Exhaust gas aftertreatment systems

a technology of exhaust gas aftertreatment and exhaust gas, which is applied in the direction of electrical control, machines/engines, mechanical equipment, etc., can solve the problems of inherently inaccurate systems, difficult catalytic reduction of nox emissions via conventional means in such systems, and insufficient accuracy of tailpipe ammonia, so as to improve nox conversion efficiency, reduce ammonia slip, and accurate estimate of ammonia storage

Inactive Publication Date: 2007-06-21
FORD GLOBAL TECH LLC
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Benefits of technology

[0009] An advantage of the present invention is that ammonia slip can be minimized by performing ammonia storage estimates under known operating conditions by releasing only an insignificant amount of ammonia. Another advantage of the present invention is that an accurate estimate of the amount of ammonia stored in the SCR catalyst is obtained. Therefore, improved NOx conversion efficiency can be achieved by maintaining an optimum ammonia storage amounts in the SCR catalyst. Yet another advantage of the present invention is that cost savings can be...

Problems solved by technology

Vehicles equipped with diesel or other lean burn engines offer the benefit of increased fuel economy, however, catalytic reduction of NOx emissions via conventional means in such systems is difficult due to the high content of oxygen in the exhaust gas.
Under-injection of urea may result in sub-optimal NOx conversion, while over-injection may cause tai...

Method used

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[0015] Internal combustion engine 10, comprising a plurality of cylinders, one cylinder of which is shown in FIG. 1, is controlled by electronic engine controller 12. Engine 10 includes combustion chamber 30 and cylinder walls 32 with piston 36 positioned therein and connected to crankshaft 40. Combustion chamber 30 is shown communicating with intake manifold 44 and exhaust manifold 48 via respective intake valve 52 and exhaust valve 54. Intake manifold 44 is also shown having fuel injector 80 coupled thereto for delivering liquid fuel in proportion to the pulse width of signal FPW from controller 12. Both fuel quantity, controlled by signal FPW, and injection timing are adjustable. Fuel is delivered to fuel injector 80 by a fuel system (not shown) including a fuel tank, fuel pump, and fuel rail (not shown).

[0016] Controller 12 is shown in FIG. 1 as a conventional microcomputer including: microprocessor unit 102, input / output ports 104, read-only memory 106, random access memory 1...

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Abstract

A method are presented for monitoring an amount of ammonia stored in a urea-based SCR catalyst based on a response of a sensor coupled downstream of the catalyst to a periodic desorbtion of a small amount of ammonia. The sensor could be an ammonia sensor, or a NOx sensor whose signal is sensitive to presence of both NOx and ammonia. The method can be performed at engine start to establish initial ammonia storage amount, or, alternatively, to adjust ammonia storage amounts or diagnose degradation when NOx conversion efficiency of the catalyst is below a predetermined value.

Description

FIELD OF INVENTION [0001] The present invention relates to an emission control system for diesel and other lean-burn vehicles, and more specifically, to achieving optimal NOx conversion efficiency while minimizing ammonia slip in a urea-based Selective Catalytic Reduction (SCR) catalyst by maintaining an optimum amount of ammonia stored in the catalyst. BACKGROUND AND SUMMARY OF THE INVENTION [0002] Current emission control regulations necessitate the use of catalysts in the exhaust systems of automotive vehicles in order to convert carbon monoxide (CO), hydrocarbons (HC), and nitrogen oxides (NOx) produced during engine operation into unregulated exhaust gasses. Vehicles equipped with diesel or other lean burn engines offer the benefit of increased fuel economy, however, catalytic reduction of NOx emissions via conventional means in such systems is difficult due to the high content of oxygen in the exhaust gas. [0003] In this regard, Selective Catalytic Reduction (SCR) catalysts, i...

Claims

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Application Information

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IPC IPC(8): F01N3/00
CPCF01N3/0253F01N3/035F01N3/208F01N9/005F01N11/002F01N2550/02F01N2560/021F01N2560/026F01N2570/18F01N2610/02F02D41/027F02D41/146F02D2041/1468F02D2200/0802Y02T10/47Y02T10/24F01N13/009Y02T10/12Y02T10/40
Inventor UPADHYAY, DEVESHNIEUWSTADT, MICHIEL VAN
Owner FORD GLOBAL TECH LLC
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