Hybrid Combustor Bypass Modulation for Idle Lean Blow-Out
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Solution Overview
Problem
Hybrid propulsion systems face challenges in managing events like rapid transients and thermal-mechanical stress due to separate control laws for gas turbine and electric power, and the engine idle condition impacts fuel efficiency, particularly with lean blow-out issues in gas turbine combustors.
Innovation Solution
A hybrid propulsion system with a gas turbine engine and a motor that includes a flow modulation device to control combustor bypass air flow, allowing the controller to adjust fuel-air ratios based on operational modes and supplemental power applied to the high speed spool, thereby modulating the combustor bypass air flow to prevent lean blow-out during idle operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If motor power is added to the high speed spool during idle operation, then rotational power is augmented, but fuel-air ratio is driven down causing lean blow-out of the combustor
Solution Approach 1:
A flow modulation device is introduced as an intermediary component to control combustor bypass air flow. This device mediates between the motor power addition and combustor stability by regulating the amount of bypass air that mixes with combustion gases, preventing lean blow-out while allowing motor augmentation of the high speed spool during idle operation
Solution Approach 2:
The system changes the parameter of bypass air flow rate through the flow modulation device. By dynamically adjusting this parameter based on operational mode and motor power level, the system maintains optimal fuel-air ratio in the combustor even when motor power is added during idle, thus preventing lean blow-out while enabling power augmentation
2Adaptability or versatility
If separate control laws are used for gas turbine and electric power, then each system can be controlled independently, but challenges in managing rapid transients and thermal-mechanical stress increase
Solution Approach 1:
The control system merges gas turbine control and electric power control into a unified control architecture. The controller integrates commands from both systems and coordinates their interaction, particularly during transient conditions, reducing control complexity while maintaining independent adaptability of each power source
Solution Approach 2:
The control system implements feedback mechanisms that monitor system state and automatically adjust control parameters. This feedback loop manages the interaction between gas turbine and electric power systems, handling rapid transients and thermal-mechanical stress by coordinating power delivery based on real-time system conditions
3Reliability
If combustor bypass air flow is increased to prevent lean blow-out, then combustor stability is improved, but fuel efficiency during idle operation deteriorates
Solution Approach 1:
The flow modulation device dynamically adjusts bypass air flow based on real-time operational conditions, particularly motor power level and throttle position. During idle with motor augmentation, it provides minimal bypass flow sufficient to prevent lean blow-out. During transient conditions or higher power demands, it increases bypass flow to maintain combustor stability, optimizing the trade-off between stability and fuel efficiency across different operating modes
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 solution effectively manages idle operation in hybrid propulsion systems by optimizing fuel-air ratios and preventing lean blow-out, enhancing fuel efficiency and reducing thermal stress, thus improving overall system performance.
Implementation Method 1
a flow modulation device configured to control a combustor bypass air flow around the combustor to the turbine section
Implementation Method 2
a motor configured to augment rotational power of the high speed spool
Implementation Method 3
adjust a fuel-air ratio at the combustor based on modulation of the combustor bypass air flow and the supplemental power applied to the high speed spool
Data Source
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AI summary
A hybrid propulsion system (100) includes a gas turbine engine (20) having a low speed spool, a high speed spool (32), and a combustor (56). The low speed spool (30) includes a low pressure compressor (44) and a low pressure turbine (46), and the high speed spool includes a high pressure compressor (52) and a high pressure turbine (54). The hybrid propulsion system also includes a motor (212B) configured to augment rotational power of the high speed spool, a flow modulation device (226) configured to control a combustor bypass air flow (230) around the combustor (56) to the turbine section (28), and a controller (256). The controller (256) is operable to determine a mode of operation, apply supplemental power to the high speed spool using the motor, modulate the combustor bypass air flow using the flow modulation device, and adjust a fuel-air ratio (410) at the combustor based on modulation of the combustor bypass air flow and the supplemental power applied to the high speed spool.