Elliptical Diverging Nozzle for Vacuum Ejector Flow Control
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Solution Overview
Problem
Vacuum ejectors face a compromise in design to achieve both high-volume flow rate and high negative pressure, with multi-stage ejectors typically sacrificing one performance characteristic to optimize the other, limiting their effectiveness in applications requiring both high suction forces and rapid evacuation.
Innovation Solution
The design incorporates a drive nozzle array with multiple nozzles, each having an inlet and outlet flow section aligned in the direction of fluid flow, where the outlet flow section is more divergent near the inlet and less divergent near the exit, allowing for rapid acceleration of air flow to supersonic speeds and focused flow downstream, enhancing vacuum generation efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If multi-stage ejectors are designed to achieve high negative pressure, then the suction force is improved, but the volume flow rate decreases
Solution Approach 1:
The ejector is divided into multiple stages, with each stage comprising a drive nozzle and outlet nozzle pair that operates independently to generate vacuum. This segmentation allows each stage to be optimized for specific pressure and flow requirements, resolving the contradiction between high negative pressure and high volume flow rate by distributing functionality across stages.
Solution Approach 2:
Each stage of the multi-stage ejector is designed with locally optimized nozzle geometries and configurations tailored to its specific function. The drive nozzles and outlet nozzles in different stages have different design parameters, allowing each local region to achieve optimal performance for its designated pressure and flow rate requirements.
2Productivity
If multi-stage ejectors are designed to achieve high volume flow rate, then the evacuation speed is improved, but the negative pressure decreases
Solution Approach 1:
The ejector system is segmented into multiple stages, where earlier stages are optimized for high volume flow rate to quickly evacuate large volumes, while subsequent stages are optimized for generating high negative pressure. This segmentation resolves the contradiction by assigning different functional priorities to different parts of the system.
Solution Approach 2:
The earlier stages of the multi-stage ejector perform preliminary evacuation at high flow rates to rapidly reduce the volume to be evacuated, preparing the system for the subsequent stages to achieve high negative pressure. This preliminary action resolves the contradiction by sequencing operations to achieve both high flow rate and high negative pressure at different times.
3Reliability
If traditional multi-stage ejectors are used to achieve both high negative pressure and high volume flow rate, then the performance is improved, but the device size increases
Solution Approach 1:
The multi-stage ejector stages are arranged in a nested or compact configuration where later stages are positioned to utilize the flow paths and pressure differentials created by earlier stages. This nesting allows multiple functional stages to be integrated into a smaller overall device volume while maintaining both high negative pressure and high volume flow rate performance.
Solution Approach 2:
The ejector stages are arranged in a three-dimensional compact layout rather than a simple linear sequence, utilizing vertical and radial spacing to reduce the overall device footprint. This dimensional optimization allows the multi-stage ejector to achieve both high performance characteristics in a smaller device size.
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 enables the generation of high negative pressure and high-volume flow rates simultaneously, improving the overall performance of vacuum ejectors by allowing them to achieve equivalent performance with a smaller size and reduced footprint compared to traditional multi-stage ejectors.
Implementation Method 1
accelerating the high pressure air through a drive nozzle and ejecting it as an air jet at high speed
Implementation Method 2
Fluid medium in the surrounding space between the drive nozzle and outlet nozzle is entrained into the high-speed flow of compressed air
Implementation Method 3
As the fluid in the space between the drive and outlet nozzles is ejected in this way, a negative pressure or vacuum is created in the volume surrounding the air jet
Data Source
Figure 1A~1B
Figure 2~3A
Figure 3B~4
AI summary
So as to more rapidly accelerate the air flow in a vacuum ejector to supersonic speed whilst focussing the exiting flow of air to downstream of the exit of the nozzle, the invention provides an ejector for generating a vacuum comprising, a drive nozzle for generating a drive jet of air from a compressed air source and directing said drive jet of air into an outlet flow passage at the outlet of a drive stage of the ejector in order to entrain air in a volume surrounding said jet of air into the jet flow to generate a vacuum across said drive stage, wherein said drive nozzle substantially consists of an inlet flow section and an outlet flow section aligned in a direction of air flow through the nozzle, the outlet flow section diverging in the direction of airflow, from an outlet end of the inlet flow section substantially to an exit of the nozzle, the outlet flow section having a shape which is more divergent near the outlet of the inlet flow section and less divergent near the exit of the nozzle.