The present invention relates generally to diesel engines and more specifically to improving the robustness of aftertreatment systems of diesel engines.
Diesel engines are known to emit pollutants such as sulphur, nitrous oxide (NOx), particulate matter, and unburned hydrocarbons. Despite new technologies and modern electronic control devices that aid in reducing engine-out exhaust emissions, these pollutants remain a subject of concern. In addition to adversely affecting the environment, these contaminants also hinder the overall performance of the diesel engine aftertreatment systems they are linked with. The most commonly used catalytic converter in today's modern diesel engines is the Diesel Oxidation Catalyst (DOC), which uses oxygen (O2) in the exhaust gas stream to convert carbon monoxide (CO) and unburned hydrocarbons to water and to carbon dioxide (CO2). The DOC however, does not effectively treat the nitrous oxide (NOx) emissions from the diesel engines.
In addition to the DOC, selective catalytic reduction converter (SCR) and ammonia oxidation (AMOx) catalysts are both copper-zeolite and iron-zeolite based catalysts used in diesel engine aftertreatment systems which decrease NOx and ammonia (NH3) emissions to help achieve near-zero emissions standards. However, a loss in oxidation functionality of the SCR and AMOx catalysts often leads to a decrease in the intended catalyst functions. The loss of catalysts' oxidation functionality, can some times be linked to long idling periods of the diesel engine, or exposure of the catalyst to ambient conditions for extended periods of time.
The decrease in the catalyst's oxidation functionality (also referred to as catalyst degradation) can adversely impact the performance of the diesel engine aftertreatment system. For example, in the SCR catalyst, a decrease in oxidation functionality would lead to a decrease in the catalyst's ability to convert NOx to NO2 and to adsorbed nitrogen oxides and also a decrease in the catalyst's ability to convert unburned hydrocarbons to CO2. The AMOx and DOC catalysts would be similarly affected since each of these catalysts often have zeolite-based components in its formulation. Therefore, the SCR, DOC, and AMOx catalysts having copper-zeolite- or iron-zeolite based catalysts that would experience a decline in the aftertreatment system's feed gas quality while experiencing an increase in the diesel exhaust emissions output. Each of these undesired affects result from a loss of oxidation functionality of the copper-zeolite or iron-zeolite catalysts.
Accordingly, what is needed is a system and method of regenerating diesel engine aftertreatment catalysts in an internal combustion engine.
The present invention satisfies this need, and presents a method and system for treating a catalyst in an internal combustion engine. To achieve the above object, the present method is described as detecting the efficiency of a catalyst; sending the catalyst efficiency to a threshold monitor; and heating the catalyst when the detected catalyst efficiency is below a predetermined percentage.
The present invention relates generally to diesel fuel engines and more specifically to the improved robustness of aftertreatment catalysts.
The following description is presented to enable one of ordinary skill in the art to make and use the invention and is provided in the context of a patent application and its requirements. Various modifications to the preferred embodiment and the generic principles and features described herein will be readily apparent to those skilled in the art. Thus, the present invention is not intended to be limited to the embodiment shown but is to be accorded the widest scope consistent with the principles and features described herein.
A method and system in accordance with the present invention improves the robustness of Cu-zeolite aftertreatment catalysts by using a controller for predictive and corrective actions, and also to detect and remove poisoning species from aftertreatment catalysts.
Next, in step 708, the amount of accumulated sulphur is calculated as the difference between the sulphur stored (via step 704) and the amount of sulphur released (via step 706). The accumulated sulphur from step 708 is then sent to the threshold comparator via step 710, and is also the input variable 711 for the SCR storage estimator in step 714. In step 710, the threshold comparator compares the accumulated sulphur to a predetermined threshold that is based upon NO2/NOx. The output of the threshold comparator in step 710 is then sent to the deSOx threshold monitor 712. In step 714, the inlet sulphur's temperature and mass flow rate are utilized by the SCR storage estimator to calculate stored sulphur, which is then sent to the SCR release estimator via step 716. In step 716, the SCR release estimator calculates the amount of sulphur released as a function of temperature, storage, and timing variables. The sulphur released in step 716 is then sent to step 718. In step 718, the amount of accumulated sulphur is calculated as the difference between the stored sulphur from step 714 and the released sulphur from step 716. The accumulated sulphur from step 718 is then sent to a threshold comparator via step 720, and is also the input variable 721 for the AMOx storage estimator in step 722. In step 720, the threshold comparator compares the accumulated sulphur to a predetermined threshold that is based on SCR catalyst efficiency. The output of the threshold comparator in step 720 is then sent to the deSOx threshold monitor 712. Note that for aftertreatment systems that do include a DPF, a suitable block needs to be included to accommodate the storage, release dynamics of sulphur on the DPF. The basic structure of the DPF block would remain the same as that of the DOC or the SCR ones.
