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This paper proposes a method of determining residual gas fraction (RGF) by sampling the CO2 concentration in the exhaust manifold of a single cylinder HSDI diesel engine. During a skip-fire event, the CO2 concentration in the exhaust gas for the last firing cycle and the subsequent motoring cycle were measured using a fast-response emissions analyzer. The ratios of these two values are shown to be indicative of the RGF. To simulate the increase in exhaust pressure found with EGR or aftertreatment systems, the exhaust back pressure was elevated using an exhaust throttle. The intake pressure was held constant over a range of engine speed and load conditions. The results demonstrate that the RGF increases linearly with increasing exhaust back pressures for all engine operating conditions.

Particle Image Velocimetry (PIV) has been used to investigate flame propagation and unburned gas velocity fields within an optically accessed cylindrical combustion chamber. The flame propagation process and the flame structure of the quiescent and swirling flow inside the chamber is presented. An ionisation probe technique and also a nonintrusive laser refraction technique were used to determine the local flame speed in conjunction with the PIV measurement. The laminar burning velocity of quiescent propane-air mixtures initially at atmospheric condition for different equivalence ratios ranging from 0.7 - 1.4 were measured. These were determined directly from the difference between the local flame propagation speed and the unburned gas velocity immediately ahead of the flame front. Close agreement with other measurements and predicted results was found.

A generalized model describing oxidation in a porous substance is developed and applied to the thermal regeneration of both monolithic and fibrous diesel particulate traps. With typical engine and trap data the regeneration process is analysed using the model. A parametric study demonstrates how the exhaust gas oxygen concentration, flow rate and initial trap particulate loading affect the regeneration time and peak trap temperatures. The model is shown to be in reasonable agreement with published experimental results.