Turboshaft Load Power Management Control System
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Solution Overview
Problem
Gas turbine engines, particularly turboshaft engines used in helicopters, face challenges in maintaining constant rotor speed during changes in power demand, which affects handling qualities and efficiency.
Innovation Solution
A control system with an outer loop control module and an inner loop control module, utilizing a hybrid control component that includes a Proportional Integral control component and a feed-forward component for load anticipation, to regulate power turbine torque and manage fuel flow and inlet guide vane schedules, ensuring consistent rotor speed and power delivery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If proportional control regulates fuel flow based on demanded and actual speed signals, then power turbine torque is controlled, but rotor speed varies during load changes affecting handling qualities
Solution Approach 1:
The feed-forward component anticipates load changes on the power turbine and proactively adjusts fuel flow and inlet guide vane positions before speed deviations occur. This preliminary action prevents rotor speed variation during load changes, maintaining constant rotor speed while delivering requested power demand changes.
Solution Approach 2:
The feedback control component continuously monitors actual rotor speed and compares it with demanded speed, adjusting fuel flow accordingly. This closed-loop feedback ensures that any speed deviations are corrected, maintaining stable rotor speed during power demand changes.
2Power
If integrator accumulates control signal to match power demand, then torque regulation improves, but integrator wind-up occurs causing delayed response to load changes
Solution Approach 1:
The hybrid control component dynamically switches the integrator between accumulation mode (when torque error exists) and decay mode (when torque is delivered). This dynamic adjustment prevents integrator wind-up during transient conditions, allowing immediate response to load changes while maintaining accurate torque regulation during steady-state operation.
3Speed
If feed-forward component anticipates load changes, then rotor speed stability improves, but control system complexity increases
Solution Approach 1:
The control system is divided into distinct functional modules: feed-forward component for load anticipation, feedback control component for speed regulation, and hybrid control component for integrator management. This segmentation allows each component to perform its specific function independently, making the complex control logic more manageable and maintainable while achieving superior rotor speed stability.
Data Source
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AI summary
A control system for a gas turbine engine including a power turbine is disclosed. The control system may also include an outer loop control module to determine a torque request. The outer loop control module may include a feedback control component operative to provide regulation of the power turbine, a feed-forward component operative to anticipate a load on the power turbine, and a hybrid control component operative to prevent output of a torque request that cannot currently be delivered by the power turbine. The control system may also include an inner loop control module to receive the torque request from the outer loop control module, to determine fuel flow and inlet guide vane schedules based at least in part on the received torque request, and to send signals to a gas generator of the gas turbine engine in order to control the gas generator according to the determined fuel flow and inlet guide vane schedules.