Sensor for In-cylinder Gas Temperature Based on H2O Absorption Spectroscopy and Applied an HCCI Engine Chun Lan, Scott T. Sanders wavelength region of interest Overcome challenge by: • Absorption spectroscopy technology • Utra-low emissions and Particulate Matter • High thermal efficiency Objectives: Most challenge of HCCI: •Design the sensor system • Combustion control HCCI (HCCI is a combustion process governed by chemical kinetics) •Measure the H2O mole fraction and temperature immediately Suppercontinua wavelength 0.20 power [relative to peak power at 1064 nm] Merits of Homogeneous Charge Compression Ignition (HCCI) : A single color (1064 nm) enters the supercontinuum generation fiber, but a broad spectrum emerges By carefully choosing the fiber length and dispersion, we can select the fiber providing the highest power in our 1330 nm – 1380 nm wavelength range of interest (50 m Corning® LEAF fiber) Sensor system applied to HCCI engine 100 m Metrocor 0.15 50 m LEAF (best choice) 0.10 100 m LEAF 150 m LEAF 0.05 Detector 50/50 0.00 1100 1200 1300 1400 1500 1600 (around) Io 1700 wavelength [nm] (through) Io I HCCI engine Oscilloscope Detector Absorption Spectroscopy Theory Fiber Bragg Gratings Experiment Results Temperature [K] with crank angle FBG = fiber Bragg grating each Fiber Bragg grating is designed to reflect one color of light (e.g., 1342 ± 0.05 nm) the fiber Bragg gratings are based on modulation of the refractive index of the fiber along the direction of light propagation: the resonant wavelength is reflected back towards the source Beer’s Law: T I exp( k L) Io k v = f ( ,T,P) Water [%] fraction with crank angle color burst as a function of wavelength: all-fiber system: no purge gas required, no alignment screws need entire system currently fits on a 0.3m x 0.9m x 0.2m-high space, can be reduced in size if needed wavelengths chosen to align with absorption features of H2O: power [nW] FBG Wavelength choice 0.00020 0.00015 0.00010 0.00005 spectral absorption coefficient [cm-1] Sensor system design 0.00000 P=20 bar, T=1500K, H2O mole fraction = 0.05 0.015 0.010 Future work 0.005 • Improve the sensor system 0.000 1330 • provides gas temperature every 16.6 ms (= 0.3 CAD at 3000 rpm) • laser operation and fiber coupling to engine are both userfriendly • gas temperature can be viewed directly in the laboratory; there is potential to provide a real-time voltage proportional to gas temperature • system runs using LabVIEW software • H2O mole fraction information is also provided • the sensor works over the entire range of HCCI combustion conditions 1340 1350 1360 wavelength [nm] 1370 1380 • Develop to provide a real-time voltage proportional to gas temperature University of Wisconsin Engine Research Center • Test in different engines