Dual-Fuel Engine Control With Nested Knock Compensation
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Solution Overview
Problem
Dual fuel internal combustion engines face challenges in maintaining engine knock and nitrogen oxides (NOx) emission levels while maximizing fuel economy and secondary fuel substitution rate, particularly when using different fuels with varying properties.
Innovation Solution
An engine control system with a controller that adjusts injection timing, substitution rate, and air-to-fuel ratio using nested control loops to manage engine knock and NOx levels, allowing for efficient operation with secondary fuels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the start of injection is adjusted to satisfy the engine knock threshold, then engine knock is reduced, but the start of injection moves away from the target start of injection
Solution Approach 1:
The controller adjusts the substitution rate of secondary fuel as a parameter change to compensate for the start of injection timing shift caused by knock reduction. By modifying the fuel composition ratio between primary and secondary fuels, the system restores the start of injection to its target timing while maintaining reduced knock levels.
2Manufacturing precision
If the substitution rate of secondary fuel is adjusted to restore start of injection to target timing, then start of injection timing is improved, but the substitution rate moves away from target substitution rate
Solution Approach 1:
The controller adjusts the air-to-fuel ratio as a compensating parameter change. By modifying the amount of air supplied to the engine, the system restores the substitution rate of secondary fuel to its target value while maintaining the corrected start of injection timing.
3Productivity
If the air-to-fuel ratio is adjusted to restore substitution rate to target, then substitution rate is improved, but engine knock may increase
Solution Approach 1:
The controller continuously monitors engine knock levels and uses this feedback to dynamically adjust the start of injection timing. This closed-loop control ensures that knock remains suppressed while the other parameters (substitution rate, air-to-fuel ratio) are restored to their target values.
4Object-generated harmful factors
If dual fuel operation is implemented to reduce emissions and improve fuel economy, then environmental performance is improved, but engine control complexity increases
Solution Approach 1:
The controller implements nested control loops where the outer loop manages substitution rate and air-to-fuel ratio restoration, while the inner loop handles start of injection timing adjustment for knock suppression. This hierarchical nesting organizes the complex control tasks into manageable layers, reducing overall system complexity.
Data Source
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AI summary
An engine control system for an engine using a primary fuel and a secondary fuel is provided. The engine control system includes a controller configured to determine a first adjusted start of injection to satisfy an engine knock threshold responsive to an engine knock signal value exceeding the engine knock threshold. The controller is further configured to determine, based at least in part on the first adjusted start of injection and a target start of injection, a first adjusted substitution rate of the secondary fuel to adjust the first adjusted start of injection to the target start of injection and determine, based at least in part on the first adjusted substitution rate of the secondary fuel and a target substitution rate of the secondary fuel, an adjusted air-to-fuel ratio to adjust the first adjusted substitution rate of the secondary fuel to the target substitution rate of the secondary fuel.