Thermal Flow Meter Bypass Guide for Reverse Flow Accuracy
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Solution Overview
Problem
Thermal flow meters face challenges in accurately measuring gas flow rates in both forward and backward directions due to vortex interference, particularly in applications like internal combustion engines where pulsing motion and backward flows are common, leading to reduced measurement accuracy.
Innovation Solution
A thermal flow meter design with a bypass passage system that includes an inlet port, a flow rate measurement passage unit, and an outlet port side chamber, where the outlet port is positioned downstream to redirect backward flows, and a guide is used to change the flow direction, reducing vortex impact and improving measurement accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a thermal flow meter measures flow rates in both forward and backward directions using a bypass passage, then the measurement capability is improved, but vortex interference increases and reduces measurement accuracy
Solution Approach 1:
The patent extracts the harmful vortex from the measurement system by providing a separate discharge passage that diverts the vortex away from the bypass passage. The vortex generated in the main passage is extracted and discharged separately, preventing it from entering the bypass passage and interfering with the flow rate measurement, thus resolving the contradiction between measurement capability and measurement accuracy.
Solution Approach 2:
The patent segments the flow paths by providing distinct passages for different functions: a bypass passage for retrieving measurement target gas, a separate vortex discharge passage for removing vortices, and a main passage for the primary gas flow. This segmentation allows the measurement system to handle forward and backward flows while isolating the measurement path from vortex interference.
2Adaptability or versatility
If the outlet port is positioned to discharge backward flows, then the ability to measure backward flow is improved, but vortex generation increases and affects measurement accuracy
Solution Approach 1:
The patent introduces an intermediary vortex discharge passage that acts as a mediator between the main passage and the bypass passage. This intermediary passage receives vortices generated by backward flow discharge and transports them away from the measurement area, preventing direct interference with the flow rate measurement while maintaining the ability to measure backward flows.
3Productivity
If a bypass passage retrieves measurement target gas from the main passage, then the flow rate measurement function is improved, but the retrieval process generates vortex that reduces measurement accuracy
Solution Approach 1:
The patent extracts the harmful vortex generated during gas retrieval by providing a separate vortex discharge passage. The bypass passage continues to retrieve measurement target gas for flow rate measurement, while the extracted vortex is diverted through the discharge passage away from the measurement path, eliminating the harmful effect while maintaining the measurement function.
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 enables accurate measurement of gas flow rates in both forward and backward directions by minimizing vortex interference, enhancing the overall measurement accuracy and reliability, especially in applications with pulsing and reversing gas flows.
Implementation Method 1
a flow rate measurement circuit configured to measure a flow rate by performing heat transfer with the measurement target gas flowing in the bypass passage
Data Source
AI summary
A thermal flow meter capable of measuring flow rates of a gas flowing in a forward direction and a backward direction with a high degree of accuracy is provided. A thermal flow meter 300 according to the present invention includes a bypass passage configured to retrieve and flow a measurement target gas 30 received from a main passage 124 and a flow rate measurement circuit 601 configured to measure a flow rate by performing heat transfer with the measurement target gas flowing in the bypass passage. In an outlet port side chamber 4216 provided at an upstream with respect to an outlet port 352 of the bypass passage which is formed to be open in a downstream direction in a flow direction of the measurement target gas, a guide 4217 is provided to oppose the outlet port to change a direction of a flow of the measurement target gas flowing in from the opposite side, and the outlet port and an inflow unit of the outlet port side chamber are arranged to be eccentric when they are seen in a direction along the flow direction of the measurement target gas flowing in the main passage.