Hybrid Spool Start Architecture for Faster Gas Turbine Relight
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Solution Overview
Problem
Existing gas turbine engines face challenges in achieving faster and more reliable startups, particularly in cold start conditions and relight situations, with conventional starting systems taking minutes and sometimes failing due to insufficient airflow.
Innovation Solution
A hybrid electric configuration is introduced, incorporating an electric motor coupled to the low-speed spool for propulsive power and an accessory gearbox and starter motor connected to the high-speed spool, with a clutch to interconnect both spools, reducing inertial lag and enabling quicker, more reliable engine startups and relights.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional starting system is used, then the engine can be started, but the startup process takes minutes and may fail due to insufficient airflow
Solution Approach 1:
The patent combines an electric motor and a starter motor into a hybrid starting system. The electric motor is coupled to the low-speed spool while the starter motor (via accessory gearbox) is coupled to the high-speed spool. This merging of electrical and mechanical starting systems allows simultaneous action on both spools, reducing startup time and improving reliability by providing dual-path torque application.
Solution Approach 2:
The controller is configured to operate the electric motor and starter motor simultaneously during engine startup, performing preliminary acceleration of both spools before the gas turbine reaches self-sustaining operation. This preliminary action on both spools reduces the overall startup time and ensures sufficient airflow generation for reliable ignition.
2Power
If the electric motor is coupled to the low-speed spool, then propulsive power is improved, but inertial lag between spools increases
Solution Approach 1:
The controller performs preliminary simultaneous operation of both motors to accelerate both spools before the clutch engages. This preliminary action reduces inertial lag by ensuring both spools are already rotating at appropriate speeds when the mechanical coupling occurs, rather than allowing the clutch to handle inertial mismatches during power transmission.
Solution Approach 2:
The system uses a controllable clutch that can be engaged or disengaged dynamically based on operating conditions. The controller manages the engagement timing to optimize power transmission while minimizing inertial lag effects, allowing flexible adaptation to different startup and relight scenarios.
3Speed
If a hybrid electric configuration is used, then startup speed is improved, but device complexity increases
Solution Approach 1:
The electric motor serves multiple functions: it provides propulsive power during normal operation and assists with engine startup and relight operations. The starter motor similarly serves dual purposes for starting and relight scenarios. This multi-functionality reduces the need for separate dedicated components, thereby limiting the increase in overall system complexity despite the hybrid configuration.
Solution Approach 2:
The clutch acts as an intermediary mechanical coupling element between the high-speed and low-speed spools. It provides controlled power transmission while allowing the system to manage inertial effects and optimize power flow during startup and relight operations, simplifying the overall system architecture compared to direct rigid coupling.
4Power
If the clutch is used to interconnect spools, then power transmission is improved, but reliability may be reduced due to potential failure points
Solution Approach 1:
The clutch is designed to be dynamically controllable, allowing the system to engage or disengage based on operating conditions. During normal operation, the clutch transmits power between spools. During startup and relight operations, the controller can manage clutch engagement timing to optimize power transmission while minimizing stress on the clutch, thereby maintaining reliability.
Solution Approach 2:
The controller performs preliminary simultaneous operation of both motors to accelerate both spools before the clutch engages during power transmission. This preliminary cushioning action reduces the mechanical shock and stress on the clutch by ensuring both spools are already rotating at appropriate speeds, thereby protecting the clutch from excessive wear and potential failure.
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 hybrid electric configuration facilitates faster and more reliable engine startups and relights, expanding the relight envelope and allowing simultaneous left and right engine starts, and includes a redundant system for backup power.
Implementation Method 1
an electric motor coupled to the low-speed spool for propulsive power
Implementation Method 2
an accessory gearbox and starter motor connected to the high-speed spool
Implementation Method 3
a clutch to interconnect both spools, reducing inertial lag
Data Source
AI summary
A gas turbine engine includes a turbomachine comprising a low pressure (LP) spool and a high pressure (HP) spool that rotate about a central axis, an electric motor mechanically coupled to the LP spool for selectively rotating the LP spool, a starter assembly mechanically coupled to the HIP spool for selectively rotating the HP spool, and a controller in operative communication with the electric motor and the starter assembly, the controller being configured to operate the electric motor to rotate the LP spool and operate the starter assembly to rotate the HIP spool during engine startup.