Low Solidity Axial Fan Reduces Ram Air Resistance
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Solution Overview
Problem
Heavy duty trucks face inefficiencies in engine cooling due to high solidity fans, which restrict ram air flow and increase power consumption, as existing fan designs do not account for unique vehicular operating conditions, leading to suboptimal performance in both 'on' and 'off' conditions.
Innovation Solution
A low solidity axial flow fan with five blades, each featuring a unique shape and configuration, including a hub ramp, high camber, and varying thickness, achieving a solidity of less than 25% and a maximum total turning angle of approximately 90°, allowing for efficient airflow and pressure development without increased blade depth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If a high solidity fan is used, then the fan can build more fluid pressure, but it creates more ram air resistance and restricts cooling airflow
Solution Approach 1:
The patent changes the solidity parameter from conventional high values (typically 0.4-0.6) to a low value of approximately 0.2. This parameter change fundamentally alters the fan's interaction with ram air, reducing resistance while maintaining adequate pressure generation through optimized blade geometry and vehicle speed utilization
2Productivity
If the fan solidity is increased to provide more cooling flow, then pressure building capability improves, but the restriction of ram air flow increases
Solution Approach 1:
The patent applies parameter changes by reducing solidity to 0.2 and optimizing blade geometry parameters (pitch, camber, skew) to achieve maximum cooling flow efficiency at low solidity, allowing the fan to move more air with less resistance
Solution Approach 2:
The patent utilizes the dynamic interaction between vehicle motion and fan operation, where the low solidity fan leverages vehicle speed to generate ram air that drives cooling flow, reducing the need for high fan-generated pressure while maintaining productivity
3Ease of manufacture
If a conventional six-blade fan design is used, then manufacturing is simplified, but the solidity is too high causing excessive ram air resistance
Solution Approach 1:
The patent changes the blade count parameter from six to five, which reduces solidity from approximately 0.47 to 0.2. This parameter change maintains manufacturing feasibility while dramatically reducing ram air resistance and improving cooling efficiency
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 low solidity fan enhances ram air cooling efficiency and reduces power consumption by maintaining sufficient static pressure across various operating conditions, outperforming traditional six-blade fans in terms of airflow and pressure delivery.
Implementation Method 1
the fan must develop enough pressure to draw the required cooling air flow through the vehicle's heat exchanger
Implementation Method 2
A low solidity axial flow fan with five blades
Implementation Method 3
When such a vehicle is being driven at relatively high speeds, motion of the vehicle is generally enough to cool the internal combustion engine. As the vehicle travels forward, air is forced through one or more heat exchangers, cooling the engine. This air flow from vehicle motion is often referred to as ram air.
Implementation Method 4
air is forced through one or more heat exchangers, cooling the engine
Data Source
Figure 1A~1B
Figure 2
Figure 3
AI summary
An axial flow fan (20; 120) for use with a vehicle cooling system includes a hub (22) defining an axis of rotation (A), and at least five blades (24) supported on the hub. Each blade includes a leading edge (24-3), a trailing edge (24-4) opposite the leading edge, a pressure side (24-1) extending between the leading edge and the trailing edge, a suction side (24-2) opposite the pressure side, a tip (24-5), and a root (24-6) opposite the tip along a blade length. A solidity of the axial flow fan, measured as a percentage of an annular flow area between an outer diameter of the hub (22) and an outer diameter of the tips (24-5) of the blades (24) projected onto a plane perpendicular to the axis of rotation (A) that is occupied by the blades (24), is less than 40%.