Optical sensors based on III-nitride photodetectors for flame sensing and combustion monitoring.
Combustion control requires visible photodetectors to sense the CH* CL emission at 430 nm that combined with a visible-blind UV photodetector allows us to obtain the OH*/CH* ratio. UV-visible P-InGaN/GaN multiple quantum well-N photodiodes with 15-18 mm2 areas were fabricated to conduct OH* (308 nm) and CH* CL detection without external filters. Bandpass detectors at 230-390 nm and 360-450 nm presented linear responses over five decades and rejection ratios >10(3) at 430 and 308 nm, respectively. A full optical sensor system was built and detectors operated at 120 degrees C in a combustion chamber, showing linear responses within the dynamic range, maximum signal-to-noise ratios of 103 and response times of <1 s. An exponential association dependence between the optical OH*/CH* CL signals and the gas/air ratios was found.
Pau
Jose Luis
JL
Instituto de Sistemas Optoelectrónicos y Microtecnología, Departamento Ingeniería, Escuela Técnica superior de Ingenieros de Telecomunicación, Universidsad Politécnica de Madrid, Madrid, Spain. jlpau@die.upm.es
Anduaga
Javier
J
Rivera
Carlos
C
Navarro
Alvaro
A
Alava
Isabel
I
Redondo
Marcos
M
Muñoz
Elías
E