Multicolour pyrometers were used to measure the cylinder and cycle specific cylinder out soot emissions in a direct injection passenger car diesel engine. The small size of the sensors made it possible to carry out the measurements in a production engine. Contamination of the pyrometer windows was prevented by maintaining a window temperature of 550 Degree celsius. The light intensities were recorded at three wavelengths rather than just two, as is typically done, which allowed pyrometer calibrations to be verified. The end values summed over all measured cylinders were found to correlate well with the FSN measured in the exhaust stream, indicating that end is a suitable measure for the cylinder out soot emissions. Using this measure, the cylinder out soot emissions from one cylinder during steady state operation were found to fluctuate by 25 %, predominantly due to fluctuations in the oxidation process. The soot emissions from two similar cylinders had a mean variation of 41 %, over all steady state operating points. Neither the cylinder, nor the cycle specific variations can easily be captured using conventional soot instrumentation. In addition to providing the cycle resolved soot concentration measurements, the three colour pyrometers provided the in-cylinder soot concentration history. By considering the maximum and final in cylinder soot concentrations, it is possible to characterize the soot formation and oxidation processes. In agreement with other works, the maximum soot concentration was found to be proportional to the engine load (injected fuel quantity), while the dependence of soot oxidation on the engine operating point was more complex. In particular, soot oxidation was found to be influenced by the engine speed, injection pressure, oxygen availability and in cylinder temperature, whereby each of these parameters themselves are strongly influenced by the engine operating point. A quantitative investigation of these effects requires detailed knowledge of the injection parameters, which were not available for this study.
Correlation and analysis of in-cylinder and engine-out soot emission measurements from a multi-cylinder diesel engine
2008
15 Seiten, 15 Bilder, 2 Tabellen, 7 Quellen
Aufsatz (Konferenz)
Datenträger
Englisch
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