Challenges to laser-based imaging techniques in gas turbine combustor systems for aerospace applications

Increasingly severe constraints on emissions, noiseand fuel efficiency must be met by the nextgeneration of commercial aircraft powerplants. AtNASA Lewis Research Center (LeRC) a cooperativeresearch effort with industry is underway to designand test combustors that will meet theserequirements. To accomplish these tasks, it isnecessary to gain both a detailed understanding ofthe combustion processes and a precise knowledge ofcombustor and combustor subcomponent performanceat close to actual conditions. To that end,researchers at LeRC are engaged in a comprehensivediagnostic investigation of high pressure reactingflowfieids that duplicate conditions expected withinthe actual engine combustors. Unique, opticallyaccessible flametubes and sector rig combustors,designed especially for these tests, afford theopportunity to probe these flowfields with the mostadvanced, laser-based optical diagnostic techniques.However, these same techniques, tested and provenon comparatively simple bench-top gaseous flameburners, encounter numerous restrictions andchallenges when applied in these facilities. Theseinclude high pressures and temperatures, large flowrates, liquid fuels, remote testing, and carbon orother material deposits on combustor windows.Results are shown that document the success andversatility of these nonintrusive optical diagnosticsdespite the challenges to their implementation inrealistic systems.IntroductionThe next generation of aircraft powerplants willoperate at conditions resulting in much higher overall* Senior Research Engineer, Aeropropulsion Systems Dept.Senior Research Engineer. Optical Instr.Tech. BranchResearch Engineer. Optical Instrumentation Tech.. BranchResearch Engineer, Combustion Technology BranchCopyright © 1998. The American Institute of Aeronautics andAstronautics Inc. All