EXPERIMENTAL INVESTIGATION OF THE FLOW INSIDE A WATER MODEL OF A GAS-TURBINE COMBUSTOR .2. HIGHER-ORDER MOMENTS AND FLOW VISUALIZATION

The measurements of mean and turbulent quantities presented in Part 1 showed a strong influence of the primary jet system and evidence of th e existence of bimodal distributions of the azimuthal velocity was als o noted. Due to the importance of this Exhibition Road, phenomenon for combustor operation, a further study was carried out and measurements of higher order moments (skewness and flatness) were taken, followed by spectral analysis and high-speed flow visualization These showed th at, under the present flow conditions, the time behavior of the six ra dially impinging primary jets is similar to that encountered in single jet instability studies, with a dominant frequency corresponding to a Strouhal number of 0.27, when correlated with the primary jet charact eristics. The unsteady nature of the flow around the primary jets and the high turbulence anisotropies observed suggest that accurate calcul ations of gas turbine combustor flows are likely to be impossible with models based on time-averaged version of the governing equations, eve n with closure at the second moment level.