Three-Stream Gas Turbine Nozzle Mixing for Lower Jet Noise
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Solution Overview
Problem
Conventional gas turbine engine designs face challenges in achieving high propulsive efficiency while managing noise emissions and thermal demands, particularly with larger fan diameters that increase installation difficulties and weight, and require improved packaging and weight management.
Innovation Solution
A three-stream gas turbine engine design incorporating a primary and secondary fan with a third stream airflow through chevrons at the exhaust nozzle, promoting jet exhaust mixing to reduce noise and enhance propulsive efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a core exhaust nozzle is used for independently discharging core exhaust gases from a concentric fan exhaust nozzle, then thrust is produced, but substantial noise is generated along the take-off path
Solution Approach 1:
The patent merges the core exhaust stream and fan exhaust stream into a common exhaust nozzle, allowing the two high-velocity jets to mix and discharge together. This combining of separate exhaust flows reduces noise by eliminating the interaction between separate high-velocity jets and reducing jet mixing noise, while still producing the required thrust through the combined momentum of the mixed exhaust gases.
2Power
If larger fan diameters are used to improve propulsive efficiency, then propulsive efficiency is improved, but installation difficulties and weight increase
Solution Approach 1:
The patent changes the exhaust flow parameters by combining core and fan streams in a common nozzle, optimizing the exhaust velocity and mass flow distribution. This allows the engine to achieve high propulsive efficiency without requiring excessively large fan diameters, as the improved exhaust mixing and momentum distribution compensates for the reduced fan size, thereby reducing overall engine weight.
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 design maintains or improves propulsive efficiency, reduces jet noise, and addresses packaging and thermal management concerns, resulting in a quieter and more efficient engine operation.
Implementation Method 1
A three-stream gas turbine engine design incorporating a primary and secondary fan with a third stream airflow through chevrons at the exhaust nozzle, promoting jet exhaust mixing to reduce noise and enhance propulsive efficiency
Data Source
AI summary
A gas turbine engine includes a turbomachine defining an engine inlet to an inlet duct, a fan duct inlet to a fan duct, and a core inlet to a core duct; a primary fan driven by the turbomachine; and a secondary fan located downstream of the primary fan within the inlet duct. The gas turbine engine defines a thrust to power airflow ratio between 3.5 and 100 and a core bypass ratio between 0.1 and 10. The thrust to power airflow ratio is a ratio of airflow through a bypass passage over the turbomachine plus airflow through the fan duct to airflow through the core duct. The core bypass ratio is a ratio of airflow through the fan duct to airflow through the core duct. The fan duct includes an exhaust nozzle having a plurality of chevrons disposed at its aft end to define an exhaust outlet.