Thermal regeneration of diesel particulate in metallic fibrous filter

Abstract

Experiments were performed to study the aerodynamic thermal regeneration of a metallic fibrous particulate filter, which was used to reduce particulate emissions from diesel vehicles. Heated air diluted with nitrogen was used to initiate the regeneration process. Temperatures at 11 locations inside the filter were measured with embedded thermocouples which were equally spaced in the axial direction. Based on the temperature data, the instantaneous heat release of the filter was derived and analyzed. The peak regeneration temperature was found to occur at the region near the filter exit, and fibers in this region could melt when the temperature was sufficiently high. The normal regeneration temperature was around 800°C to 1000°C but local temperature could be as high as 1300°C. Thermal regeneration of the filter was found to depend on several factors, including, oxygen concentration in the heated air, initial particulate loading, packing density, thickness of the filtering element, and flow rate of the heated air. It was found that for regeneration to occur, the temperature of the heated air should exceed 500°C, the filtering element should have a minimum thickness of 50mm and a minimum initial particulate loading of 2 gram. Regeneration, and hence, heat release, was found to start earlier at higher oxygen concentration in the heated air, higher heated air flow rate, lower packing density and higher initial particulate loading. Regeneration temperature was higher at higher oxygen concentration in the heated air, lower heated air flow-rate, higher packing density and higher initial particulate loading. The results had also been compared with those of Kim et al. [12] and Park et al. [13] obtained on ceramic filter and those simulated by Garner and Dent [7].