DOC Fuel Injection for SCR Catalyst Temperature Control

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Solution Overview

Problem

Conventional selective catalytic reduction (SCR) systems for NOx emissions reduction in diesel engines face inefficiencies at low exhaust gas temperatures, requiring external heating to maintain catalyst temperatures above 220°C.

Innovation Solution

A control module manages the injection of fuel into a diesel oxidation catalyst (DOC) and a dosing agent into the exhaust gas, adjusting temperatures to optimize SCR catalyst performance by terminating fuel injection when the DOC temperature exceeds a certain limit and terminating dosing agent injection when the SCR catalyst temperature falls below a specific limit, ensuring efficient NOx reduction.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If external heating devices are used to maintain SCR catalyst temperatures above 220°C, then SCR process effectiveness is improved, but device complexity and energy consumption increase

Engineering Contradiction:

ImproveSCR process effectivenessVSAvoidexternal heating devices

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The system uses the diesel oxidation catalyst's own exothermic oxidation reactions to generate heat for maintaining SCR catalyst temperature, eliminating the need for separate external heating devices. The DOC naturally produces sufficient heat during normal operation to warm the SCR catalyst to its light-off temperature.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The patent combines the DOC and SCR catalyst into a single integrated assembly where the DOC is positioned upstream of the SCR catalyst. This merging allows the DOC's thermal output to directly benefit the SCR catalyst, creating a synergistic thermal management system.

Inventive Principle:

Principle #5Merging (Combining)

2Temperature

If fuel is continuously injected into DOC to maintain temperature, then SCR catalyst temperature is maintained, but hydrocarbon interference with SCR process increases

Engineering Contradiction:

ImproveSCR catalyst temperatureVSAvoidhydrocarbon interference

Core Design Contradiction:

TemperatureVSObject-generated harmful factors

Solution Approach 1:

The system implements periodic or conditional fuel injection into the DOC based on monitored temperature conditions. Fuel injection is activated only when the DOC temperature falls below a threshold (e.g., 150°C) and terminated when the SCR catalyst temperature exceeds a threshold (e.g., 220°C), creating a responsive on-demand heating strategy.

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The control system continuously monitors DOC and SCR catalyst temperatures and adjusts fuel injection accordingly. When SCR catalyst temperature exceeds the threshold, fuel injection is terminated; when it falls below the threshold, injection resumes, creating a closed-loop feedback control system.

Inventive Principle:

Principle #23Feedback

3Productivity

If SCR catalyst temperature is maintained above 220°C, then NOx reduction efficiency is improved, but energy consumption increases

Engineering Contradiction:

ImproveNOx reduction efficiencyVSAvoidenergy consumption

Core Design Contradiction:

ProductivityVSUse of energy by moving object

Solution Approach 1:

The system performs preliminary heating of the SCR catalyst using the DOC's exothermic reactions before dosing agent injection begins. This preliminary action ensures the SCR catalyst reaches optimal temperature (above 220°C) in advance, preparing it for efficient NOx reduction without requiring continuous additional energy input during the dosing phase.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system dynamically adjusts the dosing agent injection rate based on SCR catalyst temperature. When temperature exceeds 220°C, dosing is terminated; when it falls below, dosing resumes at adjusted rates, optimizing NOx reduction efficiency while minimizing energy consumption through adaptive parameter control.

Inventive Principle:

Principle #35Parameter changes

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This strategy enhances NOx reduction efficiency by maintaining optimal catalyst temperatures, reducing the need for external heating and minimizing interference with hydrocarbons, thereby improving emissions control across a broader temperature range.

Implementation Method 1

diesel oxidation catalyst (DOC) are commonly used with diesel engines for emissions reduction

Methodology Applied

Scientific EffectOxidation: Oxidation

Implementation Method 2

selective catalytic reduction (SCR) catalysts and diesel oxidation catalysts (DOC) are commonly used with diesel engines for emissions reduction

Methodology Applied

Scientific EffectCatalysis: Catalysis

Implementation Method 3

injecting a fuel into an engine exhaust gas provided to a diesel oxidation catalyst (DOC)

Methodology Applied

Scientific EffectCombustion: Combustion

Data Source

PatentUS8176729B2Perturbation control strategy for low-temperature urea SCR NOx reduction

Publication Date: 2012.05.15 GM GLOBAL TECHNOLOGY OPERATIONS LLC

AI summary

An emissions control method may include injecting a fuel into an engine exhaust gas provided to a diesel oxidation catalyst (DOC) when a DOC operating temperature is greater than a first limit, terminating the injecting when a temperature of a catalyst in communication with exhaust gas exiting the DOC is greater than a second limit, and injecting a dosing agent into the exhaust gas after the terminating.