Hydrogen Engine Startup Using Dual Tanks and Boil-Off Recovery
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Solution Overview
Problem
Existing gas turbine engines face challenges in transitioning from hydrocarbon-based fuels to hydrogen-based fuels due to issues with ignition and boil-off of liquid hydrogen, which affect weight, volume, and efficiency, particularly in aircraft applications.
Innovation Solution
A dual-tank system comprising a main liquid hydrogen tank and a smaller gaseous hydrogen tank, supplemented by boil-off gas, with waste heat from the engine used to convert liquid hydrogen to gaseous hydrogen for efficient startup and operation, and redundant hydrogen supply for emergency restarts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If liquid hydrogen is used as fuel in the main tank, then energy density and weight efficiency are improved, but ignition difficulty and boil-off issues worsen
Solution Approach 1:
The hydrogen storage system is divided into two separate tanks: a main tank for liquid hydrogen storage and a starter tank for gaseous hydrogen storage. This segmentation allows each tank to serve its specific function optimally - the main tank provides high energy density while the starter tank ensures reliable ignition.
Solution Approach 2:
A heat exchanger is introduced as an intermediary component between the liquid hydrogen main tank and the gaseous hydrogen starter tank. This heat exchanger facilitates the phase change from liquid to gas hydrogen, enabling the system to leverage both the high energy density of liquid hydrogen and the ease of ignition of gaseous hydrogen.
2Volume of stationary object
If liquid hydrogen is stored in the main tank, then volume efficiency is improved, but boil-off losses increase
Solution Approach 1:
The system recovers boil-off gaseous hydrogen from the liquid hydrogen main tank and redirects it to the starter tank. This recovery process prevents hydrogen loss and simultaneously maintains the pressure differential needed for efficient phase change during engine startup.
3Reliability
If a dedicated gaseous hydrogen starter tank is added, then startup reliability is improved, but system complexity increases
Solution Approach 1:
The gaseous hydrogen starter tank serves multiple functions: it provides ignition fuel for the main engine, stores recovered boil-off hydrogen, and maintains pressure differential for phase change. This multi-functionality reduces the need for additional separate components.
Solution Approach 2:
The heat exchanger serves dual purposes by facilitating both the phase change of hydrogen and the recovery of boil-off gas. This merging of functions into a single component reduces overall system complexity despite adding the starter tank.
4Loss of energy
If waste heat is used to convert liquid hydrogen to gaseous hydrogen, then energy efficiency is improved, but heat transfer requirements worsen
Solution Approach 1:
The phase change of hydrogen from liquid to gas occurs periodically during engine operation rather than continuously. The waste heat from the engine is utilized during operation to convert liquid hydrogen to gaseous hydrogen for the starter tank, creating a periodic heat transfer cycle that improves overall energy efficiency.
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 efficient startup and operation of hydrogen-burning engines, minimizing weight and volume requirements while providing redundancy for emergency situations, and effectively utilizing boil-off gases.
Implementation Method 1
waste heat from the main engine is used to convert liquid hydrogen to gaseous hydrogen
Implementation Method 2
waste heat from the main engine is used to convert liquid hydrogen to gaseous hydrogen within a main engine fuel conditioning heat exchanger
Implementation Method 3
an auxiliary power unit configured to heat the liquid hydrogen to generate gaseous hydrogen
Implementation Method 4
an auxiliary power unit configured to heat the liquid hydrogen to generate gaseous hydrogen to be supplied to the main engine, wherein the auxiliary power unit includes an APU fuel conditioning heat exchanger
Implementation Method 5
a pump configured to boost a pressure of the gaseous hydrogen from boil-off prior to being supplied into the starter tank
Implementation Method 6
a hydrogen burning main engine
Implementation Method 7
the main engine generates waste heat during the normal operation
Data Source
AI summary
Aircraft hydrogen fuel systems and methods and systems of starting such systems are described. The aircraft hydrogen fuel systems include a hydrogen burning main engine, a main tank configured to contain liquid hydrogen to be supplied to the main engine during a normal operation, and a starter tank configured to contain gaseous hydrogen to be used during a startup operation of the main engine. Methods and processes for starting and/or restarting such systems are described.