PIV Measurements of Combustor Turbulence Fields

Abstract

An experimental study has been conducted on a full-scale, three-sector, isothermal model of a gas turbine combustor. PIV has been used as the main instrumentation technique and this has been validated against LDA and hot-wire velocity measurements of the same geometry. These data combine to provide high quality boundary condition and validation data for CFD predictions. Substantial care has been taken in assuring the quality of the PIV data. In high turbulence intensity flow fields, low pass spatial filtering can artificially reduce the Reynolds stresses calculated from the PIV measured velocities. The level of this filtering depends upon the ratio of the integral lengthscales in the flow field to the size of the measurement volume of the PIV interrogation cell. Within the highly turbulent flow field of a combustor there exist a very wide range of turbulent length scales. Consideration should therefore be given to any measurements taken in a combustor, hot or cold, to take account of this sub-grid filtering effect. A method is described to overcome this problem and it is demonstrated to be successful by comparing with LDA and PIV data (at increased magnification) that does not suffer this problem. Sparse LDA and HWA data for the combustor is thus complemented by more dense planar PIV data to allow a more complete mapping of the velocity field. This has allowed better understanding of the processes occurring in the combustor such as the jet impingement process and the fuel injector swirler flow interaction with the primary jets. In addition detailed information on turbulence statistics, integral lengthscales, spatial correlation and energetic structure identification is available.