Split Lambda Fueling for Engine NVH and Thermal Management
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Solution Overview
Problem
Existing engine control strategies using split lambda fueling face challenges in maintaining engine performance while minimizing noise, vibration, and harshness (NVH) issues, particularly due to resonance amplification and inaccurate torque output calculations, and fail to effectively reduce emissions and exhaust temperatures.
Innovation Solution
Implementing a rolling split lambda fueling strategy that alternates between rich and lean engine cycles, allowing for non-stoichiometric engine operations while maintaining stoichiometric conditions at the emission control device, and using port fuel injection (PFI) for rich cylinders and direct injection (DI) for lean cylinders to prevent overheating, along with torque output calculations based on air-fuel ratio and spark timing modifiers.
Engineering Contradictions & Design Principles
Engineering 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 (HC) and carbon monoxide (CO) emissions increase and fuel consumption increases
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 minimize emissions. This segmentation allows simultaneous achievement of cooling and emission control by directing rich exhaust to the catalyst while maintaining overall stoichiometric balance.
Solution Approach 2:
Different air-fuel ratios are applied to different cylinder groups based on their exhaust routing. Cylinders whose exhaust flows to the catalyst are operated rich to provide cooling, while other cylinders are operated at stoichiometry. This local differentiation optimizes both thermal management and emission control in specific zones of the exhaust system.
2Object-generated harmful factors
If the engine is operated at stoichiometry over all conditions to avoid HC and CO emission increase, then emissions are controlled, but exhaust temperatures increase and engine performance is reduced
Solution Approach 1:
The engine operation is segmented into different modes: stoichiometric operation for emission control, and split lambda operation with rich/lean cylinder groups for thermal management. The controller selects between these modes based on operating conditions, allowing the engine to maintain stoichiometry when emissions are the priority while enabling rich operation in specific cylinders when cooling is needed.
Solution Approach 2:
The engine dynamically transitions between different operating modes (stoichiometric vs. split lambda) based on real-time conditions such as exhaust temperature, engine load, and speed. This dynamic adjustment allows the system to optimize between emission control and thermal management requirements as operating conditions change.
3Power
If default split lambda fueling pattern is used to increase engine power output, then torque is improved, but noise, vibration, and harshness (NVH) issues occur due to resonance amplification
Solution Approach 1:
The fueling pattern dynamically switches between default split lambda and rolling split lambda based on engine operating conditions, particularly engine speed and resonant frequency characteristics. This dynamic adaptation allows the system to maintain power output while avoiding NVH issues by selecting the appropriate fueling pattern for current operating conditions.
Solution Approach 2:
The rolling split lambda fueling pattern uses a periodic sequence that rolls through all cylinders over multiple cycles, creating a different frequency spectrum compared to the fixed default pattern. This periodic variation in fuel distribution avoids exciting resonant frequencies that cause NVH, while still achieving the power benefits of split lambda operation.
4Object-generated harmful factors
If complex fueling strategy is implemented to address emissions and temperature control, then emission control efficiency is improved, but torque output calculation accuracy decreases
Solution Approach 1:
The torque output calculation incorporates feedback from actual oxygen sensor readings and modeled exhaust gas composition to compensate for the effects of split lambda operation. By using real-time feedback on actual exhaust conditions and updating torque calculations accordingly, the system maintains accurate torque measurement despite the complex fueling strategy being employed for emission and thermal control.
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
The rolling split lambda approach reduces NVH by avoiding resonant frequencies, improves engine torque output, and decreases exhaust temperatures, enabling higher engine performance and reduced emissions without sacrificing emission control efficiency.
Implementation Method 1
the fuel will be scheduled rich of stoichiometry to cool a catalyst of the emission control device, as excess unburned fuel may help to cool the engine and exhaust components
Implementation Method 2
using port fuel injection (PFI) for rich cylinders and direct injection (DI) for lean cylinders to prevent overheating
Implementation Method 3
carrying out a plurality of non-stoichiometric engine cycles while maintaining substantially stoichiometric conditions at an emission control device
Data Source
AI summary
Methods and systems for operating an engine with split lambda modes are provided. At least one example method comprises, calculating a stoichiometric torque output of the plurality of cylinders; then applying one or more lean torque modifiers for every lean cylinder of the one or more non-stoichiometric cylinders to the stoichiometric torque output to calculate a lean torque output. In at least one example, one or more rich torque modifiers for every rich cylinder of the one or more non-stoichiometric cylinders may be applied to the stoichiometric torque output to calculate a rich torque output. Further, the lean torque output and the rich torque output may be summed to calculate a total engine torque output.