Vane Axial Fan with Intermediate Flow Control Rings to Reduce Stall
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Solution Overview
Problem
Vane-axial flow fans are limited by their operating range due to blade stall, which restricts their application in systems requiring extended operating ranges and is exacerbated by radial flow migration causing stall and reduced recovery performance, particularly in HVAC applications.
Innovation Solution
The implementation of flow control rings between the rotor trailing edge and stator leading edge to redirect radial airflow components into an axial direction, mitigating stall and recirculation by positioning them at specific spans and optimizing their thickness for structural rigidity and manufacturability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If vane-axial fans operate at high static efficiency, then energy conversion is improved, but the operating range is limited due to blade stall
Solution Approach 1:
Flow control rings are introduced as intermediary components between the rotor and stator. These rings act as mediators that modify the flow field by redirecting radial flow components, preventing stall conditions while maintaining the high efficiency characteristics of vane-axial fans across an extended operating range.
Solution Approach 2:
The flow control rings change the flow parameters by redirecting radial flow components into more axial flow. This parameter modification allows the fan to operate efficiently across a broader range of flow rates and pressure ratios without encountering blade stall, thus expanding the operating range while maintaining energy efficiency.
2Object-generated harmful factors
If radial flow migration occurs in the axial spacing between rotor and stator, then flow dynamics are altered, but stall performance deteriorates and recovery hysteresis increases
Solution Approach 1:
Flow control rings serve as intermediary structures positioned in the axial spacing between rotor and stator. They intercept and redirect the harmful radial flow migration before it can cause stall, thereby improving stall recovery performance and reducing hysteresis effects.
Solution Approach 2:
The flow control rings convert the harmful radial flow migration into beneficial axial flow components. By redirecting the radial flow that would otherwise cause stall, the rings transform a detrimental flow pattern into one that maintains attached flow and improves stall recovery characteristics.
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 solution enhances stall performance and reduces stall recovery hysteresis, expanding the operating envelope of shrouded axial fans, making them more applicable to various conditions such as rooftop HVAC systems.
Implementation Method 1
The implementation of flow control rings between the rotor trailing edge and stator leading edge to redirect radial airflow components into an axial direction
Data Source
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AI summary
A fan assembly includes a shrouded fan rotor (18) having a plurality of fan blades (22) extending from a rotor hub (24) and rotatable about a central axis (20) of the fan assembly and a fan shroud (26) extending circumferentially around the fan rotor (18) and secured to an outer tip diameter of the plurality of fan blades (22). A stator assembly (28) is located downstream of the fan rotor (18), relative to an airflow (14) direction through the fan assembly. The stator assembly (28) includes a plurality of stator vanes (30) extending between a stator hub (32) and a stator shroud (34). A flow control ring (36) is positioned between the fan rotor (18) and the stator assembly (28) to block radial flow migration in an axial spacing between the fan rotor and the stator assembly resulting from a radial flow component of an airflow (14) exiting the fan rotor (18).