Fuel Metering Pressure Regulation with Downstream Leak Isolation
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Solution Overview
Problem
Turbine engine fuel metering systems face challenges in maintaining consistent delta pressure due to variations in flow and pressure, leading to inefficiencies and inaccuracies in metered flow, exacerbated by internal leaks in pressure regulating valves.
Innovation Solution
A fuel metering system is designed with a metering valve, pressure regulating valve, and pilot valve configuration that uses downstream pressure signals to control the pressure regulating valve, minimizing the impact of internal leaks on accuracy and efficiency by ensuring fuel leakage occurs downstream of the metering valve, thus affecting only the pumping system's efficiency and not the metered flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a second valve is used to sense the delta pressure of the metering window and send a signal pressure to the pressure regulating valve, then the accuracy of the pressure regulating valve is improved, but internal leak paths are introduced that reduce metered flow efficiency
Solution Approach 1:
A pilot valve is introduced as an intermediary component that senses delta pressure through high and low pressure windows and transmits signal pressure to the pressure regulating valve's control chamber. This intermediary mechanism enables accurate delta pressure sensing while directing any potential leakage downstream of the metering valve, thus preserving metered flow efficiency.
Solution Approach 2:
The pilot valve is segmented into distinct high pressure and low pressure windows that separately sense pressures upstream and downstream of the metering valve. This segmentation allows independent pressure sensing paths that can be controlled to minimize leakage impact on the main fuel flow path.
2Measurement precision
If a second valve is used to sense the delta pressure of the metering window, then the accuracy of the pressure regulating valve is improved, but the pumping system efficiency is reduced due to internal leaks
Solution Approach 1:
The pilot valve design accepts that some internal leakage will occur in the pressure sensing mechanism, but converts this potential harm into a beneficial arrangement by directing the leakage downstream of the metering valve. The leaked fuel still serves the system by being delivered to the combustion chamber, thus converting the harmful leakage effect into a beneficial outcome that maintains pumping efficiency.
3Stress or pressure
If the pressure regulating valve uses a spring load to regulate delta pressure, then the valve can maintain pressure regulation, but large variations in flow and pressure make it difficult to maintain consistent delta pressure
Solution Approach 1:
The pilot valve provides a feedback mechanism by continuously sensing the actual delta pressure across the metering valve through its high and low pressure windows and transmitting this information as signal pressure to the pressure regulating valve's control chamber. This feedback loop enables the system to automatically adjust and maintain consistent delta pressure despite large variations in overall system flow and pressure conditions.
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 maintains accurate metered flow and improves pumping system efficiency by isolating fuel leakage from the metered output, reducing the impact of internal leaks on the overall system performance.
Implementation Method 1
a pilot valve spool with a high pressure window fluidically connecting the supply port to the setting orifice, and a low pressure window fluidically connecting the return port to the signal port
Data Source
AI summary
A fuel system includes a system inlet and a system outlet. The fuel system also includes a metering valve with a metering valve inlet fluidically connected to the system inlet, and a metering valve outlet fluidically connected to the metering valve inlet. A pressure regulating valve includes an inlet fluidically connected to the metering valve outlet, and an outlet fluidically connected to the system outlet. A spool of the pressure regulating valve is configured to fluidically open and close the inlet to the outlet. The pressure regulating valve also includes a control chamber on a control side of the spool. A pilot valve includes a return port fluidically connected to the system outlet, and a supply port fluidically connected to a line fluidically connecting the metering valve outlet to the inlet of the pressure regulating valve. The pilot valve also includes a signal port fluidically connected to the control chamber.