Hydrogen Fuel Pump Cavitation Prevention via Tank Ullage Duct
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Solution Overview
Problem
Pumping hydrogen in aircraft propulsion systems, particularly when stored as a liquid, faces challenges such as high power requirements and the risk of cavitation within fuel pumps.
Innovation Solution
The propulsion system includes a hydrogen-burning gas turbine engine, an auxiliary power unit, and a tank arrangement with vaporisers and ducts to maintain pressure in the tank, preventing cavitation and efficiently delivering hydrogen to the engines and auxiliary units.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If liquid hydrogen is pumped at high flow rates and pressures, then the hydrogen delivery requirement is met, but cavitation occurs within the fuel pump
Solution Approach 1:
A vaporiser is introduced as an intermediary component between the fuel pump and the combustion apparatus. The vaporiser converts liquid hydrogen to gaseous hydrogen, allowing the fuel pump to operate with liquid hydrogen while the vaporisation process occurs separately. This mediator component resolves the cavitation issue by separating the pumping function from the phase change function.
Solution Approach 2:
The system changes the physical state parameter of hydrogen from liquid to gas through controlled vaporisation. By maintaining hydrogen in liquid state during pumping (where it can be pumped efficiently) and then transforming it to gaseous state before combustion, the system optimizes both pumping efficiency and combustion performance without causing cavitation.
2Volume of stationary object
If hydrogen is stored as a liquid to reduce volume, then storage efficiency is improved, but high power is required to pump the liquid hydrogen
Solution Approach 1:
The system segments the hydrogen delivery process into distinct stages: liquid hydrogen storage, liquid hydrogen pumping, vaporisation, and gaseous hydrogen delivery. By dividing the process, the pumping operation handles only liquid hydrogen at manageable pressures, while the energy-intensive vaporisation occurs separately, reducing the power requirement on the fuel pump itself.
Solution Approach 2:
The vaporiser acts as an intermediary that handles the energy-intensive phase change process separately from the pumping operation. This allows the fuel pump to operate with lower power requirements, pumping liquid hydrogen efficiently, while the vaporiser provides the necessary energy input to convert the liquid to gas for combustion.
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
This solution effectively addresses the challenges of hydrogen pumping by maintaining tank pressure and preventing cavitation, ensuring efficient operation of the gas turbine engines and auxiliary power units.
Implementation Method 1
the first and second vaporisers are arranged to receive and vaporise liquid hydrogen from the first and second fuel pumps respectively and provide resulting gaseous hydrogen
Implementation Method 2
pressure within the first tank is maintained by gaseous hydrogen provided to the ullage of the first tank via the duct, thus avoiding cavitation of liquid hydrogen within the first and second fuel pumps
Implementation Method 3
the auxiliary power unit being arranged to provide electrical power to the at least one electric fuel pump
Implementation Method 4
The first vaporiser may comprise a heat exchanger arranged to receive compressor bleed air from the hydrogen-burning gas turbine engine and transmit heat from the compressor bleed air to liquid hydrogen within the first fuel line
Data Source
Figure 1
Figure 2
AI summary
A propulsion system 100 comprises a propulsive hydrogen-burning gas turbine engine 190A, a fuel cell stack auxiliary power unit (APU) 142 and a first tank 106 arranged to store liquid hydrogen with an ullage 105. A first fuel line 108 includes a first pump 107 and a first vaporiser 116 and transports hydrogen from the first tank to combustion apparatus 194A of the engine during operation of the propulsion system. A second fuel line 109 includes a second fuel pump 181 and a second vaporiser 185 and transports hydrogen from the first tank to the fuel cell stack APU. A duct 111 connects the second fuel line at a position thereon between the second vaporiser and the fuel cell stack to the ullage of the first tank, providing for pressure in the first tank to be maintained therein as liquid hydrogen within the first tank is depleted, thus avoiding cavitation of liquid hydrogen within the first fuel pump.