摘要:
A lean NOX trap is a diesel exhaust aftertreatment system is selectively denitrated in a manner that addresses unreliability of NOX sensor data. According to one concept, data from a NOX is ignored or given decreased weight in a period immediately following a denitration. According to another concept, denitration is made contingent on both a first and a second criteria being met. The first criteria relates to the amount of NOX stored in the LNT or remaining NOX storage capacity of the LNT. The second criteria relates to the current performance of the exhaust treatment system, or a portion thereof, as determined from one or more measurements of NOX concentration in the exhaust. This reduces premature denitrations and associated unnecessary fuel expenditures resulting from inaccurate NOX concentration data and transient events
摘要:
Desulfation methods for an exhaust treatment system having a fuel reformer configured upstream of a LNT. Reductant is injected upstream of the fuel reformer. The reductant reacts within the reformer to generate heat, but the system is configured for some reductant to breakthrough and react in the LNT to generate further heat. This configuration allows the LNT to operate at temperatures higher the than first device and facilitates independent control of the LNT and first device temperatures.
摘要:
In an exhaust aftertreatment system, two LNTs having differing compositions are configured in series downstream from an inline fuel reformer. The downstream LNT is adapted for desulfation at higher temperatures than the upstream LNT. During desulfation, the system develops temperature gradients with the temperatures increasing in the direction of exhaust flow. The ordering of the LNTs is designed utilize these gradients. In a preferred embodiment, the system also includes two SCR catalysts having different compositions. The SCR catalyst with a composition adapted to tolerate higher temperatures is located nearer the downstream end of the system.
摘要:
The exhaust from a diesel-fueled internal combustion engine is treated by a lean NOX trap. The maximum temperature used for desulfating the lean NOX trap is kept relatively lower during early life and progressively increased as the trap ages. Designing for adequate late life performance entails excess capacity during early life. The method utilizes the excess capacity available during early life to slow aging of the trap and thereby extend the trap lifetime. The method facilitates meeting durability requirements for diesel-powered vehicles with exhaust aftertreatment.
摘要:
An exhaust aftertreatment system having a NOX absorber-catalyst and an ammonia-SCR reactor. During regenerations, the NOX absorber-catalyst generates ammonia. The ammonia-SCR reactor captures this ammonia and later uses it to reduce NOX. A Venturi is provided in an exhaust conduit connecting the NOX absorber-catalyst to the ammonia-SCR reactor. The Venturi draws sufficient air to keep the ammonia-SCR reactor under lean conditions throughout the NOX absorber-catalyst regenerations. Maintaining lean conditions for the ammonia-SCR reactor in this manner mitigates poisoning of the ammonia-SCR reactor by hydrocarbons slipping from the NOX absorber-catalyst during the regenerations. Mitigating this poisoning improves the performance of the exhaust aftertreatment system and reduce the loss of useful ammonia to oxidation.
摘要:
A diesel exhaust aftertreatment system comprises an LNT within an exhaust line. A low thermal mass DPF and a low thermal mass fuel reformer are configured within the exhaust line upstream from the LNT. A thermal mass is configured downstream from the fuel reformer and the DPF, but upstream from the LNT. For LNT denitration, the fuel reformer is rapidly heated and then used to catalyze steam reforming. The DPF is also rapidly heat each time the fuel reformer is heated and the LNT denitrated. The system operates to regenerate the DPF each time the LNT is denitrated. Preferably, a second DPF is provided to augment the performance of the first DPF. Preferably, the first DPF is small and of the flow through type whereas the second DPF is much larger and of the wall flow filter type. The second DPF can be used as the thermal mass.
摘要:
A lean NOX trap is a diesel exhaust aftertreatment system is selectively denitrated based on a measure relating to the state and/or the performance of the exhaust aftertreatment system, or a portion thereof comprising the lean NOX trap, reaching a critical value. The critical value is varied according to the demands currently being place on the exhaust aftertreatment system. In one embodiment, the critical value is set based on engine speed-load information. The method regenerates more frequently when exhaust aftertreatment demands are high and less frequently when demands are low. The method improves aftertreatment performance while reducing aftertreatment fuel penalty.