Closed-Loop Pressure Metering for Stable Low-Flow Dosing
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Solution Overview
Problem
Conventional metering systems for low-viscosity liquids and gases face challenges in precise control of small metering volumes, limited flow range, and susceptibility to malfunctions due to pressure fluctuations, especially in needle valves, which restrict the ability to cover a wide range of metering quantities.
Innovation Solution
A system and method utilizing a closed loop control circuit with a pressure control valve and mass flow sensor to regulate metering pressure, allowing for precise control of metering quantity independently of pressure differences between pre-pressure and metering pressure, enabling a wide range of metering quantities from very small to very large with minimal deviation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a piston pump or diaphragm pump is used for metering low-viscosity liquids, then the delivery rate can be controlled by pump rotational speed, but the metering volume becomes very small compared to the piston chamber volume in the lower metering quantity range, resulting in pulsating flow and imprecise control
Solution Approach 1:
The patent replaces the mechanical displacement principle (piston/diaphragm pumps) with a pressure-controlled valve system. Instead of using mechanical pump rotation to control delivery rate, the invention uses a pressure control valve regulated by a controller to maintain constant metering pressure, thereby achieving precise metering control without the pulsating flow issues inherent in mechanical pump systems.
Solution Approach 2:
The invention changes the control parameter from pump rotational speed to metering pressure. By maintaining constant metering pressure through the pressure control valve and controller, the system achieves precise control of small metering quantities without the delivery rate fluctuations that occur when trying to control small volumes with mechanical pumps.
2Quantity of substance
If needle valves are used for metering, then the metering quantity can be adjusted by needle position, but the metering quantity is dependent on pressure difference across the valve, causing metering quantity fluctuations when upstream or downstream pressure is not constant
Solution Approach 1:
The patent introduces a feedback control system where a controller receives information about the metering pressure and adjusts the pressure control valve accordingly to maintain constant metering pressure. This feedback mechanism compensates for pressure fluctuations in the system, ensuring stable and reliable metering quantity control independent of upstream or downstream pressure variations.
Solution Approach 2:
The invention changes the control approach from direct needle position control to pressure-based control. Instead of relying on needle position to determine metering quantity (which is affected by pressure differences), the system uses a pressure control valve to maintain constant metering pressure, making the metering quantity stable and independent of pressure fluctuations.
3Quantity of substance
If needle valves are used with large pressure differences, then small metering quantities can be achieved, but pulsating metering behavior occurs; if small pressure differences are used, then large metering quantities cannot be adjusted sufficiently
Solution Approach 1:
The patent fundamentally changes the control parameter from pressure difference to metering pressure. By controlling the metering pressure to remain constant regardless of pressure difference conditions, the system achieves both small and large metering quantities without pulsating behavior. The pressure control valve and controller work together to maintain stable pressure conditions that eliminate the pulsating metering issues inherent in needle valve systems.
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 system achieves reliable and precise control of metering quantities across a large spectrum, ensuring consistent delivery regardless of pressure fluctuations, with metering quantity ranges up to 1:1000 and rapid adjustment without significant overshoot or undershoot, suitable for both small and large flow rates.
Implementation Method 1
a metering quantity is determined by the pressure difference between the metering pressure (p2) and the process pressure (p3)
Implementation Method 2
A pressure control valve and a flow sensor are arranged in the feed line, wherein the pressure control valve and the flow sensor are configured as a closed loop control circuit
Data Source
AI summary
A system for metering a liquid or gaseous medium comprises a pressure control valve and a flow sensor, the pressure control valve and the flow sensor forming a closed control circuit. The required metering quantity can be adjusted by controlling the metering pressure by means of the pressure control valve.