Fuel Metering Circuit With Density-Compensated Return Flow
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Solution Overview
Problem
Current fuel metering circuits in turbomachines lack precision in adapting fuel flow rates due to variability in fuel density, leading to significant inaccuracies, which affect turbomachine sizing and operation, especially during speed changes.
Innovation Solution
A fuel metering circuit with a regulating valve that modulates excess fuel flow based on fuel density variations, using a high-pressure feed line and low-pressure return line, along with a flow sampling system to maintain constant fuel pressure, reducing inaccuracies in fuel delivery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If volumetric flow meters are used to measure fuel flow rate, then the measurement system is simple, but the measurement precision is insufficient due to inability to adapt to fuel density variations
Solution Approach 1:
The invention changes the operating parameters of the metering device based on fuel density measurements. A density sensor measures fuel density and provides feedback to adjust the metering device position, thereby adapting the volumetric flow rate to compensate for density variations and achieve accurate mass flow rate measurement without using complex mass flow meters.
Solution Approach 2:
The invention implements a feedback control system where fuel density is continuously measured and used to adjust the metering device in real-time. The density sensor provides feedback signals that modify the metering device position, creating a closed-loop system that maintains measurement precision despite fuel density variations.
2Adaptability or versatility
If control laws are designed for fixed temperature and fuel type conditions, then the control system is simple, but the adaptability to varying fuel density conditions is poor
Solution Approach 1:
The invention dynamically changes control parameters based on measured fuel density. Instead of using fixed control laws for specific fuel types and temperatures, the system continuously adjusts the metering device position according to real-time density measurements, enabling adaptation to any fuel condition without requiring multiple pre-programmed control laws.
Solution Approach 2:
The control system automatically adapts to varying fuel conditions through self-regulation. The density sensor and feedback mechanism enable the system to self-adjust the metering device position without external intervention or complex pre-programming, making the control system both adaptable and relatively simple.
3Reliability
If turbomachine is oversized to accommodate flow rate variations, then the operating reliability is improved, but the device complexity and size increase
Solution Approach 1:
The invention changes the mass flow rate delivery by adjusting the metering device position based on fuel density. This ensures that the turbomachine receives the precise mass flow rate required for its current operating speed, eliminating the need for oversized components to accommodate flow rate variations caused by density changes.
Solution Approach 2:
The invention replaces mechanical oversizing with a controlled adjustment mechanism. Instead of designing the turbomachine with excessive capacity to handle flow rate variations, the system uses a density-based feedback control to precisely deliver the required mass flow rate, thereby maintaining reliability without increasing physical size or complexity.
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 enhances precision in fuel metering by reducing flow rate inaccuracies by over 30% and simplifies control electronics, ensuring accurate fuel delivery to the combustion chamber regardless of fuel density changes.
Implementation Method 1
a flow sampling line which connects the high-pressure line to a chamber of the regulating valve, said line comprising a pump adapted to deliver to said chamber a constant flow of fuel at a pressure greater than the fuel pressure in the high-pressure line
Implementation Method 2
said lines ensuring the supply to the chamber with a constant flow of fuel the pressure of which depends only on the density of the fuel
Data Source
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AI summary
The invention relates to a circuit for metering fuel (1) for a turbomachine, comprising: - a fuel metering element (20), – a pump (10) designed to pump a flow of fuel to the metering element, and – a control valve (30) 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, characterized in that 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. The invention also relates to a turbomachine comprising such a circuit.