Abstract

Sensors for rapid, in-situ measurements of hydrocarbon combustion intermediates and products are required for applications ranging from advanced combustor testing to aeropropulsion engine health monitoring. Recent developments in room temperature diode laser technology and sensitive detection strategies now permit development of a new class of combustion sensors for simultaneous measurements of the speciation of the combustion gases as well as gasdynamic performance parameters of interest, including temperature, velocity, and mass flux.1,2 This work focusses on absorption measurements of CO, CO₂, H₂O, and OH in combustion gases near 1.57 µm. Experiments are conducted in low-pressure, room-temperature absorption cells and combustion gases of a flat-flame burner with hydrogen and methane fuels. The laser source is a New Focus Model 6262 external cavity diode laser, generating over 1 mW of output power across an 80 nm tuning range centered at 1.55 µm. High sensitivity detection is achieved using a dual-beam, Balanced Ratiometric Detector (BRD)¹ which cancels common-mode laser amplitude noise in the signal channel (passing through the absorbing medium) and reference channel (passing through a non-absorbing gas or fiber).

© 1996 Optical Society of America