Piston Cavity Geometry for Stratified Combustion Stability
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Solution Overview
Problem
Existing internal-combustion engines face challenges in achieving stable stratified combustion under low load and low rotational speed conditions, as fuel mists often flow towards the exhaust port instead of being effectively guided to the spark plug, resulting in inadequate air-fuel mixture distribution and combustion stability.
Innovation Solution
The engine design incorporates a piston cavity with a vertical wall and sidewalls that guide fuel mists injected at specific angles during the compression stroke, ensuring a rich air-fuel mixture is produced around the spark plug, with a third fuel mist colliding with the cavity's bottom surface to lift and direct the mists towards the spark plug, reducing kinetic energy and minimizing fuel flow towards the exhaust port.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If fuel is injected obliquely toward the piston top surface during compression stroke, then a rich air-fuel mixture can be produced in the combustion chamber, but the fuel mist flows towards the exhaust port instead of being guided to the spark plug, resulting in poor combustion stability
Solution Approach 1:
The cavity is divided into multiple functional regions with different wall orientations: a first region with a first wall having a first angle (30-60 degrees) to guide fuel mist toward the spark plug, and a second region with a second wall having a second angle (10-30 degrees) to prevent fuel mist from flowing to the exhaust port. This segmentation allows different parts of the injected fuel mist to be directed to different locations, ensuring both rich mixture formation and combustion stability.
Solution Approach 2:
Different regions of the cavity are given different geometric properties (different wall angles) to perform different functions. The first wall region provides stronger guidance for fuel mist toward the spark plug area, while the second wall region provides gentler guidance to prevent exhaust port flow, creating local quality variations that solve the overall contradiction.
2Productivity
If the cavity extends toward the fuel injection valve, then fuel mist can be effectively captured and distributed, but the complex cavity structure increases manufacturing difficulty
Solution Approach 1:
The cavity structure is segmented into distinct regions (first region with first wall, second region with second wall) that can be independently defined in CAD software and manufactured using standard piston manufacturing processes. Each region has clearly defined geometric parameters (angles of 30-60 degrees and 10-30 degrees respectively), making the complex structure manufacturable with conventional techniques.
3Quantity of substance
If multiple injection ports inject fuel mists at different angles, then comprehensive fuel distribution can be achieved, but the increased number of injection ports and angles complicates the fuel injection system
Solution Approach 1:
The fuel injection valve is designed with multiple injection ports (first, second, third, and fourth injection ports) positioned at different locations and angles to match the different regions of the cavity. Each injection port targets a specific region: some ports inject toward the first wall area, others toward the second wall area, creating local quality variations in fuel distribution that correspond to the cavity's segmented structure.
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 ensures a stable and efficient stratified combustion by accurately distributing a rich air-fuel mixture around the spark plug, enhancing combustion stability and reducing fuel mist flow towards the exhaust port, thereby improving engine performance.
Implementation Method 1
A pair of second fuel mists are to be injected at the predetermined crank angle from the second injection ports to respectively collide with the first and second sidewalls
Implementation Method 2
The first and second sidewalls are provided to guide the second fuel mists to flow along the first and second sidewalls
Implementation Method 3
A third fuel mist is to be injected from the third injection port to collide with the bottom surface of the cavity
Implementation Method 4
The bottom surface is provided to lift the first fuel mist and the second fuel mists to flow toward the spark plug
Implementation Method 5
The spark plug is provided above the combustion chamber to generate a spark that ignites a mixture of fuel and air in the cylinder
Implementation Method 6
a plurality of fuel mists are to be obliquely injected toward the top surface of the piston in respectively different directions at a predetermined crank angle in a compression stroke
Data Source
AI summary
An internal-combustion engine includes a cylinder, a piston, a spark plug, and a fuel injection valve. The piston includes a top surface and a cavity provided in the top surface. The cavity includes a bottom surface, a vertical wall, a first sidewall, and a second sidewall. The fuel injection valve includes a plurality of injection ports from which a plurality of fuel mists are to be obliquely injected toward the top surface of the piston in respectively different directions at a predetermined crank angle in a compression stroke. The cavity extends from a position close to a center of the piston toward the fuel injection valve when viewed from above the top surface of the piston. The first and second sidewalls extend toward the fuel injection valve when viewed from above the top surface of the piston.