1. Laura Kranendonk and Scott T. Sanders
Wavelength-Agile H2O Absorption Spectrometer for Thermometry of General Combustion Gases
Laura Kranendonk and Scott T. Sanders
Spectral Results:
Introduction:
Engine Measurements:
Absorption spectroscopy can quantitatively measure temperature, mole fraction, and/or pressure
HCCI is a combustion process governed by temperature, mole fraction, and pressure
Experimental Setup:
Combustion (red) and motoring (grey) results. Pressure (top panel) was measured with a pressure transducer. Water mole fraction (middle) and temperature (bottom) were calculated using absorption spectra.
Plot A shows a measured absorption spectrum (red) taken 12o before top dead center, and the corresponding spectrum (black) from the HITEMP database.
Plot B shows differences in line widths (due to pressure) of the measured (red) and database (black).
Plot C shows the smoothed, differentiated spectra. These are the plots used to calculate temperature.
Precision:
Calculating Temperature:
Conclusions:
Absorption spectra measured from -90 to +60 CAD (0.25 CAD resolved)
Temperature Measurements:
Better than 1% precision with 50 averages
± 2.3% accuracy to ~1000 K with 30 averages
Single shot measurements show potential but need improvement
Pros:
Quantitative measurements
Non-invasive measurements (optical measurement, no tracer)
Extremely simple set-up
Can measure wide range of conditions (entire cycle if air is humid)
Cons:
Line of sight average
Requires heavy averaging
Potential future applications include spatial tomography, multi-species concentration measurements
Single shot (grey) shows, at best, ±3% precision, and as poor as 50% (low XH2O and low P).
50 averaged spectra (red) are better than ± 1% precision throughout engine cycle.
Accuracy:
Using a well defined shock tube, the absolute accuracy was measured to be ±2.2% up to 1000K (with 30 averages).