Axial Fan Motor Cooling via Offset Flow Duct
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Solution Overview
Problem
Axial fans poorly cool the motor housing due to detached airflow from the hub region and increased back-pressure, exacerbated by protective screens and large fastening flanges that impede airflow onto the motor housing.
Innovation Solution
A flow duct with an offset inflow and outflow opening is attached behind the fan wheel, directing airflow onto the motor housing, enhancing thermal transfer through pressure differences and optimizing airflow speed and volumetric flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the axial fan operates with increasing back-pressure and motor loading, then the fan can deliver higher power output, but the airflow detaches from the hub region resulting in poor cooling of the motor housing
Solution Approach 1:
The invention divides the airflow path into two separate channels: one for power delivery and one for cooling. The first flow channel handles the main airflow for power output, while the second flow channel is specifically designed to guide cooling airflow along the motor housing, separating these two functions to resolve the contradiction between power delivery and cooling effectiveness.
Solution Approach 2:
A protective screen is introduced as an intermediary element between the fan wheel and holding struts. This screen is strategically positioned to guide and direct the airflow onto the motor housing, ensuring that even under high back-pressure conditions, the cooling function is maintained by mediating the airflow path to prevent detachment and ensure consistent cooling.
2Reliability
If a protective screen with large fastening flange is installed between the fan wheel and holding struts, then protection is improved, but the incident flow onto the motor housing is further impaired
Solution Approach 1:
The protective screen is designed with differentiated local qualities: it provides robust protection where needed while incorporating specific geometric features and positioning that optimize airflow guidance. The screen's structure is tailored to maintain protective function in critical areas while creating favorable flow conditions for cooling in other areas, resolving the contradiction between protection and cooling.
3Temperature
If the flow duct directs airflow onto the motor housing, then thermal transfer is improved, but the device complexity increases due to additional components
Solution Approach 1:
The flow duct is merged with the existing holding struts structure, integrating the cooling function into the structural support elements. By combining the flow duct with the holding struts, the invention reduces the number of separate components and simplifies the overall device structure while still achieving improved thermal transfer to the motor housing.
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
Significantly improves cooling of the motor housing by increasing thermal transfer compared to natural convection, ensuring reliable cooling even under increasing back-pressure conditions.
Implementation Method 1
an approaching flow speed of the flow medium out of the flow duct onto the motor housing results via the pressure difference between the inflow opening into the flow duct and the outflow opening
Implementation Method 2
an axial fan, consisting of an inner electric motor and a fan wheel which is connected fixedly to the electric motor so as to rotate with it
Implementation Method 3
an approaching flow speed of the flow medium out of the flow duct onto the motor housing results via the pressure difference between the inflow opening into the flow duct and the outflow opening, which approaching flow speed considerably increases the thermal transfer in comparison with natural convection
Data Source
AI summary
An axial fan, having an inner electric motor and a fan wheel connected to the electric motor so as to rotate with it and has a plurality of wheel blades defining a blade length and extend outwardly from the electric motor. A fan housing surrounds the fan wheel. The fan housing is connected to the motor via holding struts which extend to the outside from the motor to the fan housing. A motor housing is provided on the motor behind the fan wheel and accommodates a motor electronics system. A flow duct having an inflow opening and an outflow opening is fastened to the motor behind the fan wheel such that the inflow opening is arranged offset to the outside with respect to the outflow opening. The outflow opening is oriented in such a way that an air flow which exits the outlet opening is guided onto the motor housing.