Investigating the Mixture Quality in Multi-Injector Burner Systems--Part I: Experimental Setup.

A new approach to calculate the mixture statistics in multi-injector burner (MIB) systems from a single injector database is presented in the paper. In such systems, the mixture quality is highly sensitive to the flowrate and the skewness of the inflow velocity profile. To determine the mixture fraction statistics from these two parameters for a particular injector in a multi-injector configuration, output-based proper orthogonal decomposition (O-POD) is suggested using results from Reynolds-averaged Navier Stokes (RANS)-computational fluid dynamics (CFD) as the observable. The O-POD mixing database is determined experimentally from two setups: First, the mixture quality in a single injector at ideal inflow conditions is studied. Then the same injector type is investigated in a generic MIB system. To characterize the mixture quality, the mixing probability mass function (PMF) at the injector exit is measured by means of laser-induced fluorescence (LIF) and high speed imaging. The data obtained for both the single injector under ideal inflow and the MIB are presented. These studies of the mixture behavior reveal that an asymmetric inflow velocity profile leads to a significant increase of unmixedness, which is seen as a negative skewness of the mixing PMFs. This effect becomes stronger at higher momentum flux density ratios due to the higher penetration depth of the fuel jets. The application of the O-POD to the database shows that the PMF can be accurately modeled with only three modes. [ABSTRACT FROM AUTHOR]