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Filter regeneration systems require an accurate and reliable measurement of diesel particulate (soot) accumulation. This paper describes recent advances in the development of a device that uses radio-frequency (RF) technology to measure filter soot loads. A one-point calibration method is presented that provides a means to significantly reduce filter system development costs. Results from both on-vehicle and laboratory testing programs are discussed. The on-line monitoring of catalytic and energy-addition regeneration processes is also described.

Control of the diesel particulate filter regeneration process requires a reliable and accurate on-line measurement of the amount of carbon particulates or soot accumulated in the filter. Both RF- and back-pressure-based measurement methods have been developed for this purpose. Under lowload conditions, the collection of condensed organic material can adversely affect the accuracy of back-pressure-based measurements. Experiments described here illustrate that the RF-based measurement method gives a direct measurement of filter soot load, which, is independent of exhaust gas flow conditions and condensed organic material.

A new method of measuring diesel-particulate accumulation has been developed that uses electromagnetic energy to interrogate a ceramic filter and to give a real-time measurement of the trapped-soot level. The measurement method is inherently independent of engine-exhaust-gas volumetric flow rates and is relatively insensitive to changes in filter temperature. This paper presents laboratory data, derived from testing of full-scale, wall-flow filter systems, demostrating the viability of the measurement method. The implementation of the measurement method in on-vehicle regeneration system is also discussed.