Piston Engine Dynamic Combustion Mode Switching
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Solution Overview
Problem
Piston engines using fuels with low cetane numbers face issues with premature ignition (knocking) at high loads and increased NOx emissions when employing premixed combustion, while switching to diesel combustion reduces knocking but increases NOx emissions.
Innovation Solution
A method and engine design that dynamically switches between premixed and diesel combustion modes based on auto-ignition indicators, using a higher cetane number pilot fuel to ignite the main fuel, allowing for operation in two modes: introducing main fuel after pilot fuel injection at high loads to prevent knocking and before pilot fuel injection at low loads to minimize NOx emissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If premixed combustion is used to reduce NOx emissions, then NOx emissions are reduced, but knocking occurs at high loads
Solution Approach 1:
The invention dynamically switches between premixed combustion mode (for low loads with lower NOx emissions) and diesel combustion mode (for high loads to prevent knocking). The control system monitors engine operating conditions and adjusts the combustion mode in real-time, making the system adaptive rather than static.
Solution Approach 2:
The invention changes the combustion mode parameter based on engine load conditions. By switching between premixed and diesel combustion processes, the system optimizes the balance between NOx emissions and knocking prevention across different operating ranges.
2Reliability
If diesel combustion process is used to avoid knocking, then knocking is avoided, but NOx emissions increase
Solution Approach 1:
The system dynamically selects between diesel combustion mode (for knocking prevention at high loads) and premixed combustion mode (for lower NOx emissions at low loads). This dynamic adaptation allows the engine to avoid knocking when necessary while minimizing NOx emissions when possible.
Solution Approach 2:
The invention changes the combustion process parameter based on engine load. By switching between diesel and premixed combustion modes, the system optimizes the trade-off between knocking prevention and NOx emissions across different operating conditions.
3Object-generated harmful factors
If constant premixed combustion is used, then NOx emissions are reduced, but engine efficiency is limited due to compression ratio constraints
Solution Approach 1:
The invention dynamically switches between premixed and diesel combustion modes, allowing the engine to operate at higher compression ratios when in diesel mode (improving efficiency) while still maintaining low NOx emissions during premixed mode operation at appropriate load conditions.
Solution Approach 2:
By changing the combustion mode parameter, the system enables higher compression ratios to be used overall, particularly in diesel mode, which improves thermal efficiency and energy utilization while maintaining acceptable NOx emissions through selective premixed mode operation.
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 low NOx emissions at low loads, avoids knocking at high loads, and enables a higher compression ratio, improving engine efficiency compared to constant premixed combustion.
Implementation Method 1
igniting the pilot fuel by auto-ignition
Implementation Method 2
igniting the pilot fuel by auto-ignition
Implementation Method 3
igniting the main fuel by the combustion of the pilot fuel
Data Source
Figure 1
AI summary
In the method for operating a piston engine, the engine is operated in a first operating mode by introducing main fuel into the cylinders (1) after pilot fuel injection has started, and in a second operating mode by introducing the main fuel into the cylinders (1) before the pilot fuel. One or more indicators of auto- ignition and/or a risk of auto-ignition of the main fuel are monitored and com- pared to predetermined ranges indicating auto-ignition or the risk of auto- ignition. If one or more of the monitored indicators is within the predetermined range, the engine is operated in the first operating mode, and if none of the monitored values is within the predetermined range, the engine is operated in the second operating mode.