Spark-Assisted HCCI Combustion Control for Low Load Efficiency
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Solution Overview
Problem
Existing HCCI combustion methods face challenges in achieving auto-ignition at low engine speeds and loads, leading to degraded thermal efficiency and emissions, and produce undesirable NOx levels when spark-assisted HCCI is implemented.
Innovation Solution
The method involves adjusting engine operating conditions to bring the combustion chamber to auto-ignition temperature without a spark in one mode, and using spark-assisted ignition in a stratified air-fuel mixture at lower engine speeds and loads to promote auto-ignition at other sites, while maintaining HCCI combustion stability and reducing NOx production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If HCCI combustion is used at low engine speeds and loads, then thermal efficiency is improved, but auto-ignition cannot occur at the appropriate time leading to degraded performance
Solution Approach 1:
The patent applies parameter changes by adjusting the air-fuel mixture composition (adding reactive species through controlled combustion) and temperature parameters to enable auto-ignition at low engine speeds and loads. The ECU monitors combustion parameters and adjusts fuel injection timing and amount to maintain auto-ignition capability across different operating conditions.
2Reliability
If spark-assisted HCCI combustion is implemented, then auto-ignition is promoted at low speeds and loads, but NOx production increases at high speeds and loads
Solution Approach 1:
The patent applies local quality by providing spark assistance only in specific local conditions (low engine speeds and loads) where it is beneficial for initiating auto-ignition. The ECU determines operating conditions and applies spark ignition selectively rather than continuously, avoiding NOx production during high speed and load operations where HCCI alone is sufficient.
3Reliability
If fuel is injected during negative overlap period, then auto-ignition is promoted through active air-fuel mixture, but thermal efficiency degrades at low temperatures
Solution Approach 1:
The patent applies dynamics by making the fuel injection strategy adaptive and dynamic. The ECU continuously monitors engine operating conditions (temperature, speed, load) and adjusts the fuel injection timing and amount accordingly. The system transitions between different injection strategies (negative overlap period injection vs. other timing) based on real-time conditions to optimize both auto-ignition reliability and thermal efficiency.
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 improves thermal efficiency and emissions by ensuring auto-ignition at low engine speeds and loads, and decreases NOx production under high engine speed and load conditions by limiting spark-assisted HCCI to lower conditions, while maintaining stable HCCI combustion.
Implementation Method 1
a pre-mixed air-fuel mixture is compressed in a combustion chamber such that the mixture combusts without using a spark plug to initiate the combustion
Implementation Method 2
a pre-mixed air-fuel mixture is compressed in a combustion chamber such that the mixture combusts
Implementation Method 3
igniting the fuel cloud by a spark from the spark plug, and then causing cylinder pressure to rise
Implementation Method 4
injecting a part of the fuel directly into the combustion chamber in the negative overlap period. This process causes the injected fuel to evaporate immediately into the higher temperature exhaust gases
Implementation Method 5
the fuel is broken down into radical molecules having broken molecular chains
Implementation Method 6
providing a negative overlap period wherein both of an intake and an exhaust valve are closed. This increases the temperature inside of the combustion chamber because a higher quantity of exhaust gases is retained in the combustion chamber
Data Source
AI summary
A method of operating an internal combustion engine having a combustion chamber with a piston and a spark plug, comprising during a first mode, bringing the temperature of the combustion chamber to auto-ignition temperature by adjusting engine operating conditions and producing auto-ignition in said combustion chamber without requiring spark from said spark plug; and during a second mode, bringing the temperature of the combustion chamber close to auto-ignition temperature by adjusting engine operating conditions, forming a small cloud of stratified air-fuel mixture near said spark plug, igniting said fuel cloud by a spark form said spark plug, and then causing cylinder pressure to rise, thereby producing auto-ignition at other sites in said combustion chamber wherein said first mode is implemented in a first operating range and said second mode is implemented only in a second operating range where engine speed and load are lower than said first operating range.