Pitot Tube Traverse Assembly for Accurate Flow Measurement
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Solution Overview
Problem
Traditional methods for measuring flow rate across a conduit's cross-section, such as pitot traverses, are less accurate when an averaging pitot tube is present due to interference with flow patterns, leading to inaccurate calibration data.
Innovation Solution
A pressure measurement system with slidable upstream and downstream pitot tubes within a bluff body, similar in profile to an averaging pitot housing, allows for accurate measurement of pressure differences across the conduit's diameter, incorporating changes caused by the averaging pitot sensor and providing support against high-velocity flows.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional pitot tubes are used for traverse measurements, then cross-sectional flow measurements can be obtained, but measurement accuracy deteriorates when an averaging pitot tube is present due to flow interference
Solution Approach 1:
The traverse assembly is segmented into multiple independent pitot tubes (first pitot tube and second pitot tube) that can be positioned at different locations within the conduit. Each pitot tube independently measures pressure at its specific position, allowing the system to map the flow profile across the conduit cross-section without requiring a single large averaging pitot tube that would interfere with the flow.
Solution Approach 2:
The measurement approach transitions from a single-point averaging measurement to a multi-point distributed measurement across the conduit cross-section. By positioning pitot tubes at multiple radial positions and measuring pressure differences at each position, the system captures the two-dimensional flow profile, thereby avoiding the flow interference caused by a single large averaging pitot tube.
2Measurement precision
If averaging pitot tube is inserted to measure average pressure difference, then flow rate can be measured, but pitot traverse accuracy deteriorates due to different profile interference
Solution Approach 1:
The system performs preliminary traverse measurements using multiple pitot tubes positioned at known locations before final calibration. By pre-measuring the pressure distribution across the conduit cross-section at multiple positions, the system can characterize the flow profile and use this information to accurately calibrate the averaging pitot tube, ensuring that the calibration data reflects the actual flow conditions.
Solution Approach 2:
The traverse assembly acts as an intermediary measurement system that bridges the gap between the flow conditions and the averaging pitot tube measurement. By using multiple pitot tubes to map the pressure distribution and flow profile, the system creates an intermediary data set that can be used to calibrate and accurate the averaging pitot tube readings, compensating for the flow interference caused by the averaging pitot tube's unique profile.
3Measurement precision
If pitot tubes are positioned to measure pressure differences, then flow profile can be established, but device complexity increases with multiple movable tubes
Solution Approach 1:
Multiple pitot tubes are combined into a single integrated traverse assembly that can be positioned and manipulated as one unit. The assembly includes a support structure that holds multiple pitot tubes at predetermined positions relative to each other, allowing them to be moved simultaneously through the conduit. This merging reduces the complexity of controlling and positioning multiple independent tubes while maintaining the ability to measure pressure differences at multiple locations.
Data Source
AI summary
A pressure measurement system for measuring pressure in a conduit has a bluff body extending into the conduit. The bluff body has an upstream opening and a downstream opening. An upstream pitot tube is slidably engaged within the bluff body and has an open end positioned in the upstream opening. A downstream pitot tube is slidably engaged within the bluff body and has an open end positioned in the downstream opening. A differential pressure sensor is fluidly coupled to the upstream pitot tube and the downstream pitot tube to measure a pressure difference between the upstream pitot tube and the downstream pitot tube.