Features of heat exchange processes when starting a ship turbine engine

Abstract

The article is devoted to the study of the starting mode of a gas turbine engine, which relates to transient or unsteady modes, in which the temperature of the working fluid increases in a short period of time and, as a result, the whole situation associated with heat transfer changes. There is practically no information in the literature about experimental studies of highly dynamic non-stationary aperiodic processes. The experiment was carried out on an open gas-dynamic circuit with electric arc heating of the flowing gas flow. A thin-walled cylindrical pipe was used as a physical model. During the research, the following were measured: gas flow rate, total pressure in the flow, gas temperature at the entrance to the channel, wall temperatures along the length of the experimental channel, static pressures and tangential friction stresses as a function of time and longitudinal coordinates. All measuring instruments have been certified or preliminary studies have been carried out on them to determine their inertia. Experimental studies carried out with a sharp increase in the temperature of the working fluid showed that the simultaneously formed effects of thermal and hydrodynamic unsteadiness, affecting the flow, accelerate it. The acceleration of the flow, caused by a sharper increase in the temperature of the working fluid with high values of the temporary derivatives of temperature and flow velocity, leads to a 2 — 3-fold decrease in heat transfer coefficients. A highly dynamic process in which a temperature pressure is formed, which determines the boundaries of the emerging phenomenon of laminarization of a turbulent boundary layer, was recorded for the first time with a heat flow directed from the gas flow to the channel wall.