Annular Core Bleed for Gas Turbine Surge Control
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Solution Overview
Problem
Gas turbine engines face inefficiencies and noise issues when using traditional bleed methods to manage surge margins, particularly at low power settings, as they result in limited thrust recovery and interference with bypass duct flow.
Innovation Solution
A controllable bleed system is introduced, allowing selective air bleeding from the core downstream of the combustor and upstream of the turbine stages, which reduces the pressure ratio across the turbine and compressor, thereby controlling power delivery and reducing mechanical complexity and noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional bleed methods are used to manage surge margins, then surge margin control is achieved, but thrust recovery is limited and bypass duct flow is interfered with
Solution Approach 1:
The patent extracts the bleed inlet from the traditional location (upstream of combustor) and repositions it downstream of the combustor and upstream of the turbine stages. This extraction of the bleed function from its conventional location allows air to be bled from a position where it can be more effectively recovered and utilized, improving thrust recovery while maintaining surge margin control.
Solution Approach 2:
The patent introduces a controlled bleed system that acts as an intermediary between the core flow and the bypass duct. By positioning the bleed inlet downstream of the combustor and using controlled bleeding, the system mediates between maintaining compressor surge margins and preserving bypass duct flow integrity, preventing the harmful interference that occurs with traditional bleed methods.
2Reliability
If traditional bleed methods are used to manage surge margins, then surge margin control is achieved, but noise increases
Solution Approach 1:
The patent extracts the bleed operation from the high-noise environment of the bypass duct and repositions it to occur upstream of the turbine stages. By taking out the bleed function from its traditional location and performing it in a different part of the engine core, the system maintains surge margin control while significantly reducing the noise generated by bleed air interaction with bypass duct flow.
3Reliability
If bleed air is vented into bypass duct, then surge margin is increased, but flow through bypass duct is impacted and pressure field variations occur
Solution Approach 1:
The patent extracts the bleed inlet from the bypass duct environment and repositions it within the core flow downstream of the combustor. This extraction prevents bleed air from directly impacting bypass duct flow, eliminating the flow interference and pressure field variations that occur when bleed air is vented into the bypass duct, while still achieving surge margin control through controlled bleeding.
Data Source
AI summary
A gas turbine engine including a compressor, a turbine having one or more stages and a combustor, the combustor being located between the compressor and turbine. The gas turbine engine further includes a bleed from a core defined by a core duct, the core duct surrounding and extending between the turbine and combustor at least. The bleed includes at least one inlet located downstream of the combustor and upstream of at least one of the turbine stages. The turbine is arranged in use to drive the compressor. The bleed is arranged to be controllable in use to selectively bleed air from the core through the inlet and to thereby control the power delivered by the turbine to the compressor.