Variable Area Nozzle for Gas Turbine Engine Restart
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Gas turbine engines face challenges in restarting during flight due to insufficient airflow at certain altitudes and airspeeds, requiring rapid adjustments or reliance on starter-assistance, which may not always ensure successful ignition.
Innovation Solution
A turbofan engine restarting system that dynamically adjusts the effective nozzle exit area using flaps controlled by a controller, in conjunction with a starter to increase rotational speed and airflow, allowing for engine restarts within a broader range of flight conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the rotational speed of the fan section is increased using starter-assistance, then the airflow supply to the engine is augmented, but the device complexity and reliability are compromised due to dependence on additional starting equipment
Solution Approach 1:
The nozzle effective area is made variable rather than fixed, allowing dynamic adjustment during engine operation. The nozzle area control system modifies the bypass flow path area to optimize airflow distribution between core and bypass flows, enabling engine restart without starter-assistance by creating favorable flow conditions through geometric adjustment
Solution Approach 2:
The physical parameter of nozzle effective area is changed to alter the airflow characteristics. By adjusting the nozzle area, the system changes the mass flow rate distribution, enabling sufficient airflow for combustion support during restart conditions without requiring additional starting equipment
2Quantity of substance
If the rotational speed of the fan section is increased to generate adequate airflow, then combustion support is improved, but the loss of time increases due to rapid aircraft adjustments required
Solution Approach 1:
The nozzle area is adjusted in advance of the restart attempt to pre-establish favorable airflow conditions. By modifying the nozzle effective area before ignition is attempted, the system prepares the flow path to deliver adequate air to the combustor, eliminating the need for time-consuming altitude or airspeed changes
Solution Approach 2:
The nozzle area parameter is dynamically changed to directly control airflow delivery. This parameter adjustment provides immediate airflow modification without requiring changes in aircraft flight conditions, thereby reducing the time loss associated with altitude or airspeed adjustments
3Quantity of substance
If the nozzle effective area is increased to increase mass flow rate, then the airflow supply is improved, but the area of the bypass flow path is reduced
Solution Approach 1:
The nozzle effective area is dynamically adjusted based on operational requirements. During restart conditions, the nozzle area is increased to maximize mass flow rate to the combustor. The system accepts temporary reduction in bypass flow path area as a trade-off for achieving sufficient airflow for ignition, with the understanding that bypass flow can be restored after restart
Data Source
AI summary
An example turbofan engine starting system includes a core nacelle housing a compressor and a turbine. The core nacelle is disposed within a fan nacelle. The fan nacelle includes a turbofan. A bypass flow path downstream from the turbofan is arranged between the two nacelles. A controller is programmed to manipulate the nozzle exit area to facilitate startup of the engine. In one example, manipulates the nozzle exit area using nozzles, in response to an engine shutdown condition. The nozzles open and close to adjust the nozzle exit area.