Arcuate Indent Piston Crown for Combustion Chamber Flow Control
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Solution Overview
Problem
Direct injection engines face inefficiencies and increased emissions due to fuel dispersion issues, where fuel jets interact with combustion chamber surfaces, leading to uneven burning, higher temperatures, and heat rejection.
Innovation Solution
The engine design incorporates arcuate indents on the piston crown surface to redirect and segregate fuel jets, creating a spiral motion within the combustion chamber, keeping combustion away from surfaces and promoting uniform fuel/air mixing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If fuel jets are injected directly into the combustion chamber and allowed to disperse naturally, then the fuel injection system remains simple, but fuel dispersion becomes uneven causing localized rich and lean areas, increased emissions, and higher temperatures
Solution Approach 1:
The piston crown surface is segmented into multiple arcuate indents (typically 3-6) arranged circumferentially around the combustion chamber center. Each indent acts as an independent flow redirection element, dividing the fuel spray into multiple controlled streams that swirl around the chamber center, ensuring more uniform fuel distribution and preventing localized rich/lean areas.
Solution Approach 2:
The arcuate indents feature curved surfaces with specific radii of curvature designed to redirect fuel flow in a swirling motion. The curved geometry of the indents, including the arcuate entry surfaces and rounded bottom portions, creates centrifugal forces that promote uniform fuel/air mixing while maintaining combustion away from the cylinder walls, reducing heat rejection and emissions.
2Quantity of substance
If deflection foils are used to redirect fuel spray into a combined radial path, then fuel mixing is improved, but fuel momentum is maintained parallel to the piston surface causing fuel to migrate toward cylinder walls and increase heat rejection
Solution Approach 1:
Instead of redirecting fuel in a planar radial path parallel to the piston surface (2D flow), the arcuate indents create a three-dimensional swirling motion that directs fuel along a helical path through the combustion chamber. This dimensional change in flow pattern keeps fuel suspended in the chamber center away from the cylinder walls, improving mixing while reducing heat transfer to surfaces.
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 enhances fuel efficiency, reduces emissions, and maintains lower component temperatures by ensuring uniform fuel/air mixing and minimizing interaction with cylinder walls, resulting in improved combustion efficiency and reduced heat rejection.
Implementation Method 1
a recirculation surface having a concave shape and extending along a spiral direction adjacent the entry surface
Implementation Method 2
the at least one arcuate indent is aligned with the fuel jet centerline and includes an entry surface extending from a central portion of the piston, a recirculation surface having a concave shape and extending along a spiral direction
Data Source
AI summary
An internal combustion engine includes an engine block having a cylinder bore and a cylinder head having a flame deck surface disposed at one end of the cylinder bore. A piston connected to a rotatable crankshaft and configured to reciprocate within the cylinder bore has a piston crown portion facing the flame deck surface such that a combustion chamber is defined within the cylinder bore and between the piston crown and the flame deck surface. A fuel injector having a nozzle tip disposed in fluid communication with the combustion chamber has at least one nozzle opening configured to inject a fuel jet into the combustion chamber along a fuel jet centerline. At least one arcuate indent is formed in the top surface in aligned fashion with the fuel jet and including an entry surface, a recirculation surface and a wall.