Split Lambda Fueling for Engine NVH and Emission Control

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Solution Overview

Problem

Existing engine control strategies for split lambda fueling operations face challenges in maintaining engine performance while minimizing noise, vibration, and harshness (NVH) issues, particularly due to resonance frequency amplification and inaccuracies in torque output calculation, and fail to effectively reduce emissions and exhaust temperatures.

Innovation Solution

Implementing a rolling split lambda fueling strategy that alternates fueling schedules between rich and lean cylinders, using port fuel injection (PFI) for rich cylinders and direct injection (DI) for lean cylinders, and calculating torque output based on air-fuel ratio and spark timing modifiers to avoid resonant frequencies and maintain stoichiometric conditions at the emission control device.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Temperature

If the engine is operated rich of stoichiometry to cool the catalyst and exhaust components, then the exhaust temperatures are reduced, but hydrocarbon and carbon monoxide emissions increase and fuel consumption increases

Engineering Contradiction:

Improveexhaust temperatureVSAvoidhydrocarbon and carbon monoxide emissions

Core Design Contradiction:

TemperatureVSObject-generated harmful factors

Solution Approach 1:

The engine cylinders are divided into two groups: a first group operated rich of stoichiometry to cool exhaust components, and a second group operated at stoichiometry to maintain low emissions. This segmentation allows simultaneous achievement of exhaust cooling and emission control by directing rich exhaust to the catalyst and stoichiometric exhaust to the environment.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different air-fuel ratios are applied to different cylinder groups based on their exhaust destination. Cylinders whose exhaust flows to the catalyst receive rich mixtures for cooling, while cylinders whose exhaust is discharged directly maintain stoichiometric operation for emission control.

Inventive Principle:

Principle #3Local quality

2Object-generated harmful factors

If the engine is operated at stoichiometry over all conditions to avoid emission increase, then emissions are controlled, but exhaust temperatures are not reduced and engine performance is limited

Engineering Contradiction:

ImproveemissionsVSAvoidexhaust temperature

Core Design Contradiction:

Object-generated harmful factorsVSTemperature

Solution Approach 1:

The exhaust system is segmented into two pathways: one leading to the catalyst and one for direct discharge. This allows the engine to operate with different air-fuel ratios in different cylinder groups, achieving both emission control and exhaust temperature reduction simultaneously.

Inventive Principle:

Principle #1Segmentation

3Object-generated harmful factors

If load limit operations are carried out to avoid cooling operations, then emissions and fuel consumption are controlled, but engine speed, airflow, and torque output are limited

Engineering Contradiction:

Improveemissions and fuel consumptionVSAvoidengine torque output

Core Design Contradiction:

Object-generated harmful factorsVSPower

Solution Approach 1:

The air-fuel ratio parameter is changed locally in different cylinder groups rather than applying load limiting. By operating some cylinders rich and others at stoichiometry, the system achieves exhaust cooling and emission control while maintaining higher overall engine power output compared to global load limiting.

Inventive Principle:

Principle #35Parameter changes

4Power

If a default split lambda fueling schedule is used to increase engine power, then torque output is increased, but noise, vibration, and harshness issues occur due to resonance frequency amplification

Engineering Contradiction:

Improveengine torque outputVSAvoidnoise, vibration, and harshness

Core Design Contradiction:

PowerVSObject-affected harmful factors

Solution Approach 1:

The fueling schedule is made dynamic by adjusting the pattern of rich and stoichiometric cylinder operation based on engine speed and load conditions. The system selectively operates cylinders with different air-fuel ratios to avoid resonant frequencies that cause NVH, while maintaining the power benefits of split lambda fueling.

Inventive Principle:

Principle #15Dynamics

5Object-generated harmful factors

If a complex fueling strategy is implemented to achieve split lambda control, then emissions and temperature are controlled, but torque output calculation accuracy is reduced

Engineering Contradiction:

Improveemissions and exhaust temperatureVSAvoidtorque output calculation accuracy

Core Design Contradiction:

Object-generated harmful factorsVSMeasurement precision

Solution Approach 1:

The torque calculation is segmented by calculating torque output separately for rich cylinders and stoichiometric cylinders, then summing the results. This segmented approach maintains calculation accuracy despite the complex fueling strategy by treating each cylinder group according to its specific operating conditions.

Inventive Principle:

Principle #1Segmentation

Data Source

PatentUS20210310435A1Split lambda fueling operation systems and methods

Publication Date: 2021.10.07 FORD GLOBAL TECH LLC

AI summary

Methods and systems for engine operation are provided. In at least one example method, the method comprises, while operating an engine with at least one lean cylinder and at least one rich cylinder, delivering fuel to the at least one lean cylinder via direct fuel injection (DI) and delivering fuel to the at least one rich cylinder via port fuel injection (PFI).