Hydrogen Gas Turbine Fuel System Priming Without External Gases
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Solution Overview
Problem
Operating hydrogen fueled gas turbine engines in aircraft poses challenges such as overpressure due to vaporization of liquid hydrogen, blockages from freezing water and liquified gases, and fire risks from oxygen, necessitating complex purging and priming procedures that require external gases and increase fueling complexity.
Innovation Solution
A fuel system utilizing a main hydrogen storage tank with an ullage space and integrated priming line, heaters to warm ullage fluid, and a dual priming valve system to manage ullage fluid flow, eliminating the need for separate priming fluid tanks and reducing system complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If liquid hydrogen is flowed into the fuel system for engine starting, then the engine can be started, but the cold liquid hydrogen will vaporize when it contacts the warm fuel system components, causing overpressure
Solution Approach 1:
The fuel system is pre-filled with liquid hydrogen before engine start, and the ullage space contains cold gaseous hydrogen that has been pre-cooled to match the temperature of the liquid hydrogen. This preliminary cooling action prevents thermal shock and vaporization when liquid hydrogen contacts warm components during engine starting.
2Reliability
If liquid hydrogen is flowed into the fuel system, then the engine can be started, but any water present in the system will freeze, and gases such as air may liquify and solidify which may cause potential blockages
Solution Approach 1:
The ullage space is filled with pure gaseous hydrogen at controlled pressure, creating an inert atmosphere that prevents oxygen from contacting the liquid hydrogen and forming explosive mixtures. This inert environment eliminates fire risks while the controlled pressure prevents condensation and freezing of contaminants that could cause blockages.
3Reliability
If a purging and priming procedure is used prior to flowing liquid hydrogen, then safety is improved, but the requirement for purging and priming gases increases the complexity of fueling operations
Solution Approach 1:
The system uses its own ullage space containing gaseous hydrogen to perform the purging and priming functions. The gaseous hydrogen from the ullage space flows through the fuel system to displace air and warm the components, eliminating the need for external purging and priming gases and simplifying fueling operations.
4Device complexity
If the ullage space stores gaseous or supercritical hydrogen, then the main hydrogen storage tank can provide priming fluid, but the temperature of the ullage fluid may be too cold and cause liquefaction of gases in the fuel conduit
Solution Approach 1:
The system controls the temperature and pressure parameters of the ullage space to maintain gaseous or supercritical hydrogen in a state suitable for priming. By adjusting these parameters, the ullage hydrogen can serve dual purposes: providing priming fluid and maintaining appropriate temperature to prevent liquefaction of other gases in the fuel conduit.
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
Enables effective purging and priming of the fuel system without external gases, reducing weight and turnaround time, while maintaining safety and efficiency in hydrogen fuel delivery.
Implementation Method 1
The fuel system may comprise at least a first ullage fluid heater configured to heat ullage fluid. Advantageously, the temperature of the relatively cold ullage fluid can be increased, thereby preventing liquefaction of any gases in the fuel conduit due to excessive cooling by the ullage fluid.
Implementation Method 2
The second ullage fluid heater may be provided downstream in purging fluid flow of the first priming valve. Advantageously, the volume between the first priming valve and the second priming valve can be heated by the second heater, thereby increasing its pressure prior to release downstream.
Data Source
AI summary
A fuel system for a hydrogen fueled gas turbine engine comprises a main hydrogen fuel storage unit configured to store liquid hydrogen. The main fuel storage unit comprises an ullage space configured to store ullage fluid comprising gaseous or supercritical hydrogen. The system further comprises a liquid hydrogen drain line configured to provide liquid hydrogen from the main hydrogen fuel storage unit to a fuel conduit, the fuel conduit being configured to supply hydrogen fuel to a combustor of the gas turbine engine. A priming line is provided, which is configured to provide ullage fluid to the fuel conduit, and a priming valve is configured to selectively control flow through the priming line.