Power Turbine Torque Limiter for Gas Turbine Overshoot Control
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Solution Overview
Problem
Helicopter turboshaft engines face challenges in preventing power turbine speed overshoots due to changing load and power demands, which can lead to inefficient rotor speed management and reduced flight handling quality.
Innovation Solution
A control system for gas turbine engines that includes a controller with an engine control module, a power turbine governor module, and a power turbine torque optimal limiter module, which receives real-time signals from the load system to output a maximum torque limiter signal, ensuring the power turbine torque is limited by calculating a relative torque limiter signal and adding it to the estimated torque signal of the load system to prevent overshoot.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the power turbine governor module outputs a preliminary torque request based on load changes, then the rotor speed response is improved, but power turbine speed overshoot increases
Solution Approach 1:
The optimal limiter module calculates and outputs a maximum torque topper signal in advance based on the current speed error between desired and actual power turbine speeds. This preliminary action prevents overshoot before it occurs by establishing a torque ceiling that accounts for the system's inertial characteristics and current deviation from target speed.
Solution Approach 2:
The system continuously monitors the real-time power turbine speed and compares it with the desired speed to generate a speed error signal. This feedback is fed into the optimal limiter module, which dynamically adjusts the maximum torque topper based on the magnitude and direction of the speed error, creating a closed-loop control that actively prevents overshoot.
2Device complexity
If a traditional governor system is used to control power turbine torque, then the system complexity is reduced, but the ability to prevent speed overshoot deteriorates
Solution Approach 1:
The optimal limiter module is integrated within the existing governor control architecture, with the governor module generating a preliminary torque request that is then processed by the nested optimal limiter module. This nested structure allows the enhanced control functionality to be embedded within the conventional system framework, adding overshoot prevention capability without completely redesigning the control architecture.
3Power
If the torque request is increased to meet power demand changes, then the power delivery is improved, but the speed overshoot and rotor load instability increase
Solution Approach 1:
The maximum torque topper signal is dynamically adjusted based on real-time speed error conditions rather than being a fixed value. When the power turbine speed deviates from the desired speed, the optimal limiter module modifies the torque ceiling accordingly, allowing high torque delivery when needed while automatically reducing torque to prevent overshoot, thus adapting the power delivery characteristics to current operational conditions.
Data Source
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AI summary
A control system (50) for limiting power turbine torque (QPT) of a gas turbine engine (10) includes a controller (40) including a processor and memory configured to control the gas turbine engine (10), the controller (40) including an engine control module (54) that provides an effector command signal to a gas generator of the gas turbine engine (10); a power turbine governor module (60) that outputs a preliminary torque request (QPT_req_pre); and a power turbine torque (QPT) optimal limiter module (58) that outputs a maximum torque topper (QPT_max) to limit a power turbine speed overshoot of the gas turbine engine (10); wherein the controller (40) outputs a minimum value between the preliminary torque request (QPT_req_pre) and the maximum torque topper (QPT_max) to the engine control module (54).