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Numerous investigations have been conducted to determine the effect of fuel composition and molecular structure on particulate emissions using exhaust gas analysis, but relatively few measurements have been obtained in-cylinder or under conditions where fuel effects can be isolated from other variables. Recent work has shown that the amount of air entrained upstream of the lift-off length is critical to soot formation and therefore must be controlled when making relative comparisons of soot formed from various fuels. In this work, dimethoxymethane was used as the base fuel to produce a non-sooting flame with relatively constant lift-off length in a constant volume combustion vessel at 1000 K, and a density of 16.6 kg/m3. A second fuel was then mixed into the dimethoxymethane (DMM) to determine a point at which soot formation begins.

The two-color method for measuring temperature and optical thickness of soot (KL) has become a standard diagnostic tool for the evaluation of engine designs and technologies relative to soot formation and flame temperature. Implementation of the two-color technique typically requires two cameras or a set of half-pass mirrors and optical narrow band-pass filters. In this paper, a technique for collecting and interpreting two-color images with a single calibrated camera without image splitting and filtering hardware is demonstrated and discussed. This method uses a relatively inexpensive commercial, 10-bit, RGB color, CCD camera capable of 16 μs exposure times. The CCD has published spectral response curves in the visible range, but a method for obtaining the spectral response for the optical system using a monochromator is discussed.