Air Duct Damper Pre-Throttle Control for Precise Low Flow
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Solution Overview
Problem
Existing volume flow controllers in air-conditioning and ventilation systems face challenges in achieving precise control, especially at low volume flows, due to varying drag coefficients and pressure losses, leading to significant deviations from target values under fluctuating conditions.
Innovation Solution
The method involves storing angular positions for pre-throttle positions in addition to control positions in a database, allowing the damper leaf to be moved to a pre-throttle position when the actual value is less than the setpoint, increasing effective pressure and reducing measuring tolerances, and shifting to the control position when the setpoint is exceeded, thus achieving more precise control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the damper leaf is moved directly from maximum open position to control position, then the control response is simple and fast, but the control precision is poor due to high measuring tolerances at low effective pressure
Solution Approach 1:
The damper leaf is moved to a pre-throttle position before the final control position when the actual volume flow is below the setpoint. This preliminary action increases the effective pressure to a level where measurements are more accurate, reducing measuring tolerances. The pre-throttle position serves as an intermediate state that prepares the system for more precise control by optimizing the pressure conditions for measurement.
2Measurement precision
If the damper leaf is kept in maximum open position for low volume flow control, then the device operation is simple, but the control accuracy is poor due to very small effective pressure and high tolerances
Solution Approach 1:
The control range is segmented into different operational zones: maximum open position for high volume flows, pre-throttle position for low volume flows, and control position for precise regulation. By segmenting the operational ranges, the system can optimize the damper position for each specific flow condition, ensuring accurate measurements and control across the entire operating spectrum rather than relying on a single position.
3Reliability
If the drag coefficient is allowed to vary with damper position, then the system adapts to different operating conditions, but the control precision deteriorates due to non-constant effective pressure and varying tolerances
Solution Approach 1:
The system changes the operational parameter (effective pressure) by adjusting the damper to a pre-throttle position when needed. This parameter change ensures that measurements occur within an optimal pressure range where tolerances are minimized. The drag coefficient is allowed to vary naturally with position, but the system compensates by operating in pressure ranges that maintain measurement precision.
4Productivity
If the damper pivoting path is long from maximum open to control position, then the damper can achieve full range control, but the control time increases and response speed decreases
Solution Approach 1:
The damper is moved to a pre-throttle position as a preliminary step before final control adjustments. This preliminary positioning reduces the remaining travel distance to the control position, thereby decreasing the time required for final adjustments and improving overall response speed while maintaining the ability to achieve full range control when needed.
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 enables more precise regulation of volume flow by maintaining a consistent pressure loss across the setpoint range, reducing deviations from target values and improving control accuracy even at low volume flows.
Implementation Method 1
A differential pressure sensor with at least two tapping points is usually used to determine the volume flow. The differential pressure, i.e. the effective pressure, is determined via the tapping points. The volume flow is then determined from the differential pressure.
Implementation Method 2
the angular position of the pre-throttle positions being greater than the maximum open position and smaller than the control position... the throttling effect of the flap leaf is lower in the pre-throttle position corresponding to the setpoint to be controlled than in the control position
Data Source
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AI summary
The invention relates to a method for controlling a volume flow in an air duct of an air conditioning and/or ventilation system by means of a damper blade (3) pivotably mounted in the air duct about a pivot axis (2), wherein the damper blade (3) can be pivoted between a maximum open position and a maximum closed position by means of a drive (11), wherein the actual volume flow is determined by detecting at least one suitable actual value and wherein setpoints and associated angular positions of the control position of the damper blade (3) are stored in a database for various operating states.wherein an electronic control and/or regulating device (12) compares the currently determined actual value of the volume flow with the currently preselected setpoint, and wherein the damper blade (3) is pivoted between a basic position and a controlled position by means of the actuator (11) during operation, depending on the actual value, wherein the control and/or regulating device (12) outputs a control signal to the actuator (11) when the actual value is above the currently preselected setpoint, whereupon the actuator (11) moves the damper blade (3) from its current position to its controlled position stored for the currently set setpoint. To specify a method that enables more precise control of a volume flow in an air duct,The database for the various operating states should contain, in addition to the setpoints and the associated angular positions of the control position, angular positions for pre-throttle positions, wherein the angular position of the pre-throttle positions is greater than the maximum open position and less than the control position, and wherein the control and/or regulating device (12) already outputs a control signal to the actuator (11) when the actual value is less than the stored setpoint, whereupon the actuator (11) moves the damper blade (3) from its current position to a pre-throttle position stored for the currently set setpoint. The invention also relates to a system for regulating a volume flow in an air duct of an air conditioning and/or ventilation system.