Accessory Transmission Shifting Using Drag Torque Speed Matching
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Solution Overview
Problem
Modern gas turbine engines face challenges in transferring accessory power from high-pressure to low-pressure spools, resulting in sudden speed changes and torque transients that cause stress, wear, and reduced life in downstream components due to misalignment between typical speed ranges.
Innovation Solution
A transmission assembly with sensors and clutches that control the opening and closing of clutch packs in an alternating sequence, using drag torque from generators to gradually match output speeds with shifting gears, minimizing speed changes and torque transients.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multi-speed shifting transmissions are used to condition LS output speeds, then accessory speed range alignment is improved, but sudden speed changes occur causing torque transients and increased stress on driveline components
Solution Approach 1:
The control system pre-conditions the transmission by gradually reducing the output speed to match the target gear speed before the clutch engagement. This preliminary speed matching prevents sudden speed changes and torque transients when the clutch engages, thereby protecting driveline components while achieving the desired speed range alignment.
Solution Approach 2:
The transmission control system dynamically adjusts the output speed during the shifting process rather than maintaining a fixed speed. The controller continuously monitors and modulates the output speed to match the target gear characteristics, enabling smooth transitions without torque transients while maintaining adaptability across different operating conditions.
2Productivity
If transmission shifts are performed quickly to improve response time, then productivity is improved, but torque transients increase causing wear and stress on components
Solution Approach 1:
The system performs preliminary speed conditioning by gradually reducing the output speed to match the target gear speed before clutch engagement. This pre-synchronization enables quick shifting without generating torque transients, as the speed matching is already completed before the engagement event occurs.
Solution Approach 2:
The control system maintains continuous control of the output speed throughout the shifting process, ensuring that the speed reduction to match the target gear is a continuous, controlled action rather than a discontinuous jump. This continuous conditioning eliminates torque transients while maintaining efficient shifting response.
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 approach reduces torque transients and extends the life and reliability of driveline components by minimizing speed changes and clutch wear, while maintaining efficient power extraction.
Implementation Method 1
clutches (133)... transmitting the input torque to the output shaft
Implementation Method 2
using the drag torque of a generator and/or other engine accessories to reduce an output speed of the transmission
Data Source
Figure 1
Figure 2
AI summary
A power extraction system (101) is provided and includes a low-pressure spool (116) of a gas turbine engine, the low-pressure spool being rotatable at an input rotational speed between a first minimum speed and a first maximum speed, downstream components (120) rotatable at an output rotational speed between a second minimum speed and a second maximum speed and a transmission assembly (130) by which rotations of the low-pressure spool at the input rotational speed are transmittable at the output rotational speed to the downstream components. The transmission assembly includes clutches (133) and a controller (135) configured to control openings and closings of the clutches according to an upshifting algorithm whereby a torque applied by the downstream components is used to reduce the output rotational speed to an output speed of a gear into which the transmission assembly is shifting.