Starter-Drive Generator System for Aircraft Engine Starting
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Solution Overview
Problem
Aircraft engines require varying speed ranges to start, which is outside the narrow frequency band of conventional constant speed drives (CSDs), necessitating the use of air turbine starters since existing methods cannot vary the speed output from CSDs.
Innovation Solution
A starter-drive generator (SDG) system that utilizes an external constant frequency power supply, a motor drive with an active rectifier and inverter, and a generator with a hydraulic gearbox and servo valves to regulate torque, allowing the CSD to perform engine starts and power generation, enabling electrical control of engine starts and reducing the need for air turbine starters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional constant speed drive (CSD) is used to drive the synchronous generator, then the generator produces constant frequency output current suitable for aircraft electrical systems, but the CSD cannot vary its speed output to accommodate the varying speed ranges required for engine starting
Solution Approach 1:
The CSD is modified to include a variable speed capability during engine starting operations. The system transitions from a fixed-speed architecture to a dynamic speed control system that can adapt to the engine's varying speed requirements during start-up, while maintaining constant speed during normal generation operations.
Solution Approach 2:
The system changes the operational parameters of the CSD by introducing variable frequency control during engine starting. The CSD operates at variable speeds during start-up to match engine requirements, then transitions to constant speed operation for normal power generation, effectively changing the speed parameter based on operational mode.
2Adaptability or versatility
If an air turbine starter is used to start the engine, then the engine can be started with varying speed ranges, but the aircraft system requires additional heavy equipment and cannot use the synchronous generator for starting
Solution Approach 1:
The synchronous generator is designed to perform dual functions: it serves as the primary power generation device during normal operations and as the starting motor during engine start-up. This multi-functionality eliminates the need for a separate air turbine starter, reducing aircraft weight while maintaining the capability to provide varying speed ranges for engine starting.
Solution Approach 2:
The system merges the starting function with the existing synchronous generator and CSD assembly. By combining the motor drive functionality with the generator, the system eliminates the need for separate starting equipment, integrating multiple functions into a single unified system that reduces overall weight and complexity.
3Weight of moving object
If the synchronous generator is used to start the engine, then aircraft weight is reduced and start capability is improved, but additional controllers would be needed to manage the dual functionality
Solution Approach 1:
The control system is designed to automatically detect the operational mode (starting or generation) and adjust parameters accordingly without requiring complex external control logic. The system self-regulates by monitoring operational conditions and transitioning between modes autonomously, reducing the need for additional controllers while managing the dual functionality of the synchronous generator.
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
Enables engine starting without air turbine starters, reducing aircraft weight, improving start capability, and allowing the use of constant frequency buses, while eliminating the need for additional controllers by integrating functions into existing systems.
Implementation Method 1
a motor drive with an active rectifier and inverter
Implementation Method 2
a motor drive with an active rectifier and inverter
Implementation Method 3
a generator with a hydraulic gearbox and servo valves to regulate torque
Implementation Method 4
a generator with a hydraulic gearbox and servo valves to regulate torque
Data Source
Figure 1~2
Figure 3
Figure 4
AI summary
A method of starting an aircraft engine (17) is provided. The method includes providing motive power from a generator (14) for starting an engine (17) during an engine start mode and deriving electrical power by way of the generator (14) from rotation of the engine (17) during a generate mode, transmitting the motive power from the generator (14) to the engine (17) during the engine start mode by way of a constant speed drive (CSD) (15) and regulating a frequency of the electrical power output from the generator (14) during the generate mode by way of the CSD (15) and coupling a generator and CSD controller (GCC) (16) to the generator (14) and the CSD (15) and operating the generator (14) and the CSD (15) by the GCC (16) to execute at least the engine start mode and the generate mode.