Probe Effects in Gas Turbine Combustor Emission Measurements

Four geometrically distinct, stainless steel probes are used to study the concentrations of CO, HC, NO, and NO_x at several different radial and two different axial positions within a simplified gas turbine combustor. The probes are all water cooled but do not employ an aerodynamic quench. They are designed to assess the effect of tip shape, tip to body proximity (for right angle configurations), and probe entry point into the flowfield on measured pollutant concentrations. Though probe entry point and tip to body proximity are shown to imperceptibly affect the pollutant concentrations, probe tip geometry has a marked impact on the measured pollutant levels. Specifically, the tapered-tip probe yields depressed CO and HC, and elevated NO concentrations compared to the other three blunt-tipped probes. Regarding reproducibility, the pollutant concentrations measured with one of the blunt-tipped probes in this study are compared to pollutant levels measured with the same probe three years ago (Tuttle et al., 1976).