Hydrogen Fuel Priming Tank Layout for Safe Gas Turbine Starts
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Solution Overview
Problem
The challenge of operating hydrogen-fueled gas turbine engines in aircraft is the need for a priming and purging procedure due to the cold liquid hydrogen causing vaporization, water freezing, and oxygen fire risk, which complicates fuel system operations.
Innovation Solution
A fuel system with a hydrogen priming tank and preheater that uses high-pressure gaseous hydrogen to maintain ambient pressure and temperature, eliminating the need for external refilling and reducing complexity by integrating the priming process into engine operation.
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 contacting warm fuel system components causing overpressure
Solution Approach 1:
The fuel system is pre-filled with gaseous hydrogen before liquid hydrogen is introduced. This preliminary action ensures that the system is already pressurized and filled with hydrogen gas, which prevents overpressure when liquid hydrogen vaporizes during engine starting.
Solution Approach 2:
Gaseous hydrogen acts as an intermediary substance between the liquid hydrogen and the warm fuel system components. By introducing gas first, it creates a buffer that absorbs the pressure surge from vaporization and prevents direct contact between cold liquid hydrogen and warm components.
2Reliability
If liquid hydrogen is flowed into the fuel system, then engine starting is enabled, but water present in the system will freeze causing potential blockages
Solution Approach 1:
The system is pre-filled with gaseous hydrogen before liquid hydrogen is introduced. This preliminary action displaces moisture and water from the fuel system components, preventing water freezing when cold liquid hydrogen is subsequently introduced.
Solution Approach 2:
Gaseous hydrogen creates an inert atmosphere in the fuel system before liquid hydrogen is introduced. This inert environment prevents water from freezing by displacing it and creating a protective gas layer that reduces the impact of cold liquid hydrogen on any remaining moisture.
3Reliability
If liquid hydrogen is flowed into the fuel system, then engine starting is enabled, but oxygen present in the system represents a fire risk
Solution Approach 1:
The fuel system is pre-filled with gaseous hydrogen before liquid hydrogen is introduced. This preliminary action displaces oxygen from the fuel system, creating a hydrogen-rich environment that reduces the fire risk when liquid hydrogen is subsequently introduced and vaporized.
Solution Approach 2:
Gaseous hydrogen creates a reducing atmosphere in the fuel system before liquid hydrogen is introduced. This atmosphere displaces oxygen and creates conditions less favorable for combustion, thereby reducing the fire risk associated with introducing liquid hydrogen into the system.
4Reliability
If a purging and priming procedure is used with purging and priming gases, then the fuel system can be prepared safely, but the complexity of fuelling operations increases between flights
Solution Approach 1:
The purging and priming functions are merged into a single operation by using gaseous hydrogen for both purposes. The same hydrogen gas that is used for priming also serves to purge the system, eliminating the need for separate purging and priming procedures and reducing operational complexity.
Solution Approach 2:
Gaseous hydrogen is used for multiple functions: it serves as the priming gas, the purging gas, and the fuel itself. This multi-functionality eliminates the need for separate purging and priming operations, thereby reducing the complexity of fuelling operations between flights while maintaining safety.
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 simplifies fuel system operations by maintaining stable pressure and temperature, reducing the need for venting and insulation, and enhancing safety by avoiding overpressure and fire hazards, while enabling efficient hydrogen delivery to the combustor.
Implementation Method 1
a hydrogen fuel preheater configured to be supplied with high pressure gaseous hydrogen from the hydrogen fuel pump, and configured to supply heated gaseous hydrogen to a combustor
Implementation Method 2
The pre-heater may comprise an auxiliary combustor configured to combust a portion of hydrogen fuel with air to produce a heated exhaust flow
Implementation Method 3
the preheater may comprise a recuperator configured to exchange heat between gas turbine engine exhaust gases and hydrogen fuel
Data Source
AI summary
A fuel system for a hydrogen fuelled gas turbine engine includes a main hydrogen fuel storage unit, a hydrogen fuel pump configured to be supplied with hydrogen from the hydrogen storage unit, a hydrogen fuel preheater configured to be supplied with high pressure hydrogen from the hydrogen fuel pump, and configured to supply heated gaseous hydrogen to a combustor of the gas turbine engine, and a hydrogen priming tank configured to store compressed gaseous hydrogen and to deliver gaseous hydrogen to at least the hydrogen fuel pump and preheater. The fuel system comprises a high-pressure gaseous hydrogen fuel offtake downstream in hydrogen fuel flow of the fuel pump in fluid communication with the hydrogen priming tank, and configured to fill the hydrogen priming tank with high pressure gaseous hydrogen.