Investigation of supersonic isobaric submerged turbulent jets

Abstract

Turbulent supersonic submerged air jets have been investigated on the Mach number interval Ma = 1.5–3.4 and on the interval of ratios of the total enthalpies in the external medium and the jet i0 = 0.01 – 1. Oxyhydrogen jets with oxidizer ratios α = 0.3–5 flowing from a nozzle at Mach numbers Ma = 1 and 2.4 have also been investigated. When α < 1 the excess hydrogen in the jet burns up on mixing with the air. Special attention has been paid to obtaining experimental data free of the influence on the level of turbulence in the jet of the initial turbulence in the nozzle forechamber, shock waves occurring in the nozzle or in the jet at the nozzle exit, and the external acoustic field. The jet can be divided into two parts: an initial part and a main part. The initial part extends from the nozzle exit from the section x′, in which the dimensionless velocity on the jet axis um = ux/ud = 0.75. Here, ux is the velocity on the jet axis at distance x from the nozzle exit, and ua is the nozzle exit velocity. The main part of the jet extends downstream from the section x′. For the dimensionless length of the initial part xm′ = x′/da, where da is the diameter of the nozzle outlet section, empirical dependences on Ma and i0 are obtained. It is shown, that in the main part of the jet the parameters on the flow axis — the dimensionless velocity and temperature — vary in inverse proportion to the distance, measured in units of length x′, and do not depend on the flow characteristics which determine the length of the initial part of the jet. The angles of expansion of the viscous turbulent mixing layer in the submerged heated or burning jet increase with decrease in i0 and Ma and are practically independent of the afterburning process.