Split Gear System for Gas Turbine Engine Speed Reduction
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Solution Overview
Problem
In geared turbofan engines, the increased rotational speed of lower speed turbines leads to undesirable aerodynamic shock losses and structural challenges when directly driving the low pressure compressor, as it results in the compressor rotating too fast.
Innovation Solution
A split gear system with two gear sets arranged in series is used, where the first gear set steps down the rotational speed of the low speed spool to drive the low pressure compressor, and the second gear set further steps down the speed to drive the fan, allowing both to operate at lower speeds than the high speed turbine, thereby mitigating the issues of excessive speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the low speed turbine rotational speed is increased, then the power output and productivity are improved, but aerodynamic shock losses and structural challenges occur in the compressor
Solution Approach 1:
The gear system is divided into two separate gear sets: a first gear set connecting the low speed turbine to the low pressure compressor, and a second gear set connecting the low speed turbine to the fan. This segmentation allows independent speed control for each driven component, enabling the compressor to operate at optimal speed while the turbine runs at higher speeds for improved productivity.
Solution Approach 2:
The dual gear set system acts as an intermediary mechanism between the low speed turbine and the driven components. By introducing this intermediate transmission system, the patent decouples the turbine speed from the compressor speed, allowing the turbine to operate at higher speeds for improved power output while the compressor receives reduced speed to avoid aerodynamic shock losses.
2Power
If the low speed turbine rotational speed is increased, then the power output is improved, but structural challenges occur in the compressor
Solution Approach 1:
The gear system is divided into two separate gear sets: a first gear set connecting the low speed turbine to the low pressure compressor, and a second gear set connecting the low speed turbine to the fan. This segmentation allows independent speed control for each driven component, enabling the compressor to operate at optimal speed while the turbine runs at higher speeds for improved productivity.
Solution Approach 2:
The dual gear set system acts as an intermediary mechanism between the low speed turbine and the driven components. By introducing this intermediate transmission system, the patent decouples the turbine speed from the compressor speed, allowing the turbine to operate at higher speeds for improved power output while the compressor receives reduced speed to avoid aerodynamic shock losses.
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 split gear system enables the low speed spool to drive the fan and low pressure compressor at lower speeds, reducing aerodynamic shock losses and structural challenges, while maintaining efficient operation of the high speed turbine.
Implementation Method 1
A first gear set of a split gear reduces a rotational speed of the low speed spool to drive a low pressure compressor at a lower speed
Implementation Method 2
A second gear set of the split gear reduces the rotational speed of the low speed spool to drive a fan at a lower speed
Data Source
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AI summary
A gas turbine engine (20) includes a fan section (22), a compressor section (24) aft of the fan section (22), a combustor (36) fluidly connected to the compressor section (24) and a turbine section (28) fluidly connected to the combustor (56). The turbine section (28) includes at least a first turbine (46) and a second turbine (54) that operates at a higher pressure than the first turbine (46). A shaft (150) is connected to the first turbine section (142) such that the first turbine section (142) is operable to drive rotation of the shaft (150). The shaft (150) is a rotational input for a split gear (160) that is connected to the fan (22) and at least one of a multiple of compressors (122).