Variable Orifice Restrictor for Boiler Airflow Turndown
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Solution Overview
Problem
Existing air handling systems in gas fired boilers are limited by a 5 to 1 turndown ratio of airflow, requiring complex and costly solutions to achieve flexibility in air flow rates, and lack effective backflow prevention capabilities.
Innovation Solution
A variable orifice restrictor device that incorporates a flap assembly hinged to a housing, using gravity, magnets, or weights to control airflow, providing a turndown ratio better than 5 to 1, and includes a mechanism to prevent backflow without additional electrical components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a variable speed blower/fan is used to control airflow, then the system can operate at different speeds, but the turndown ratio is limited to 5 to 1 due to minimum operating RPM constraints
Solution Approach 1:
The patent combines the variable orifice restrictor with the blower housing to form an integrated assembly. The restrictor is positioned within the housing such that airflow passes through both the variable orifice and the blower inlet, merging two flow control functions into a single compact unit. This integration eliminates the need for separate complex control systems while achieving extended turndown ratios beyond the blower's inherent 5:1 capability.
Solution Approach 2:
The variable orifice restrictor acts as an intermediary device between the atmosphere and the blower inlet. By positioning the restrictor upstream of the blower, it pre-regulates airflow before it enters the blower, allowing the system to operate at lower effective flow rates than the blower could achieve alone. This intermediary mechanism enables turndown ratios greater than 5:1 without requiring the blower to operate below its minimum RPM.
2Adaptability or versatility
If complex electrical components are added to achieve higher turndown ratios, then airflow flexibility improves, but system cost and complexity increase
Solution Approach 1:
The patent replaces complex electrical flow control systems with a purely mechanical variable orifice restrictor. The restrictor uses a movable plate with an adjustable aperture that mechanically regulates airflow based on pressure differential and spring force, eliminating the need for electronic controllers, sensors, and actuators. This mechanical approach achieves extended turndown ratios while reducing manufacturing cost and system complexity.
Solution Approach 2:
The variable orifice restrictor is designed to operate autonomously without external control systems. The movable plate responds automatically to pressure differential across the restrictor and spring force, self-regulating airflow based on system conditions. This self-service mechanism eliminates the need for complex electrical control circuits, microprocessors, and associated components, thereby reducing manufacturing cost while maintaining airflow flexibility.
3Reliability
If backflow prevention is implemented using secondary equipment, then backflow protection is achieved, but space requirements and cost increase
Solution Approach 1:
The patent integrates backflow prevention functionality directly into the variable orifice restrictor assembly. The movable plate and housing configuration create a check valve effect that prevents backflow into the restrictor, merging flow regulation and backflow protection into a single compact unit. This integration eliminates the need for separate backflow prevention devices, reducing space requirements while maintaining reliability.
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 device enhances airflow control efficiency, reduces system complexity and cost, and provides backflow prevention, aligning appliance operation with building load demands, while maintaining flexibility across varying capacity requirements.
Implementation Method 1
The flap assembly may be held shut in low flow situations, by the forces of gravity
Implementation Method 2
The flap assembly may be held shut in low flow situations, by the forces of gravity, and the use of one or more of the following: magnets
Implementation Method 3
As the RPM of the fan increases, pressure differential increases to a designed set-point whereupon the flap assembly overcomes the gravitational forces applied to the flap assembly and begins to open
Data Source
AI summary
This application is directed to a device and method for providing a variable orifice restrictor to an air induction system to achieve an improved turndown ratio of an airflow rate. The devices of the invention improve turndown ratio by relying on a pressure differential.