Sheet-Stacked Flow Restrictor for Precise Gas Flow Measurement
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Solution Overview
Problem
Existing flow restrictors in fluid flow devices like mass flow controllers and flow meters exhibit high uncertainty in flow rate measurements, particularly in semiconductor manufacturing applications where precise gas delivery is critical.
Innovation Solution
The flow restrictor design comprises a first sheet with a flow passage, including a groove that communicates with an expansion zone, and a second sheet stacked on the first sheet, with a hole in its center. This configuration reduces uncertainty by mitigating geometrical uncertainties at the end of the flow passages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional flow restrictor design is used, then the device structure is simple, but the uncertainty in flow rate measurement is high
Solution Approach 1:
The flow restrictor is segmented into multiple functional zones within the flow passage: an expansion zone at the inlet, a restriction zone with controlled cross-section, and a contraction zone at the outlet. This segmentation allows each zone to perform its specific function optimally, reducing flow rate uncertainty while maintaining a relatively simple overall structure.
Solution Approach 2:
Different sections of the flow passage are given different geometric qualities tailored to their specific functions. The expansion zone has increasing cross-sectional area to stabilize incoming flow, the restriction zone has controlled dimensions for precise flow control, and the contraction zone tapers to facilitate smooth flow transition. This local optimization reduces measurement uncertainty without requiring complete structural redesign.
2Reliability
If the flow passage geometry is simplified, then the manufacturing is easier, but the uncertainty in flow restriction performance increases
Solution Approach 1:
The flow passage is pre-designed with specific geometric features (expansion zone, restriction zone, contraction zone) that prepare the flow in advance before it reaches the measurement point. The expansion zone pre-stabilizes the flow, and the contraction zone pre-conditiones it for measurement, reducing uncertainty without requiring complex real-time adjustments or post-manufacturing calibration.
Solution Approach 2:
The flow passage geometry parameters (cross-sectional area, length, taper angles) are optimized to achieve the desired flow characteristics. By carefully selecting these parameters, the design achieves reliable flow restriction performance while maintaining manufacturability through standard fabrication processes.
3Measurement precision
If a long flow passage is used, then the flow stabilization is improved, but the device length increases
Solution Approach 1:
Instead of achieving flow stabilization solely through increased passage length in one dimension, the design uses dimensional changes in the cross-sectional area (expansion and contraction zones) to achieve flow conditioning. This allows effective flow stabilization in a more compact overall length by utilizing the second dimension (cross-sectional area variation) rather than only extending the passage length.
Data Source
AI summary
A flow restrictor is provided, comprising a first sheet including a flow passage, and a second sheet stacked on the first sheet. A hole is provided in a center of the second sheet. The flow passage includes a groove cut into a surface of the first sheet that communicates with an expansion zone at a peripheral area of the first sheet. A peripheral edge of the second sheet contacts the first sheet in the expansion zone between an inner diameter and an outer diameter of the expansion zone.