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