INVESTIGATING THE MIXTURE QUALITY IN MULTI-INJECTOR BURNER SYSTEMS, PART I: EXPERIMENTAL SETUP

A new approach to calculate the mixture statistics in multiinjector burner systems from a single injector data base is presented in the paper. In such systems, the mixture quality is highly sensitive to the flow rate 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, O-POD is suggested using results from RANS-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 multi-injector burner system (MIB). To characterise the mixture quality, the mixing probability mass function (PMF) at the injector exit is measured by means of 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 behaviour 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 3 modes.