Variable Exhaust Nozzle Dynamics for Noise and Efficiency Trade-offs
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Solution Overview
Problem
Gas turbine engines face challenges in optimizing exhaust nozzle designs for both low noise emissions during take-off and increased efficiency at higher altitudes, as existing nozzles either compromise on noise or efficiency depending on their shape and configuration.
Innovation Solution
A variable exhaust nozzle system comprising an inner plug and an outer shroud, actuated by a controller, which can change its shape from convergent to convergent-divergent configurations to optimize mass flow and thrust, allowing for noise reduction during take-off and efficiency enhancement at cruise modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a convergent exhaust nozzle shape is used, then noise emissions are reduced during take-off, but engine efficiency decreases at higher altitudes
Solution Approach 1:
The exhaust nozzle is designed with movable components (inner plug and outer shroud) that can dynamically change the nozzle geometry between convergent and convergent-divergent configurations based on flight conditions. The actuator controller adjusts the position of these components to optimize performance for specific operating regimes, resolving the contradiction between noise reduction and efficiency.
Solution Approach 2:
The nozzle design allows changing geometric parameters (area distribution, throat location, divergence angle) through movable components. By adjusting the position of the inner plug relative to the outer shroud, the system can modify the effective nozzle area and shape parameters to match different flight conditions, thereby optimizing both noise and efficiency performance.
2Productivity
If a convergent-divergent exhaust nozzle shape is used, then engine efficiency increases at higher altitudes, but noise emissions increase during take-off
Solution Approach 1:
The system uses movable inner plug and outer shroud components that can be repositioned to change the nozzle from convergent-divergent to convergent configuration. This dynamic adaptability allows the engine to achieve high efficiency at altitude when needed while reducing noise during take-off operations, resolving the trade-off between these two performance parameters.
Solution Approach 2:
The design enables changing the nozzle area distribution parameters by adjusting component positions. The effective throat area, divergence angle, and overall nozzle shape can be modified to optimize for either efficiency or noise reduction depending on the operational requirements, thus resolving the contradiction.
3Quantity of substance
If the exhaust nozzle throat area is increased, then mass flow of exhaust air increases, but overall velocity of exhaust air decreases
Solution Approach 1:
The movable inner plug and outer shroud allow dynamic adjustment of the nozzle throat area and downstream geometry. The system can optimize the balance between mass flow and velocity by changing the effective area distribution, enabling higher mass flow when needed while maintaining adequate velocity for thrust and noise control.
Solution Approach 2:
The design permits changing the throat area parameter and velocity parameter independently by adjusting the position of movable components. This allows optimization of the mass flow-velocity trade-off by selecting appropriate geometric parameters for different operating conditions.
4Speed
If the exhaust nozzle throat area is decreased, then overall velocity of exhaust air increases, but mass flow of exhaust air decreases
Solution Approach 1:
The system uses adjustable components to dynamically change the nozzle geometry. By moving the inner plug and outer shroud to different positions, the system can optimize the balance between velocity and mass flow, achieving higher velocity when needed while maintaining adequate mass flow for engine performance.
Solution Approach 2:
The design enables independent adjustment of velocity and mass flow parameters through movable components. The throat area and downstream geometry can be modified to optimize the velocity-mass flow trade-off according to operational requirements.
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 variable exhaust nozzle system effectively reduces noise emissions during take-off while improving engine efficiency at higher altitudes by dynamically adjusting its shape to accommodate different flight conditions, thus meeting stringent noise requirements and enhancing performance.
Implementation Method 1
Subsonic exhaust nozzles typically have a convergent shape which causes expansion of the gases to atmospheric pressure downstream of the exhaust nozzle. This creates some thrust from the imbalance of the static pressure at the throat of the exhaust and the atmospheric pressure.
Implementation Method 2
The convergent section of the exhaust nozzle may be sized to choke the flow so that the flow is sonic at the throat.
Data Source
AI summary
A variable exhaust nozzle for a gas turbine engine includes an outer shroud and an inner plug. The outer shroud is arranged circumferentially about an axis. The inner plug extends along the axis and is at least partially located within the outer shroud. At least one of the outer shroud and the inner plug are movable selectively to cause a variable area region of the variable exhaust nozzle to change.