A standard addition LIF method for measuring nitrogen oxide concentration was applied to a quartz glass model of double-pipe type radiant tube burner. The measurement technique was developed for establishing a quick practical diagnostics to find the optimal conditions of the widely used burners. Nitrogen oxide of 90ppm was doped to the natural gas of fuel injector and the surrounding air. Mole fractions were determined comparing the LIF intensities of the doped and non-doped cases. Gas temperatures were also obtained using the two-line method. Horizontal distributions of temperature and NO mole fractions were obtained at the several different distances from the fuel injector. The temperature and NO emission level were higher in comparison with the usual diffusion burner because of the preheating effects of the burned gas in the outer annular space to the inlet gas mixture in the inner tube.
