Weak Tumble Flow Combustion System for Natural Gas Engines
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Solution Overview
Problem
Natural gas engines using diesel engine cylinder heads struggle with inefficient combustion due to unbroken vortices, leading to suboptimal energy use and increased cycle variations, which limits thermal efficiency and increases the likelihood of engine knock.
Innovation Solution
A weak tumble flow fast combustion system is introduced, featuring a piston with a dish or reentrant combustion chamber and an intake duct structure with a tumble guide duct, eccentric chamfer, and flow regulating valve, which guides airflow to form a weak tumble flow that breaks into small-scale turbulence during compression, enhancing flame propagation and thermal efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If the natural gas engine adopts the cylinder head of the diesel engine, then the vortex intensity is improved, but the vortex does not break into small-scale turbulence, which is not conducive to flame propagation
Solution Approach 1:
The patent changes the geometric parameters of the combustion chamber, specifically using a reentrant combustion chamber design with specific depth and diameter ratios. This modifies the flow field characteristics to transform large-scale vortex into small-scale turbulence, enabling effective flame propagation while maintaining the benefit of the diesel engine cylinder head adaptation.
Solution Approach 2:
The reentrant combustion chamber employs curved surfaces and spherical-like geometry to guide the airflow. The curved walls of the reentrant chamber interact with the incoming vortex flow, causing it to break down into smaller eddies and turbulence structures that are essential for premixed gas combustion, thereby resolving the contradiction between maintaining vortex intensity and generating small-scale turbulence.
2Ease of manufacture
If a shallow basin combustion chamber structure is adopted, then the manufacturability is improved, but the vortex cannot be broken into small-scale turbulence
Solution Approach 1:
The reentrant combustion chamber uses curved, spherical-like geometry that is relatively simple to manufacture compared to complex multi-cavity structures. The curvature of the reentrant chamber walls naturally guides the vortex flow and promotes its breakdown into turbulence, achieving both manufacturability and effective turbulence generation.
Solution Approach 2:
The patent specifies particular dimensional parameters for the reentrant combustion chamber, including the depth-to-diameter ratio and the radius of curvature of the reentrant portion. These parameter optimizations ensure that the chamber is manufacturable while simultaneously creating the right flow conditions to break the vortex into small-scale turbulence.
3Power
If the compression ratio is increased to improve thermal efficiency, then the thermal efficiency is improved, but the engine knock tendency increases due to slow flame propagation speed
Solution Approach 1:
The reentrant combustion chamber design changes the combustion chamber geometry parameters to optimize flame propagation. The specific shape and dimensions of the reentrant chamber create favorable flow patterns that accelerate flame speed, allowing the engine to operate at higher compression ratios without experiencing knock, thus resolving the contradiction between thermal efficiency and knock resistance.
4Device complexity
If the diesel engine cylinder head is used directly, then the device complexity is reduced, but the energy of airflow movement is not fully utilized
Solution Approach 1:
The patent modifies the combustion chamber parameters within the existing cylinder head structure. By optimizing the depth, diameter, and reentrant geometry of the combustion chamber, the system fully utilizes the kinetic energy of the incoming airflow to generate effective turbulence, maximizing airflow energy utilization while maintaining the simplicity of using the diesel engine cylinder head.
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 system accelerates flame propagation, improves combustion characteristics, increases gas utilization rate, and allows for higher compression ratios, reducing gas consumption by 2%-3% while maintaining existing engine interfaces and air distribution mechanisms, thus reducing design changes and costs.
Implementation Method 1
the intake airflow injected from the duct generates vortex motion around the cylinder axis
Implementation Method 2
with the upward motion of the piston, the vortex is squeezed into the combustion chamber, and the intensity of the vortex is continuously improved
Implementation Method 3
the vortex may not break into small-scale turbulence... small-scale turbulence plays an important role in flame propagation
Implementation Method 4
Squeeze flow refers to the centripetal movement formed by the piston squeezing the gas near the edge of the cylinder into the combustion chamber at the end of the compression stroke
Data Source
AI summary
A weak tumble flow fast combustion system is provided. An intake throat and an exhaust throat are provided on a cylinder head, a section of an intake duct close to the intake throat is a tumble guide duct, an axis of the tumble guide duct is arranged obliquely with respect to the bottom surface of the cylinder head, and an upper side surface of the tumble guide duct is a flowing-down guide surface arranged obliquely with respect to the bottom surface of the cylinder head, a lower side surface of the tumble guide duct is an arc-shaped guide surface recessed toward the bottom surface of the cylinder head, an eccentric chamfer is provided at the lower end of the intake throat, and the eccentric direction of the eccentric chamfer is offset along the direction connecting the center of the intake throat to the exhaust throat.