Wavelength-Agile Laser Sensors for Measuring Gas Properties in Engines

Internal combustion engines present a harsh environment for optical sensors, owing to challenges such as high pressures, multiple phases, and window fouling. Fortunately, a new class of “wavelength-agile” light sources that rapidly scan through a broad wavelength range facilitates accurate absorption spectroscopy in engines. Gas temperature and species concentrations can be monitored with fast time response (down to ∼ 1 μs). Here, two strategies for generating wavelength-agile light are introduced. We present in-cylinder results obtained by applying one of the strategies to monitor gas temperature and H₂O concentration during compression in a single-cylinder optical engine operating in HCCI mode. Such data will be useful for improving the understanding of engine phenomena and offer the potential for active engine control.