Piston Cavity Design for Tumble Flow Control
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Solution Overview
Problem
Pistons with crown surface cavities in internal combustion engines experience deterioration in tumble flow quality due to non-uniform flow speeds, which affects fuel economy and combustion stability.
Innovation Solution
The piston design includes a first cavity that guides tumble flow and a second cavity that guides fuel to the ignition plug, with the upstream portion of the first cavity extending further than the downstream portion to prevent tumble flow from entering the second cavity, maintaining high flow speed and preventing non-uniform flow speed deterioration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a cavity is provided to guide sprayed fuel to the ignition plug for stratified lean burn mode, then fuel economy is improved, but the tumble flow quality deteriorates due to non-uniform flow speed
Solution Approach 1:
The first cavity is divided into an upstream portion and a downstream portion, with the upstream portion extending further in the flow direction. This segmentation allows the upstream portion to guide tumble flow while the downstream portion allows fuel to pass through, preventing flow speed non-uniformity and maintaining tumble flow quality while still enabling stratified lean burn mode for improved fuel economy.
Solution Approach 2:
Different portions of the first cavity are given different functions: the upstream portion is designed to guide tumble flow along the crown surface, while the downstream portion allows fuel to pass through to the second cavity. This local differentiation of function allows the cavity to simultaneously maintain tumble flow quality and enable fuel guidance for improved fuel economy.
2Stability of the object's composition
If a cavity follows tumble flow for homogeneous combustion mode, then combustion stability is improved, but the flow speed becomes non-uniform when fuel enters the cavity
Solution Approach 1:
The first cavity is segmented into upstream and downstream portions, where the upstream portion follows tumble flow to maintain combustion stability, while the downstream portion is designed to allow fuel to pass through without significantly reducing flow speed, thus maintaining flow speed uniformity.
Solution Approach 2:
The first cavity serves multiple functions: it guides tumble flow along the crown surface to maintain combustion stability, and simultaneously allows fuel to pass through to the second cavity without significantly reducing flow speed. This multi-functionality resolves the contradiction between combustion stability and flow speed uniformity.
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 inhibits the deterioration of tumble flow quality by ensuring high flow speed and preventing the tumble flow from entering the second cavity, thereby maintaining efficient fuel economy and combustion stability.
Implementation Method 1
a first cavity that is a depression provided in the crown surface and that guides tumble flow
Data Source
AI summary
A piston of an internal combustion engine includes a crown surface, a first cavity, and a second cavity. The crown surface forms an internal wall surface of a combustion chamber. The first cavity is a depression provided in the crown surface. The second cavity is a depression provided inside the first cavity. The first cavity includes an upstream portion located upstream of the second cavity in a flow direction of a tumble flow flowing along the crown surface and a downstream portion located downstream of the second cavity in the flow direction. The upstream portion extends further in the flow direction than the downstream portion.