Bleed Expander Cooling with Turbine for Aircraft Thermal Management
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Solution Overview
Problem
Thermal management systems in gas turbine engine powered vehicles, such as aircraft, face challenges in efficiently managing high heat loads from electrical systems, particularly during idle-descent or in warm climates, where heat rejection to fuel or ambient air is limited, and ice formation can occur during bleed air expansion.
Innovation Solution
The system expands bleed air from a turbine engine using an air turbine engine starter or a dedicated turbine to cool the air below its initial temperature, increasing cooling capacity and reclaiming energy lost as shaft work, which is then used to drive a shaft and enhance thermal management efficiency, while controlling bleed airflow to minimize engine power impact and prevent ice formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If bleed air is expanded to cool the air, then cooling capacity is improved, but ice formation may occur
Solution Approach 1:
The system uses temperature sensors to monitor the temperature of the expanded bleed air and feed this information back to the control system. When the temperature approaches the freezing point, the control system adjusts the expansion ratio or adds heating elements to prevent ice formation while maintaining maximum cooling capacity.
Solution Approach 2:
The system dynamically changes the expansion ratio parameter of the bleed air through adjustable turbines or throttles. By varying the degree of expansion based on operating conditions, the system achieves optimal cooling while preventing temperature drops that would cause ice formation.
2Temperature
If bleed air is expanded using a turbine, then cooling capacity is improved, but device complexity increases
Solution Approach 1:
The expanded bleed air system serves multiple functions: it provides cooling for the engine, generates power through the turbine, and can be used for air conditioning. This multi-functionality reduces the need for separate dedicated systems, thereby reducing overall device complexity despite the added cooling capability.
Solution Approach 2:
The system uses the bleed air itself as both the working fluid for expansion and the cooling medium. The turbine extracts work from the bleed air to drive cooling components, and the expanded air directly cools engine parts, eliminating the need for separate cooling systems and reducing complexity.
3Temperature
If bleed air is expanded to cool the air, then thermal performance is improved, but engine power is reduced
Solution Approach 1:
The system extracts only the necessary amount of work from the bleed air to achieve the required cooling effect. By controlling the turbine expansion ratio and working fluid flow, the system prevents excessive power extraction that would harm engine performance, while still achieving adequate thermal management.
Solution Approach 2:
The system dynamically adjusts the bleed air flow rate and expansion ratio parameters based on real-time engine operating conditions. During high power demand, the system reduces bleed air extraction to maintain engine power. During cooling demand, it increases expansion to improve thermal performance, optimizing the trade-off continuously.
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 approach provides improved cooling capacity and thermal performance for high heat load electrical systems, reduces the need for supplemental cooling, and decreases ram drag by lowering heat sink temperatures, thus enhancing fuel efficiency and operational reliability.
Implementation Method 1
The air starter turbine may be configured to drive a shaft mechanically coupled to the air starter turbine in response to expansion of the cooled bleed air through the air turbine starter
Implementation Method 2
Expanding the bleed air may enable cooling the air below the temperature of the bleed air pulled from the turbine engine
Implementation Method 3
The first heat exchanger includes a bleed air inlet configured to receive bleed air from a gas turbine engine and a bleed air outlet configured to output cooled bleed air from the first heat exchanger
Implementation Method 4
The second heat exchanger may be configured to extract heat from at least one heat source using the expanded bleed air
Data Source
AI summary
An example thermal management system may include a first heat exchanger including a bleed air inlet configured to receive input bleed air from a gas turbine engine and a bleed air outlet configured to output cooled bleed air. A turbine including a turbine inlet may be fluidically coupled to the bleed air outlet. The turbine may be configured to drive a shaft mechanically coupled to the turbine in response to expansion of the cooled bleed air through the turbine. A second heat exchanger may include an expanded bleed air inlet fluidically coupled to a turbine outlet of the turbine. The second heat exchanger may be configured to extract heat from at least one heat source using the expanded bleed air.