Control Valve Redundant Flow Measurement via Pressure Drop
Solution Overview
Problem
Conventional mass flow rate measurement systems in controlled systems, such as burner control systems, are prone to inaccuracies and errors over time, especially in existing systems, due to systematic errors and complex, expensive redundant measurement arrangements that are difficult to implement.
Innovation Solution
A method and device utilizing the control valve in the system to record mass flow rate redundantly by measuring pressure drop according to the orifice principle, with continuous monitoring of upstream and downstream pressures and valve lift, and using a characteristic curve of the flow coefficient to validate measurements, while incorporating temperature measurement to account for density changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If two independent flow meters operating on different measuring principles are used for redundant measurement, then measurement reliability is improved, but device complexity and cost increase significantly
Solution Approach 1:
The control valve is made to serve dual functions: flow control and flow measurement. By utilizing the pressure drop across the control valve and combining it with valve position and characteristic curve data, the system achieves redundant flow measurement without adding dedicated measurement devices, thus resolving the contradiction between reliability and complexity
Solution Approach 2:
The control valve's inherent pressure drop characteristic is exploited for measurement purposes. The system uses data already available from the control valve operation (pressure differential, valve stroke, flow coefficient) to derive flow rate information, making the control valve serve its own measurement needs and eliminating the requirement for additional measurement infrastructure
2Reliability
If two independent flow meters operating on different measuring principles are used for redundant measurement, then measurement reliability is improved, but installation cost increases significantly
Solution Approach 1:
The control valve is made to serve dual functions: flow control and flow measurement. By utilizing the pressure drop across the control valve and combining it with valve position and characteristic curve data, the system achieves redundant flow measurement without adding dedicated measurement devices, thus resolving the contradiction between reliability and complexity
Solution Approach 2:
The control valve's inherent pressure drop characteristic is exploited for measurement purposes. The system uses data already available from the control valve operation (pressure differential, valve stroke, flow coefficient) to derive flow rate information, making the control valve serve its own measurement needs and eliminating the requirement for additional measurement infrastructure
3Reliability
If serial arrangement of flow measurement systems is used, then redundant measurement is achieved, but pressure losses increase considerably
Solution Approach 1:
The measurement function is extracted from separate physical measurement devices and integrated into the control valve's operational parameters. By using the pressure drop across the control valve itself rather than adding separate measurement elements in series, the system achieves measurement redundancy without introducing additional pressure losses
Solution Approach 2:
The control valve's inherent pressure drop characteristic is exploited for measurement purposes. The system uses data already available from the control valve operation (pressure differential, valve stroke, flow coefficient) to derive flow rate information, making the control valve serve its own measurement needs and eliminating the requirement for additional measurement infrastructure
4Device complexity
If control valve is used for flow rate measurement, then device complexity is reduced, but measurement precision may be affected by flow coefficient variability
Solution Approach 1:
The system continuously monitors the valve stroke position and uses it to dynamically adjust the flow coefficient value based on the characteristic curve. This feedback mechanism ensures that the most accurate flow coefficient corresponding to the current valve position is used in calculations, maintaining measurement precision while using the simpler control valve-based approach
Solution Approach 2:
The system accounts for changes in flow coefficient by dynamically selecting values from the characteristic curve based on the current valve stroke position. This parameter adjustment approach compensates for the variability in flow coefficient across different valve openings, maintaining measurement precision without requiring additional hardware
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
This approach allows for reliable, efficient, and cost-effective redundant mass flow rate determination with minimal flow losses, easily applicable to existing systems, enabling early detection of errors and maintaining precise combustion air ratios.
Implementation Method 1
This utilizes the fact that a significant pressure drop occurs within the supply line at the control valve, which allows for flow rate measurement based on the orifice plate principle
Data Source
Figure 1
AI summary
The device has flow rate measuring devices (6, 11) integrated into supply pipes (5, 13) of control paths (3, 4), respectively. Control valves (7, 12) limit mass flow rate of the medium in the pipes, and a control unit (10) adjusts the valves based on values of the mass flow rate. A measuring unit for measuring system pressure and back pressure at the valves is connected with the control unit. The control unit determines value for mass flow rate of the medium from measured values of the system pressure, back pressure, valve lift and values for discharge coefficient of the valves. An independent claim is also included for a method for redundant determination of mass flow rate of a fluid medium in control paths.