Scarfed Jet Engine Exhaust Nozzle for Thrust Vectoring
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Solution Overview
Problem
Current jet engine exhaust systems face challenges in optimizing thrust vector direction and aerodynamic efficiency across varying nozzle pressure ratios and flight conditions, leading to suboptimal take-off stability and high-speed cruise performance.
Innovation Solution
The design incorporates a curved exhaust duct with a scarfed exhaust nozzle that follows a concave or planar bounding surface, allowing the exhaust stream to deflect automatically in response to nozzle pressure ratio changes, aligning the thrust vector closer to the aircraft's center of gravity during take-off and parallel to the flight path during high-speed cruise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a conventional straight exhaust nozzle is used, then the structure is simple and easy to manufacture, but the thrust vector cannot be automatically aligned with the center of gravity during take-off, resulting in poor take-off stability
Solution Approach 1:
The exhaust nozzle is designed with an asymmetric scarfed configuration where the trailing edge is angled relative to the exhaust flow direction. This asymmetric geometry causes the exhaust stream to deflect toward the center of gravity during take-off conditions, automatically providing stability without complex active control systems
Solution Approach 2:
The scarfed nozzle trailing edge incorporates a curved or angled surface rather than a straight edge, creating a bounded surface that guides the exhaust flow in a specific direction. This curved geometry enables automatic thrust vector alignment with the center of gravity during take-off
2Stability of the object's composition
If the exhaust nozzle is designed to align thrust with the center of gravity during take-off, then take-off stability improves, but aerodynamic drag increases during high-speed cruise
Solution Approach 1:
The scarfed nozzle design creates a dynamic system where the effective thrust vector direction changes with operating conditions. During take-off at lower speeds, the scarfed geometry deflects exhaust toward the center of gravity for stability. During high-speed cruise, the exhaust flow naturally aligns with the flight path, minimizing drag automatically
Solution Approach 2:
The nozzle geometry is designed to respond to changes in exhaust flow parameters (pressure, velocity) that occur with different flight conditions. The scarfed trailing edge creates different flow patterns at different operating points, automatically optimizing performance for both take-off and cruise
3Stability of the object's composition
If the exhaust nozzle deflects the thrust vector away from the flight path during cruise, then take-off stability improves, but fuel economy deteriorates
Solution Approach 1:
The scarfed nozzle creates a dynamic thrust vectoring system that automatically adjusts with flight conditions. During cruise, the exhaust flow naturally aligns with the flight path through the scarfed geometry, maximizing propulsive efficiency and fuel economy while maintaining the same structure that provides take-off stability
4Adaptability or versatility
If a scarfed exhaust nozzle following a concave bounding surface is used, then the thrust vector automatically aligns with flight conditions, but manufacturing complexity increases
Solution Approach 1:
The scarfed nozzle employs an asymmetric trailing edge configuration that is relatively simple to manufacture compared to complex curved surfaces. The asymmetric cut provides sufficient flow direction control while maintaining manufacturing feasibility
Solution Approach 2:
The concave bounding surface of the scarfed nozzle is designed with moderate curvature that balances aerodynamic performance with manufacturability. The curvature is sufficient to guide the exhaust flow appropriately but not so complex as to make manufacturing prohibitively difficult
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
This configuration enhances take-off stability, reduces the need for elevator and trim deflections, improves fuel economy, and minimizes aerodynamic drag by adjusting the thrust vector direction in response to changing flight conditions.
Implementation Method 1
a stream of exhaust gas is ejected in a first direction from a nozzle operatively coupled to or a part of a jet engine attached to a jet engine aircraft at a location that is offset from a center of gravity of the jet engine aircraft relative to a central longitudinal axis of the jet engine aircraft through the center of gravity
Data Source
AI summary
A first trailing edge portion of a scarfed jet engine exhaust nozzle aft of a second trailing edge portion relative to a central axis of an associated exhaust duct causes an automatic nozzle-pressure-ratio responsive transverse deflection of the associated exhaust flow away from the first trailing edge portion. When offset from both the center of gravity (CG) and the central longitudinal axis of an aircraft, at a relatively low nozzle pressure ratio, e.g. during takeoff, the thrust vector from the exhaust flow acts relatively close to the CG, whereas at a relatively high nozzle pressure ratio, e.g. during relatively high-speed cruise, the scarfed exhaust nozzle deflects the exhaust flow so that the resulting thrust vector is relatively parallel to the path of the aircraft. With the final portion of the exhaust duct skewed, the primary axis of the jet engine can be relatively parallel to the path of the aircraft.