Symmetrical Compound Epicyclic Gear Assembly for High Turbomachine Ratios
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Solution Overview
Problem
Existing gear assemblies in turbomachines, including open rotor engines, often provide inadequate gear ratios, leading to inefficient operations where the fan rotor operates too fast and the turbine operates too slow, limiting the ability to effectively utilize larger rotor blades and improve propulsive efficiency.
Innovation Solution
A single-stage epicyclic gear assembly with a sun gear, planet gears, and a ring gear is used, where the sun gear and ring gear mesh regions are axially offset, allowing for increased gear ratios suitable for turbomachines, including open rotor engines, by reducing the output rotational speed relative to the input speed, thus optimizing the operation of fan and turbine components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If known gear assemblies are used, then the structure is simple, but the gear ratio is inadequate for desired operations
Solution Approach 1:
The patent introduces a second degree of freedom by allowing the planet carrier to rotate independently while the sun gear and ring gear remain stationary. This dimensional change in the mechanism's motion space enables the planet gears to traverse different radial positions, effectively creating variable gear ratios without increasing the number of gear stages or complexity of the assembly structure.
Solution Approach 2:
The mechanism transitions from a static gear ratio to a dynamic, variable gear ratio system. By enabling the planet carrier to rotate and change the radial position of planet gears relative to the sun gear, the system dynamically adjusts its transmission ratio during operation, allowing optimization of both fan rotor speed and turbine speed for different operating conditions.
2Speed
If the fan rotor operates at high speed, then the gear assembly is compact, but the fan rotor operates inefficiently
Solution Approach 1:
The system changes the operational parameters of the fan rotor by enabling variable speed control through the variable gear ratio mechanism. Instead of being constrained to high-speed operation, the fan rotor can now operate at optimized speeds that maximize propulsive efficiency while the gear assembly adapts its ratio to maintain appropriate speed relationships between the turbine and fan.
3Speed
If the turbine operates at low speed, then the gear ratio is high, but the turbine operates inefficiently
Solution Approach 1:
The variable gear ratio mechanism enables the turbine to operate at higher, more efficient speeds by adjusting the transmission ratio dynamically. When the planet gears are positioned to provide a lower gear ratio, the turbine can rotate faster while still driving the fan at the appropriate speed, thereby improving turbine efficiency and overall system productivity.
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 gear assembly achieves gear ratios up to 14:1, enabling efficient operation of large-diameter fan blades and turbines, improving propulsive efficiency and reducing installed drag, which enhances specific fuel consumption and allows for operation at higher cruise altitudes and speeds.
Implementation Method 1
The sun gear rotates about a longitudinal centerline of the gear assembly and has a sun gear-mesh region along the longitudinal centerline of the gear assembly where the sun gear is configured to contact the plurality of planet gears. A ring gear-mesh region is provided along the longitudinal centerline of the gear assembly where the ring gear is configured to contact the plurality of planet gears.
Data Source
AI summary
A gear assembly for use with a turbomachine comprises a sun gear, a plurality of planet gear layshafts that each support a first stage planet gear and a second stage planet gear, and a ring gear. The sun gear is configured to rotate about a longitudinal centerline of the gear assembly, and the plurality of planet gear layshafts have a tubular shape.