Diesel Spray Ignition Detection and Spatial/Temporal Correction 2012-01-1239

Methods for detection of the spatial position and timing of diesel ignition with improved accuracy are demonstrated in an optically accessible constant-volume chamber at engine-like pressure and temperature conditions. High-speed pressure measurement using multiple transducers, followed by triangulation correction for the speed of the pressure wave, permits identification of the autoignition spatial location and timing. Simultaneously, high-speed Schlieren and broadband chemiluminescence imaging provides validation of the pressure-based triangulation technique. The combined optical imaging and corrected pressure measurement techniques offer improved understanding of diesel ignition phenomenon. Schlieren imaging shows the onset of low-temperature (first-stage) heat release prior to high-temperature (second-stage) ignition. High-temperature ignition is marked by more rapid pressure rise and broadband chemiluminescence. The use of multiple pressure sensors also permits charge-amplifier gain optimization tailored to characterize spray behavior rather than the global combustion chamber, thereby providing significantly improved pressure-rise measurement and derived heat-release rate for the fuel spray. Based on pressure data only, this study provides ignition measurement accuracy with temporal resolution below 20 μs, and with spatial resolution below 5 mm, thereby fulfilling the need for better model validation data.