Offset Fan Turbojet Differential Transmission
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Solution Overview
Problem
Existing propulsion units with multiple fans face challenges in achieving non-uniform kinematic distribution, leading to stray shearing stresses due to inevitable differences in fan operations, such as torque asymmetry and differing air flow angles, which restrict the ability to handle differential loads without constraining the entire transmission chain.
Innovation Solution
A differential power transmission system with a planet carrier, planet gears, idler gears, and radial shafts, allowing for differential load distribution between fans with offset axes, enabling independent rotation speeds and reducing bulk and mass imbalance around the input shaft axis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single angular member with bevel gears is used to transmit power from the turbine shaft to two radial shafts, then the transmission structure is simplified, but the two fans are forced to rotate at the same speed causing stray shearing stresses due to torque asymmetry and different operating conditions
Solution Approach 1:
The patent introduces a differential mechanism that segments the power transmission path, allowing each radial shaft to receive power independently through its own planet gear system. This segmentation enables different rotation speeds for each fan while maintaining a relatively simple overall structure through the use of standardized differential components.
Solution Approach 2:
The differential mechanism acts as an intermediary between the single turbine shaft and the two radial shafts. It mediates the power transmission by allowing the turbine shaft to drive both fans while accommodating their different torque requirements and operating conditions, thereby eliminating the stray shearing stresses that would occur with direct rigid coupling.
2Productivity
If the two fans operate with different ratings and torque requirements, then the propulsion performance is optimized, but the kinematic diagram based on a single angular member becomes impossible to satisfy
Solution Approach 1:
The patent employs a differential mechanism that provides dynamic kinematic distribution to the two radial shafts. Instead of a fixed rigid connection that forces uniform rotation, the differential allows each shaft to rotate at different speeds dynamically adjusted to the torque requirements and operating conditions of each fan, thereby enabling optimized propulsion performance.
Solution Approach 2:
The differential mechanism changes the kinematic parameters (rotation speeds) of the two radial shafts independently based on the different torque requirements and operating conditions of each fan. This parameter adjustment allows each fan to operate at its optimal rating while maintaining a manageable transmission structure through standardized differential components.
3Stability of the object's composition
If rigid power transmission is used between the turbine and fans, then the transmission chain is constrained, but the ability to handle differential loads is reduced
Solution Approach 1:
The differential mechanism transforms the rigid constrained transmission chain into a dynamic system that can adapt to differential loads. Each radial shaft can independently adjust its rotation speed to handle varying torque requirements and operating conditions, providing versatility in load handling while maintaining overall transmission stability through the structured differential architecture.
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
The differential system effectively manages differential loads on fans with offset axes, reducing stray shearing stresses and allowing for balanced operation, thereby enhancing propulsion unit efficiency and reducing stress on transmission components.
Implementation Method 1
planet gears (13) mounted on the planet carrier (12), the planet carrier (12) forming a hub on which the rotation axes of the planet gears (13) are radially arranged
Data Source
AI summary
A propulsion unit of an aircraft including a turbine (15), at least one fan (10) with an axis offset relative to the axis of the turbine and a power transmission mechanism between the turbine and the fan. The power transmission mechanism includes a speed reducing gear (20) with an input and a movement output, the input being in the extension of the axis (16) of the turbine and the output connected to the fan.