Comparison of the efficiencies of spike and combined annular nozzles

Abstract

The comparative efficiency of two layouts of self-adjusted annular nozzles operating over a wide flight altitude range is studied. One of the layouts is presented by the so-called spike nozzles (plane or antisymmetric, with a central body) having the property of self-adjustment when operating in different regions of the flight trajectory. The possibility of locating an annular plug nozzle or a conventional round nozzle in the base region of an axisymmetric spike is considered as a possible means for reducing its base losses. Two layouts of annular self-adjusted nozzles (in combination with internal nozzles or without them) are optimized for the mean thrust in operation in the launch and altitude flight regimes using the “classical” and “genetic” approaches. It is shown that optimal annular spike nozzles in combination with internal nozzles do not provide considerable advantages in the thrust compared with purely spiked optimal configurations. At the same time, an effective optimization of spike nozzles with account for the contribution made by the base thrust can ensure a comparatively low level of the losses.