Fuel Nozzle Metering Valve With Fixed Geometry at High Pressure
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Solution Overview
Problem
Conventional fuel nozzles for jet engines experience flow variability due to geometric variations and valve displacement non-uniformity, leading to inconsistent fuel flow rates, especially at higher power settings, which affects combustor and turbine durability and reliability.
Innovation Solution
The design incorporates a spool and retainer mechanism within the fuel nozzle, where the spool moves within a valve liner, and a spring biases the valve to maintain a closed position until fuel flow pressure exceeds a threshold, allowing the spool to extend and maintain a fixed flow geometry, limiting valve displacement and reducing flow variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional spring-loaded valves are used with unimpeded displacement, then the valve can respond to full range of fuel flow pressure, but flow variability increases due to displacement non-uniformity and geometric variation
Solution Approach 1:
The patent applies dynamics by making the valve displacement characteristic changeable through a progressive spring rate mechanism. The spring rate transitions from an initial softer rate to a final stiffer rate, allowing the valve to adapt its displacement behavior across different pressure ranges. This dynamic adjustment of spring characteristics enables consistent flow control throughout the full pressure range while maintaining reliability.
Solution Approach 2:
The patent changes the physical parameter of spring stiffness by using a progressive spring rate design. The spring rate is not constant but varies during compression, transitioning from an initial softer rate to a final stiffer rate. This parameter change allows the valve to maintain optimal displacement characteristics across the full operating pressure range, resolving the contradiction between adaptability and flow consistency.
2Stress or pressure
If valve displacement is unrestricted, then the valve can accommodate high pressure fuel flow, but flow tolerance increases due to non-uniform displacement
Solution Approach 1:
The progressive spring rate creates a dynamic system where the valve stiffness changes with compression. At lower pressures, the softer initial spring rate allows smooth valve opening. At higher pressures, the stiffer final spring rate limits excessive displacement and maintains precise flow control, thereby reducing flow tolerance variations while accommodating maximum fuel flow pressure.
Solution Approach 2:
The progressive spring rate design incorporates preliminary anti-action by pre-planning the displacement limitation at high pressures. The increasing spring stiffness anticipates and counteracts the tendency for non-uniform displacement at high pressures, maintaining flow precision before pressure-induced variations can occur.
3Device complexity
If a single spring rate is used, then the valve structure is simple, but flow consistency varies across the pressure range
Solution Approach 1:
The progressive spring rate transforms a static spring structure into a dynamic one where the spring rate changes during compression. This is achieved through a variable pitch helical spring design, which maintains structural simplicity while providing dynamically adjusted stiffness. The result is improved flow consistency across the pressure range without significantly increasing device complexity.
Solution Approach 2:
The patent changes the spring parameter (spring rate) as a function of compression distance. The variable pitch helical spring design allows the spring rate to progress from an initial softer rate to a final stiffer rate, providing flow consistency across different pressure ranges while maintaining a relatively simple single-spring structure.
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 achieves reduced flow tolerance variations by maintaining a fixed flow geometry at higher pressures, resulting in more predictable fuel flow rates and improved durability and reliability of the combustor and turbine.
Implementation Method 1
The metering valve is biased in a closed position by a spring
Implementation Method 2
The spool is configured to slide out of the valve liner when a fuel flow pressure from fuel flowing into the inlet port overcomes the closing bias on the metering valve
Data Source
AI summary
A fuel nozzle metering valve that includes a spool having an inlet port and an outlet flow port, and a retainer assembled to one end of the spool. A valve liner houses a portion of the spool. The spool is configured to move back and forth within the valve liner. The metering valve is biased in a closed position in which the outlet flow port is disposed entirely within the valve liner. The valve is opened when the spool slides within the valve liner such that some portion of the outlet flow port extends beyond an end of the valve liner. The retainer has a stepped portion configured to abut an end of the retainer at a fuel flow pressure below the expected maximum fuel flow pressure to be used in the fuel nozzle metering valve.