Lean-Burn Pre-Combustion Chamber for Natural Gas Engines
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Solution Overview
Problem
Existing pre-combustion chamber designs for natural gas engines operate under rich burn conditions, leading to suboptimal combustion efficiency and increased NOx emissions, as they fail to efficiently handle lean fuel-air mixtures.
Innovation Solution
A lean-burn pre-combustion chamber with a unique flow dynamic method and structure, featuring nozzles with offsets, a spark-gap electrode assembly, and a fuel admission valve, generates a compound vortex flow pattern that promotes efficient flame propagation and prevents the formation of high NOx and CO concentrations by maintaining a lean fuel-air mixture.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If existing pre-combustion chamber designs operate under rich burn conditions, then flame propagation is maintained, but combustion efficiency decreases and NOx emissions increase
Solution Approach 1:
The patent changes the fundamental operating parameter from rich burn to lean burn conditions by modifying the fuel-air mixture ratio in the pre-combustion chamber. This is achieved through adjusted fuel injection timing, duration, and amount, allowing efficient combustion at leaner mixtures that reduce NOx emissions while maintaining combustion efficiency.
Solution Approach 2:
The pre-combustion chamber performs preliminary combustion of the fuel-air mixture before it enters the main combustion chamber. This preliminary action allows the mixture to be pre-heated and partially burned, improving overall combustion efficiency and reducing the load on the main chamber, thereby enabling leaner overall operation with lower emissions.
2Object-generated harmful factors
If lean fuel-air mixture is used in pre-combustion chamber, then NOx emissions are reduced, but flame propagation efficiency decreases
Solution Approach 1:
The pre-combustion chamber performs preliminary combustion that pre-heats the fuel-air mixture before it enters the main combustion chamber. This preliminary heating action raises the initial temperature of the mixture, which significantly increases the flame propagation speed in the main chamber when the mixture is introduced, thereby maintaining fast flame propagation even under lean burn conditions.
Solution Approach 2:
The pre-combustion chamber acts as an intermediary between fuel injection and main chamber combustion. It prepares the fuel-air mixture by controlling the initial combustion stage, creating optimized conditions (higher temperature, controlled radical species) that facilitate rapid and efficient flame propagation in the main combustion chamber when the mixture is introduced.
3Loss of energy
If fuel injection timing is advanced, then combustion efficiency improves, but combustion variability increases
Solution Approach 1:
The pre-combustion chamber performs preliminary combustion that completes the burning process before the main combustion chamber pressure peak. This timing adjustment allows the fuel to be injected and burned in advance, ensuring combustion is largely complete by the time the main chamber reaches its peak pressure, thereby reducing combustion variability while maintaining efficiency.
Solution Approach 2:
The system uses feedback control based on combustion chamber pressure measurements to dynamically adjust fuel injection timing and duration. By monitoring pressure variations and adjusting injection parameters accordingly, the system maintains optimal combustion efficiency while reducing variability caused by variations in operating conditions.
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 design achieves improved engine efficiency, reduced NOx emissions, and stable combustion by ensuring nearly complete burning of the fuel-air mixture before flame jets exit the pre-combustion chamber, enhancing Indicated Thermal Efficiency and maintaining low combustion variability.
Implementation Method 1
a spark-gap electrode assembly, comprising: a primary electrode disposed within the prechamber volume; and one or more ground electrodes disposed within the prechamber volume and offset from the primary electrode to form one or more electrode gaps
Implementation Method 2
generates a compound vortex flow pattern that promotes efficient flame propagation
Implementation Method 3
ensuring nearly complete burning of the fuel-air mixture before flame jets exit the pre-combustion chamber
Data Source
Figure 1
Figure 2
Figure 3A~3B
AI summary
In certain embodiments, a unique method and pre-combustion chamber (PCC) structure may ensure very efficient flame propagation of lean fuel-air mixture in natural gas engines by reducing the amount of fuel admitted to the PCC. A PCC may include an enclosed volume of 1-3% of the main combustion chamber volume, with a spark plug and a fuel passage located opposite one or more PCC discharge nozzles to create a relatively richer fuel-air mixture with relatively lower turbulence in the spark plug region and a relatively leaner fuel-air mixture with relatively high turbulence in the nozzle region, which can be reliably and efficiently ignited, resulting in a high velocity flame jet/torch emerging from the prechamber into the main chamber. The PCC may be threaded with a 22mm x 1.5 or 7/8"-18 thread size, to allow the PCC to be screwed into a cylinder head in place of a spark plug.