Optical Measurements of the Reacting Two-Phase Flow in a Realistic Gas Turbine Combustor at Elevated Pressures

Abstract

A rectangular sector of a realistic axially staged gas turbine combustor of Rolls-Royce Deutschland was operated at elevated pressures. Optical measurements of the reacting two-phase flow were performed using Phase Doppler Anemometry (PDA) and two planar light sheet techniques, laser induced fluorescence (LIF) and Mie scattering. The constraints, e.g. limited optical access, combustor with several injectors in line and strong soot luminescence, affecting the optical set-up for PDA measurements are discussed. The PDA measurements were conducted at a combustor inlet pressure of p = 6 bar. With an estimated error in the size measurement of up to  = 10 % caused by the change of the refractive index, it was still possible to obtain quantitative results of the mean diameter. The error of the liquid volume concentration is higher and difficult to assess. Images of the planar Mie scattering are used as a consistency check of the PDA data. The light sheet techniques deliver supplementary information. Imaging of kerosene LIF of an isothermal spray at atmospheric pressure was used to calculate the liquid volume concentration. A comparison with results from PDA measurements revealed a good agreement. Under reacting conditions kerosene LIF was limited to qualitative information on the distribution of liquid and vaporized fuel mainly because of the temperature dependency of the fluorescence quantum yield. At higher pressure the applicability of LIF was limited by the absorption of the UV laser light in the dense spray. Imaging of the planar Mie scattered light was possible at combustor inlet pressures up to p = 20 bar, giving qualitative information on the distribution of the liquid fuel.