Gas Turbine Rotor Disk Bore Preheating for Thermal Stress Reduction
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Solution Overview
Problem
The thermal gradient stress challenge in gas turbine engine rotor disks, particularly during take-off when the high pressure compressor experiences rapid temperature increases, leading to potential material stress exceeding allowable limits and reducing disk life.
Innovation Solution
A method to preheat the rotor bore and turbine disk using hot air tapped from the combustor, regulated by temperature controlling valves, ensuring the disks reach operating temperatures closer to the blade temperatures, thereby managing thermal gradients and increasing compressor exit pressure for improved efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the compressor exit temperature T3 is increased to improve efficiency, then the thermal gradient stress on the rotor disk increases, but the material allowable stress is exceeded, reducing disk life
Solution Approach 1:
The patent applies preliminary action by preheating the rotor disk bore to a predetermined temperature before take-off operation. This preheating is performed during ground operation or idle periods, preparing the disk in advance so that when rapid power increase occurs, the thermal gradient is minimized and the disk can withstand higher T3 temperatures without exceeding material stress limits
Solution Approach 2:
The patent changes the temperature parameter of the rotor disk bore by introducing heated air from the combustor through a passage into the bore region. This parameter change (increasing bore temperature) allows the disk to operate at higher T3 temperatures by reducing the thermal gradient between the bore and outer rim, thereby resolving the contradiction between productivity and reliability
2Productivity
If the compressor exit pressure is increased to improve efficiency, then the thermal stress on the rotor disk increases, but the material strength limits are exceeded, requiring operation at lower pressure
Solution Approach 1:
The system performs preliminary heating of the rotor disk bore before high-power operation, preparing the material in advance to withstand the increased thermal and mechanical stresses that result from operating at higher compressor exit pressures and temperatures
Solution Approach 2:
By changing the thermal parameter (bore temperature) through controlled heating, the patent enables the rotor disk to sustain higher mechanical parameters (compressor exit pressure and temperature) without exceeding material strength limits, thus resolving the contradiction between productivity and material strength
3Speed
If rapid power increase is implemented during take-off, then the thermal gradient between disk outer rim and bore increases, but severe thermal stress develops, limiting the ability to operate at optimal pressure
Solution Approach 1:
The patent implements preliminary heating of the rotor disk bore during ground operation and idle periods, so that when rapid power increase is needed for take-off, the disk is already prepared with reduced thermal gradient, allowing fast engine speed increase without developing severe thermal stresses
Solution Approach 2:
By preheating the bore region to a predetermined temperature, the patent changes the initial thermal parameter distribution in the disk, thereby reducing the thermal gradient that would otherwise develop during rapid power increases, enabling both high speed increase rate and acceptable thermal stress levels
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 preheating method reduces thermal stress on rotor disks, allows higher compressor exit temperatures without exceeding material limits, and enhances combustion efficiency by maintaining higher pressures during operation.
Implementation Method 1
a passage (132) through the turbine disk (110) and into the compressor rotor disk bore (109) to allow the hot air to flow into the rotor disk bore
Implementation Method 2
regulated by temperature controlling valves
Data Source
Figure 1
Figure 2
AI summary
A gas turbine engine has a compressor rotor with blades and a disk. A bore is defined radially inwardly of the disk. A combustor includes a burner nozzle. A tap taps air that has been combusted in the combustor section through a valve, and into the bore of the disk. A method is also disclosed.