Thermal Bus Vapor Cycle Architecture for Lower-Weight Engine Cooling

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Solution Overview

Problem

Existing gas turbine engine architectures face significant size, weight, and complexity issues due to fan case-mounted oil thermal management systems, which impact specific fuel consumption, performance, and maintenance efficiency.

Innovation Solution

A power and thermal management system thermal bus vapor cycle architecture is introduced, featuring a bypass duct with a condenser and evaporator coils configured as annulus disk shape heat exchangers, a gearbox, and a variable speed compressor, optimizing thermal management through staged evaporator coils and sink-source pairing.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Temperature

If fan case-mounted oil thermal management systems are used, then oil cooling function is provided, but system size, weight, and complexity increase

Engineering Contradiction:

Improveoil temperature controlVSAvoidthermal management system weight

Core Design Contradiction:

TemperatureVSWeight of stationary object

Solution Approach 1:

The patent merges the oil thermal management system with the engine core structure by integrating heat exchangers and thermal management components directly into the engine housing and oil flow path. This consolidation eliminates separate fan case-mounted systems, reducing overall weight while maintaining oil temperature control functionality through shared structural components.

Inventive Principle:

Principle #5Merging (Combining)

2Temperature

If fan case-mounted oil thermal management systems are used, then oil cooling function is provided, but system size and complexity increase

Engineering Contradiction:

Improveoil temperature controlVSAvoidthermal management system complexity

Core Design Contradiction:

TemperatureVSDevice complexity

Solution Approach 1:

The patent integrates multiple thermal management functions into a unified system where heat exchangers, oil flow paths, and engine components are merged. This consolidation reduces the number of separate components and interconnections, simplifying the overall system architecture while maintaining effective oil temperature control.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The engine housing and core structures are designed to serve multiple functions: structural support, heat dissipation, and oil flow management. By making components multi-functional, the patent reduces the need for dedicated separate components, thereby reducing system complexity while maintaining oil cooling effectiveness.

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Temperature

If conventional heat exchanger configurations are used, then thermal management is achieved, but weight and size are significant

Engineering Contradiction:

Improvethermal management efficiencyVSAvoidheat exchanger weight

Core Design Contradiction:

TemperatureVSWeight of moving object

Solution Approach 1:

The patent integrates heat exchanger surfaces with existing engine structures such as the housing and oil galleries. By merging the heat exchanger function into components that already exist in the engine architecture, the patent eliminates the weight of separate heat exchanger assemblies while maintaining thermal management efficiency through direct heat transfer paths.

Inventive Principle:

Principle #5Merging (Combining)

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

This architecture reduces weight, eliminates and consolidates heat exchangers, enhances cooling efficiency, and optimizes sink-source pairing, resulting in reduced losses and improved thermal management.

Implementation Method 1

a condenser coil located within the bypass duct, the condenser coil being configured as an annulus disk shape heat exchanger; at least one evaporator coil fluidly coupled to the condenser coil and located within the bypass duct

Methodology Applied

Scientific EffectHeat exchanger: Heat Exchanger

Implementation Method 2

bypass air is configured to flow within the bypass duct from the fan aft toward the low pressure turbine; condenser coil being configured as a heat exchanger configured to contact the bypass air

Methodology Applied

Scientific EffectConvection: Convection

Implementation Method 3

condenser coil being configured as a heat exchanger configured to contact the bypass air

Methodology Applied

Scientific EffectCondensation: Condensation

Implementation Method 4

an expansion valve fluidly coupled between the condenser coil and the at least one evaporator coil

Methodology Applied

Scientific EffectPressure drop: Pressure Drop

Implementation Method 5

a variable speed compressor in operative communication with the gearbox, the variable speed compressor being fluidly coupled with the at least one evaporator coil and the condenser coil

Methodology Applied

Scientific EffectCompression: Compression

Data Source

PatentEP4592511A1Ptms thermal bus vapor cycle architecture

Publication Date: 2025.07.30 RTX CORP

Figure 1~2
Figure 3A
Figure 3B

AI summary

A power and thermal management system thermal bus vapor cycle architecture including a bypass duct formed between a gas turbine inner fan duct and a gas turbine outer fan duct; a condenser coil located within the bypass duct, the condenser coil being configured as an annulus disk shape heat exchanger; at least one evaporator coil fluidly coupled to the condenser coil and located within the bypass duct upstream of the condenser coil relative to a bypass air flow direction; a gearbox in operative communication with the gas turbine engine; and a variable speed compressor in operative communication with the gearbox, the variable speed compressor being fluidly coupled with the at least one evaporator coil and the condenser coil.