCormack explicit predictor-corrector method, and the boundary point unit processes are based on a variation of the method of characteristics due to Kentzer. The overall numerical algorithm is an explicit second-order accurate time-marching procedure. Steady flow solutions are obtained as the asymptotic solution in time. Results are presented for several two-dimensional and three-dimensional inviscid nozzle flowfields. Solutions obtained by the present method agree well with solutions obtained by method of characteristics algorithms and experimental data.
Thrust Nozzles for Supersonic Transport Aircraft
Supersonic transports will require jet-engine thrust nozzles that are highly efficient from take-off to supersonic cruise in order to minimize the direct operating costs. Variable-area ejectors, plug nozzles, and modifications of these basic types have been tested extensively during the past several years. Performance trends for these nozzles are presented with the emphasis on external flow effects. A new ejector which utilizes aerodynamically actuated doors to admit external air into the ejector shroud is discussed.