Hybrid-Electric Engine Speed Control Using Shaft Torque Feedback
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Solution Overview
Problem
Conventional hybrid electric propulsion systems for aircraft face challenges in efficiently regulating the rotational speed of gas turbine engines, leading to oscillations and inefficiencies due to nonlinear fuel flow dynamics and the need for frequent control adjustments.
Innovation Solution
A hybrid electric propulsion system that integrates an electric machine and a control scheme with both a fuel flow control circuit and an electric machine control circuit, using a fuel flow control circuit to manage fuel flow and an electric machine control circuit to adjust torque, thereby stabilizing the rotational speed of the engine shaft.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional fuel flow control is used to regulate engine speed, then the engine can maintain basic operational speed, but rotational speed oscillations occur and control adjustments must be made frequently
Solution Approach 1:
The system implements a feedback control mechanism where the actual rotational speed is continuously monitored and compared with the desired rotational speed. The difference (error signal) is fed back to the controller, which adjusts the fuel flow control valve and electric machine output accordingly. This closed-loop feedback eliminates oscillations and reduces the need for frequent control adjustments by automatically compensating for speed deviations.
Solution Approach 2:
The electric machine acts as an intermediary device between the fuel flow control system and the engine shaft. Instead of directly controlling fuel flow to regulate speed, the system uses the electric machine to provide auxiliary torque that supplements or compensates for fuel flow variations. This intermediary approach smooths out rotational speed fluctuations and reduces the aggressiveness of fuel control adjustments.
2Reliability
If frequent control adjustments are made to regulate engine speed, then speed regulation can be achieved, but component wear increases and efficiency decreases
Solution Approach 1:
The feedback control system continuously monitors rotational speed and makes only the necessary minimal adjustments to maintain the desired speed. By using real-time speed information to guide control actions, the system avoids excessive control adjustments that would cause energy losses and component wear, while still achieving accurate speed regulation.
Solution Approach 2:
The system replaces aggressive mechanical fuel flow control with a hybrid approach that incorporates electric machine assistance. The electric machine can provide smooth, electronically controlled torque adjustments that are less mechanically stressful than frequent fuel valve adjustments, reducing component wear and energy losses associated with aggressive mechanical control.
3Use of energy by moving object
If hybrid electric propulsion is integrated to improve efficiency, then engine efficiency can be improved, but the system complexity increases
Solution Approach 1:
The system merges the conventional fuel flow control system with an electric machine in a hybrid propulsion configuration. The electric machine is integrated into the existing engine architecture, sharing the same shaft and control framework. This merging approach improves engine efficiency by allowing electric assistance during certain operating conditions while avoiding the need for completely separate propulsion systems, thus managing complexity.
Solution Approach 2:
The control system is designed to handle multiple functions: it regulates rotational speed, controls fuel flow, and manages electric machine output all through a unified control architecture. The same feedback mechanism and controller serve both the traditional fuel control and the electric machine integration, making the system multi-functional and reducing overall complexity compared to separate control systems for each function.
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 reduces rotational speed variance to less than ±0.05%, improving engine efficiency and reducing component wear by minimizing frequent control changes and optimizing fuel consumption.
Implementation Method 1
an electric machine that is drivingly coupled to the shaft, wherein the electric machine is operable to add power to the shaft or extract power from the shaft
Data Source
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AI summary
A method for operating a hybrid-electric gas turbine engine (10) is provided. The method includes: receiving data indicative of an actual rotational speed of a shaft; calculating an error between the actual rotational speed of the shaft and a commanded rotational speed of the shaft; providing the calculated error to a fuel flow control circuit operable with a fuel delivery system of the hybrid-electric propulsion engine; providing the calculated error to an electric machine control circuit operable with an electric machine (102A, 102B) of the hybrid-electric propulsion engine, the electric machine drivingly coupled to the shaft; and modifying a torque on the shaft from the electric machine with the electric machine control circuit based on the calculated error.