Cryogenic Bottoming Cycle Loop Split for Adaptive Heat Recovery

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Existing gas turbine engines waste a significant amount of thermal energy in the exhaust, and the capability of working fluids in bottoming cycles to absorb heat is limited, restricting energy recovery.

Innovation Solution

Aircraft propulsion systems incorporate a cryogenic fuel system, a primary and secondary compressor loop, and recuperative heat exchangers to optimize heat absorption and recovery, with a controller adjusting fluid flow through these loops based on thermal capacity, and a charging system to manage working fluid volume.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If a working fluid is used in a bottoming cycle to recover heat from exhaust, then energy recovery is improved, but the capability of the working fluid to absorb heat is limited

Engineering Contradiction:

Improveheat recoveryVSAvoidheat absorption capacity

Core Design Contradiction:

Loss of energyVSUse of energy by moving object

Solution Approach 1:

The patent changes the temperature parameter of the working fluid by using cryogenic fuel (at approximately 400 K) instead of conventional fuels. This low temperature allows the working fluid to absorb more heat from the exhaust stream, thereby improving heat recovery capability while resolving the limitation of conventional working fluids

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The cryogenic fuel acts as an intermediary substance that transfers heat from the exhaust stream to the working fluid. The fuel's low temperature and high heat capacity allow it to serve as an effective heat transfer medium, enabling greater energy recovery than direct working fluid heating

Inventive Principle:

Principle #24Intermediary (Mediator)

2Adaptability or versatility

If a single compressor loop is used in the bottoming cycle, then device complexity is reduced, but adaptability to varying thermal demands is limited

Engineering Contradiction:

Improvethermal demand adaptationVSAvoidcompressor loop configuration

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent divides the compressor loop into multiple independent circuits (first and second compressor loops) that can operate independently or in combination. This segmentation allows the system to adapt to varying thermal demands by activating only the necessary number of loops, improving versatility while managing complexity through modular design

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The system dynamically adjusts its configuration by selectively operating one or both compressor loops based on thermal demand. The controller adjusts working fluid flow distribution to match actual heat recovery needs, enabling adaptive operation that optimizes performance across different operating conditions

Inventive Principle:

Principle #15Dynamics

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

Enhances energy recovery by adapting to varying thermal demands, improving efficiency and power generation in the bottoming cycle.

Implementation Method 1

an exhaust gas heat exchanger where heat from the exhaust gas flow heats the working fluid of the bottoming cycle

Methodology Applied

Scientific EffectHeat transfer: Heat Exchanger

Implementation Method 2

a fuel/working fluid heat exchanger for cooling the working fluid within the primary compressor loop

Methodology Applied

Scientific EffectHeat transfer: Heat Exchanger

Implementation Method 3

a controller for operating the valve system to adjust operation of the bottoming cycle in response to available thermal capacity of the cryogenic fuel system to absorb heat

Methodology Applied

Scientific EffectThermal energy absorption: Heat Sink

Implementation Method 4

a first recuperation heat exchanger that communicates thermal energy between a working fluid flow downstream from both the first bottoming compressor and the second bottoming compressor with working fluid flow downstream from the bottoming turbine

Methodology Applied

Scientific EffectThermal energy transfer: Heat Exchanger

Data Source

PatentUS20260015973A1Cryogenic bottoming cycle adaptable heat rejection loop split

Publication Date: 2026.01.15 RTX CORP

AI summary

An aircraft propulsion system includes a core engine that includes a main compressor where an inlet airflow is compressed and communicated to a combustor to generate an exhaust gas flow that is expanded through a main turbine section to generate power that is used to drive the main compressor and a propulsive fan, a bottoming cycle where a working fluid is heated and expanded through a bottom turbine to generate shaft power, the bottoming cycle includes a primary compressor loop that includes a first bottoming compressor and a secondary compressor loop that includes a second bottoming compressor and the flow of working fluid flow is adjusted to flow through at least one of the primary compressor loop and the secondary compressor loop, an exhaust gas heat exchanger where heat from the exhaust gas flow heats the working fluid of the bottoming cycle, a cryogenic fuel system that includes a cryogenic fuel storage tank, a fuel flow path for routing the cryogenic fuel to the combustor of the core engine, and a fuel/working fluid heat exchanger for cooling the working fluid within the primary compressor loop. The secondary compressor loop bypasses the fuel/working fluid heat exchanger.