Multiple Pitot Tubes with Shared Tube Segments for Non-Uniform Flow Measurement
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Solution Overview
Problem
Existing flow measurement technologies, such as pitot tubes, struggle to provide accurate measurements in pipes with non-uniform flow across the cross-section, especially in large pipes like those used for exhaust gas, and often result in significant pressure drops or clogging issues.
Innovation Solution
A device comprising multiple pitot tubes and sensing units with shared tube segments for averaging pressures, allowing for accurate flow measurement even in non-uniform flows without the need for flow straighteners, which reduces pressure drops and enhances redundancy for fail-safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single pitot tube is used for flow measurement, then the device complexity is low, but the measurement precision deteriorates in non-uniform flows
Solution Approach 1:
The measurement system is segmented into multiple independent measurement channels, each with its own pitot tube and sensing unit. This allows parallel measurement at multiple locations, improving overall measurement precision in non-uniform flows while keeping each individual channel relatively simple
Solution Approach 2:
Multiple measurement channels are merged through shared tube segments that combine the pressure signals. The shared tube segments integrate measurements from multiple pitot tubes and provide averaged pressure readings, enhancing measurement accuracy while reducing the complexity of having completely separate measurement systems
2Measurement precision
If flow straighteners are used to improve measurement accuracy, then the measurement precision improves, but the pressure drop increases significantly
Solution Approach 1:
Instead of using flow straighteners that modify the entire flow, the system segments the measurement approach by taking multiple localized measurements at different positions. This allows accurate flow characterization without introducing energy losses associated with flow conditioning devices
Solution Approach 2:
Multiple pitot tubes act as intermediaries that sample the flow at different locations without directly interfering with the overall flow pattern. This provides accurate measurement information while avoiding the significant pressure drops caused by flow straighteners
3Measurement precision
If multiple pitot tubes are used with separate connection lines, then the measurement precision improves, but the device complexity increases
Solution Approach 1:
The connection system merges multiple separate connection lines into shared tube segments. These shared segments combine pressure signals from multiple pitot tubes and provide integrated readings to the sensing units, reducing the overall complexity while maintaining the benefits of multiple measurement points
Solution Approach 2:
The shared tube segments serve multiple functions: they connect multiple pitot tubes, provide signal averaging, and reduce the number of individual connection lines needed. This multi-functionality reduces device complexity while maintaining measurement precision
4Measurement precision
If traditional pitot tubes are used in large pipes, then the device complexity is low, but the measurement precision deteriorates due to non-uniform flow
Solution Approach 1:
The measurement approach is segmented into multiple spatial locations within the pipe cross-section. By distributing pitot tubes at different positions, the system captures the non-uniform flow characteristics of large pipes, providing a more representative measurement without requiring a single complex measurement device
Solution Approach 2:
The system transitions from a single-point measurement to a multi-point spatial distribution. By adding the spatial dimension with multiple measurement locations across the pipe cross-section, the system accurately captures the non-uniform flow profile characteristic of large diameter pipes
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 device achieves accurate flow measurement at an accuracy of 2% with a length-to-diameter ratio of 5 for pipes over 2 meters in diameter without significant pressure drops, and is fail-safe against clogging, ensuring reliable operation even with partial system failure.
Implementation Method 1
A pitot tube has a first opening exposed directly to the flowing medium. Via the first opening, the total pressure can be determined. Further, a pitot tube has a second opening that faces away from the flow. Hence, via the second opening the static pressure can be measured. The difference of the total pressure and the static pressure is the dynamic pressure, from which the flow can be calculated.
Implementation Method 2
all of the total pressure outlets are fluidly connected to all of the total pressure inlets by respective first connection lines, wherein all of the static pressure outlets are fluidly connected to all of the static pressure inlets by respective second connection lines
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
Device (1) for measuring a flow of a medium through a pipe (2), wherein the device (1) comprises multiple pitot tubes (3) and multiple sensing units (4), wherein each of the pitot tubes (3) has a respective total pressure outlet (5) and a respective static pressure outlet (6), wherein each of the sensing units (4) has a respective total pressure inlet (7) and a respective static pressure inlet (8), wherein all of the total pressure outlets (5) are fluidly connected to all of the total pressure inlets (7) by respective first connection lines (9), wherein all of the static pressure outlets (6) are fluidly connected to all of the static pressure inlets (8) by respective second connection lines (10), wherein each of the sensing units (4) is configured to determine the flow of the medium through the pipe (2) by comparing the pressures at the respective total pressure inlet (7) and the respective static pressure inlet (8) with each other, and wherein all first connection lines (9) include a first shared tube segment (11) and/or all second connection lines (10) include a second shared tube segment (12). With the described device (1) the flow of a medium through a pipe (2) can be measured reliably and accurately even if the flow is not uniform across the cross-section of the pipe (2). This is due to the fact that the connection lines (13,14) between the outlets (5,6) of the pitot tubes (3) and the inlets (7,8) of the sensing units (4) include the shared tube segments (11,12).