Dual Fuel Engine Combustion Control via Secondary Injection
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Solution Overview
Problem
Dual fuel diesel-type internal combustion engines face issues with knock, reduced fuel efficiency, and increased exhaust emissions of unburned hydrocarbons and CO, particularly in heavy-duty applications with large combustion chamber volumes and low engine speeds.
Innovation Solution
The method involves pre-mixing a first fuel with air and/or recycled exhaust gas in the combustion chamber, followed by a first injection of a second fuel to initiate auto-ignition, and subsequent injections to enhance turbulence and late mixing, thereby improving flame propagation speed and oxidation efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If pre-mixed flame propagation combustion is used in heavy-duty dual fuel engines, then alternative fuels like natural gas can be utilized, but knock problems occur due to uncontrolled auto-ignition of unburned fuel ahead of the flame
Solution Approach 1:
The patent applies preliminary action by injecting a portion of the second fuel (e.g., diesel) before the main fuel (e.g., natural gas) to create a controlled ignition source. This preliminary fuel injection ensures that the combustion process is initiated in a controlled manner, preventing uncontrolled auto-ignition and knock while maintaining the ability to use alternative fuels in heavy-duty engines
Solution Approach 2:
The patent uses the second fuel (e.g., diesel) as an intermediary substance that facilitates controlled ignition of the first fuel (e.g., natural gas). The second fuel acts as a mediator between the compression process and the main fuel combustion, creating a controlled flame propagation that prevents knock while enabling alternative fuel operation
2Power
If large combustion chamber volumes and low engine speeds are used in heavy-duty engines, then engine power output is increased, but knock is enhanced due to extended combustion time and reduced flame propagation velocity
Solution Approach 1:
The patent applies preliminary action by injecting a portion of the second fuel before the main fuel to create a controlled ignition source. This preliminary fuel injection ensures that the combustion process is initiated in a controlled manner, preventing uncontrolled auto-ignition and knock while maintaining the ability to use alternative fuels in heavy-duty engines
Solution Approach 2:
The patent employs periodic action through multiple fuel injection events: a first injection of the second fuel to initiate combustion, followed by a second injection of the first fuel. This periodic injection strategy maintains controlled combustion timing and flame propagation velocity even in large combustion chambers operating at low speeds, thereby preventing knock while preserving engine power output
3Use of energy by moving object
If conventional diesel fuel is used in heavy-duty engines, then fuel efficiency is high, but emissions of soot and NOx are increased
Solution Approach 1:
The patent applies parameter changes by altering the fuel type and combustion parameters. By using alternative fuels like natural gas or biogas combined with a small amount of diesel for ignition, the system maintains high fuel efficiency while reducing soot and NOx emissions. The controlled combustion process and optimized injection timing further enhance emission reduction while preserving energy efficiency
4Productivity
If subsequent fuel injection is used to enhance turbulence and flame propagation, then combustion efficiency is improved, but device complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the fuel injection process into distinct phases: a first injection of the second fuel to initiate combustion, and a second injection of the first fuel to enhance turbulence and flame propagation. This segmented approach improves combustion efficiency while keeping the injection system relatively simple, as each injection event serves a specific function and can be controlled independently
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 reduces the risk of knock, enhances fuel efficiency, and decreases emissions of unburned hydrocarbons and CO, achieving combustion performance comparable to conventional diesel engines with lower soot and NOx emissions.
Implementation Method 1
compressing the charge containing the first fuel to conditions that allow auto-ignition of the second fuel
Implementation Method 2
performing a first injection of the second fuel into said combustion chamber to initiate auto-ignition of said second fuel for igniting said first fuel
Implementation Method 3
thereby initiating conditions for pre-mixed flame propagation combustion of the first fuel
Implementation Method 4
performing at least one subsequent injection, said subsequent injection supplying additional kinetic energy into the combustion process to thereby enhance turbulence intensity and propagation speed of said flame
Data Source
Figure 1~4
Figure 2a~3c
AI summary
A method of operating a dual fuel internal combustion engine of the diesel-type is provided. The method includes pre-mixing a first fuel in a combustion chamber and/or in an inlet port, compressing a charge containing the first fuel to conditions that allow auto-ignition of a second fuel, performing a first injection of the second fuel into the combustion chamber to initiate auto-ignition of the second fuel for igniting the first fuel, thereby initiating conditions for pre-mixed flame propagation combustion of the first fuel. At least one subsequent injection is performed in which additional kinetic energy is supplied into the combustion process to thereby enhance turbulence intensity and propagation speed of the flame and/or enhance late mixing in the combustion chamber, so a to improve late oxidation during combustion. A dual fuel combustion engine of the diesel engine type.