Ram Fan Motor Cooling via Downstream Inlets and Air Scoop
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Solution Overview
Problem
Conventional ram air fan cooling systems for motors are inadequate at low airspeeds, leading to motor overheating and potential clogging from fine object debris, resulting in insufficient heat removal and airflow.
Innovation Solution
A ram fan device with a housing that includes cooling inlets and an air scoop to enhance airflow through the motor cavity, allowing increased airflow rates and preventing debris entry by using a motor with a gap between the rotor and stator and cooling passages, and positioning the cooling inlets downstream of the fan to improve airflow and heat transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a conventional cooling duct is used to cool the motor, then the motor can be cooled at high airspeeds, but the motor overheats at low airspeeds due to insufficient induced airflow
Solution Approach 1:
The cooling system is segmented into multiple independent cooling inlets positioned at different locations around the motor housing. This allows each inlet to independently draw airflow from different sources (ram air at high speed, induced flow at low speed), ensuring adequate cooling airflow reaches the motor across all airspeed conditions.
Solution Approach 2:
The cooling inlets serve multiple functions: they draw cooling airflow for the motor, position the cooling air source downstream of the fan, and work in conjunction with the air scoop to enhance overall airflow management. This multi-functionality allows the system to maintain effective motor cooling regardless of aircraft airspeed.
2Temperature
If the cooling duct is positioned upstream of the motor, then it can provide cooling airflow, but fine object debris (FOD) clogs the duct and motor housing airflow passages
Solution Approach 1:
Instead of positioning cooling inlets upstream of the motor where debris would enter, the cooling inlets are positioned downstream of the fan. This inverts the conventional approach, allowing the fan's airflow to draw cooling air through the inlets from a location where debris has already been processed by the fan, significantly reducing FOD clogging of the cooling passages.
3Temperature
If the cooling inlet is positioned upstream of the motor, then cooling airflow can reach the motor, but the airflow rate is insufficient to prevent overheating
Solution Approach 1:
The air scoop is positioned to preliminarily direct and concentrate airflow toward the cooling inlets before the air enters the motor housing. This preliminary action enhances the velocity and directionality of the cooling airflow, ensuring adequate airflow rates reach the motor even at low airspeeds where induced flow is limited.
Solution Approach 2:
Multiple cooling inlets are positioned at specific locations downstream of the fan where local airflow conditions are most favorable. This local positioning optimizes the quality and quantity of cooling airflow at each inlet, maximizing heat removal from the motor across varying flight 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
The solution provides improved thermal efficiency and prevents motor overheating by increasing airflow through the motor cavity, reducing debris entry, and enhancing heat transfer from the heat exchanger, even at low airspeeds.
Implementation Method 1
airflow can pass through the cooling inlet through the motor cavity and out the outlet
Implementation Method 2
a liquid/air heat exchanger disposed between the ram inlet header and the ram outlet header
Data Source
AI summary
A ram fan device includes a motor disposed in a housing that defines a motor cavity with a fan operatively connected to be driven by the motor and an outlet in fluid communication with the motor cavity. The housing includes a cooling inlet therethrough downstream of the fan and upstream of the motor, the cooling inlet being in fluid communication with the outlet through the motor cavity such that airflow can pass through the cooling inlet through the motor cavity and out the outlet.