Full Coverage Film Cooling for Combustor Transition Sections

Abstract

Concern for the environment has led to world-wide emissions legislation. Under such legislation, land based gas turbines in particular are required to meet stringent emissions levels of NOx and CO. In response, Rolls-Royce has designed and developed a retro fit dry low emission (DLE) module for the industrial RB211 aero-derivative engine. The DLE combustion system achieves low emissions through the use of staged premixed lean burn combustion. The paper reports detailed measurements of heat transfer coefficient and film cooling effectiveness for full coverage film cooling systems suitable for cooling the transition section between the combustor and the nozzle guide vanes. The experiments were performed at large scale using the transient liquid crystal method of measuring heat transfer. The film cooling data are unusual since the film injection angle is 20°. Extensive arrays with hole spacings of 16d and 10d have been investigated with air and with CO2 as the coolant. The latter tests achieved engine representative film to free-stream density ratios. The paper discusses in detail the experimental strategy and compares the data to results from the literature.