Hybrid Hydrogen Aircraft Engine Using Excess Fuel Cell Power

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Solution Overview

Problem

Existing gas turbine engines face inefficiencies due to the use of hydrocarbon-based fuels, particularly in aircraft applications, where the weight and volume of hydrogen or methane fuels require high efficiency propulsion, and transitioning to hydrogen-based fuels poses challenges in managing cryogenic fuel states and energy waste in exhaust heat.

Innovation Solution

A hybrid electric hydrogen aircraft engine system that incorporates a cryogenic fuel system, heat exchangers, and a fuel cell to manage hydrogen fuel from a cryogenic state to efficient combustion, utilizing heat exchangers and expansion turbines to prepare hydrogen for combustion, and employing a fuel cell to generate electrical power from excess hydrogen.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If hydrogen or methane fuels are used in gas turbine engines, then combustion efficiency and environmental performance are improved, but the weight and volume of fuel storage systems increase

Engineering Contradiction:
Improvecombustion efficiencyVSAvoidfuel storage system weight
Core Design Contradiction:
Loss of energyVSWeight of moving object

Solution Approach 1:

The patent utilizes phase change of hydrogen fuel from liquid to gas state during combustion, and employs cryogenic temperature storage to maintain hydrogen in liquid form, thereby increasing energy density and reducing storage volume while maintaining combustion efficiency

Inventive Principle:
Principle #35Parameter changes

Solution Approach 2:

The invention extracts and recovers waste heat from exhaust gases through heat exchangers, converting it to useful thermal energy for preheating combustion air or generating electrical power, thereby improving overall energy utilization and reducing the fuel storage requirements

Inventive Principle:
Principle #2Taking out (Extraction)

2Quantity of substance

If cryogenic hydrogen fuel is stored and transported, then energy density is improved, but system complexity and thermal management requirements increase

Engineering Contradiction:
Improveenergy densityVSAvoidthermal management system complexity
Core Design Contradiction:
Quantity of substanceVSDevice complexity

Solution Approach 1:

The patent combines the fuel storage system with heat exchanger components, where the same thermal infrastructure used for combustion air preheating also serves to manage cryogenic fuel temperature, thereby reducing overall system complexity while maintaining high energy density

Inventive Principle:
Principle #5Merging (Combining)

Solution Approach 2:

The thermal management system performs multiple functions simultaneously: cooling hydrogen fuel to maintain liquid state, preheating combustion air using waste heat, and generating electrical power through thermoelectric generators, thereby reducing the need for separate dedicated systems

Inventive Principle:
Principle #6Universality (Multi-functionality)

3Loss of energy

If waste heat from exhaust is recovered, then energy efficiency is improved, but additional system components and complexity are added

Engineering Contradiction:
Improvewaste heat recoveryVSAvoidheat exchanger system complexity
Core Design Contradiction:
Loss of energyVSDevice complexity

Solution Approach 1:

The heat exchanger system uses the engine's own exhaust heat to preheat the combustion air and thermal management fluids, creating a self-sufficient thermal cycle that improves efficiency without requiring external energy inputs or complex control systems

Inventive Principle:
Principle #25Self-service

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 efficiently manages hydrogen fuel from cryogenic to combustion-ready states, reduces energy waste, and provides additional electrical power through a fuel cell, optimizing engine performance and reducing weight and complexity.

Implementation Method 1

employing a fuel cell to generate electrical power from excess hydrogen

Methodology Applied
Scientific EffectFuel cell electrochemical conversion: Fuel Cell

Implementation Method 2

utilizing heat exchangers and expansion turbines to prepare hydrogen for combustion

Methodology Applied
Scientific EffectHeat exchange: Heat Exchanger

Implementation Method 3

utilizing heat exchangers and expansion turbines to prepare hydrogen for combustion

Methodology Applied
Scientific EffectGas expansion work: Turbine

Data Source

PatentEP4303417B1Hybrid electric hydrogen engine for aircraft
Publication Date: 2026.03.04 RTX CORP
  • EP4303417B1 patent drawingFigure 1
  • EP4303417B1 patent drawingFigure 2
  • EP4303417B1 patent drawingFigure 3

AI summary

An aircraft engine system includes a core assembly having at least a burner section and a fuel cell (344) configured to generate electrical power. A cryogenic fuel source (324) is configured to supply a fuel through a fuel supply line (326) to each of the burner section and the fuel cell (344) for reaction to generate the electrical power. A system controller (342) is configured to direct fuel to each of the combustor section (310) and the fuel cell (344). The controller determines if an amount of fuel in the fuel supply line (326) is in excess of that necessary for operation of the core assembly and, based on a determination that excess fuel is present, the controller is configured to direct at least a portion of the excess fuel from the fuel supply line (326) to the fuel cell (344) to generate the electrical power.