Active Air Fuel Ratio Control for Multi-Fuel Engine Knock
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Solution Overview
Problem
Multi-fuel engines, such as hydrogen/diesel engines, are prone to engine knock due to the faster combustion rate of hydrogen, which can lead to unstable combustion and increased emissions, necessitating a method to stabilize combustion and reduce knock likelihood.
Innovation Solution
Active adjustment of the air-to-fuel ratio (AFR) and substitution ratio of hydrogen to diesel, leveraging the wide flammability range of hydrogen to promote stable combustion and reduce knock, by increasing airflow and adjusting engine operating conditions based on current engine load, temperature, and ambient conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If hydrogen is used as a fuel in multi-fuel engines, then energy density and flame speed are improved, but engine knock and combustion stability deteriorate
Solution Approach 1:
The patent combines hydrogen and diesel fuels in a dual-fuel system, merging the high energy density and fast flame speed of hydrogen with the combustion stability and knock resistance of diesel. The hydrogen is injected into the combustion chamber and mixes with diesel and air, creating a composite fuel system that leverages the complementary properties of both fuels to achieve both high power output and stable combustion.
Solution Approach 2:
The patent actively adjusts the air-to-fuel ratio (AFR) and the substitution ratio of hydrogen to diesel based on real-time engine operating conditions such as load, temperature, and ambient conditions. By dynamically changing these parameters, the system optimizes combustion stability and prevents engine knock while maintaining the energy benefits of hydrogen combustion.
2Power
If hydrogen combustion rate is increased, then power output is improved, but engine knock likelihood increases
Solution Approach 1:
The patent uses diesel as an intermediary fuel that provides controlled ignition sources for hydrogen combustion. The diesel injection creates localized combustion zones that initiate and control the hydrogen burning process, preventing uncontrolled auto-ignition and knock while maintaining high power output from the fast-burning hydrogen.
Solution Approach 2:
The system incorporates sensors and control logic that monitor engine operating conditions, combustion characteristics, and knock indicators in real-time. Based on this feedback, the control system dynamically adjusts the hydrogen injection rate, air-to-fuel ratio, and diesel injection timing to maintain optimal power output while preventing engine knock.
3Reliability
If air-to-fuel ratio is increased to reduce knock, then combustion stability is improved, but fuel efficiency deteriorates
Solution Approach 1:
The patent employs dynamic adjustment of the air-to-fuel ratio based on real-time engine operating conditions. Rather than maintaining a fixed lean mixture, the system actively modulates the AFR and hydrogen-diesel substitution ratio to achieve the minimum air excess needed for stable combustion at each operating point, thereby maintaining fuel efficiency while ensuring combustion stability.
4Object-generated harmful factors
If hydrogen substitution ratio is increased, then emissions are reduced, but combustion control becomes more difficult
Solution Approach 1:
The system uses feedback control through sensors that monitor combustion characteristics, exhaust gas composition, and engine performance. Based on this feedback, the control system automatically adjusts the hydrogen-diesel substitution ratio and air-to-fuel ratio to maintain optimal combustion control and minimize emissions across varying operating conditions.
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 stabilizes combustion, increases engine performance, and decreases emissions by optimizing the combustion conditions of hydrogen and diesel, thereby mitigating engine knock and enhancing fuel efficiency.
Implementation Method 1
mixing an amount of a first fuel with an amount of a second fuel to combust a fuel mixture
Implementation Method 2
signaling a turbocharger to adjust an air output level of the turbocharger
Data Source
AI summary
Various methods and systems are provided for controlling emissions and a likelihood of engine knock during combustion in a multi-fuel engine. A method for an engine includes mixing an amount of a first fuel and an amount of a second fuel to combust a fuel mixture having a fuel ratio of the first fuel relative to the second fuel, the first fuel having a faster combustion flame speed relative to the second fuel, the fuel mixture having an air-to-fuel ratio with an amount of air delivered to the engine. The method further includes controlling either or both of a speed of combustion and a stability of combustion of the fuel mixture with the amount of air delivered to the engine by changing at least one of the fuel ratio, the air-to-fuel ratio, or both of the fuel ratio and the air-to-fuel ratio.