Redundant EHSV Control via Secondary Valve Merging
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Solution Overview
Problem
Multi-stage gas turbine fuel systems face increased weight and cost due to redundant control components for primary combustor stages, which are not justified for less critical secondary stages, leading to inefficiencies and additional complexity.
Innovation Solution
A fuel control system utilizing only two dual channel servo valves for normal and redundant operation, with a multi-land transfer valve to switch control from a failed primary to a secondary servo valve, eliminating dedicated redundant components and minimizing hardware, thereby reducing weight and cost.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If redundant EHSV control is implemented for primary combustor stage, then reliability is improved, but weight and cost increase
Solution Approach 1:
The patent merges the secondary stage EHSV into the primary stage redundant control system. The secondary EHSV is repurposed to serve as a backup for the primary stage, eliminating the need for a dedicated redundant EHSV. This combining of functions reduces the total number of components while maintaining the required reliability level for the primary combustor stage.
Solution Approach 2:
The secondary stage EHSV is given multiple functions: it controls the secondary combustor stage during normal operation and serves as a redundant backup for the primary stage when needed. This multi-functionality allows the system to achieve high reliability for the primary stage without adding dedicated redundant components, thereby reducing weight and cost.
2Reliability
If redundant EHSV control is implemented for primary combustor stage, then reliability is improved, but device complexity increases
Solution Approach 1:
The control systems are merged by having the secondary EHSV serve dual purposes. The same valve and its control circuitry are used for both secondary stage control and primary stage redundancy, reducing the number of independent control paths and simplifying the overall device architecture while maintaining reliability.
Solution Approach 2:
The secondary EHSV and its associated control logic perform multiple functions depending on system state. During normal operation, it controls the secondary stage; during primary stage failure, it switches to provide redundant control. This universal functionality reduces device complexity compared to having separate dedicated redundant systems.
3Reliability
If redundant EHSV control is implemented for primary combustor stage, then reliability is improved, but cost increases
Solution Approach 1:
The patent combines the secondary stage control system with the primary stage redundant control system, eliminating the need for a separate dedicated redundant EHSV. This merging reduces the total component count and assembly requirements, leading to lower manufacturing costs while maintaining the required reliability level.
Solution Approach 2:
The secondary EHSV is designed to perform multiple functions (secondary stage control and primary stage backup), which reduces the total number of components that need to be manufactured and assembled. This multi-functionality approach lowers overall system cost while achieving the desired reliability improvement for the primary combustor stage.
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 approach reduces system complexity, weight, and electrical components while maintaining reliability by ensuring prime combustor metering system operation during failures, increasing the mean time between failures and providing cost-effective redundant control without adding undesirable bulk.
Implementation Method 1
The EEC positions the FMV by supplying an electrical signal to the Electro-Hydraulic Servo Valve (EHSV) that provide the hydraulic muscle to adjust the FMV to the desired position
Implementation Method 2
The FMV may include a dual channel linear variable displacement transducer (LVDT) to provide feedback of the fuel metering valve position
Implementation Method 3
A centrifugal pump delivers fuel from the tank to a fuel metering unit (FMU)
Data Source
AI summary
A redundant fuel metering system and method for a multi-stage combustor that utilizes a fuel metering valve EHSV from a less critical combustor stage fuel metering system as a redundant backup to the main metering valve EHSV. In the event of a failure of the main FMV EHSV, a control module signals a transfer system to switch control of the main FMV to the less critical combustor stage fuel metering system EHSV, thus maintaining control of the FMV for the main combustor. In doing this, the transfer valve then drives the less critical combustor stage fuel metering system FMV to its failsafe position while maintaining control of the main system.