Variable Nozzle Control via Fuel Flow Feedback
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Solution Overview
Problem
Existing variable nozzle control systems for turbojet engines, particularly in civil aircraft, face inaccuracies due to structural distortions, wear, and manufacturing tolerances, leading to inefficiencies and premature wear, especially in subsonic flow regimes where closed-loop systems are unreliable and prone to sensor inaccuracies.
Innovation Solution
A control device that uses a calculator and instantaneous fuel flow rate sensors to determine and correct the nozzle position based on theoretical fuel flow rates, accounting for flight parameters and engine wear, with a management system that adjusts the nozzle position to optimize efficiency and records correction values for future reference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If open loop servo-control is used for variable nozzle position control, then the system is simple and reliable, but the positioning accuracy deteriorates due to structural distortions, wear, and manufacturing tolerances
Solution Approach 1:
The patent introduces a feedback mechanism by measuring the actual fuel flow rate and comparing it with the theoretical fuel flow rate. The difference (error signal) is used to generate a correction value that adjusts the nozzle position setpoint, creating a closed-loop control system that compensates for inaccuracies without requiring direct position sensing
Solution Approach 2:
The patent uses fuel flow rate as an intermediary parameter to indirectly control nozzle position. Instead of directly measuring or controlling nozzle position, the system measures fuel flow rate and uses it as a mediator to determine the appropriate nozzle position, bypassing the need for direct position measurement and reducing the impact of mechanical wear and tolerances
2Measurement precision
If closed loop pressure sensor control is used for variable nozzle, then positioning accuracy is improved, but the system becomes unreliable and prone to sensor inaccuracies
Solution Approach 1:
The patent replaces direct position measurement with fuel flow rate measurement as an intermediary. The fuel flow rate sensor provides a more reliable signal that can be used to infer the optimal nozzle position, avoiding the reliability issues of direct position sensing in harsh environments
Solution Approach 2:
The patent substitutes mechanical position sensing systems with a fuel flow rate-based control system. By using fuel flow rate measurements and theoretical calculations to determine nozzle position, the system replaces unreliable mechanical or direct position sensors with a more robust measurement approach
3Productivity
If continuous nozzle position adjustment is implemented, then engine efficiency is optimized for varying flight conditions, but premature wear of movable parts occurs
Solution Approach 1:
The patent calculates and stores optimal nozzle position setpoints for different flight conditions and fuel flow rates in advance. During operation, the system retrieves pre-calculated setpoints and applies correction values, reducing the need for continuous complex adjustments and minimizing the frequency of movable part actuation
Solution Approach 2:
The system adjusts the nozzle position based on periodic measurements of fuel flow rate and changes in flight conditions, rather than continuous adjustment. This periodic control approach maintains engine efficiency while reducing the wear caused by excessive or unnecessary actuations of the nozzle mechanism
Data Source
AI summary
The present disclosure provides a device for controlling a variable section ejection nozzle of a turbojet engine nacelle of an aircraft. The device includes a calculator adapted to determine a position setpoint of the nozzle and a management system of the servo-control of the position of the variable nozzle depending on the flow rate of the fuel supplying the turbojet engine. The management system includes at least one instantaneous flow rate sensor of the fuel and a management unit which is designed to compare the flow rate measured by the flow rate sensor with a theoretical fuel flow rate depending on the parameters of the flight of the aircraft, to determine a correction value of the position of the nozzle depending on the comparison of the measured flow rate and the theoretical fuel flow rate, and to correct the position setpoint of the nozzle according to the correction value.