Gas Turbine Starter Torque Control via Speed and Temperature
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Solution Overview
Problem
Current gas turbine engine starting systems face challenges in efficiently delivering torque to overcome drag torque variations due to environmental conditions, leading to excessive current draw and potential failed starts, as they are sized to handle peak conditions and may accelerate the engine too quickly or cause electrical potential drops.
Innovation Solution
A start system that adjusts starter current delivery based on measured engine rotational speed and oil temperature, using a baseline current signal and an offset current selector to compensate for adverse conditions, ensuring sufficient torque while minimizing current draw and preventing failed starts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the start system is sized to provide enough torque to overcome peak drag torque under severe environmental conditions, then the APU can start under all conditions, but the system draws excessive current under average conditions and may cause electrical potential drops
Solution Approach 1:
The starter motor operates in two distinct modes: a high-torque mode for initial acceleration to overcome peak drag torque, and a normal-torque mode for continued acceleration. The system dynamically switches between modes based on engine speed thresholds, optimizing current draw at different operating phases
Solution Approach 2:
The control system implements periodic monitoring of engine speed and conditional switching between torque modes. When engine speed exceeds a threshold, the system transitions from high-torque to normal-torque mode, creating a time-based action sequence that reduces overall current consumption
2Reliability
If the start system generates high torque to ensure starting under severe conditions, then the APU can overcome peak drag torque, but the APU may accelerate too quickly and pass through the light-off window causing failed starts
Solution Approach 1:
The system dynamically adjusts torque output based on real-time engine speed feedback. By switching from high-torque to normal-torque mode when speed threshold is exceeded, the system controls acceleration rate to keep the APU within the light-off window
Solution Approach 2:
The control system continuously monitors engine speed and uses this feedback to determine when to transition between torque modes. This closed-loop control prevents over-acceleration by reducing torque when the APU approaches the upper speed limit of the light-off window
3Reliability
If a DC brushed starter motor is used to provide sufficient torque, then the system can start the APU under severe conditions, but the system complexity increases and maintenance requirements rise
Solution Approach 1:
The patent replaces the mechanical DC brushed starter motor with an electrically controlled starter system that uses electronic torque modulation. This substitution eliminates mechanical wear components while achieving the same starting performance through electronic control
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 provides reliable engine starts under all environmental conditions by optimizing current delivery according to rotational speed and oil temperature, reducing energy consumption and preventing premature acceleration.
Implementation Method 1
an engine oil temperature sensor that produces an oil temperature signal representing oil temperature for the gas turbine engine
Implementation Method 2
an engine rotational speed sensor that produces an engine rotational speed signal representing rotational speed of the engine
Implementation Method 3
a starter or starter generator initiates ignition of the APU... a DC brushed starter motor
Data Source
AI summary
A start system for a gas turbine engine delivers starter current according to a schedule selected according to measured rotational speed and oil temperature of the gas turbine engine.