Multi-Fuel Engine Cylinder Knock Control via Segmented Substitution Ratios
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Solution Overview
Problem
Multi-fuel engines face challenges in efficiently mitigating knocking combustion across cylinders, as existing methods either penalize all cylinders by increasing diesel fuel use or result in complex and costly individual cylinder control, especially when one cylinder experiences knock.
Innovation Solution
A system that divides engine cylinders into groups based on individual knock sensor outputs, applying a common higher substitution ratio to non-knocking or lightly knocking cylinders and a lower ratio to more heavily knocking cylinders, dynamically adjusting the makeup and substitution ratios to mitigate knock while maximizing natural gas usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If individual cylinder control is implemented to mitigate knock, then knock control precision is improved, but device complexity and cost increase
Solution Approach 1:
The engine cylinders are segmented into multiple groups based on their knock characteristics. Each group is controlled with a specific substitution ratio tailored to its knock level, allowing precise knock control without requiring individual cylinder control for every cylinder. This segmentation approach reduces control complexity while maintaining effectiveness.
Solution Approach 2:
Different substitution ratios are applied to different cylinder groups based on their local knock characteristics. Non-knocking or lightly knocking cylinders receive a higher substitution ratio (more natural gas), while heavily knocking cylinders receive a lower substitution ratio (more diesel fuel). This local differentiation achieves precise knock control without uniform treatment of all cylinders.
2Reliability
If diesel fuel is increased to mitigate knock in one cylinder, then knock control is improved, but natural gas consumption decreases and costs increase
Solution Approach 1:
Cylinders are divided into groups based on knock severity. Only the subset of cylinders experiencing heavy knock receives increased diesel fuel, while non-knocking and lightly knocking cylinders continue to operate with higher natural gas substitution ratios. This segmentation prevents unnecessary diesel fuel consumption across the entire engine.
Solution Approach 2:
The fuel mixture is locally optimized for each cylinder group according to its specific knock characteristics. Heavily knocking cylinders receive a lower natural gas/diesel ratio, while other cylinders maintain higher natural gas ratios. This local optimization maximizes natural gas consumption overall while controlling knock only where necessary.
3Ease of operation
If a single uniform substitution ratio is applied to all cylinders, then control simplicity is maintained, but knock control effectiveness decreases
Solution Approach 1:
The control system segments cylinders into distinct groups based on knock detection, applying different substitution ratios to each group. This segmentation enables effective knock control while maintaining a relatively simple control architecture that does not require complex individual cylinder management.
Solution Approach 2:
Different substitution ratios are implemented for different cylinder groups based on their knock characteristics. This local differentiation improves knock control effectiveness while avoiding the complexity of completely individualized control, striking a balance between simplicity and effectiveness.
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 effectively reduces engine knock while simplifying control and reducing costs by using a finite number of substitution ratios, ensuring efficient knock control and maximizing gaseous fuel consumption within cylinder torque limits.
Implementation Method 1
Knock sensors coupled to the engine may indicate when knocking occurs
Implementation Method 2
A multi-fuel engine may combust more than one fuel in engine cylinders of the engine
Data Source
AI summary
Various methods and systems are provided for adjusting fueling to groups of cylinders of an engine based on individual cylinder knock sensor outputs. As one example, a system for an engine includes: a controller with computer readable instructions stored on non-transitory memory that when executed during operation of the engine cause the controller to: deliver natural gas and diesel fuel to a first group of cylinders at amounts that produce a common, first substitution ratio of natural gas; deliver natural gas and diesel fuel to a second group of cylinders at amounts that produce a common, second substitution ratio of natural gas; and change a makeup of each of the first group of cylinders and the second group of cylinders based on individual knock sensor outputs of each cylinder of the first group of cylinders and the second group of cylinders.