Boost Spool Transmission Control for Gas Turbine Thermal Limits
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Solution Overview
Problem
Gas turbine engines face inefficiencies due to limited overall pressure ratio (OPR) to avoid exceeding thermal limits, particularly during hot day take-off conditions, which reduces efficiency and payload capacity.
Innovation Solution
A dual spool gas turbine engine with a boost spool that can be selectively engaged to increase OPR during cruise power, coupled with a transmission to manage speed profiles and fuel flow, allowing efficient operation within thermal limits across varying ambient conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If OPR is increased to improve thermodynamic efficiency and reduce fuel consumption, then engine efficiency improves, but air temperatures within the compressor and turbine sections increase and can exceed permissible material and structural limits
Solution Approach 1:
The gas turbine engine is divided into multiple independent spool systems (first spool with first compressor and first turbine, second spool with second compressor and second turbine, third spool with third compressor and third turbine). Each spool can operate independently at different pressure ratios, allowing the engine to achieve high overall pressure ratio while managing temperature distribution across different compressor and turbine sections through selective engagement of boost spool during cruise power
2Reliability
If OPR is limited to maintain acceptable turbine temperatures during hot day take-off, then thermal limits are maintained, but engine efficiency decreases during cruise power operation
Solution Approach 1:
The engine employs dynamic configuration changes through selective engagement and disengagement of the boost spool based on operating conditions. During cruise power, the boost spool is engaged to achieve high OPR for improved efficiency. During hot day take-off or when ambient temperatures are high, the boost spool is disengaged to maintain acceptable turbine temperatures. This dynamic adaptation allows the engine to optimize efficiency during cruise while ensuring thermal limit compliance during take-off and hot day operations
3Adaptability or versatility
If a single spool system is used, then device complexity is low, but the ability to adapt to varying ambient conditions and operate at high OPR is limited
Solution Approach 1:
The gas turbine engine is divided into multiple independent spool systems (first spool with first compressor and first turbine, second spool with second compressor and second turbine, third spool with third compressor and third turbine). Each spool can operate independently at different pressure ratios, allowing the engine to achieve high overall pressure ratio while managing temperature distribution across different compressor and turbine sections through selective engagement of boost spool during cruise power
Solution Approach 2:
The multi-spool architecture provides universal adaptability across different operating conditions. The first spool, second spool, and third spool can be selectively engaged or disengaged based on ambient conditions, power requirements, and thermal constraints. This multi-functional design allows the same engine to efficiently operate during cold day take-off, hot day take-off, and cruise power by activating appropriate spool combinations
Data Source
AI summary
A gas turbine engine includes a first spool associated with a primary combustor, a second spool associated with a secondary combustor, and a third spool, each spool including a compressor and a turbine mounted to a shaft. A transmission and accessory gearing are enclosed within a housing of an accessory gearbox. The transmission rotationally couples the third spool to the second spool and accessory gearing. A method of operating the gas turbine engine includes supplying a first fuel flow rate to the primary combustor and supplying a second fuel flow rate to the secondary combustor within an intermediate speed range of the gas turbine engine.