Open-Rotor Starter/Generator Clutch Segmentation
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Solution Overview
Problem
The existing starter/generator arrangements for gas turbine engines are unsuitable for open-rotor aeroengines due to the high speed range of intermediate-pressure systems, requiring excessive starter power and prolonged engine starting times, as they need to drive both low-pressure and free power turbine shafts simultaneously, which is inefficient and undesirable.
Innovation Solution
An open-rotor gas turbine engine design featuring a starter/generator connected to a low-pressure and free power turbine spool via one-way clutches, allowing the starter/generator to drive the low-pressure spool for starting and the free power turbine spool for electricity generation, with a gearbox and potentially sprag-type or electronically controlled clutches to manage the power transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the starter/generator is permanently connected to drive both low-pressure and free power turbine shafts simultaneously, then the engine can be started, but the starter power required becomes excessively large
Solution Approach 1:
The patent divides the starting function into two separate modes: a first mode where the starter/generator drives only the low-pressure spool, and a second mode where it drives only the free power turbine spool. This segmentation allows the starter/generator to be sized for the smaller of the two tasks rather than the combined task, significantly reducing the required starter power while maintaining full starting capability.
Solution Approach 2:
The patent employs dynamically controllable clutches that can selectively engage or disengage the connection between the starter/generator and either spool. This dynamic control allows the system to adapt its configuration based on operational requirements, enabling the starter/generator to drive only one spool at a time rather than both simultaneously, thereby reducing power requirements.
2Productivity
If the starter/generator drives both low-pressure and free power turbine shafts simultaneously, then the engine can be started, but the starting time becomes prolonged
Solution Approach 1:
The starting process is segmented into two distinct phases: first accelerating the low-pressure spool alone, then accelerating the free power turbine spool alone. This segmentation allows each spool to be accelerated independently to its required speed, avoiding the inefficiency of simultaneously driving both heavy rotating masses and significantly reducing the overall starting time.
Solution Approach 2:
The dynamically controllable clutches enable rapid transition between the two starting modes, allowing the system to optimize the starting sequence. By engaging and disengaging clutches at appropriate moments, the system can quickly switch between driving different spools, maintaining high starting speed while minimizing total starting time.
3Power
If the starter/generator is connected via one-way clutches to both spools, then the starter size is minimized, but the clutch system complexity increases
Solution Approach 1:
The patent introduces controllable clutches as intermediary components between the starter/generator and the two spools. These clutches act as mediators that selectively transmit or block power flow, enabling the starter/generator to connect to only one spool at a time. While this adds components, the clutches are relatively simple mechanical or electromagnetic devices that enable the overall system to be more efficient and compact.
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 configuration minimizes starter/generator size, ensures sufficient air flow at lower rotational speeds, and reduces fuel consumption by leveraging the higher efficiency of the free power turbine, enabling faster engine starts and more efficient electricity generation.
Implementation Method 1
the starter/generator is connected to the first and second spools via one-way and oppositely driving first and second clutches respectively
Data Source
AI summary
An open-rotor gas turbine engine comprising a starter/generator, a first spool and a second spool, the second spool is of a lower pressure than the first spool; wherein the starter/generator is connected to the first and second spools via first and second clutches respectively. The method of operating the open-rotor engine comprises the step of supplying power to the starter/generator to drive the first spool via the first clutch to start the engine and, once the engine is self-propelling, a step of driving the starter/generator from the second spool via the second clutch to generate electricity.