In this program, a research gas turbine combustor is used to study the influence of individual variables (in particular, fuel spray characteristics) on the local level of emissions species concentrations within the primary zone flame. The unique combustor is designed to provide realistic conditions and to allow for independent control of drop size, fuel-air ratio, residence time, air inlet temperature, pressure and reference velocity. This is one of the few combustors in which the residence time has been measured and controlled. The simple flow pattern, with no large scale recirculation, allows for unambiguous interpretation of results