Model-Based NOx Storage Management for Cold Start Exhaust Systems

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Solution Overview

Problem

Lean NOx traps in exhaust systems for internal combustion engines face inefficiencies in NOx storage at low temperatures, leading to reduced capacity and inability to store NOx during subsequent cold starts due to thermal release thresholds.

Innovation Solution

A passive NOx absorber device and a model-based controller that computes predicted NOx storage levels and adjusts engine operations, such as fuel injection and exhaust gas recirculation, to raise exhaust temperature, allowing the NOx absorber to release stored NOx, which is then converted by a downstream NOx reduction device, like a selective catalytic reduction device, into nitrogen and water.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If the PNA device stores NOx at low temperatures during cold starts, then NOx storage capacity is improved, but the stored NOx is thermally released when temperature increases, reducing available storage capacity for subsequent cold starts

Engineering Contradiction:

ImproveNOx storage capacityVSAvoidexhaust gas temperature

Core Design Contradiction:

Quantity of substanceVSTemperature

Solution Approach 1:

The system performs preliminary heating of the exhaust gas before cold start events by operating the engine at higher loads or speeds, which pre-conditions the PNA device to release stored NOx in advance, ensuring storage capacity is restored for the upcoming cold start

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The model-based controller continuously monitors engine operating conditions, exhaust temperature, and PNA device state to predict NOx storage levels, and adjusts engine operation in real-time to maintain optimal NOx storage capacity by triggering heating events when storage drops below thresholds

Inventive Principle:

Principle #23Feedback

2Quantity of substance

If the engine operation is changed to raise exhaust temperature, then NOx release from PNA device is improved, but fuel consumption increases

Engineering Contradiction:

ImproveNOx release rateVSAvoidfuel consumption

Core Design Contradiction:

Quantity of substanceVSUse of energy by moving object

Solution Approach 1:

The system uses periodic or event-driven engine operation changes rather than continuous operation, raising exhaust temperature only when needed to release stored NOx from the PNA device, thereby minimizing fuel consumption while maintaining effective NOx management

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The model-based controller adjusts engine parameters such as load, speed, or injection timing to raise exhaust temperature only to the extent necessary for NOx release, optimizing the balance between NOx release effectiveness and fuel consumption by avoiding excessive temperature increases

Inventive Principle:

Principle #35Parameter changes

3Object-generated harmful factors

If the PNA device is used to store NOx during cold starts, then cold start emissions are reduced, but the device lacks sufficient storage capacity for subsequent cold starts due to thermal release

Engineering Contradiction:

Improvecold start NOx emissionsVSAvoidstorage capacity availability

Core Design Contradiction:

Object-generated harmful factorsVSDuration of action of stationary object

Solution Approach 1:

The system pre-heats the exhaust gas and triggers NOx release from the PNA device before subsequent cold start events, ensuring the device regains its storage capacity in advance, so it can effectively store and manage NOx during the next cold start

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The model-based controller continuously manages the PNA device storage state across multiple drive cycles, ensuring uninterrupted NOx storage capability by coordinating thermal release events with upcoming cold start conditions, maintaining continuous emission control effectiveness

Inventive Principle:

Principle #20Continuity of useful action

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 actively manages NOx storage capacity, ensuring the exhaust system maintains sufficient storage for subsequent cold starts and optimizes NOx emissions control within stringent regulatory limits.

Implementation Method 1

a passive NOx absorber (PNA) device... absorbing, by the PNA device, NOx from exhaust gas

Methodology Applied

Scientific EffectAdsorption: Adsorption

Implementation Method 2

raising a temperature of the exhaust gas by changing an operation of the internal combustion engine... the raised temperature causes the PNA device to release stored NOx

Methodology Applied

Scientific EffectThermal release: Heating

Implementation Method 3

a NOx reduction device that converts the released NOx into nitrogen (N2) and/or water (H2O)... the NOx reduction device comprises a selective catalytic reduction device

Methodology Applied

Scientific EffectCatalytic reduction: Catalysis

Data Source

PatentUS10947885B2Passive nitric oxide storage catalyst management

Publication Date: 2021.03.16 GM GLOBAL TECHNOLOGY OPERATIONS LLC

AI summary

According to one or more embodiments described herein, an exhaust system for treating exhaust gas from an internal combustion engine in a motor vehicle includes a passive NOx absorber (PNA) device, and a model-based controller that controls an amount of NOx stored by the PNA device. Controlling of the amount of NOx stored includes computing a predicted NOx storage level of the PNA device using a prediction model of the PNA device, and in response to the predicted NOx storage level of the PNA device being greater than a predetermined cold-start threshold, raising a temperature of the exhaust gas by changing an operation of the internal combustion engine.