Method of calibrating an after-treatment system retrofitted to an engine

Patent metadata

Field	Value
Publication number	US-2016201535-A1
Application number	US-201615075213-A
Country	US
Kind code	A1
Filing date	Mar 21, 2016
Priority date	Mar 21, 2016
Publication date	Jul 14, 2016
Grant date	—

Abstract

A method is provided for calibrating an after-treatment system retrofitted onto an engine, the after-treatment system including a Selective Catalytic Reduction (SCR) device therein. The method is implemented using a controller having a memory pre-fed with an Engine-out NOx map, a SCR conversion map, a maximum SCR capability map, and a NOx dosing map corresponding to bench-run conditions for the given engine and the after-treatment system configurations. The method includes updating the Engine-out NOx map, the SCR conversion map, the maximum SCR capability map, and the NOx dosing map by the controller on the basis of actual sensed parameters of an exhaust stream associated with operation of the given engine and after-treatment system. The method further includes directing the controller to vary a feed-forward reductant dosing quantity at the SCR device during a subsequent operation of the engine based on the updated NOx dosing map stored at the controller.

First claim

What is claimed is:

1 . A method of calibrating an after-treatment system retrofitted onto an engine, the method including:
updating an Engine-out NO x map pre-fed at a memory of a controller on the basis of an input obtained from a NOx sensor disposed upstream of a Selective Catalytic Reduction (SCR) device for a given configuration and operating condition of the engine; determining, using the controller, a conversion factor of the SCR device by performing adaptive calibration of the SCR device, wherein the adaptive calibration includes a comparison of a NOx conversion desired from the SCR device with an actual NOx conversion of the SCR device measured from inputs from the NOx sensor upstream and a NOx sensor downstream of the SCR device for the given operating condition of the engine; updating a SCR conversion map for the given SCR device at the memory of the controller on the basis of the determined conversion factor for the SCR device; determining, by the controller, a maximum conversion capability of the SCR device for the given configurations of the engine and the retrofitted after-treatment system based on inputs from a sensor package including at least the NO x sensor disposed downstream of the SCR device, the sensor package being configured to output at least an amount of Ammonia (NH 3 ) slip downstream of the SCR device; obtaining, by the controller, a pre-determined reductant dosing quantity for the given operating condition of the engine from a maximum SCR capability map pre-fed at the memory of the controller; updating the maximum SCR capability map at the memory of the controller on the basis of the determined maximum conversion capability of the SCR device; determining, by the controller, an adjustment factor on the basis of a dosing offset value obtained from comparison between a current reductant dosing quantity at the SCR device with a pre-determined dosing quantity of the reductant required at the SCR device corresponding to the NOx conversion desired from the SCR device and minimal NH 3 slip for the given configuration and operating condition of the engine; updating a NOx dosing map for the SCR device at the memory by the controller based on the determined adjustment factor, the adjustment factor being obtained from the dosing offset value for the SCR device; storing the updated Engine-out NO x map, the updated SCR conversion map, the maximum SCR capability map, and the NOx dosing map at the memory of the controller; and varying, by the controller, a feed-forward reductant dosing quantity at the SCR device during a subsequent operation of the engine based on at least the updated NOx dosing map stored at the memory.

Assignees

• Caterpillar Inc

Inventors

• Pokharel Shikha
• Mutti Jr James Harris
• Segebart Matthew Jay

Classifications

• F01N3/208 Primary

  Control of selective catalytic reduction [SCR], e.g. by adjusting the dosing of reducing agent · CPC title

• F01N11/00

  Monitoring or diagnostic devices for exhaust-gas treatment apparatus · CPC title

• F01N2900/1402

  Exhaust gas composition · CPC title

• F01N2900/0412

  using pre-calibrated maps, tables or charts · CPC title

• F01N9/005

  using models instead of sensors to determine operating characteristics of exhaust systems, e.g. calculating catalyst temperature instead of measuring it directly · CPC title