A Turbulent Bounbary Layer Effect of the De-Laval Nozzle on the Combustion Chamber Pressure

De-Laval 노즐의 난류 경계층 유동이 연소실 압력에 미치는 영향

A Compuressible turbulent boundary layer effect of the high temperature, accelerating gas flow through the De-Laval nozzle on combustion chamber pressure is numerically investigated. For this purpose, the coupled momentum integral equation and energy integral equation are solved by the Bartz method, and 1/7 power law for both the turbulent boundary layer velocity distribution and temperature distribution is assumed. As far as the boundary layer thicknesses are concerned, we can obtain reasonable solutions even if relatively simple approximations to the skin friction coefficient and stanton number have been used. The effects of nozzle wall cooling and/or mass flow rate on the boundary layer thicknesses and the combustion chamber pressure are studied. Specifically, negative displacement thickness is appeared as the ratio of the nozzle wall temperature to the stagnation temperature of the free stream decreases, and, consequently, it makes the combustion chamber pressure low.