Ethanol Injection for Knock Prevention in Direct Injection Engines
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Solution Overview
Problem
Knocking in gasoline engines occurs due to self-ignition of fuel, leading to engine damage and performance deterioration, and existing methods to prevent knocking, such as reducing compression ratio or ignition timing, result in decreased engine performance and fuel economy, especially in gasoline direct injection engines with weak swirl flow.
Innovation Solution
A system and method that involves directly injecting ethanol with a higher octane number into the combustion chamber in a hollow right circular cone shape, targeting the end-gas zone before injecting gasoline, using a second injector positioned on the central axis of the piston, to prevent knocking, and controlling engine operations by adjusting compression ratio and ignition timing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If compression ratio is reduced to prevent knocking, then knocking is prevented, but engine performance deteriorates
Solution Approach 1:
The invention extracts the harmful self-ignition process from the end-gas zone by injecting ethanol specifically into this region. The ethanol acts as a localized intervention that prevents knocking without requiring global reduction of compression ratio, thus maintaining engine performance while eliminating the harmful effect.
Solution Approach 2:
The invention applies local quality by creating a distinct fuel injection strategy for the end-gas zone versus the rest of the combustion chamber. Ethanol is injected specifically into the end-gas zone with different timing and positioning than main fuel injection, creating localized fuel distribution that prevents knocking in the critical region while maintaining overall combustion efficiency.
2Object-affected harmful factors
If ignition timing is lagged to prevent knocking, then knocking is prevented, but fuel economy decreases
Solution Approach 1:
The invention removes the need for ignition timing adjustment by directly addressing the knocking source through ethanol injection into the end-gas zone. This extraction of the problem at its source allows maintenance of optimal ignition timing for fuel economy while preventing knocking through localized ethanol action.
3Quantity of substance
If ethanol is injected using swirl flow to move to end-gas zone, then ethanol reaches end-gas zone, but precise operation cannot be guaranteed in engines with weak swirl flow
Solution Approach 1:
The invention segments the fuel injection system into two distinct injection paths: main fuel injection for general combustion and ethanol injection specifically targeted at the end-gas zone. This segmentation allows independent control of ethanol delivery, ensuring reliable operation regardless of swirl flow strength by using a dedicated injection strategy for the anti-knocking function.
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
Effectively prevents knocking by ensuring reliable ethanol injection to the end-gas zone, maintaining engine performance and fuel economy, even in engines with weak swirl flow, by using a targeted ethanol injection method that suppresses hot spots and vapor pressure.
Implementation Method 1
a second injector mounted at the upper surface of the cylinder on the central axis of the piston, and directly injecting a sub fuel including ethanol into the combustion chamber
Implementation Method 2
The second injector may be adapted to inject the sub fuel in a hollow right circular cone shape. An angle between confronting generating lines of the right circular cone shape may be 150-160°
Implementation Method 3
In an end of combustion stroke, pressure and temperature at an end-gas zone in of a combustion chamber may increase and fuel may be self-ignited
Data Source
AI summary
A system and method for preventing knocking prevents knocking by injecting a sub fuel including ethanol having high octane number to a combustion chamber in a case that the knocking occurs. The system for preventing knocking may include a cylinder, a piston moving in the cylinder reciprocally, forming a combustion chamber with the cylinder, and having a central axis, a first injector mounted at an upper surface of the cylinder with a distance from the central axis of the piston, and directly injecting a main fuel including gasoline into the combustion chamber, a second injector mounted at the upper surface of the cylinder on the central axis of the piston, and directly injecting a sub fuel including ethanol into the combustion chamber, and a spark plug disposed at the upper surface of the cylinder near the second injector.