Turbine Ring Clearance Control via Transient Airflow
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Solution Overview
Problem
Gas turbine engines face challenges in maintaining a positive EGT margin over their life cycle due to increasing clearance between turbine blades and the casing, leading to temperature overshoot and potential damage during acceleration phases, which affects performance and requires careful management to avoid premature wear.
Innovation Solution
A method for controlling the clearance between turbine blades and the casing by detecting transient acceleration phases and adjusting airflow to the turbine ring using a valve control system, taking into account the temperature of combustion gases and engine aging, to minimize temperature overshoot and maintain a positive EGT margin.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the clearance between turbine blades and turbine ring is minimized to improve turbine performance, then turbine efficiency increases, but the risk of blade contact during acceleration phases increases
Solution Approach 1:
The control system performs preliminary action by detecting transient acceleration phases and preemptively adjusting the turbine ring clearance before blade contact can occur. The method monitors engine parameters to identify acceleration events and activates cooling air flow to the turbine ring in advance, preventing the harmful effect of blade contact while maintaining minimal clearance for optimal performance.
Solution Approach 2:
The system dynamically adjusts the turbine ring clearance based on real-time operating conditions. During transient acceleration phases, the clearance is increased by cooling the turbine ring to prevent blade contact. During steady-state operation, the clearance is minimized to optimize turbine performance. This dynamic adaptation allows the system to resolve the contradiction between maintaining small clearance for performance and preventing blade contact for reliability.
2Productivity
If cooling air is directed onto the turbine ring to minimize clearance and reduce temperature overshoot, then turbine performance improves, but the EGT margin decreases due to reduced thermal expansion
Solution Approach 1:
The control system applies periodic or transient cooling action rather than continuous cooling. Cooling air is directed onto the turbine ring specifically during transient acceleration phases when temperature overshoot occurs, and is deactivated during steady-state operation. This periodic application of cooling allows the system to reduce temperature overshoot and improve performance during critical transient events while maintaining adequate thermal expansion and EGT margin during normal operation.
3Productivity
If the turbine ring is cooled to limit thermal expansion and minimize clearance, then blade tip clearance is reduced for improved efficiency, but the risk of premature wear increases during transient phases
Solution Approach 1:
The control system detects transient acceleration phases in advance and performs preliminary action by adjusting the turbine ring clearance before blade contact or excessive wear can occur. By monitoring engine parameters and identifying acceleration events, the system activates cooling air flow to the turbine ring preemptively, preventing the harmful effects of blade contact and premature wear while maintaining minimal clearance during steady-state operation for optimal efficiency.
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 adaptively regulates the clearance and temperature overshoot throughout the engine's life cycle, optimizing performance and extending maintenance intervals by minimizing the risk of blade damage and maintaining a positive EGT margin.
Implementation Method 1
the centrifugal force exerted on the turbine rotor tends to bring the blade tips closer to the turbine ring before the turbine ring has had time to expand under the effect of the increase in temperature linked to the increase in speed
Implementation Method 2
A system of this type generally operates by directing air taken, for example, from a compressor and/or the fan of the turbomachine onto the outer surface of the turbine ring. Fresh air sent onto the outer surface of the turbine ring has the effect of cooling the latter
Data Source
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AI summary
Method for controlling a play between apexes of vanes of a high-pressure turbine of a gas turbine aircraft engine and a turbine shroud, comprising the control of a valve which supplies an air flow to the turbine shroud, this method further comprising the following steps: - detection (301) of a transitory acceleration phase of the engine; - receiving (302) a data item which represents the temperature of the gas being discharged from the combustion chamber of the engine; - an instruction (304) to open the valve in order to supply the air flow to the turbine shroud or to increase the flow rate of the air flow supplied if the transitory acceleration phase is detected and if the temperature of the gas being discharged from the combustion chamber is greater than a first temperature threshold (TI) corresponding to a degraded play which is characteristic of an ageing engine, this threshold being less than a limit operating temperature of the engine.