Fuel Metering Circuit Density Compensation
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Solution Overview
Problem
Current fuel metering systems in turbomachines suffer from significant inaccuracies in mass flow rate delivery due to the variability of fuel density, which is not accurately accounted for in control laws, leading to variations in flow rates that affect turbomachine sizing and operation.
Innovation Solution
A fuel metering circuit that includes a diaphragm and volume flow meter in a bypass duct, along with an electronic card to adjust the metering device setpoint based on fuel density measurements, allowing for precise determination and compensation of fuel density variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If control laws are used to link target mass flow rate to metering device position based on defined temperature and fuel type conditions, then the metering device can be controlled, but the variability of fuel density cannot be taken into account, resulting in significant inaccuracy (around 12%) in the mass flow rate delivered
Solution Approach 1:
The invention introduces a feedback mechanism by measuring the actual fuel density (or temperature) and using this information to adjust the metering device control. A sensor measures fuel density/temperature, and this measurement feeds back to the control system, which modifies the metering device position or control parameters to compensate for density variations, thereby maintaining accurate mass flow rate delivery despite changing fuel conditions
Solution Approach 2:
The invention changes the control parameters dynamically based on fuel density variations. Instead of using fixed control laws based on defined conditions, the system adjusts control parameters (such as metering device position, pump speed, or valve opening) according to actual fuel density measurements, allowing the system to adapt to different fuel types and temperatures while maintaining precision
2Device complexity
If volume flow meters are used to measure the amount of fuel delivered, then the measurement system is simple, but the mass flow rate cannot be accurately known because volume flow meters do not account for fuel density variations
Solution Approach 1:
The invention introduces an intermediary measurement approach by adding a density sensor (or temperature sensor) as a mediator between the volume flow measurement and the mass flow calculation. The volume flow meter continues to measure volume flow, but the density sensor provides additional information that allows the system to calculate mass flow rate accurately by combining volume flow and density data, thus maintaining system simplicity while improving measurement precision
Solution Approach 2:
The invention makes the flow measurement system multi-functional by enabling it to perform both volume flow measurement (using the existing volume flow meter) and mass flow rate measurement (by combining volume flow data with density/temperature measurements). This allows a single measurement system to serve multiple purposes without requiring separate dedicated mass flow meters
3Adaptability or versatility
If the turbomachine is oversized to accommodate surge and shutdown margins due to flow rate inaccuracy, then the turbomachine can operate across wider conditions, but the device complexity and size increase
Solution Approach 1:
The invention uses feedback control to maintain accurate mass flow rate delivery across varying operating conditions, which allows the turbomachine to be sized more precisely without requiring excessive oversizing for surge and shutdown margins. The real-time density measurement and control adjustment enable the system to adapt to different operating points, providing the necessary adaptability without increasing physical size
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 significantly reduces the inaccuracy in fuel flow rate delivery, improving it from 12% to within ±1.6% or ±3% range, enhancing the accuracy and adaptability of the turbomachine's operation across varying conditions.
Implementation Method 1
a volume flow meter configured to determine the volume flow rate of the fuel passing through the diaphragm
Implementation Method 2
the diaphragm and the volume flow meter are mounted in parallel with the metering device in a bypass duct, downstream of the regulating valve, in order to determine a density of the fuel circulating in the metering circuit
Data Source
AI summary
A fuel metering circuit for a turbomachine includes: a meter; a pump; a control valve configured to return an excess flow of fuel delivered to the meter towards the pump on the basis of a fuel pressure differential at the terminals of the meter; a diaphragm; and a volumetric flow meter. The diaphragm and the volumetric flow meter are mounted parallel to the meter, downstream of the control valve, in order to determine a density of the fuel flowing in the metering circuit.