Engine Knock Suppression via Early Fluid Injection
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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 limit fuel efficiency, as methods like ignition timing retardation reduce compression ratio and restrict operating ranges.
Innovation Solution
The engine incorporates a knock occurrence prediction system that uses a pressure sensor to detect cylinder inner pressure and inject additional fuel before the burned mass fraction reaches 50% during combustion, agitating the air-fuel mixture to equalize temperature and prevent local hot spots, thereby suppressing intense knocks without restricting operating conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If ignition timing is retarded to suppress intense knock, then knock intensity is reduced, but compression ratio decreases and fuel efficiency deteriorates
Solution Approach 1:
The system performs preliminary detection of knock occurrence at an early stage (when burned mass fraction is 10-30%) and takes preventive action by injecting fluid before the knock fully develops. This preliminary intervention prevents the need for later ignition timing retardation, thereby maintaining compression ratio and fuel efficiency while still suppressing intense knock.
Solution Approach 2:
A fluid (water or ethanol) is introduced as an intermediary substance into the combustion chamber to suppress knock. The fluid absorbs heat and reduces peak temperatures, preventing intense knock without requiring ignition timing retardation. This intermediary approach allows the engine to maintain optimal ignition timing and compression ratio for fuel efficiency.
2Object-affected harmful factors
If ignition timing is restricted to suppress knock, then knock is reduced, but feasible operating range is limited
Solution Approach 1:
The system continuously monitors combustion pressure and burned mass fraction in real-time, providing feedback to the control device. When knock is detected, the system responds by injecting fluid at the optimal timing. This feedback mechanism allows the engine to maintain optimal ignition timing across a wide operating range while dynamically suppressing knock only when necessary, thereby preserving adaptability.
Solution Approach 2:
The system changes the physical state of the combustion chamber by introducing a fluid substance that alters thermal characteristics. This parameter change (adding fluid) provides a new degree of freedom to control knock without changing ignition timing parameters, thereby maintaining the full feasible operating range.
3Use of energy by moving object
If high compression ratio is used to improve fuel efficiency, then thermal efficiency increases, but intense knock occurrence increases
Solution Approach 1:
The system performs preliminary detection of knock tendency at an early stage of combustion (10-30% burned mass fraction) and takes preventive action before intense knock develops. This allows the engine to maintain high compression ratio for fuel efficiency while preventing knock through early fluid injection, resolving the contradiction between compression ratio and knock suppression.
Solution Approach 2:
A fluid (water or ethanol) is introduced as an intermediary to manage the thermal effects of high compression ratio. The fluid absorbs excess heat and reduces peak temperatures, allowing the engine to operate at high compression ratios for improved fuel efficiency without suffering from intense knock.
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 suppression of intense knocks, enhancing engine reliability and maintaining fuel efficiency by injecting fuel before the end of combustion, thus preventing damage and improving operational stability.
Implementation Method 1
When the fluid is injected into the combustion chamber, an air-fuel mixture under combustion is agitated. When the air-fuel mixture is agitated during the combustion, a temperature of the entire air-fuel mixture is equalized.
Implementation Method 2
a knock occurrence prediction means for predicting occurrence of a knock; When the knock occurrence prediction means predicts occurrence of an intense knock with a predetermined intensity or higher
Data Source
Figure 1
Figure 2~3
Figure 4~5
AI summary
To effectively suppress an intense knock and improve reliability of an engine. The engine includes: a combustion chamber 17 defined in a cylinder 11 by a piston 3; a fuel supply device 61 that supplies fuel containing gasoline into the combustion chamber 17; an ECU 8 having knock occurrence prediction means 80 for predicting occurrence of a knock; and an injector 6 that injects the fuel into the combustion chamber 17. When the knock occurrence prediction means 80 predicts occurrence of an intense knock with a predetermined intensity or higher, the injector 6 injects the fuel into the combustion chamber 17 within a period before the burned mass fraction reaches 50% after a start of combustion.