Fuel Metering Circuit With Density-Compensated Return Valve
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current fuel metering systems in turbomachines lack precision in adapting to fuel density variations, leading to significant imprecision in mass flow delivery to the combustion chamber, which affects turbomachine sizing and operation, especially during regime changes.
Innovation Solution
A fuel metering circuit with a control valve that modulates excess fuel flow based on fuel density differences, using a high-pressure line and a low-pressure return line, along with a diaphragm and slide gate mechanism to adjust the fuel flow, ensuring the pressure is dependent solely on fuel density, thereby reducing imprecision in fuel delivery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional control laws are used for the metering element, then the control system remains simple, but the mass flow delivery precision deteriorates due to inability to compensate for fuel density variations
Solution Approach 1:
A diaphragm is introduced as an intermediary element that translates fuel density variations into positional changes of the metering element. The diaphragm is subjected to fuel pressure on one side and reference pressure on the other, causing it to move and adjust the metering element position proportionally to density changes, thereby achieving precision improvement without complex electronic controls
Solution Approach 2:
The invention uses pneumatic-hydraulic principles by applying fuel pressure directly to the diaphragm to mechanically adjust the metering element. The control valve modulates excess fuel flow based on pressure differences, and the diaphragm converts this pressure information into mechanical displacement, eliminating the need for electronic sensors and control algorithms while improving measurement precision
2Measurement precision
If volumetric flowmeters are used to measure fuel flow, then the device complexity remains low, but the measurement precision deteriorates because they cannot provide accurate mass flow information under varying density conditions
Solution Approach 1:
The invention changes the measurement parameter from volumetric flow to mass flow by using a diaphragm that responds to fuel density variations. The diaphragm's position is directly proportional to the mass flow required, as it is influenced by fuel pressure which varies with density. This transforms the measurement approach without requiring complex electronic flowmeters
Solution Approach 2:
The invention replaces electronic mass flowmeters with a mechanical-diaPhragm-based system. Instead of using electronic sensors and digital processing to determine mass flow, the system uses the physical properties of the diaphragm and fuel pressure to mechanically indicate the correct metering element position for accurate mass flow delivery
3Reliability
If the turbomachine is oversized to accommodate flow imprecision, then the operational reliability improves during regime changes, but the device complexity and size increase
Solution Approach 1:
The diaphragm performs preliminary adjustment of the metering element position based on anticipated fuel density variations before the turbomachine operates. By pre-positioning the metering element according to fuel pressure (which reflects density), the system ensures accurate mass flow delivery from the start, eliminating the need for oversized components to compensate for potential imprecision
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 solution achieves a reduction of over 30% in flow imprecision, allowing for precise adaptation to fuel density variations without the need for additional electronic controls, thereby enhancing the accuracy and reliability of fuel metering.
Implementation Method 1
a diaphragm, said lines ensuring the feeding of the chamber with a constant fuel flow the pressure of which is solely dependent on the fuel density
Data Source
AI summary
A circuit for metering fuel for a turbomachine, including a fuel metering element, a pump designed to pump a flow of fuel to the metering element, and a control valve designed to return, toward the pump, an excess flow of fuel delivered to the metering element as a function of a fuel pressure difference at the terminals of the metering element, the control valve is designed to modulate the excess flow returned toward the pump as a function of variations in the density of the fuel delivered to the metering element. A turbomachine can include such a circuit.