Exhaust Catalyst Temperature Control via EGR Bypass Valve

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Solution Overview

Problem

Engine systems with dedicated EGR cylinder groups face challenges in maintaining exhaust catalyst temperature, particularly during cold-start and extended light load operations, leading to degraded emissions conversion rates and fuel economy due to limited diverter valve options that either reduce catalyst temperature or disable EGR.

Innovation Solution

A method involving a continuously variable bypass valve that concurrently directs exhaust from a dedicated EGR cylinder to both the engine intake and exhaust catalyst, adjusting the flow ratio based on catalyst temperature, and enriching the EGR cylinder to generate a hydrogen-rich exhaust stream for catalyst heating, while maintaining overall engine fuel efficiency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Temperature

If all exhaust from dedicated EGR cylinder is directed to exhaust catalyst via diverter valve, then catalyst temperature is improved, but fuel economy deteriorates and EGR is temporarily disabled

Engineering Contradiction:

Improveexhaust catalyst temperatureVSAvoidfuel economy

Core Design Contradiction:

TemperatureVSLoss of energy

Solution Approach 1:

The exhaust flow from the dedicated EGR cylinder is segmented into two separate paths: one path directs exhaust to the exhaust catalyst for temperature maintenance, while the other path directs exhaust to the engine intake for EGR purposes. This segmentation allows simultaneous achievement of catalyst heating and EGR delivery without the need to disable EGR during catalyst warm-up.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

A continuously variable bypass valve is used to dynamically adjust the proportion of exhaust flow between the two paths based on catalyst temperature requirements. The valve provides continuous control rather than fixed positions, enabling optimal balance between catalyst heating and EGR delivery under varying operating conditions.

Inventive Principle:

Principle #15Dynamics

2Loss of energy

If diverter valve directs exhaust to intake manifold, then fuel economy is improved, but exhaust catalyst temperature reduces

Engineering Contradiction:

Improvefuel economyVSAvoidexhaust catalyst temperature

Core Design Contradiction:

Loss of energyVSTemperature

Solution Approach 1:

The exhaust flow is divided into two streams: a portion is directed to the exhaust catalyst to maintain adequate temperature, while the remaining portion is directed to the engine intake for EGR. This segmentation ensures both catalyst temperature maintenance and fuel economy improvement can occur simultaneously.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The system changes the flow distribution parameter dynamically based on catalyst temperature feedback. When catalyst temperature is sufficient, more exhaust is directed to the intake for fuel economy; when temperature drops, the proportion to the catalyst increases to maintain temperature.

Inventive Principle:

Principle #35Parameter changes

3Quantity of substance

If high levels of EGR are added to combustion chamber, then engine dilution is improved, but exhaust catalyst temperature drops below optimal conversion temperature

Engineering Contradiction:

Improveengine dilutionVSAvoidexhaust catalyst temperature

Core Design Contradiction:

Quantity of substanceVSTemperature

Solution Approach 1:

The exhaust flow is segmented so that high levels of EGR can be delivered to the engine intake while a separate portion of exhaust is directed to the catalyst for temperature maintenance. This resolves the conflict between achieving high engine dilution and maintaining catalyst temperature.

Inventive Principle:

Principle #1Segmentation

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 approach enables continuous catalyst temperature control without disabling EGR, improving emissions conversion rates and fuel economy by generating an exothermic reaction directly at the catalyst, reducing heat loss to other engine components, and maintaining optimal catalyst operation.

Implementation Method 1

By diverting exhaust from the dedicated EGR cylinder to the exhaust catalyst, heat flow to the catalyst can be increased

Methodology Applied

Scientific EffectHeat transfer: Conduction (thermal)

Implementation Method 2

The rich exhaust from the dedicated EGR cylinder may then be combined with the lean exhaust from the remaining cylinders to generate a significantly exothermic reaction at the catalyst, further expediting catalyst heating

Methodology Applied

Scientific EffectExothermic reaction: Exothermic Reaction

Implementation Method 3

An EGR passage coupling a dedicated EGR cylinder to an engine intake may include a continuously variable bypass valve that allows a portion of the exhaust gas to be metered to an exhaust catalyst in the exhaust manifold via a bypass passage

Methodology Applied

Scientific EffectWater-gas shift reaction: Chemical Transport Reactions

Data Source

PatentUS9297320B2Systems and methods for exhaust catalyst temperature control

Publication Date: 2016.03.29 FORD GLOBAL TECH LLC

AI summary

Methods and systems are provided for exhaust catalyst temperature control by metering exhaust bypass flow from a dedicated EGR cylinder. A continuously variable bypass valve may be adjusted to vary an amount of exhaust directed to an exhaust catalyst from a dedicated EGR cylinder via a bypass passage relative to exhaust recirculated to the engine intake via an EGR passage. At lower catalyst temperatures, more exhaust is metered via the bypass passage to enable catalyst temperature to be maintained above an activation level.