Turbomachine Windmill Bypass Valve Spool Design
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Solution Overview
Problem
Existing turbomachine fuel delivery systems face challenges in managing fuel flow during engine shutdown, particularly in preventing fuel delivery to the combustion section when transitioning to a bypass position, which can lead to unstable flow characteristics and potential damage.
Innovation Solution
A windmill bypass valve design featuring a sleeve with a bore and a spool that moves axially within the bore, allowing for controlled flow through windows, with a diameter ratio between the spool and bore optimized for smooth transition and reduced resonance, facilitating a gradual increase in fuel flow and minimizing flow perturbations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the spool outer diameter is made close to the bore diameter (99.90-99.95%) to reduce flow leakage and improve flow control precision, then flow control precision is improved, but manufacturing precision requirements increase significantly
Solution Approach 1:
The patent specifies a precise diameter ratio parameter (99.90-99.95%) between the spool outer diameter and bore diameter. This parameter optimization achieves the dual benefit of minimizing flow leakage (improving flow control precision) while remaining achievable with standard manufacturing capabilities. The specific numerical range represents an optimized parameter that balances performance requirements with manufacturing feasibility.
2Adaptability or versatility
If the spool is designed to move axially within the bore to control flow through windows, then flow control capability is improved, but device complexity increases due to additional moving parts and sealing requirements
Solution Approach 1:
The spool serves multiple functions: it acts as a flow control element by moving axially to expose or cover windows in the sleeve, serves as a sealing element against the sleeve bore, and functions as a mechanical linkage connected to the valve stem. This multi-functionality reduces the need for separate components, thereby managing device complexity while achieving versatile flow control capability.
Solution Approach 2:
The spool is nested within the sleeve bore, with the spool diameter closely matching the bore diameter (99.90-99.95%). This nested configuration allows the spool to move axially within the constrained space of the sleeve, enabling flow control through the windows without requiring additional external mechanisms or increasing overall valve complexity.
3Reliability
If the valve restricts flow through windows during engine shutdown to prevent fuel delivery, then safety is improved, but flow stability during transition may deteriorate due to abrupt flow changes
Solution Approach 1:
The axial movement of the spool within the sleeve allows for gradual exposure or coverage of the windows, enabling a progressive transition in flow restriction. This preliminary gradual action prevents abrupt flow changes during engine shutdown transitions, maintaining flow stability while ultimately achieving complete flow restriction for safety.
Data Source
AI summary
An example bypass valve includes a sleeve providing a bore that extends along an axis. The sleeve has at least one window. The bypass valve also includes a spool received within the bore. The spool is configured to move within the bore between a first position that restricts flow through at least one window and a second position that permits flow through the at least one window of the sleeve. An outer diameter of the spool is from 99.90 to 99.95 percent of a diameter of the bore.