Engine Combustion Chamber Cavity Water Injection Timing
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Solution Overview
Problem
The challenge is to maintain combustion stability in engines while injecting water into the combustion chamber to improve torque, as excessive water concentration near the spark plug hinders ignition.
Innovation Solution
A combustion chamber structure with a cavity and a water injection system that injects water during the compression stroke, using nozzle holes aligned to intersect the cavity, reducing water diffusion and maintaining low water concentration near the spark plug, and utilizing a heat barrier layer to enhance thermal efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If water is injected into the combustion chamber to improve torque, then engine torque increases, but combustion stability deteriorates due to high water concentration near the spark plug
Solution Approach 1:
The combustion chamber is segmented into two distinct regions: a cavity region where water is injected and accumulated, and a spark plug region where combustion occurs. The cavity acts as a separate zone that traps water away from the spark plug, allowing water injection for torque improvement without compromising combustion stability in the spark plug region
Solution Approach 2:
Different regions of the combustion chamber are given different functional qualities: the cavity region is designed to accumulate and retain water (high water concentration zone), while the spark plug region maintains low water concentration to ensure reliable ignition. This local differentiation of water concentration zones resolves the contradiction between torque improvement and combustion stability
2Power
If a large amount of water is injected into the combustion chamber, then engine torque improves, but the concentration of water near the spark plug increases making ignition difficult
Solution Approach 1:
The cavity acts as an intermediary structure between the water injection system and the spark plug. It serves as a buffer zone that intercepts and retains injected water, preventing it from reaching the spark plug region. This intermediary cavity enables large amounts of water to be injected for torque improvement while maintaining low water concentration near the spark plug for reliable ignition
3Power
If water is injected during intake stroke, then water is distributed throughout the combustion chamber, but water diffusion increases causing high water concentration near spark plug
Solution Approach 1:
Water is injected during the compression stroke rather than the intake stroke, timing the injection to occur before the piston reaches top dead center. This preliminary timing allows the cavity to intercept and retain water while the combustion chamber volume is minimized, preventing water from diffusing throughout the chamber and accumulating near the spark plug
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 configuration allows for stable ignition of the mixture gas even with high water injection, improving engine torque and fuel efficiency while reducing thermal losses.
Implementation Method 1
During a compression stroke, a flow of gas inside the combustion chamber is weaker than that during an intake stroke. According to this configuration, by the water injection device injecting water in a compression stroke, diffusion of the water by the flow of gas is reduced.
Implementation Method 2
The cavity has a bottom part where the water injected by the water injection device collides, and a raising part configured to raise the water spreading along the bottom part toward the water injection device.
Data Source
AI summary
An engine system includes a combustion chamber including a cylinder formed in an engine and a piston configured to reciprocate inside the cylinder, a spark plug disposed in a ceiling part of the combustion chamber, and a water injection device configured to inject water into the combustion chamber through a plurality of nozzle holes facing the inside of the combustion chamber. The piston has a cavity in an upper surface thereof. The water injection device injects water into the cavity in a compression stroke at a timing when an extension of axes of at least some of the nozzle holes intersects the cavity. The cavity has a bottom part where the water injected by the water injection device collides, and a raising part configured to raise the water spreading along the bottom part toward the water injection device.