Boost Spool Transmission for Gas Turbine OPR Management
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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 high ambient temperatures, which reduces efficiency and fuel consumption.
Innovation Solution
A boost spool mechanism is introduced that can be selectively engaged to increase OPR during cruise power, while operating independently of the main spool during takeoff, allowing for improved speed profiles and thermal management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If OPR is limited to avoid exceeding thermal limits during hot day takeoff, then turbine temperatures remain within acceptable limits, but engine efficiency and thrust specific fuel consumption deteriorate during cruise operation
Solution Approach 1:
The gas turbine engine is divided into multiple independently controllable spools (first spool and second spool), each capable of operating at different OPR levels. This segmentation allows the engine to operate at high OPR during cruise for efficiency while limiting OPR during hot day takeoff to maintain thermal limits, resolving the contradiction between temperature control and fuel efficiency.
Solution Approach 2:
The system dynamically adjusts the operational mode by selectively engaging or disengaging the boost spool based on ambient temperature and power requirements. During hot day takeoff, the boost spool is disengaged to limit OPR and protect turbine temperatures. During cruise, the boost spool is engaged to increase OPR and improve fuel efficiency, enabling adaptive operation that resolves the contradiction.
2Use of energy by moving object
If OPR is increased to improve engine efficiency during cruise, then thrust specific fuel consumption decreases, but turbine temperatures increase and may exceed material limits
Solution Approach 1:
By segmenting the engine into multiple spools with independent control, the system can increase OPR through the first spool during cruise operation to improve fuel efficiency, while using the second spool to manage and limit temperatures in the turbine section, thus resolving the contradiction between efficiency and thermal limits.
Solution Approach 2:
The system changes operational parameters by selectively engaging the boost spool to increase OPR during cruise conditions for improved efficiency. The control system monitors temperature parameters and adjusts spool engagement accordingly, allowing high OPR operation when thermal limits are not exceeded, thus optimizing fuel consumption.
3Use of energy by moving object
If a boost spool is added to enable high OPR operation during cruise, then engine efficiency improves, but device complexity increases
Solution Approach 1:
The transmission system is designed with multi-functionality to handle both high OPR cruise operation and standard takeoff operation through a unified architecture. The boost spool and transmission components serve multiple functions: enabling high OPR mode during cruise for efficiency while providing a disengageable path during takeoff to maintain simplicity and reliability, thus reducing the net increase in device complexity.
Solution Approach 2:
The transmission system uses dynamic clutch engagement and disengagement to selectively connect or disconnect the boost spool based on operational requirements. This dynamic control allows the system to achieve high OPR efficiency during cruise when needed, while maintaining a relatively simple configuration during takeoff, thus managing device complexity through operational flexibility rather than permanent structural complexity.
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
Enhances engine efficiency and reduces thrust specific fuel consumption (TSFC) by allowing higher OPR operation during cruise conditions while maintaining thermal limits, without compromising on takeoff performance.
Implementation Method 1
The overall pressure ratio (OPR) is a measure of the total pressure rise in a gas turbine engine (i.e., a pressure ratio equal to the air pressure discharged from the last compressor stage to the ambient air pressure entering the engine). As OPR increases, the thermodynamic efficiency of the gas turbine engine increases
Implementation Method 2
gas turbine engines capable of operating in a high overall pressure ratio (OPR) mode and in a low OPR mode to adapt to the ambient conditions and to provide more efficient operation without exceeding thermal limits of the gas turbine engine
Data Source
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AI summary
A gas turbine engine (10) includes a first spool (16) rotationally coupled to a plurality of accessories via a first gearing (224, 226) and a second spool (12) rotationally coupled to a third spool (14) via a second gearing (210, 212). The first gearing (224, 226) and the second gearing (210, 212) rotate independently and are enclosed within a housing of an accessory gearbox. A method of operating the gas turbine engine (10) includes supplying a first fuel flow rate to a primary combustor (70) associated with the first and third spools and supply a second fuel flow rate a secondary combustor (84) associated with the second spool (12) based on a power lever angle within an intermediate power level range.