The effects of flame radiation on flame-tube metal temperatures

Abstract

Details are given of experiments to determine flame radiation, Red Brightness temperatures and metal temperatures in the primary zones of three aircraft combustion chambers; flame temperatures and emissivities are derived. These factors were studied using two pipe chambers (3.75 in. and 5.625 in. diam) over a range of pressures from 4–30 atm and a nominal air-inlet temperature and air/fuel ratio of 800°K and 60/1, respectively. The indications were that flame radiation, temperature, and emissivity increased with pressure, whereas metal temperatures tended to reach a maximum at about 20 atm. Predicted wall temperatures indicated a similar trend, attributed to the convective cooling that increased at a greater rate than flame radiation at the higher pressures. The effects of vitiation and subsequent oxygen replenishment were examined using a tubo-annular combustion chamber operating at a pressure of 4 atm, inlet temperature 777°K, and a nominal air/fuel ratio of 63/1. Primary-zone flame radiation, flame temperature, and metal temperature increased with the oxygen content of the inlet gas. No similar trend was noted with flame emissivity.