In-Line IR Particle Analyzer for Gas Turbine Engines

OPTRA proposes the development of a compact, ruggedized in-line IR particle analyzer for in situ, open-path, particulate matter quantification for gas turbine engines. We offer a novel approach to the in-line particle sizer, employing an IR laser diodeand IR optics that allow for 200x reduction in overall volume relative to systems traditionally operating in the visible. We have incorporated an inexpensive uncooled microbolometer focal plane array in place of the standard annular silicon detectorarray. This in-line system records the far-field diffraction pattern for all particles present in the laser beam at the focal plane of the imaging optics; concentrations of particle sizes are deduced from the distribution of the diffraction pattern overthe detector focal plane array. In addition, we employ a spectroscopic absorption technique by tuning the IR laser on and off the 3 micron H-C stretch resonance band characteristic of essentially all hydrocarbons. The change in the diffraction pattern inthe far-field provides discrimination between condensable hydrocarbons forming PM and all other scattering particulates. This system holds commercial potential in areas of jet engine PM measurement, vehicle emissions measurement, and industrial andprocess monitoring.