Contra-rotating Propeller Torque Ratio via Segmented Planetary Gears
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Solution Overview
Problem
Contra-rotating propeller systems in aircraft turbine engines face inefficiencies due to non-unitary torque ratios between propellers, leading to reduced propulsion efficiency, increased acoustic noise, and mechanical stress, which complicates engine design and increases mass and cost.
Innovation Solution
A mechanical transmission device with a planetary gear train is positioned between the propellers, optimizing the configuration to achieve a unitary torque ratio, reducing the engine's size and mass, and separating the pitch variation mechanism's energy supply to prevent breakdown-related hazards.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a planetary gear train with a differential reducer is used to drive contra-rotating propellers, then the propellers can be driven with different torques, but the torque ratio between propellers is necessarily non-unitary, reducing propulsion efficiency
Solution Approach 1:
The invention segments the power transmission path by introducing a second independent planetary gear train (second sun gear, second planet gears, second ring gear) that operates in parallel with the first. This allows each propeller to receive torque through separate, optimizable transmission paths, enabling both propellers to achieve unitary torque ratios while maintaining the ability to distribute power differently if needed.
Solution Approach 2:
The planet carrier acts as an intermediary element that connects both planetary gear trains. By coupling the first and second planetary gear trains through the shared planet carrier, the system achieves coordinated torque distribution to both propellers while maintaining mechanical simplicity and enabling unitary torque ratios.
2Productivity
If the reducing ratio R is increased to achieve a torque ratio close to unit, then the torque balance between propellers improves, but the global mass of the reducer increases significantly
Solution Approach 1:
The power transmission system is segmented into two independent planetary gear trains that share the planet carrier. This segmentation allows each gear train to operate at optimal reducing ratios, achieving unitary torque distribution without requiring an excessively high reducing ratio that would increase the mass of a single gear train.
3Object-affected harmful factors
If a sufficient gap is maintained between upstream and downstream propellers to limit noise, then acoustic level decreases, but the length of the turbine engine increases
Solution Approach 1:
The second planetary gear train acts as a mechanical intermediary that enables compact propeller spacing. By providing an additional torque transmission path, the system can maintain unitary torque ratios with smaller propeller diameter differences, allowing the propellers to be positioned closer together while still achieving effective noise reduction.
4Productivity
If the planetary gear train is used to drive variable setting type propeller blades, then propeller performance can be optimized, but any breakdown of the planetary gear train affects the setting system, creating hazardous conditions
Solution Approach 1:
The power transmission system is divided into two independent planetary gear trains that share only the planet carrier. This segmentation creates redundant power paths, so that a breakdown in one gear train does not completely disable the setting system, as the other gear train can potentially compensate or maintain partial functionality.
Data Source
AI summary
A contra-rotating propeller system for an aircraft turbine engine, including a free power turbine including a first rotor and a second rotor contra-rotating relative to the first rotor, a first contra-rotating propeller and a second contra-rotating propeller to be rotated about a longitudinal axis of the propeller system relative to a stator of the system, and a mechanical transmission device. The mechanical transmission system is provided between the first propeller and the second propeller.