Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: Partial denitrations are made practical by an SCR catalyst placed downstream of a NOx adsorber. The SCR catalyst permits partial denitrations to be extended to where a favorable fuel penalty rate presented by driving conditions can be utilized to a sufficient extent that the benefit of the favorable conditions is not offset by the increased start-up fuel penalty associated with conducting opportunistic partial denitrations. Regenerations, including both denitration and desulfations, can be initiated selectively based on a fuel penalty calculation. Examples of such calculations lead to methods in which opportunistic regenerations are based on low oxygen concentrations, condition existing while shifting gears, and throttling events for a diesel engine with a throttled air supply. The methods flexibly take advantage of driving conditions to reduce fuel penalties associated with regenerations. In one embodiment, driving conditions include future conditions predicted based on GPS and map data.

Abstract: 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. An outer loop controls the LNT temperature by issuing instructions to an inner loop that controls the reformer. Typically, the inner loop will pulse the reductant injection rate in order to limit the reformer temperature. The outer loop can pulses the loop on a longer time scale, resulting in two pulse periods. Through timing, a reformate peak from one period is made to overlap a temperature peak from a previous period.

Abstract: A power generation system comprising a LNT for exhaust aftertreatment. The LNT has an effective operating temperature range. When the LNT is near a limit of its effective operating temperature range, the transmission is used to select operating points that increase the LNT's effectiveness. Generally, these operating points reduce the exhaust flow rate, although other factors such as the exhaust temperature may also be taken into account in selecting the operating points. Preferably, the LNT's effective operating temperature-range includes exhaust temperatures produced by the engine at its point of peak power output, whereby the LNT does not approach the limits of its effective operating temperature range except when the engine is at less than peak power. At lower power levels, it is generally possible to select operating points that provide lower exhaust flow rates than the flow rate occurring at the peak power level.

Abstract: One concept relates to power generation system, comprising a diesel engine, an exhaust manifold, a turbocharger, and an exhaust line in which are configured a fuel reformer and a LNT. A fuel injector is configured to inject fuel into the manifold upstream of the turbine. The high temperatures upstream of the turbine cause the fuel to crack into smaller molecules, releasing heat and providing a boost to the turbocharger. The fuel injected into the manifold also undergoes intense mixing as it passes through the turbocharger. Injecting fuel in this manner provides several benefits for reformer operation. Another concept relates to a manifold fuel injector used to provide fuel for heating a DPF.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: An exhaust line fuel injection system and associated methods of operation and control are disclosed. The fuel passes through a regulating valve connected to a pressurized fuel source and an outlet connected to an exhaust system fuel supply line. The exhaust system fuel supply line is connected to a nozzle, which generally comprises a check-valve and is configured to inject the fuel into the exhaust line. Using a pressure measuring device, an indication of the exhaust system fuel supply line pressure is obtained. A controller provides control over the flow regulating valve using feedback from the pressure indication and a predetermined relationship between the flow rate through the nozzle and one of the exhaust system fuel supply line pressure and the pressure drop across the nozzle. The method can be implemented with a single pressure measuring device. The same pressure measurements, especially their frequency spectrum, can be used to detect system faults.

Abstract: A fuel reformer is configured in an exhaust line upstream of a LNT. To desulfate the LNT, over a first period, fuel is provided to the exhaust to make the exhaust rich. While producing reformate, the reformer is allowed to heat to a relatively large extent, typically at least about 75° C. Before the reformer overheats, the provision of fuel is reduced and typically stopped entirely for a second period, over which the reformer cools. The heating and cooling periods are repeated to complete the desulfation process. The reduced efficiency of operating the reformer over an extended temperature range is more than compensated for by the benefits of extending the rich pulse.

Abstract: Rhodium utilization in LNT/SCR-based exhaust aftertreatment systems for medium and heavy duty trucks is reduced by operating inline fuel reformers in a certain manner. The fuel processors are operated at steam reforming temperatures to produce a reformate-containing exhaust having a hydrogen to CO ratio of at least about 3:2 or at least about 3% hydrogen, This generally involves operating the fuel reformers at temperatures from about 500 to about 625° C. and with an overall fuel to air ratio from about 1.10 to about 1.40. In this manner, regeneration can be efficiently carried out while limiting the catalyst loading of the fuel processors to no more than about 1.0 grams rhodium per liter maximum displacement of the diesel engine and the catalyst loading of the LNTs to no more than about 0.50 grams rhodium per liter maximum displacement of the diesel engine.

Abstract: A method and system for repeatable diesel engine starts during a wide range of conditions that decouples fueling requirements during engine starting and normal engine operation.

Abstract: An exhaust aftertreatment system comprising two or more branches, at least one of which contains a NOx adsorber-catalyst. The branches unite downstream into a trailing conduit that contains an ammonia-SCR catalyst. Ammonia generated by the NOx adsorber-catalyst during regeneration is stored for later use by the SCR catalyst. One advantage of this configuration is a continuous or near continuous presence of oxygen within the trailing exhaust conduit. The continuous presence of improves the efficiency of the SCR catalyst. Another concept is to configure a multi-branch exhaust aftertreatment system without valves, dampers, or other electronically controlled devices adapted to selectively alter the distribution of the exhaust between the branches. The absence of such devices generally results in a comparatively balanced division of exhaust between the branches. One benefit of this configuration is improved reliability as compared to systems that use valves.

Abstract: One of the inventors' concepts relates to controlling a temperature of a diesel engine exhaust aftertreatment device, such as a DPF or a fuel reformer, in which combustion is taking place. The concept is to inject reductant to combust in an upstream device, thereby removing oxygen in the exhaust and limiting combustion in the downstream device. The same total amount of heat may be generated, but the distribution is different and limits temperatures in the downstream device. The temperature limiting effect may be through one or more of the thermal storage capacity of the upstream device, the additional heat loss to the surroundings due to higher temperatures upstream in the exhaust system, or the benefit of a more uniform distribution of heat in the downstream device, which mitigates local hot spots. This concept may be used in a temperature control system.

Abstract: A method is provided for operating a diesel engine exhaust aftertreatment system including a DPF and a LNT. The LNT is regenerated as soot is combusting in the DPF. To accomplish this, reductant is injected between the DPF and the LNT during soot combustion, whereby the LNT experiences rich conditions as the DPF experiences lean conditions. Preferably, the DPF is of small size whereby the DPF is heated easily and needs to be regenerated almost as often as the LNT needs to be denitrated. In an exemplary process, DPF regeneration begins in response to a control signal to denitrate the LNT. Preferably, the reductant is diesel fuel and there is a fuel reformer between the DPF and the LNT. Oxygen consumed by soot combustion reduces the fuel penalty for regenerating the LNT and promotes stable reformer operation. Heat generated in the DPF helps warm the fuel reformer.

Abstract: One of the inventors' concepts relates to a power generation system, comprising a diesel engine and an exhaust system. The exhaust system comprises a first oxidation catalyst, a fuel reformer, and a LNT. A fuel injector is configured to inject fuel downstream of the oxidation catalyst, but upstream of the reformer. Preferably, the first oxidation catalyst is located near the engine. The first oxidation catalyst can extend the range of exhaust temperatures at which the aftertreatment devices operate by raising the temperature through reactions with residual hydrocarbons in the exhaust. The first oxidation catalyst also stabilizes the reformer operation by reducing the exhaust oxygen concentration. In a preferred embodiment, the engine operation is changed for LNT regenerations to increase the hydrocarbon content of the exhaust.