Structure of Underexpanded Jets from Square Nozzles

摘要

The structure of underexpanded jets issuing from nozzles with square outlets is investigated numerically and experimentally. This type of nozzle is of interest for its use in the clustered combustors of linear aerospike engines. The numerical results indicate that the first shock cell is composed of two types of shock waves; intercepting shock waves corresponding to the oblique shock wave observed in underexpanded jets from two-dimensional planar nozzles, and recompression shock waves that appear downstream of the overexpanded regions. The overexpanded regions are formed by the interaction of expansion fans generated at neighboring nozzle edges. It is shown that the jet expands almost two-dimensionally on the symmetry planes, whereas shock waves suppress expansion on the diagonal planes, resulting in a cross shaped jet cross section.