Aircraft Drain Mast Airflow Suction Design
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Solution Overview
Problem
Existing aircraft drain masts for auxiliary power unit (APU) compartments face issues with fluid droplets adhering to the fuselage due to airflow, leading to contamination, cosmetic problems, and increased parasite drag, as they fail to effectively release small leakages and create a suction effect to prevent adherence.
Innovation Solution
A drain mast design featuring a tube with a coupled pipe that accelerates airflow to create a suction effect, breaking droplets into smaller sizes and ejecting them perpendicular to the fuselage, reducing momentum response time and ensuring correct detachment from the mast.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a simple tube drain mast is used, then the device complexity is reduced and manufacturing is easier, but fluid droplets adhere to the fuselage due to airflow causing contamination and increased parasite drag
Solution Approach 1:
A pipe is introduced as an intermediary component between the tube and the fuselage. This pipe serves as a mediator that captures droplets falling from the tube and redirects them away from the fuselage using airflow, preventing direct adherence to the aircraft body while maintaining a relatively simple overall structure.
Solution Approach 2:
The droplet discharge function is extracted from the simple tube structure and relocated to a separate pipe component positioned away from the fuselage. This separation allows droplets to be discharged into the airflow stream rather than directly onto the fuselage, reducing contamination and drag.
2Ease of manufacture
If the drain mast discharges droplets directly to atmosphere, then the structure is simpler, but droplets are carried by airflow onto the fuselage causing cosmetic issues and requiring cleaning operations
Solution Approach 1:
The pipe acts as an intermediary discharge pathway that intercepts droplets before they can be carried by airflow onto the fuselage. It provides a controlled discharge route that leverages the existing airflow to carry droplets away from critical areas, reducing contamination without complex active control systems.
Solution Approach 2:
The harmful airflow that was causing droplet adherence to the fuselage is converted into a beneficial force by positioning the pipe to utilize this same airflow for carrying droplets away from the fuselage. The existing airflow condition is repurposed to solve the contamination problem.
3Productivity
If droplets are released at the open end of the tube, then the discharge process is simpler, but powerful airflow promotes droplets to the rear outer surface of the drain mast or fuselage
Solution Approach 1:
The pipe serves as an intermediary discharge structure that receives droplets from the tube and provides a extended discharge point positioned in the airflow stream. This intermediary structure allows droplets to be discharged further downstream where airflow patterns are more favorable, preventing rearward redistribution onto the fuselage.
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 ensures effective detachment of fluid droplets from the drain mast, preventing adherence to the fuselage and reducing parasite drag, while maintaining lightweight and cost-effective manufacturing with minimal changes to aircraft compartment design.
Implementation Method 1
a first straight part with an inlet having its longitudinal axis configured for being confronted to the coming airflow for allowing the inlet of said coming airflow into the pipe
Implementation Method 2
the pipe coupled to the inner longitudinal surface of the tube and configured such that the drained liquid flows from the tube to the pipe
Implementation Method 3
the internal rim and the aperture being configured such that at the second end the liquid is directed by gravity through the internal rim to the aperture
Implementation Method 4
a second straight part with an outlet having its longitudinal axis inclined with respect to the longitudinal axis of the first straight part with an inlet and configured to be arranged such that it discharges the airflow and the drained liquid flowing through the pipe in a direction inclined with a component perpendicular to the fuselage of the aircraft
Data Source
Figure 1A~1B
Figure 2~3
Figure 4
AI summary
1.- A drain mast for draining liquids from an aircraft, the drain mast comprising a tube (1) and further comprising: -a pipe (4) coupled to the inner longitudinal surface (13) of the tube (1) and configured such that the drained liquid flows from the tube (1) to the pipe (4) comprising: - an inlet (5) having its longitudinal axis configured for being confronted to the coming airflow for allowing the inlet of said coming airflow into the pipe (4), and - an outlet (9) having its longitudinal axis inclined with respect to the longitudinal axis of the inlet (5) and configured for discharging the airflow flowing through the pipe (4) in a direction inclined with a component perpendicular to the fuselage of the aircraft.