Fuel Control System Shutoff via Windmill Bypass Valve
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Solution Overview
Problem
Existing fuel control systems for turbomachines face challenges in efficiently shutting off fuel flow during engine shutdown, particularly in over-speed conditions, due to pressure fluctuations that can lead to incomplete shutdown and potential damage.
Innovation Solution
A fuel control system incorporating a windmill bypass valve with a shutoff pressure line and an electromechanical valve, which directs fuel to assist the movement of the fuel delivery valve to a closed position, ensuring rapid and complete shutdown by managing pressure effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the windmill bypass valve directs fuel away from the MPSOV during shutdown, then the pressure of fuel flowing to the MPSOV drops and allows the MPSOV to close, but this may lead to incomplete shutdown and potential damage due to pressure fluctuations
Solution Approach 1:
The patent introduces a pressure equalization line as an intermediary pathway between the upstream side and downstream side of the MPSOV. This mediator allows controlled pressure equalization during valve closure, reducing harmful pressure fluctuations while maintaining reliable shutdown functionality.
Solution Approach 2:
The pressure equalization line provides beforehand cushioning by pre-establishing a pressure balancing mechanism before the MPSOV closes. This cushioning effect mitigates the impact of pressure fluctuations that would otherwise occur during shutdown, protecting the system from potential damage.
2Speed
If the fuel delivery valve shuts off fuel flow rapidly during over-speed condition, then engine shutdown is achieved, but pressure spikes may occur causing incomplete shutdown
Solution Approach 1:
The pressure equalization line acts as a mediator that allows gradual pressure equalization between upstream and downstream sides of the MPSOV during rapid closure. This intermediary pathway prevents pressure spikes by providing a controlled equalization route, enabling both rapid shutdown and pressure management.
Solution Approach 2:
The system dynamically changes pressure parameters during shutdown by utilizing the pressure equalization line. As the MPSOV closes rapidly, the equalization line adjusts pressure distribution in real-time, transforming the pressure profile to avoid spikes while maintaining shutdown speed.
3Ease of operation
If pressure is maintained for windmilling and start operations, then sufficient muscle pressure is available for actuator positioning, but this may interfere with complete fuel shutoff during shutdown
Solution Approach 1:
The fuel system is segmented into distinct pressure zones: the main fuel line for shutdown control and the pressure equalization line for pressure management. This segmentation allows independent control of fuel flow shutoff and pressure maintenance, enabling complete fuel closure while preserving necessary pressure for windmilling operations.
Solution Approach 2:
The pressure equalization line is pre-configured to maintain sufficient pressure in the fuel system for windmilling and start operations. During shutdown, this pre-established pressure pathway works in conjunction with the MPSOV closure to ensure both complete fuel shutoff and adequate pressure for operational requirements.
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 system ensures rapid and reliable shutdown of fuel flow, preventing pressure spikes and ensuring safe engine shutdown, even in over-speed conditions, while maintaining sufficient pressure for windmilling and start-up operations.
Implementation Method 1
The windmill bypass valve is selectively operable to direct fuel to the shutoff pressure line to assist the movement of the fuel delivery valve to the closed position
Data Source
AI summary
A fuel control system according to an exemplary aspect of the present disclosure includes, among other things, a fuel delivery valve selectively moveable to a closed position to shut off a flow of fuel to a downstream location. The system further includes a windmill bypass valve, and a shutoff pressure line between the windmill bypass valve and the fuel delivery valve. The windmill bypass valve is selectively operable to direct fuel to the shutoff pressure line to assist the movement of the fuel delivery valve to the closed position. A method is also disclosed.