Airflow Baffle Geometry for Rotor-Stator Gap Cooling
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing rotating electrical machines face inefficiencies in cooling due to eddy currents and turbulence introduced by air flow voids caused by end windings, leading to reduced heat transfer and air flow velocity, with a disproportionate amount of air flow passing around the outside of the stator core rather than through the rotor/stator air gap.
Innovation Solution
A novel air flow baffle with a substantially flat annular surface and a frustoconical shaped surface is introduced to redirect air flow from the stator/frame air gap around the end windings, increasing air resistance and prioritizing air flow through the rotor/stator air gap, while minimizing turbulence and eddy currents by creating a smoother, higher velocity air path.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If air flow exits the air gap between the stator core and the stator frame, then cooling of the stator core is achieved, but eddy currents are introduced into the airflow causing pressure loss and reduced air flow velocity
Solution Approach 1:
A baffle plate is introduced as an intermediary component between the air gap and the end windings. The baffle plate has a leading edge that extends into the air gap and a trailing edge that extends beyond the end windings, creating a controlled air flow path that minimizes eddy currents and turbulence while maintaining effective cooling of the stator core.
Solution Approach 2:
The baffle plate features a curved leading edge that is rounded rather than sharp. This curvature design smooths the air flow transition as air enters the region around the end windings, reducing turbulence and eddy current formation while maintaining the cooling function.
2Ease of manufacture
If the stator frame is made longer to accommodate end windings, then the machine structure is completed, but a void is created that causes eddy currents and turbulence
Solution Approach 1:
The baffle plate serves as a mediator that fills and controls the void space created by the extended stator frame accommodating end windings. It guides air flow through this previously harmful space, converting it from a source of turbulence into a controlled cooling passage.
Solution Approach 2:
The baffle plate converts the harmful void space and associated eddy currents into a beneficial controlled air flow path. The trailing edge of the baffle plate extends beyond the end windings to ensure complete coverage and maximize the conversion of the previously harmful region into an effective cooling zone.
3Ease of operation
If a flat annular baffle is provided to direct air flow radially, then air flow direction is changed, but eddy currents and turbulence are still introduced
Solution Approach 1:
The baffle plate's leading edge is curved rather than flat, creating a smooth transition surface that guides air flow radially inward without generating significant turbulence. This curved geometry allows the air to follow the contour of the baffle plate, minimizing separation and eddy current formation.
Solution Approach 2:
The baffle plate parameters are optimized including the curvature radius of the leading edge, the angle of the trailing edge, and the axial position of both edges. These parameter changes ensure that the air flow transitions smoothly from axial to radial direction while minimizing harmful flow patterns.
4Temperature
If air flow passes through the stator/frame air gap, then cooling of the stator core is achieved, but a greater proportion of air flow passes around the outside rather than through the rotor/stator air gap
Solution Approach 1:
The baffle plate segments the air flow path into distinct regions: air flow that passes through the rotor/stator air gap and air flow that passes around the end windings. By positioning the leading edge into the air gap and the trailing edge beyond the end windings, it creates separate flow channels that can be independently optimized.
Solution Approach 2:
The baffle plate creates different flow conditions in different locations: in the region near the rotor/stator air gap, the air flow is guided to maintain high velocity and minimize turbulence, while in the region around the end windings, the air flow is directed to provide cooling without interfering with the main cooling path through the rotor/stator air gap.
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 baffle enhances heat transfer to cooling air, improves air flow velocity, and rebalances air flow distribution between the stator/frame and rotor/stator air gaps, resulting in more effective cooling of the machine by ensuring a greater proportion of air flow passes through the rotor/stator air gap.
Implementation Method 1
The presence of a void causes eddy currents to be introduced into the airflow. This leads to pressure loss, reducing the air flow velocity, and resulting in a reduction in the transfer of heat to the cooling air. Furthermore, the fan itself may introduce turbulence into the air flow
Implementation Method 2
The presence of a void causes eddy currents to be introduced into the airflow
Implementation Method 3
The presence of a void causes eddy currents to be introduced into the airflow. This leads to pressure loss, reducing the air flow velocity
Implementation Method 4
This may help to ensure more efficient transfer of heat to the cooling air, thus providing more effective cooling
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A baffle 30 is disclosed for directing cooling air in a rotating electrical machine comprising a stator core and end windings extending out of the stator core. The baffle comprises a first surface 33 arranged to direct air flow 44, 45 along an end face of the stator core 16, and a second surface 35 arranged to direct air flow 46 along a radially outwards surface of the end windings 18. This may help to reduce turbulence in the airflow, thereby allowing more efficient transfer of heat. Furthermore, greater priority may be given to air flow through the rotor/stator air gap 14, and thus increasing air flow through the centre of the machine.