Aircraft Thermal Bus Cooling for Sub-Idle Heat Dissipation
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Solution Overview
Problem
Conventional thermal management systems for aircraft gas turbine engines fail to adequately cool power electronics during sub-idle engine operation and post-shutdown conditions, leading to high fuel temperatures and potential component malfunctions, especially in lean burn fuel systems, due to insufficient heat dissipation during reduced fuel flow conditions.
Innovation Solution
A recirculatory thermal management system using a closed-loop heat transfer fluid, such as a water/glycol mix, connected to a heat exchanger, which dissipates waste heat energy to air or fuel flow, and optionally incorporates a vapour compression system to elevate heat energy for efficient dissipation across various aircraft systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If heat is transferred to fuel flow during low-power conditions, then cooling demand of power electronics is met, but fuel temperature increases leading to solid fuel deposits
Solution Approach 1:
The patent introduces an intermediary thermal management system comprising a heat exchanger and controllable valve that mediates between the power electronics cooling demand and the fuel temperature control. This intermediary system allows heat to be dissipated to the ambient air through the heat exchanger rather than directly to the fuel, preventing fuel deposits while still cooling the power electronics.
Solution Approach 2:
The patent implements dynamic control of the thermal management system based on engine operating conditions. The controllable valve dynamically adjusts or redirects fuel flow paths, and the system transitions between different heat dissipation modes (to fuel vs. to ambient air) depending on whether the engine is in high-power or low-power conditions, thereby adaptively preventing fuel deposits during low-power operation.
2Reliability
If conventional heat sinks are used during sub-idle conditions, then cooling is provided when available, but heat sinks are unavailable or insufficient during sub-idle and post-shutdown conditions
Solution Approach 1:
The patent creates a universal thermal management system that can operate in multiple modes and serve multiple functions. The system can dissipate heat to both the fuel flow (when engine is running at high power) and to the ambient air (when engine is at low power or shutdown), making the cooling system adaptable to all engine operating conditions including sub- idle and post-shutdown scenarios where conventional heat sinks are unavailable.
3Loss of energy
If fuel flow rate is reduced during low-power conditions, then fuel consumption is optimized, but fuel temperature increases exacerbating deposit formation
Solution Approach 1:
The patent extracts the heat dissipation function from the fuel flow path during low-power conditions. By providing an alternative heat dissipation path through the ambient air heat exchanger, the system removes the necessity of using high fuel flow rates for cooling purposes, allowing fuel flow to be reduced for consumption optimization while preventing temperature-induced deposit formation.
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 effectively maintains desired temperature limits for heat-generating components, preventing fuel lacquering and component failures, while ensuring continuous heat dissipation even at stationary engine operation, enhancing system reliability and efficiency.
Implementation Method 1
the first heat exchanger is configured to transfer the waste heat energy from the first heat transfer fluid to a dissipation medium
Implementation Method 2
an optional vapour compression system to elevate waste heat energy to a higher temperature for efficient dissipation
Implementation Method 3
the first heat transfer fluid being in fluid communication, in a closed loop flow sequence, between the first gas turbine engine, the first heat exchanger, and the first ancillary system, such that waste heat energy generated by at least one of the first gas turbine engine
Data Source
AI summary
A thermal management system for an aircraft includes a first gas turbine engine, one or more first electric machines rotatably coupled to the first gas turbine engine, a first thermal bus, and a first heat exchanger. Waste heat energy generated by at least one first gas turbine engine, and first electric machine, transfers to the first heat transfer fluid. The first heat exchanger directs a first proportion of the first heat transfer fluid through a first heat dissipation portion wherein a first proportion of the waste heat energy transfers to a first dissipation medium dependent on the first dissipation medium temperature and mass flow rate. The first heat exchanger directs a second proportion of the first heat transfer fluid through a second heat dissipation portion wherein the second proportion of waste heat energy transfers to a second dissipation medium dependent on the second dissipation medium temperature and mass flow rate.