Self-priming Liquid Ring Pump with Air Fuel Separator
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Solution Overview
Problem
Rotary wing aircraft fuel systems face challenges with low fuel pressure suction due to gravity and inertial forces, leading to air bubble formation and non-homogeneous mixtures, which existing pumps cannot handle effectively, and lack self-priming capabilities, especially at altitude.
Innovation Solution
A self-priming fuel system incorporating a side channel liquid ring pump with an air/fuel separator and inlet ejector, which separates and recycles fuel to maintain the liquid ring, allowing for efficient air compression and suction, eliminating the need for an airframe-mounted boost pump.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional centrifugal or regenerative impeller pump is used, then the pump can provide pressure for solid fuel, but it cannot compress air bubbles and is not self-priming
Solution Approach 1:
The pump is segmented into multiple chambers including a compression chamber and a liquid ring chamber, allowing different zones to perform different functions (fuel pumping vs. air compression), enabling the pump to handle non-homogeneous mixtures effectively
Solution Approach 2:
A liquid ring acts as an intermediary medium between the air bubbles and the impeller, allowing the impeller to compress air bubbles indirectly through the liquid ring mechanism while maintaining self-priming capability
2Shape
If the fuel tank is located in the bottom part of the aircraft, then the engine can be mounted in the top part, but gravity and inertial forces reduce fuel pressure at the pump inlet below tank pressure
Solution Approach 1:
The system uses a liquid ring pump mechanism that creates a hydraulic seal and utilizes fluid dynamics to generate suction pressure, overcoming the negative pressure effects of gravity and inertial forces in the vertical aircraft configuration
3Speed
If the aircraft flies at altitude, then the engine operates in thin air, but ambient air and tank pressures drop further reducing fuel pressure
Solution Approach 1:
The pump system is designed to be self-priming, automatically replenishing its own liquid ring and maintaining suction capability without external intervention, ensuring consistent performance across varying altitude conditions
4Reliability
If a side channel liquid ring pump is used with a large fuel reservoir, then air and fuel can be separated by gravity, but the system requires large volume not practical for aerospace applications
Solution Approach 1:
The air/fuel separator is nested within the pump housing, utilizing the existing pump chamber space for separation functions, thereby eliminating the need for a separate large external reservoir while maintaining effective separation capability
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 system effectively separates air and fuel, enabling efficient fuel delivery and air compression, maintaining pump performance even at low pressures and during priming, without the need for additional airframe-mounted equipment.
Implementation Method 1
When pumping air in a liquid ring pump, centrifugal forces separate the fuel and air (or vapor during low suction pressure conditions). The heavier fuel particles are flung to the outer diameter while the air bubbles collect near the impeller hub.
Implementation Method 2
A pressure gradient is established with the pressure in the channel at the outer diameter are greater than the pressure at the interior hub.
Implementation Method 3
The side channel liquid ring pump is typically coupled with an inlet ejector to assist in suction conditions as well as to provide a conduit to replenish the liquid ring when pumping air during priming.
Data Source
AI summary
A fuel system incorporating a boost pump unit, a boost pump unit and method of pumping fuel are provided. The fuel system and boost pump unit are preferably self-priming and do not utilize an airframe mounted pump for supplying fuel for an aircraft combustor. The boost pump unit includes a liquid ring pump and an air/fuel separator. The air/fuel separator has an inlet and first and second outlet ports. The inlet is operably fluidly coupled to an outlet of the liquid ring pump. The air/fuel separator has an arcuate flow path. The first outlet port is in fluid communication with a radially outer portion of the arcuate flow path and the second outlet port is in fluid communication with a radially inner portion of the arcuate flow path. A return line connected to the first outlet port is configured to return fuel to the liquid ring pump.