Reverse-Flow Hydrogen Steam Turbine Engine for Exhaust Heat Recovery

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Solution Overview

Problem

Existing gas turbine engines suffer from reduced efficiency due to the loss of heat energy in the exhaust and have a significant environmental impact, necessitating improvements in propulsive efficiency and carbon emission reduction.

Innovation Solution

A hydrogen steam injected and intercooled turbine engine design that recovers heat energy by injecting steam generated from condensed exhaust gases into the combustor, enhancing mass flow and power output without increasing compressor work, and utilizing a power turbine independent of the core engine to drive the fan.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If heat energy is recovered from exhaust gases, then engine efficiency is improved, but device complexity increases

Engineering Contradiction:
Improveheat energy lossVSAvoidsystem complexity
Core Design Contradiction:
Loss of energyVSDevice complexity

Solution Approach 1:

The patent recovers heat energy from exhaust gases that would otherwise be discarded to the atmosphere. A heat exchanger extracts thermal energy from the exhaust stream to preheat combustion air or generate steam, converting waste heat into useful energy for improving overall engine efficiency.

Inventive Principle:
Principle #34Discarding and recovering

Solution Approach 2:

The patent combines the exhaust heat recovery system with the steam generation and injection system. The heat exchanger, steam generator, and steam injection components are integrated into the existing engine architecture, allowing heat recovery and steam injection functions to work together synergistically to enhance efficiency.

Inventive Principle:
Principle #5Merging (Combining)

2Power

If steam is injected into the combustor, then power output increases, but fuel consumption increases

Engineering Contradiction:
Improvepower outputVSAvoidfuel consumption
Core Design Contradiction:
PowerVSUse of energy by moving object

Solution Approach 1:

The patent changes the physical state of water from liquid to steam through phase change in the steam generator. This phase transition allows water to be injected as high-energy steam into the combustor, increasing mass flow and power output without requiring additional fuel, as the steam carries thermal energy from the exhaust heat recovery system.

Inventive Principle:
Principle #35Parameter changes

3Object-generated harmful factors

If hydrogen fuel is used, then carbon emissions are reduced, but fuel handling complexity increases

Engineering Contradiction:
Improvecarbon emissionsVSAvoidfuel handling complexity
Core Design Contradiction:
Object-generated harmful factorsVSDevice complexity

Solution Approach 1:

The patent extracts and separates the steam generation function from the main combustion system. By using waste heat from exhaust gases to generate steam independently, the system eliminates the need for complex fuel handling and storage infrastructure that would be required if hydrogen were used directly for steam generation, while still achieving carbon emission reductions through hydrogen combustion.

Inventive Principle:
Principle #2Taking out (Extraction)

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 engine achieves increased power output and efficiency by recycling heat energy, reducing engine size, and minimizing carbon emissions through the use of hydrogen fuel and steam injection, while improving compressor efficiency and propulsive performance.

Implementation Method 1

A condenser 62 is provided downstream of the power turbine 38 and is configured to extract water from the exhaust gas flow 52

Methodology Applied
Scientific EffectCondensation: Condensation

Implementation Method 2

from the condenser 62, expelled exhaust gases 60 are exhausted through a core nozzle 58. Water extracted from the condenser 62 is converted to steam and injected into the core engine 70

Methodology Applied
Scientific EffectEvaporation: Evaporation

Implementation Method 3

In the combustor 30, the core flow 50 is mixed with a hydrogen (H2) fuel flow 80 and ignited to generate a high energy exhaust gas flow 52

Methodology Applied
Scientific EffectCombustion: Combustion

Implementation Method 4

Some energy in the high energy exhaust flow is recovered as it is expanded through a turbine section

Methodology Applied
Scientific EffectExpansion:

Data Source

PatentEP4279721B1Reverse flow hydrogen steam injected turbine engine
Publication Date: 2025.08.27 RTX CORP
  • EP4279721B1 patent drawingFigure 1
  • EP4279721B1 patent drawingFigure 2

AI summary

A propulsion system for an aircraft includes a gas generating core engine which generates an exhaust gas flow (52) that is expanded through a turbine section (32), a power turbine (38) driven by the exhaust gas flow (52), a propulsor (22) coupled to the power turbine (38), a hydrogen fuel system (96) configured to supply hydrogen fuel to the combustor (30) through a fuel flow path (80), a condenser (62) arranged along the core flow path (50) and configured to extract water from the exhaust gas flow (52), and an evaporator (64) arranged along the core flow path (50) receiving a portion of the water extracted by the condenser (62) to generate a steam flow (56) that is injected into the core flow path (50) upstream of the turbine section (32).