Dual-Flow Mass Flow Control for Inlet Pressure Perturbations
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Mass flow controllers are sensitive to inlet pressure perturbations, leading to inaccurate mass flow measurements due to pressure gradients in the fluid path, which existing solutions attempt to address with additional sensors and flow meters but still result in inaccuracies.
Innovation Solution
A mass flow controller using at least two flow meters to generate a control signal that minimizes sensitivity to inlet pressure perturbations by calculating a control signal independent of pressure fluctuations, with the flow meters configured to detect fast and slow pressure variations and the control valve regulated to maintain setpoint flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single flow meter is used in the mass flow controller, then the device complexity is low, but the measurement precision deteriorates due to sensitivity to inlet pressure perturbations
Solution Approach 1:
The patent divides the flow measurement function into two separate flow meters: a first flow meter for measuring total flow and a second flow meter for measuring bypass flow. This segmentation allows each meter to operate in an optimized regime and enables differential measurement that compensates for inlet pressure perturbations, thereby improving measurement precision without excessive complexity increase
Solution Approach 2:
The patent introduces a bypass path with a second flow meter as an intermediary measurement channel. The bypass flow meter measures a portion of the flow that is less sensitive to inlet pressure variations. By comparing the bypass flow measurement with the total flow measurement, the system can calculate the actual flow through the main path while compensating for pressure-induced errors
2Measurement precision
If additional flow meters and sensors are added to compensate for pressure fluctuations, then the measurement precision improves, but the device complexity increases
Solution Approach 1:
The patent designs the bypass path and second flow meter to serve multiple functions: it acts as a reference measurement channel for pressure compensation, defines a controlled pneumatic volume for stability, and provides a means to calculate actual flow through differential measurement. This multi-functionality reduces the need for separate dedicated compensation mechanisms, balancing precision improvement with complexity control
Solution Approach 2:
The control device continuously monitors measurements from both flow meters and uses feedback control to maintain accurate flow measurement. The system calculates the actual flow by comparing the total flow measurement with the bypass flow measurement, and this feedback mechanism dynamically compensates for inlet pressure perturbations, improving precision while using a manageable number of components
Data Source
Figure 1~3
Figure 4~6
AI summary
A mass flow controller (10) comprises a fluid inlet (15) and at least one first flow meter (11) to measure a first flow rate (F1) and to output a first flow signal (FS1); at least one second flow meter (12) to measure a second flow (F2) rate and to output a second flow signal (FS2); a control device (13) connected to said first and second flow meters (11,12) and configured and arranged to generate a control signal (C); and at least one control valve (14) connected to said control device (13) to control a total flow rate (Fout) through the mass flow controller (10) in response to the control signal (C). The control signal (C) is generated as a function of both the first and second flow signals (FS1,FS2) such that the mass flow controller's (10) sensitivity to perturbations of said inlet pressure is minimized.