Laser-induced incandescence for soot measurements in an aero-engine combustor at pressures up to 20 bar

Abstract

Soot is one of the most discussed pollutants in ground and air traffic. Moreover, its effect as source of intense radiation is significant as soon as locally rich mixtures occur, especially at in-creased pressure. This motivates the need to better understand soot formation and oxidation in turbulent, pressurised environment in order to prevent its emission as much as possible. A detailed understanding of the underlying processes can be gained when correlating sophisticated CFD modelling with well-defined validation experiments at technical conditions. LII has proven to be a valuable diagnostic to quantitatively monitor soot distributions inside combustion processes. However, application to pressurized gas turbine combustors has rarely been published for several reasons. Here, we present trends for soot distributions inside at technical combustor operated between 4 and 20 bar at realistic geometries and flow rates. Considerations on tackling typical challenges at technical conditions are presented. The resulting time-averaged soot distributions serve to determine positions of soot formation and oxidation as well as quantification of soot concentrations under the highly challenging technical conditions of the study. In general, soot concentrations were found to be relatively low. In combination with data derived independently from the present work, involving the application of other diagnostics (OH and kerosene distributions as well as temperatures), a good validation data set is available to support soot modellers.