Gas Turbine Active Clearance Control Warm Start Management
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Solution Overview
Problem
Gas turbine engines face challenges in maintaining optimal radial tip clearance during various flight conditions, particularly during the climb segment, where existing technologies do not effectively manage thermal expansion and clearance variations post-shutdown.
Innovation Solution
An active clearance control system with a controller that adjusts a cooling air supply schedule based on engine conditions, such as elapsed time since shutdown and starting temperature, and applies a decay function to reduce the impact of these adjustments over time, ensuring optimal clearance management during takeoff and climb.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If active clearance control cooling is applied continuously, then radial tip clearance is maintained optimally, but thermal expansion management becomes excessive during warm start conditions
Solution Approach 1:
The system dynamically adjusts the active clearance control cooling schedule based on engine operating conditions, specifically detecting warm start conditions and modifying the cooling schedule accordingly. The controller adapts the cooling airflow timing and magnitude to match the thermal state of the turbine case, preventing excessive cooling during warm starts when thermal expansion is already favorable.
Solution Approach 2:
The system changes the parameters of the cooling schedule (timing, duration, magnitude of cooling airflow) based on detected engine conditions. When a warm start is detected, the controller modifies the cooling schedule parameters to reduce or delay active clearance control cooling, thereby managing thermal expansion appropriately for the warm start scenario.
2Temperature
If cooling airflow is reduced during warm start, then thermal expansion is managed, but clearance stability may be compromised
Solution Approach 1:
The controller continuously monitors engine operating conditions and uses this feedback to adjust the active clearance control cooling schedule in real-time. By detecting warm start conditions and responding with appropriate cooling modifications, the system maintains clearance stability adapted to the specific thermal state, preventing both excessive cooling and insufficient clearance management.
Solution Approach 2:
The system performs preliminary detection of warm start conditions and proactively adjusts the cooling schedule before clearance issues can develop. The controller anticipates the thermal state during warm starts and pre-modifies the cooling airflow schedule to prevent clearance instability, rather than reacting after problems occur.
3Manufacturing precision
If active clearance control is optimized for climb segment, then radial tip clearance is maintained, but post-shutdown thermal management becomes complex
Solution Approach 1:
The control system segments the operating conditions into distinct phases (such as warm start, climb, cruise) and applies specific cooling schedule strategies for each segment. The controller identifies the current operational segment and activates the appropriate clearance control schedule, simplifying the overall control logic by treating different phases separately rather than using a single complex continuous control algorithm.
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 solution effectively reduces thermal expansion and maintains a stable clearance between turbine blades and the turbine case, enhancing engine performance and preventing rubbing issues by proactively managing clearance variations through controlled cooling airflow.
Implementation Method 1
maintain a small radial tip clearance through the various engine operational conditions
Implementation Method 2
active clearance control cooling air supply
Data Source
AI summary
According to an aspect, a gas turbine engine includes a turbine section with a turbine case and a plurality of turbine blades within the turbine case. The gas turbine engine also includes an active clearance control system with an active clearance control cooling air supply, a valve pneumatically coupled to the active clearance control cooling air supply, and a controller. The controller is configured to determine an active cooling control schedule adjustment based on a condition of the gas turbine engine, operate the active clearance control system according to an active cooling control schedule as modified by the active cooling control schedule adjustment, apply a decay function to the active cooling control schedule adjustment to reduce an effect on the active cooling control schedule adjustment, and resume operating the active clearance control system according to the active cooling control schedule based on an active cooling control condition being met.