Urea Injection for DPF Regeneration Temperature Control

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Solution Overview

Problem

Existing emission control systems face challenges in managing self-sustained and self-induced temperature increases during diesel particulate filter (DPF) regeneration, which can lead to excessive temperatures damaging catalysts and reducing their lifespan and effectiveness.

Innovation Solution

A system that includes an exhaust conduit with a particulate filter, a reductant storage device for urea, and a controller to inject urea into the exhaust system upstream of the filter when temperature exceeds a threshold during regeneration, managing temperature through urea injection to prevent thermal runaway.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If exhaust temperature is increased during DPF regeneration, then soot combustion effectiveness is improved, but temperature of the emissions control system increases past acceptable levels degrading catalysts

Engineering Contradiction:

Improvesoot combustion effectivenessVSAvoidexcessive temperature damage to catalysts

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

Urea is introduced as an intermediary substance that absorbs excess heat during DPF regeneration. The urea decomposes into ammonia and carbon dioxide, and the decomposition process absorbs heat, thereby cooling the exhaust gases and protecting catalysts from thermal damage while allowing regeneration to proceed

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The invention changes the chemical composition parameter of the exhaust gas by introducing urea. This parameter change enables the system to control temperature through the endothermic decomposition reaction of urea, transforming the temperature profile during regeneration to protect catalysts

Inventive Principle:

Principle #35Parameter changes

2Temperature

If exhaust air flow is increased to cool the DPF, then temperature control is improved, but the cooling may not be sufficient to reduce self-sustained and self-induced temperature increases

Engineering Contradiction:

ImproveDPF temperature controlVSAvoidadequacy of cooling method

Core Design Contradiction:

TemperatureVSReliability

Solution Approach 1:

The invention replaces the mechanical/physical cooling method (increasing air flow) with a chemical method (urea decomposition). This substitution provides a more reliable and controllable cooling mechanism that can effectively reduce self-sustained temperature increases during regeneration

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Temperature

If oxygen is limited to control temperature, then temperature increase is reduced, but combustion may stall or stop regeneration prematurely

Engineering Contradiction:

Improveexhaust gas temperatureVSAvoidregeneration effectiveness

Core Design Contradiction:

TemperatureVSProductivity

Solution Approach 1:

Instead of changing the oxygen concentration parameter, the invention introduces a new parameter - urea decomposition - that affects temperature through heat absorption. This allows temperature control without interfering with the combustion process and regeneration effectiveness

Inventive Principle:

Principle #35Parameter changes

4Temperature

If oxygen is reduced to limit temperature, then temperature control is improved, but excessive smoking occurs in the engine

Engineering Contradiction:

Improveexhaust gas temperatureVSAvoidexcessive smoking

Core Design Contradiction:

TemperatureVSObject-generated harmful factors

Solution Approach 1:

Urea serves as an intermediary that controls temperature through its decomposition reaction, which absorbs heat without affecting oxygen availability. This eliminates the harmful side effect of excessive smoking that occurs when oxygen is restricted for temperature control

Inventive Principle:

Principle #24Intermediary (Mediator)

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

Effectively reduces exhaust gas temperatures during DPF regeneration, preventing damage to aftertreatment catalysts and filters, and maintaining the effectiveness and lifespan of these components.

Implementation Method 1

supply the urea to the exhaust system upstream of the particulate filter when exhaust gas temperature exceeds a threshold value during particulate filter regeneration

Methodology Applied

Scientific EffectDecomposition (endothermic reaction): Decomposition (biological)

Implementation Method 2

urea stored on board for NOx reduction in an SCR, for example, can also be used for managing filter regeneration

Methodology Applied

Scientific EffectHeat absorption: Endothermic Reaction

Data Source

PatentUS7987662B2Composition and method for controlling excessive exhaust gas temperatures

Publication Date: 2011.08.02 FORD GLOBAL TECH LLC

AI summary

A method of operating an internal combustion engine having a reductant delivery and storage system in an emission control system is disclosed. The method includes an approach for reducing thermal damage to aftertreatment devices in an exhaust system by reducing excessive exhaust gas temperatures created during particulate filter regeneration.