Abstract

With increasing global power demands, there is a growing need for the clean and efficient use of fossil fuel resources. Gas turbine engines are a commonly used means for generating power; from the propulsion of aircraft to electricity on municipal grids. Measuring the temperature within a turbine combustor or at a turbine inlet could provide numerous advantages related to engine control, durability, efficiency, and emissions and yet this relatively straightforward task has eluded turbine engine manufacturers, primarily because of the high temperatures and pressures, harsh environment, and limited access. Optical emissions measurements are of particular interest for this task as they only require one optical access point and can be accomplished using thin optical fibers that can be fit within existing turbine geometries.This work extends an optical emission method known as the integrated spectral band ratio (ISBR) method beyond previously obtained temperature measurements on atmospheric combustion products to temperature measurements in a pressurized turbine combustor. The ISBR correlates modeled integrated spectral band ratios of spectral water emission to gas temperature, comparable to two-color pyrometry. When the integrated spectral bands are measured, the temperature can be inferred from this correlation. This technique has previously been successfully applied at atmospheric conditions over pathlengths as short at 25 cm but in this case has been applied at pressures of 0.7 and 1.2 MPa and a pathlength of 15 cm.Optical measurements were taken in a pressurized combustion test rig at Solar Turbines Inc. in San Diego California. Two temperature sweeps at high load and low load (pressures of 1.2 and 0.7 MPa, respectively) were measured. The average ISBR optical temperature measurements were approximately 200 K higher than the downstream thermocouple measurements. Thermocouple radiative losses were predicted to yield a bias of -175 K. The slope of a change in optical temperature to change in thermocouple temperature was 1.03 over the 87 K variation seen. Repeatability of the optical measurement at a given operating condition was on the order of Â± 15 K and the absolute uncertainty of a single measurement was estimated to be Â± 70 K over a temperature range of 1350 to 1500 K. The spectra, measured with a Fourier Transform Infrared Spectrometer (FTIR), was in very good agreement with spectral emission models produced using a derivative of the HITEMP database. All of the measured peak locations matched the model, and the measured data matched changes in spectral wings with changing pressure. A linear correlation was also found between raw optical signal and thermocouple measurements.

Degree

College and Department

Ira A. Fulton College of Engineering and Technology; Mechanical Engineering

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