Aircraft Starter Generator With Continuously Variable Transmission
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Solution Overview
Problem
Conventional aircraft starter generators face challenges in accommodating increased electric power demands and risk engine stall during low-output operations due to their reliance on high-pressure rotating shafts, leading to complexity and increased costs with dual frequency systems.
Innovation Solution
A starter generator system with an electric rotating machine capable of both motor and generator operations, featuring a continuously variable transmission and dual clutches to manage rotation and frequency, allowing for constant frequency power generation and simplified engine starting without load on the rotating machine.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the starter generator is connected to the high-pressure rotating shaft, then the engine starting operation can be performed, but the risk of engine stall increases during low-output operations and the structure becomes more complex
Solution Approach 1:
The power transmission system is segmented into two independent paths: one from the high-pressure shaft for starting operations and another from the low-pressure shaft for power generation. This segmentation allows each shaft to operate independently for its specific function, eliminating the conflict between starting torque requirements and power generation stability.
Solution Approach 2:
A clutch mechanism serves as an intermediary between the high-pressure shaft and the rotating machine, enabling selective engagement and disengagement. This allows the system to connect to the high-pressure shaft only during starting operations and disconnect during power generation, preventing engine stall risk while maintaining starting capability.
2Measurement precision
If a constant frequency integrated drive generator is used, then electric power with constant frequency can be generated, but the device complexity and production cost increase
Solution Approach 1:
A single rotating machine is designed to perform multiple functions: it can operate as a motor during engine starting and as a generator during power generation. This multi-functionality eliminates the need for separate constant frequency IDG systems, reducing device complexity while maintaining frequency stability through control of the rotating machine's speed.
3Device complexity
If the electric starter is replaced by conventional air compressor starter, then the structure may be simplified, but the weight and cost increase and the risk of engine stall remains
Solution Approach 1:
The conventional mechanical air compressor starting system is replaced with an electric starting system using a rotating machine driven by the high-pressure shaft. This substitution provides more precise control over the starting process, reducing engine stall risk while maintaining structural simplicity. The electric system can be precisely controlled to match engine starting requirements without the weight and complexity of large mechanical compressors.
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 solution simplifies the starter generator's structure, reduces production costs, and minimizes the electric power needed for engine starting by using a single rotating machine for both operations, ensuring constant frequency power generation and efficient engine starting.
Implementation Method 1
an electric rotating machine (26) having a rotating shaft (29), the rotating machine being designed to carry on two reverse operations- motor and generator
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
A starter generator has an electric rotating machine having a rotating shaft. The rotating machine is designed to carry on two reverse operations- motor and generator. A first clutch is connected between the rotating machine and the first rotating shaft for transmitting rotations of the rotating machine to the first rotating shaft. A second clutch is connected between the rotating machine and the second rotating shaft for transmitting rotations of the second rotating shaft to the rotating machine. A continuously variable transmission is provided for changing the number of rotations transmitted from the second rotating shaft to the rotating machine. A control is designed to carry our first and second modes. In the first mode, the rotating machine is supplied with electric power to rotate the rotating shaft and thereby rotations of the rotating shaft are transmitted through the first clutch to the first rotating shaft. In the second mode, the number of rotations of the rotating shaft of the rotating machine is kept constant by controlling a transmission ratio of the continuously variable transmission.