Fiber-coupled, UV–SWIR hyperspectral imaging sensor for combustion diagnostics

Abstract

A fiber-coupled, hyperspectral imaging sensor (HSIS) ranging from ultraviolet (UV) to short-wavelength-infrared (SWIR) wavelengths is developed for remote detection of planar [two-dimensional (2D)], spectrally resolved flame emission. The key component of the sensor is a dimension-reduction 2D-to-1D (one-dimensional) fiber-optic array that contains 1024 fibers and features high-UV optical transmission (>30% transmission at 310-340 nm, >90% at 340-2000 nm), wide operational wavelengths (300-2400 nm), and a compact and robust design (full length <5 cm). The flame-emission signals are transmitted to the remote HSIS through a 3-m-long, UV-grade, imaging fiber bundle that consists of 30,000 single-mode fibers. The design of the 2D-to-1D fiber array, the fiber-characterization process, and the sensor development are discussed in detail. 2D spectrally resolved measurements of CH^*, OH^*, and C2* distribution are made in premixed laminar flames. Improved chemiluminescence-based fuel/air ratio measurements using spectrally resolved detection are demonstrated. The results of the current study indicate that implementation of fiber-coupled HSIS is feasible in practical gas-turbine-engine test facilities with limited optical access.