Next, in step 722, the AMOx storage estimator calculates the amount of sulphur stored as a function of the inlet sulphur temperature, and the mass flow rate. The stored sulphur from step 722 is then sent to step 724, where the AMOx release estimator calculates the amount of sulphur released as a function of stored sulphur (from step 722), temperature, and timing variables. The sulphur released from step 724 is then sent to step 726, where the accumulated sulphur is calculated as the difference between the stored sulphur from step 722, and the sulphur released from step 724. The accumulated sulphur of step 726 is then output as system-out sulphur 728, and secondly, the accumulated sulphur of step 726 is also input to the threshold comparator in step 730, which compares the accumulated sulphur to a predetermined threshold based upon performance of the AMOx catalyst.
Next, in step 808, the amount of accumulated hydrocarbon is calculated as the difference between the hydrocarbon stored (via step 804) and the amount of hydrocarbon released (via step 806). The accumulated hydrocarbon from step 808 is then sent to the threshold comparator in step 810, and is also the input variable 811 for the SCR storage estimator in step 814. In step 810, the threshold comparator compares the accumulated hydrocarbon to a predetermined threshold that is based upon NO2/NOx. The output of the threshold comparator in step 810 is then sent to the desorb threshold monitor 812. In step 814, the inlet hydrocarbon's temperature and mass flow rate are utilized by the SCR storage estimator to calculate stored hydrocarbon, which is then sent to the SCR release estimator via step 816. In step 816, the SCR release estimator calculates the amount of hydrocarbon release as a function of temperature, storage, and timing variables. The hydrocarbon released in step 816 is then sent to step 818. In step 818, the amount of accumulated hydrocarbon is calculated as the difference between the stored hydrocarbon from step 814 and the released hydrocarbon from step 816. The accumulated hydrocarbon from step 818 is then sent to a threshold comparator via step 820, and is also the input variable 821 for the AMOx storage estimator in step 822. In step 820, the threshold comparator compares the accumulated hydrocarbon to a predetermined threshold that is based on SCR catalyst efficiency. The output of the threshold comparator in step 820 is then sent to the desorb threshold monitor 812, and is also the input variable 821 for the AMOx storage estimator.
Next, in step 822, AMOx storage estimator calculates the amount of hydrocarbon stored as a function of temperature, and mass flow rate. The stored hydrocarbon from step 822 is then sent to step 824, where the AMOx release estimator calculates the amount of hydrocarbon released as a function of temperature, storage, and time. The released hydrocarbon in step 824 is then sent to step 826, where the accumulated hydrocarbon is calculated as the difference between the stored hydrocarbon from step 822, and the hydrocarbon released from step 824. In addition, the hydrocarbon released in step 824 also goes to the exotherm predictor in step 827. The accumulated hydrocarbon of step 826 is then output as system-out unburned hydrocarbon via step 830, and secondly, the accumulated hydrocarbon of step 826 is then input to the threshold comparator in 832, which compares the accumulated hydrocarbon to a predetermined threshold based upon performance of the AMOx catalyst.
One advantage of a system and method in accordance with the present invention is that the system robustness is improved due to the predictive and corrective actions produced by the proposed controller.
A second advantage of a system and method in accordance with the present invention is that the proposed controller enables the virtual sensing of the catalyst poisons, which allows for removal of the poisons from the aftertreatment system.
A third advantage of a system and method in accordance with the present invention is that the proposed controller works complementary to the existing sensor set currently available within the existing architecture of a diesel engine.
Although the present invention has been described in accordance with the embodiments shown, one of ordinary skill in the art will readily recognize that there could be variations to the embodiments and those variations would be within the spirit and scope of the present invention. Accordingly, many modifications may be made by one or ordinary skill in the art without departing from the spirit and scope of the appended claims.