Prechamber Engine Nozzle Layout to Prevent Jet Flow Peeling
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Solution Overview
Problem
In prechamber-type engines, the gas flow from the pre-combustion chamber to the main combustion chamber is prone to peeling off, leading to a weak flow and reduced engine output.
Innovation Solution
The nozzle hole is configured to extend from the prechamber-side opening toward the main chamber-side opening with a reduced distance between its center line and the cylinder's central axis, and the piston top surface features a concave cavity with specific positional relationships to minimize peeling and enhance flow continuity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the piston cavity is provided to surround the main chamber-side opening of the nozzle hole to maintain high flow coefficient, then the flow coefficient is improved, but the gas flow peels off at high flow velocity conditions
Solution Approach 1:
The patent applies asymmetry by positioning the nozzle hole offset from the central axis of the cylinder, creating an asymmetric configuration where the distance between the nozzle hole center line and cylinder central axis is reduced. This asymmetric arrangement allows the gas flow to follow a more favorable path along the piston cavity wall, preventing flow peeling while maintaining high flow coefficient. The asymmetric positioning creates a specific geometric relationship between the nozzle hole and piston cavity that optimizes flow behavior.
Solution Approach 2:
The patent applies local quality by creating a specific geometric relationship at the critical interface between the nozzle hole and piston cavity. The condition that the first end of the main chamber-side opening is located farther from the cylinder central axis than the second end of the piston cavity peripheral edge establishes a localized geometric quality that prevents flow peeling. This local geometric optimization ensures that the flow remains attached to the piston cavity wall at high velocity conditions.
2Power
If the nozzle hole flow velocity is increased to improve engine output, then the power is improved, but the gas flow peels off from the piston cavity
Solution Approach 1:
The asymmetric positioning of the nozzle hole relative to the cylinder central axis creates a geometric configuration that allows the flow to remain attached even at high velocities. The offset positioning generates a favorable pressure distribution and flow path that prevents separation, enabling the system to operate at higher power outputs without flow peeling.
Solution Approach 2:
The patent utilizes curvature in the geometric relationship between the nozzle hole and piston cavity. The curved path created by the offset nozzle hole positioning and the specific geometric relationship between the opening ends creates a smoother flow transition that reduces flow separation. The curved geometry helps the flow follow the contour of the piston cavity wall more effectively at high velocities.
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 configuration suppresses peeling and forms a strong flow from the pre-combustion chamber to the main combustion chamber, promoting mixed gas formation and increasing engine output while reducing soot and exhaust temperature.
Implementation Method 1
The combustion gas (prechamber gas) generated in the pre-combustion chamber is jetted into the main combustion chamber through the nozzle hole due to the volume change of the main combustion chamber caused by the piston movement
Implementation Method 2
by making the shape of the piston cavity of the top surface of the piston shallower from the vicinity of the nozzle hole outlet toward the center direction of the cylinder, the generation of the mixed gas in the main combustion chamber is promoted, and the diffusion combustion in the combustion chamber is promoted
Data Source
AI summary
Provided is a prechamber-type engine comprising a cylinder, a cylinder head, and a piston defining a main combustion chamber between the cylinder and the cylinder head. Inside the cylinder head, a pre-combustion chamber communicating with the main combustion chamber via an injection hole is defined. The injection hole extends such that the distance between the center of the injection hole and the central axis line of the cylinder becomes smaller from a prechamber-side opening toward a main chamber-side opening. A top surface of the piston has a recessed piston cavity. In a cross sectional view in which the central axis line of the cylinder and the center of the main chamber side opening are present, a first end that is on the side of the circumferential edge of the main chamber-side opening farther from the central axis line of the cylinder is positioned farther from the central axis line of the cylinder than a second end that is on the side of the circumferential edge of the piston cavity closer to the injection hole.