The purpose of this research was to study the pressure drop profiles and regeneration temperature characteristics of Silicon Carbide (SiC) filters with and without a copper-based additive in the fuel, and also to compare their performance with two cordierite traps designated as EX-47 and EX-80. The collection of the particulate matter inside the trap imposes a backpressure on the engine which requires a periodic oxidation or regeneration of the particulate matter. The presence of copper additive in the fuel reduces the particulate ignition temperature from approximately 500 to 375°C.
Two SiC systems were tested during this research. The first system consisted of one 14 L SiC trap, while the second system, the dual trap system (DTS), consisted of two 12 L SiC traps mounted in parallel. The test matrix included two types of regeneration tests, controlled and uncontrolled and three levels of Cu fuel additive (0, 30, and 60 ppm). A controlled regeneration test was performed by ramping the engine to full load at rated speed and running the engine at this condition until the trap pressure drop stabilized. An uncontrolled regeneration test was performed by ramping the engine to full load at rated speed and cutting the engine to idle condition (no load) at the initiation of regeneration. Trap peak temperatures around 500°C were observed for both the controlled and uncontrolled regenerations of the SiC traps. Controlled regeneration tests yielded a better regeneration efficiency (45%) over the uncontrolled regeneration (13%), with no additive in the fuel. The higher efficiency of the controlled regeneration was mainly due to the higher exhaust temperature (∼500°C) at the prevailing engine operating conditions (maximum load at rated speed). The presence of Cu additive in the fuel had a significant effect on the regeneration of particulate matter. Overall, regeneration efficiencies of about 56% and 87% were observed for the DTS, during uncontrolled regeneration tests, using 60 ppm Cu additive in the fuel.
The SiC traps passed all the controlled and uncontrolled regeneration tests without any failure. Maximum temperatures around 1150°C were reported inside the cordierite traps prior to their failure, during the uncontrolled regeneration tests when more than 110 grams of particulate matter were present. The total regeneration times for the SiC traps were twice as long as compared to the cordierite traps. The DTS consisting of SiC traps had a regeneration time of 107 seconds for a particulate loading of 10.9 g/m2 whereas, the cordierite EX-80 trap had a regeneration time of only 57 seconds for a particulate loading of 11.1 g/m2.
Trap clean pressure drop data were used to estimate the trap material (SiC) permeability using Darcy's law. Particulate layer permeabilities for the SiC were estimated by applying the modified Darcy's law to the trap pressure drop loading curve data. It was observed that the SiC had five times higher material permeability (7.54 × 10-13 m2) compared to the cordierite traps (1.54 × 10-13 and 1.45 × 10-13 m2 for the EX-47 and EX-80 traps, respectively). Estimated average particulate layer permeability of the SiC DTS (2.95 × 10-14 m2 for the region 3) and the cordierite traps (2.71 × 10-14 and 3.09 × 10-14 m2 for the region 3 of EX-47 and EX-80 traps, respectively) were similar in magnitude.