Variable Turbine Vanes for Air Turbine Starter Bowed Rotor Mitigation
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Solution Overview
Problem
Gas turbine engines often experience a 'bowed rotor' condition due to thermal expansion after shutdown, making it undesirable to restart the engine, and existing cool-down motoring methods are not efficient in mitigating this issue.
Innovation Solution
A variable turbine vane system in the air turbine starter is used to control the rotor speed of the starting spool by dynamically adjusting air pressure and valve operation during cool-down motoring, allowing for longer duration lower-speed operation to prevent bowed rotor conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If the air turbine starter operates at high speed for quick engine starting, then the starting time is reduced, but the efficiency during cool-down motoring is insufficient and cannot effectively mitigate bowed rotor conditions
Solution Approach 1:
The patent applies dynamics by making the inlet guide vanes adjustable rather than fixed. The vanes can be dynamically repositioned to different angles depending on whether the system is in rapid start mode or cool-down motoring mode, allowing the air turbine starter to optimize its performance characteristics for each operational phase and resolve the contradiction between speed and efficiency.
Solution Approach 2:
The patent changes the flow angle parameter by adjusting the inlet guide vane position. By varying the vane angle, the system modifies the airflow characteristics into the turbine, enabling optimal performance for both rapid starting (higher speed) and cool-down motoring (lower speed, longer duration), thus improving cool-down efficiency without sacrificing starting time.
2Device complexity
If the air turbine starter uses fixed inlet guide vanes for simple structure, then the device complexity is reduced, but the ability to optimize rotor speed profile during cool-down motoring is limited
Solution Approach 1:
The patent transitions from a static inlet guide vane structure to a dynamic adjustable one. The ability to change vane positions allows the system to adapt to different operational requirements, particularly for prolonged cool-down motoring operations, thereby improving reliability in mitigating bowed rotor conditions while accepting increased structural complexity.
Solution Approach 2:
The adjustable inlet guide vane system provides multi-functionality, serving both rapid engine starting and extended cool-down motoring operations. This single mechanism enables the air turbine starter to perform multiple functions optimally, enhancing reliability across different operational scenarios without requiring separate systems for each function.
3Productivity
If the air turbine starter operates at high power for rapid engine acceleration, then the productivity is improved, but the rotor speed control precision during cool-down motoring deteriorates
Solution Approach 1:
The patent changes the airflow parameters by adjusting inlet guide vane angles, which enables precise control of rotor speed during cool-down motoring. By modifying the flow angle and consequently the torque characteristics, the system can maintain lower speeds with higher precision for extended periods, effectively controlling the rotor speed profile to prevent bowed rotor conditions while preserving high power capability for rapid starting.
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 mitigates bowed rotor conditions by maintaining optimal rotor speed and profile through controlled air flow, enhancing the efficiency of the cool-down motoring process and preventing engine restart complications.
Implementation Method 1
A variable turbine vane system in the air turbine starter is used to control the rotor speed of the starting spool by dynamically adjusting air pressure and valve operation
Data Source
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AI summary
According to one embodiment, an air turbine starter (20) is provided. The air turbine starter comprising: a turbine wheel (36) including a hub (40) integrally attached to a turbine rotor shaft (42) and a plurality of turbine blades (38) extending radially outward from the hub (40); an inlet housing (46) at least partially surrounding the turbine wheel (36); a nozzle (48) located upstream from the turbine wheel (36) and contained within the inlet housing (46) defining an inlet flowpath (54) between the nozzle (48) and the inlet housing (36), the inlet flowpath (54) directs air flow into the turbine blades (38); and a plurality of turbine vanes (50) rotatably connected to the nozzle (48), each turbine vane extending radially from the nozzle (48) into the inlet flowpath (54) towards the inlet housing (46); wherein the plurality of turbine vanes (50) are operable to adjust air flow through the inlet flowpath (54) by rotating each turbine vane.