Cross-Configured Pitot Sensor for Low Velocity Flow Measurement
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Solution Overview
Problem
Existing flow measuring devices with pitot tubes struggle to accurately measure low flow velocities due to reduced differential pressure signals and increased measurement uncertainties, particularly in non-linear flow conditions such as fittings and bends.
Innovation Solution
A symmetrical measuring cross design with optimized sensor geometry and curvature ensures consistent differential pressure signals even at low velocities, minimizing flow separation and backflow, and reducing pressure losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single bar-shaped sensor is used, then the device complexity is reduced, but the measurement precision deteriorates because airflow can bypass the sensor resulting in no measurement
Solution Approach 1:
The single bar-shaped sensor is divided into multiple sensor units (at least two) arranged in a cross configuration. Each sensor unit independently measures flow in different directions, ensuring that at least one unit always encounters the airflow regardless of flow direction or turbulence patterns, thereby maintaining measurement precision while keeping the overall device relatively simple.
Solution Approach 2:
The sensor arrangement transitions from a one-dimensional single bar to a two-dimensional cross configuration. This dimensional expansion allows the sensor to intercept airflow from multiple directions simultaneously, eliminating the bypass problem while adding minimal structural complexity.
2Device complexity
If conventional pitot tubes are used, then the device structure is simple, but the measurement precision deteriorates at very low flow velocities due to reduced differential pressure signals
Solution Approach 1:
The sensor units are equipped with curved separation edges instead of sharp edges. This curvature optimizes flow separation characteristics, ensuring that flow separation occurs at a predictable location even at very low velocities. The curved geometry maintains stable differential pressure signals across a wide velocity range, enabling precise low-velocity measurements while keeping the device structure relatively simple.
Solution Approach 2:
The invention changes the geometric parameters of the sensor, specifically the curvature radius of the separation edge, to optimize performance. By carefully selecting the curvature radius, the sensor achieves stable flow separation characteristics that produce sufficient differential pressure signals even at velocities as low as 0.7 m/s, extending the measurable velocity range without significantly increasing device complexity.
3Manufacturing precision
If linear separation edges are used, then the manufacturing precision is improved, but the loss of energy increases due to vortex formation and backflow
Solution Approach 1:
The separation edges are designed with optimized curvature rather than straight linear edges. This curved geometry guides the flowing medium more smoothly around the sensor, reducing abrupt flow separation and minimizing vortex formation. The result is reduced energy loss through backflow and turbulence, while the curvature can still be manufactured with standard precision techniques.
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 design provides precise flow measurements across a wide range of velocities, including near fittings, with reduced measurement uncertainties and lower pressure losses, leading to energy savings and cost reductions.
Implementation Method 1
When the tube is immersed in a flowing medium, a pressure differential is created between these two channels. From this differential pressure, the flow velocity of the medium passing the pitot tube can be determined
Implementation Method 2
the air velocity at the separation edge is approximately three times higher than the average velocity in the channel
Data Source
Figure 1~2
Figure 3~4
AI summary
In a measuring device for determining the flow rate of a flowing medium through a channel (1), wherein a sensor (2) is exposed to the flowing medium in the channel (1) and has inlet openings (7) that are open opposite to the flowing medium and outlet openings (8) that are open in the flow direction (X) of the flowing medium, wherein inlet openings (7) and outlet openings (8) are located in a sensor (2.1 - 2.4) separated by a partition (11) and are connected to a measuring unit via a pressure sampling element (5), several measuring units (2.1 to 2.4) are to be connected to a sensor via a node (18) and only one pressure sampling element (5) connects to a measuring unit (4.2).