Cascade Aerosol Dilution With Ejector Control for Stable Sampling
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Solution Overview
Problem
Existing aerosol measurement technologies face challenges in maintaining a constant dilution factor independent of varying inlet pressure, leading to potential inaccuracies and particle loss during aerosol sampling from engines or industrial processes.
Innovation Solution
A cascade diluting apparatus with a first and second diluting unit connected in series, where the second unit includes an ejector that adjusts dilution gas flow rates based on inlet pressure to maintain a constant dilution factor, utilizing an annular protective layer to reduce particle loss and operate as both a dilution and pumping device.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a porous diluting tunnel is used to dilute aerosol samples, then particle loss and condensation are reduced, but the dilution factor becomes dependent on inlet pressure variations
Solution Approach 1:
The control unit continuously monitors the inlet pressure of the aerosol sample flow and dynamically adjusts the flow rates of diluting gas flows accordingly. This feedback mechanism ensures that the dilution factor remains constant despite variations in inlet pressure, resolving the contradiction between measurement reliability and adaptability to pressure changes.
Solution Approach 2:
The system transitions from a static dilution configuration to a dynamic one where diluting gas flow rates are continuously adjusted based on real-time inlet pressure measurements. This dynamic adaptation allows the dilution factor to remain independent of inlet pressure variations while maintaining measurement accuracy.
2Adaptability or versatility
If dilution gas flow rates are increased to maintain constant dilution factor, then independence from inlet pressure is achieved, but device complexity increases
Solution Approach 1:
The control unit serves multiple functions: it monitors inlet pressure, calculates required dilution gas flow rates, and actuates control valves to adjust flows. This multi-functionality reduces the need for separate dedicated components for each function, thereby managing device complexity while achieving inlet pressure independence.
Solution Approach 2:
The system uses the inlet pressure signal itself to control the dilution process, rather than requiring external complex control systems. The control unit automatically adjusts dilution gas flows based on the measured inlet pressure, making the system self-regulating and reducing overall complexity.
3Measurement precision
If multiple diluting units are connected in series, then constant dilution factor is achieved, but device complexity and particle loss risk increase
Solution Approach 1:
The dilution process is divided into multiple sequential stages with each diluting unit performing a portion of the total dilution. This segmentation allows for better control of the dilution factor at each stage, and the control unit coordinates the flow rates across all stages to maintain overall precision while managing complexity through modular design.
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 apparatus ensures a constant dilution factor independent of inlet pressure variations, reduces particle loss, and maintains accurate aerosol sampling by adjusting dilution gas flow rates, allowing for precise aerosol measurements.
Implementation Method 1
The second diluting unit comprises an ejector, which is arranged to draw an aerosol sample flow to the second diluting unit and to dilute the aerosol sample flow
Implementation Method 2
The first diluting unit is arranged to form an annular protective layer, which surrounds the aerosol sample flow, in order to reduce particle loss in the second diluting unit
Data Source
Figure 1
Figure 2a~2b
Figure 2c~2d
AI summary
The aerosol diluting apparatus (400) comprises: - a first diluting unit (DU1) to provide a first modified sample flow (FG1) by combining an aerosol sample flow (FG0) with a first diluting gas flow (DG1), - an ejector unit (DU2) to draw the first modified sample flow (FG1) from the first diluting unit (DU1) to the ejector unit (DU2) and to provide a second modified sample flow (FG2) by mixing a second dilution gas flow (FG2) with the first modified sample flow (FG1 ), - a control unit (REGU1), and - a control valve (VAL1 ), wherein the control unit (REGU1) and the control valve (VAL1) are arranged to adjust flow rate (m'DG2) of the second dilution gas flow (FG2) according to an inlet pressure (p0) of the aerosol sample flow (FG0), so as to keep the dilution factor (K20) of the diluting apparatus (400) substantially independent of the inlet pressure (p0).