Flow Conditioning Assembly for Stable Micromachined Mass Flow Sensing
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Solution Overview
Problem
Micromachined thermal mass flow sensors face challenges in achieving reproducible and stable measurements in large flow channels due to their small footprint, leading to installation complexities and inaccuracies, especially with elbow-like pipes and valves causing turbulence.
Innovation Solution
A flow conditioning assembly that employs a disk to manage incoming fluid, redistributing it along the disk's edge and into a buffer chamber, followed by a flow profiler, to create a stable and reproducible flow profile, allowing the micromachined sensing elements to be placed in the main flow channel without the need for long straight pipes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If micromachined sensors with small footprint are used, then device size is reduced and integration is improved, but measurement accuracy and reproducibility deteriorate in large flow channels
Solution Approach 1:
A flow conditioning assembly is introduced as an intermediary component between the turbulent flow source and the micromachined sensor. This assembly includes a flow straightener with multiple parallel channels that conditions the flow profile before it reaches the sensor, enabling accurate measurements with small-footprint sensors in large flow channels without requiring long straight pipe sections.
Solution Approach 2:
The flow conditioning assembly divides the flow into multiple parallel channels within the straightener structure. Each channel provides a controlled flow path that individually conditions the flow, and their combined effect creates a stable, reproducible flow profile at the sensor location, overcoming the limitations of small sensor footprint in large channels.
2Adaptability or versatility
If conventional flow conditioning components like elbow pipes and valves are used, then flow management is achieved, but turbulence and unpredictable flow velocity profiles are created
Solution Approach 1:
The flow conditioning assembly performs preliminary flow conditioning before the flow reaches the measurement section. The flow straightener pre-establishes a stable, predictable flow profile by removing turbulence and swirls caused by upstream components like elbows and valves, ensuring that measurements are taken under controlled conditions.
3Measurement precision
If long straight pipes are installed to maintain reproducible flow profile, then measurement accuracy is improved, but installation complexity and space requirements increase
Solution Approach 1:
The flow conditioning assembly segments the flow into multiple parallel channels within a compact structure. This segmentation allows the device to achieve flow profile stabilization in a short length, replacing the need for long straight pipes and reducing installation complexity while maintaining measurement reproducibility.
Solution Approach 2:
Instead of extending the flow path in the axial direction (requiring long straight pipes), the flow conditioning assembly uses a cross-sectional approach with multiple parallel channels. This dimensional change allows flow conditioning to occur within a compact footprint, reducing the required installation space while achieving the same measurement reproducibility.
4Reliability
If bypass design is used to place micromachined sensor in separate channel, then sensor protection from particles is achieved, but differential pressure stability deteriorates
Solution Approach 1:
The flow conditioning assembly acts as an intermediary that conditions the flow before it reaches the sensor, whether in a bypass or main channel configuration. By establishing a stable flow profile upstream, the assembly ensures that differential pressure remains stable across the sensor regardless of the specific installation configuration, while still providing protection from particles through the conditioning structure.
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 solution achieves high accuracy and reproducibility of flow measurements with low pressure loss, prevents clogging, and allows for scalable designs suitable for a wide range of flow channels, including high-flow applications.
Implementation Method 1
Micromachined thermal mass flow meters have been widely used in automotive, medical, and other process monitoring and measurement in the past 30 years
Data Source
AI summary
A flow conditioning assembly for a flow velocity and mass flow measurement apparatus utilizing micromachined flow sensing elements is disclosed for maintaining high metrological performance. The assembly introduces a flow profile shatter and redistribution mechanism before the flowing fluid enters the flow straightener and flow profiler combined flow conditioning. The assembly further removes the probability of flow clogging, has a low flow resistance, and relaxes the metrological requirements of the connecting pipework system. An alternative build with a bypass flow chamber with a flow redistribution channel allows the measurable flow velocity to extend to more than three times the configuration where the micromachined flow sensing elements are placed inside the center of the main flow channel.