Engine Knock Prediction via Cylinder Pressure Monitoring
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Solution Overview
Problem
Existing engine technologies face challenges in effectively suppressing intense knocks, particularly at high rotation speeds, which can damage the engine and reduce reliability, as methods like retarding ignition timing compromise fuel efficiency and add complexity to the engine structure.
Innovation Solution
A method that predicts intense knocks by monitoring cylinder inner pressure during the initial stage of combustion and injects additional fuel before the end of combustion to agitate the air-fuel mixture, thereby suppressing the knock without requiring complex device additions or significant structural changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ignition timing is retarded to suppress knock, then knock is suppressed, but fuel efficiency deteriorates
Solution Approach 1:
The system performs preliminary detection of knock tendency by monitoring cylinder pressure during the initial stage of combustion (5-20% burned mass fraction). When knock is predicted to occur, the control device prepares to inject additional fuel in advance before the knock actually occurs, allowing preventive action rather than reactive ignition timing retardation.
Solution Approach 2:
The system changes the parameter of fuel injection amount dynamically. When knock is detected in the initial combustion stage, additional fuel is injected to alter the combustion characteristics and suppress knock tendency, avoiding the need to change ignition timing which would affect fuel efficiency.
2Reliability
If ignition timing is retarded after knock detection, then knock is suppressed, but sudden intense knock cannot be suppressed in time
Solution Approach 1:
The system monitors cylinder pressure during the initial stage of combustion (5-20% burned mass fraction) to predict knock occurrence before it actually happens. This early detection allows the control system to prepare and execute fuel injection in advance, reducing the response time lag associated with detecting and reacting to established knock conditions.
Solution Approach 2:
The system skips the traditional sequence of detecting established knock and then retarding ignition timing. Instead, it rushes through the combustion process by detecting knock tendency in the initial stage and immediately injecting additional fuel to prevent knock development, effectively jumping ahead of the problem before it fully manifests.
3Reliability
If additional fuel is injected to suppress knock, then knock is suppressed, but air-fuel mixture composition changes
Solution Approach 1:
The system applies partial action by injecting additional fuel only in the specific case when knock is detected during the initial combustion stage (5-20% burned mass fraction). This selective injection suppresses knock only when necessary, rather than continuously altering the air-fuel mixture composition, thereby maintaining overall mixture stability while achieving knock suppression when needed.
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 allows for precise prediction and efficient suppression of intense knocks, improving engine reliability and maintaining fuel efficiency by using existing injectors to inject fuel before the knock occurs, thus preventing local temperature increases that cause engine damage.
Implementation Method 1
a knock information obtaining step of detecting or estimating pressure in the combustion chamber in an initial stage of combustion after a start of the combustion
Implementation Method 2
a knock suppression step of injecting a fluid into the combustion chamber before an end of combustion when the pressure exceeds the reference value
Data Source
Figure 1
Figure 2~3
Figure 4~5
AI summary
To effectively suppress an intense knock and improve reliability of an engine. A method for predicting occurrence of a knock with a predetermined intensity or higher (intense knock) in an engine 1 that burns an air-fuel mixture of gasoline fuel is provided. Pressure in a combustion chamber 17 (cylinder inner pressure) is detected in an initial stage of combustion. The cylinder inner pressure is compared with a preset reference value SV to determine whether or not the cylinder inner pressure exceeds the reference value SV during the course of the combustion. When the cylinder inner pressure exceeds the reference value SV, it is predicted that the intense knock occurs before an end of the combustion.