Two-Piece Ejector Design for Boosted Engine Vapor Purge
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Solution Overview
Problem
Existing ejector designs for vapor purge systems in boosted internal combustion engines are bulky, require complex manufacturing processes, and have suboptimal flow characteristics due to straight sections downstream of the throat, leading to inefficiencies and increased manufacturing costs.
Innovation Solution
A two-piece ejector design is fabricated using a venturi tube with a converging section, a throat of predetermined diameter, and a diverging section, where the first piece includes a flange and a portion of the venturi tube, and the second piece completes the venturi tube, allowing for welding or snap fit connections, and is installed into an air intake component to enhance flow efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a traditional one-piece ejector design is used, then manufacturing is simpler, but the ejector is bulky and has suboptimal flow characteristics
Solution Approach 1:
The ejector is divided into two separate pieces: a first piece containing the throat section and a second piece containing the body section. This segmentation allows each piece to be optimized independently for flow characteristics while reducing the overall bulk of the ejector assembly.
Solution Approach 2:
The invention transitions from a traditional one-piece three-dimensional design to a two-piece configuration that optimizes spatial arrangement. The separate pieces can be positioned and oriented to achieve better flow characteristics while reducing overall volume.
2Device complexity
If a traditional one-piece ejector design is used, then the structure is simpler, but flow characteristics are suboptimal
Solution Approach 1:
Dividing the ejector into two pieces allows independent optimization of the throat section (first piece) and body section (second piece). The throat can be precisely formed for optimal mixing while the body can be designed for efficient flow delivery, resulting in superior flow characteristics despite increased structural complexity.
Solution Approach 2:
Different sections of the ejector are given different geometries optimized for their specific functions. The throat section has a reduced diameter for creating vacuum and mixing, while the body section has a larger diameter for efficient vapor and air flow, achieving local optimization of flow characteristics.
3Ease of manufacture
If straight sections are used downstream of the throat, then manufacturing is easier, but flow efficiency is reduced
Solution Approach 1:
The second piece of the ejector incorporates a diverging section with curved geometry instead of straight sections. This curvature optimizes flow patterns downstream of the throat, improving flow efficiency by reducing turbulence and enhancing the mixing of vapor and air flows.
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
The design results in improved flow rates by optimizing geometry, reducing manufacturing complexity, and achieving a more compact and reliable ejector with reduced weight and lower costs, offering about 25% greater flow over the boost range compared to prior art ejectors.
Implementation Method 1
a tube with a throat (reduced diameter section) causes a higher flowrate which causes the vacuum
Implementation Method 2
a tube with a throat (reduced diameter section) causes a higher flowrate which causes the vacuum
Implementation Method 3
The venturi tube has a converging section, a throat of predetermined diameter, and a diverging section
Data Source
AI summary
Vapors in the fuel tank of a vehicle are collected in a carbon canister. An ejector or aspirator is used to purge the carbon canister in a pressure-charged engine in which a positive pressure exists in the intake. A compact ejector includes a substantially planar flange and a venturi tube coupled to the flange with a central axis of the venturi tube substantially parallel to the flange. By manufacturing the ejector in two pieces, dimensions within the ejector: throat, converging section, and diverging section, is more accurate than prior art manufacturing techniques thereby providing better flow characteristics throughout the boost range.