The axial and swirl velocity and turbulence profiles downstream of a small-scale combustor were measured using a Laser Doppler Velocimeter. The effects of combustor geometry (nozzle swirl and liner mixing and dilution holes), operating conditions (mass flow and pressure) and combustion were independently examined. For the combustion tests, the combustor exit temperature profiles were also measured with an insertion thermocouple.
The normalized velocity profiles showed no effect of mass flow, pressure or overall velocity on the combustor exit profiles. For the low-swirl fuel nozzle, levels of turbulence were fairly constant without or with combustion. However, with the high-swirl fuel nozzle, the level of swirl decreased as the firing temperature increased (to conserve angular momentum). The effect of swirl reduction could also be seen in the turbulence levels which also decreased. This showed that the mean swirl was generating much of the turbulence. It was also found from testing various combustor geometries that the dilution jets significantly disrupted and thereby reduced the level of swirl exiting from the combustor.