Boost Spool Transmission for Gas Turbine Thermal-Limit OPR Control
Find Innovative SolutionsGenerate Solutions
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 at cruise power.
Innovation Solution
A boost spool mechanism is selectively engaged to increase OPR during cruise power, while operating without it during take-off, coupled with a transmission to improve speed profiles and thermal management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If OPR is increased to improve engine efficiency and reduce fuel consumption, then thermodynamic efficiency improves, but turbine temperatures exceed permissible material and structural limits
Solution Approach 1:
The compressor system is segmented into two independent spools: a main spool and a boost spool. The boost spool can be selectively engaged to provide additional compression only when ambient conditions permit, separating the compression functions to enable higher OPR during efficient operation while maintaining lower OPR during hot day takeoff to avoid exceeding turbine temperature limits.
Solution Approach 2:
The engine transitions from a static OPR design to a dynamic system where the boost spool can be selectively engaged or disengaged based on ambient conditions. This dynamic configuration allows the engine to adapt its compression ratio in real-time, achieving high OPR during efficient cruise operations while maintaining safe temperature margins during hot day takeoff.
2Reliability
If OPR is limited to maintain acceptable turbine temperatures during hot day take-off, then thermal limits are not exceeded, but engine efficiency is reduced during cruise power operation
Solution Approach 1:
The compressor system is segmented into two independent spools: a main spool and a boost spool. The boost spool can be selectively engaged to provide additional compression only when ambient conditions permit, separating the compression functions to enable higher OPR during efficient operation while maintaining lower OPR during hot day takeoff to avoid exceeding turbine temperature limits.
Solution Approach 2:
The engine changes its operating parameters dynamically by adjusting the engagement state of the boost spool. During hot day takeoff, the system maintains lower OPR to comply with thermal limits. During cruise operation with favorable ambient conditions, the system increases OPR by engaging the boost spool, thereby improving fuel efficiency without violating thermal constraints during critical operations.
3Use of energy by moving object
If a boost spool is added to enable higher OPR operation, then engine efficiency improves during cruise, but device complexity increases
Solution Approach 1:
The compressor system is segmented into two independent spools: a main spool and a boost spool. The boost spool can be selectively engaged to provide additional compression only when ambient conditions permit, separating the compression functions to enable higher OPR during efficient operation while maintaining lower OPR during hot day takeoff to avoid exceeding turbine temperature limits.
Solution Approach 2:
The boost spool serves multiple functions: it provides additional compression capability to increase OPR during efficient cruise operation, can be disengaged during hot day takeoff to maintain thermal compliance, and offers flexibility to adapt to varying ambient conditions. This multi-functionality justifies the added complexity by providing versatile operational capabilities.
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A gas turbine engine (10) includes a first spool (16) associated with a primary combustor (70), a second spool (12) associated with a secondary combustor (84), and a third spool (14), each spool (12) including a compressor (24, 74, 18) and a turbine (26, 82, 20) mounted to a shaft (28, 76, 22). A transmission (400) and accessory gearing (402) are enclosed within a housing (420) of an accessory gearbox (422). The transmission (400) rotationally couples the third spool (14) to the second spool (12) and accessory gearing (402). A method of operating the gas turbine engine (10) includes supplying a first fuel flow rate to the primary combustor (70) and supplying a second fuel flow rate to the secondary combustor (84) within an intermediate speed range of the gas turbine engine (10).