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Silicon Carbide (SiC) has been shown to have a high melting/decomposition temperature, good mechanical strength, and high thermal conductivity, which make it well suited for use as a material for diesel particulate filters. The high thermal conductivity of the material tends to reduce the temperature gradients and maximum temperature which arise during regeneration. The purpose of this paper is to experimentally investigate the thermal loading which arise under regenerations of varying severity. An experimental study is presented, in which regenerations of varying severity are conducted for uncoated SiC and Cordierite filters. The severity is varied through changes in the particle loading on the filters and by changing the flow conditions during the regeneration process itself. Temperature distributions throughout the filters are measured during these regeneration.

Recent studies have shown that SiC provides substantial advantages for use as the material for wall flow diesel particulate filters. In addition to very advantageous thermal properties, it has been shown that SiC based filter material has higher permeability than Cordierite. This paper presents a comparison of the basic flow characteristics of SiC based and Cordierite based wall flow filter material, expressed in terms of parameters which are basic materials properties that are independent of filter geometry. In addition, the flow characteristics of the particulate matter collected on the filter during engine operation are presented. The results show that the advantageous flow characteristics observed with the basic filter material are retained for loaded filters, up to very high loadings.

A naturally aspirated, direct injection diesel engine was modified in order to be run on dimethyl ether (DME), with a conventional pump-line-nozzle system. The effects of various modifications to engine timing and the injection system as well as EGR were experimentally determined. Compared to the original diesel engine, the NOx emissions were reduced by over 70% through the use of suitable timing, lowered injector opening pressure and EGR. Particulate emissions were very low, and represent over a 90% reduction as compared to the original diesel version. The original pump-line-nozzle injection system was found to be not well suited to DME operation, CO and HC emissions were substantially higher due to secondary injections, caused by high pressure oscillations and residual pressure with the DME.

The paper presents a 2-dimensional model for the calculation of the regeneration process in a wall flow diesel particulate filter. The model includes heat transfer by conduction and convection, a model for particle combustion based on diffusive burning of individual particles, and flow through the channels and across the filter walls. It was found that only the pressure drop across the walls need be considered for normal regeneration conditions. Comparisons between model predictions and experimental results for spatial dependent temperature time histories, and integrated degree of regeneration are used to validate the model. The validations were carried out for a series of severe regenerations, where there are large changes in flow and temperature throughout the process. Relative magnitudes of energy flows due to combustion, convection, and conduction are presented, as well as parametric studies of the effects of temperature, oxygen concentration and soot loading.