Diagonal Fan Motor Cooling via Negative Pressure Zone
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Solution Overview
Problem
Diagonal fans with EC motors suffer from poor cooling, leading to reduced performance and overheating due to the 'anti-cooling' design, which restricts output compared to axial fans where the motor is better cooled by airflow.
Innovation Solution
The introduction of a negative pressure zone behind the fan blades, which utilizes the back pressure to enhance cooling airflow without changing direction, and the incorporation of an air brake mechanism to improve airflow dynamics, ensuring consistent cooling across the working area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If a diagonal fan design is used, then the fan can achieve compact structure and diagonal airflow, but the EC motor is poorly cooled leading to reduced power output
Solution Approach 1:
The fan wheel is segmented into multiple functional zones: a first region with fan blades for main airflow generation, and a second region with cooling air fan blades for dedicated motor cooling. This segmentation allows independent optimization of each function, resolving the contradiction between compact diagonal structure and effective motor cooling.
Solution Approach 2:
A cooling air auxiliary fan is introduced as an intermediary component between the main fan function and motor cooling. This auxiliary fan, driven by the same motor but with separate blades in the second region, acts as a mediator that redirects airflow to cool the motor without compromising the main diagonal airflow function.
2Temperature
If the cooling air auxiliary fan is added, then motor cooling is improved, but the device complexity increases
Solution Approach 1:
The cooling air auxiliary fan is merged with the main fan wheel structure, sharing the same hub, mounting location, and rotational axis. Both the main fan blades and cooling air fan blades are attached to the same fan wheel, eliminating the need for separate motor housings or additional drive mechanisms, thus reducing overall device complexity.
Solution Approach 2:
The fan wheel is designed with multi-functionality: the first region generates main diagonal airflow for fan operation, while the second region generates cooling airflow for motor cooling. This universal design allows a single component to perform multiple functions, avoiding the complexity of separate systems.
3Reliability
If back pressure increases, then the negative pressure zone shifts, but the core remains stable enabling consistent cooling
Solution Approach 1:
The cooling air auxiliary fan blades are pre-positioned in the second region to proactively generate cooling airflow before back pressure variations can cause overheating. The design anticipates pressure changes and maintains cooling effectiveness through the stable negative pressure zone core, ensuring reliable motor cooling across varying operating conditions.
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 effectively enhances cooling of the electric motor by maintaining a consistent airflow direction and pressure gradient, preventing overheating and increasing the fan's operational range and power output.
Implementation Method 1
a cooling air auxiliary fan (76) which is designed to transport cooling air on the inside of the fan wheel (80) from the air outlet side in the direction of the air inlet side and through this air flow to cool the electric motor (73)
Implementation Method 2
the negative pressure in a negative pressure zone on the back of at least one fan blade on the auxiliary cooling air fan becomes effective and increases its effect
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
The invention relates to a diagonal fan (30) comprising a fan housing (36) and a fan wheel (80) rotatable about a rotational axis, an electric motor (73) being associated with said fan wheel for driving the same. The fan wheel (80) extends in the direction of the rotational axis between an air intake side and an air exhaust side of the diagonal fan (30) and, on rotation thereof, serves to convey air in a main conveying direction from the air intake side to the air exhaust side. Furthermore, on the outer face of the fan wheel (80) there are provided fan blades (82) which, in relation to the direction of rotation (84) of the fan wheel (80) in operation, have a front face and a rear face, wherein in the region of the rear face of each blade (82) a negative pressure zone (110) occurs at the fan wheel (80) during operation. A cooling air auxiliary fan (76) is designed to transport cooling air in the interior of the fan wheel (80) from the air exhaust side thereof towards the air intake side and by means of said air flow to cool the electric motor (73) of the diagonal fan (30). At least one fluid connection (114; 130) leads from the outlet of the cooling air auxiliary fan (76) to at least one of the negative pressure zones (110) in order to boost a flow (126; 126') of the cooling air for the electric motor (73) from the air exhaust side of the diagonal fan (30) towards the air intake side thereof.