Jet Engine Variable Nozzle Pin with Convex Bearing Surfaces
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Solution Overview
Problem
Variable section nozzles in jet engines experience wear on pin bearing surfaces due to aerodynamic loads, vibrations, and temperature variations, leading to reduced contact surfaces, high stresses, and premature pin failure, necessitating frequent replacements and increasing maintenance costs.
Innovation Solution
The pin and its associated bores are designed with convex surfaces to maintain distributed contact, allowing the pin to bend while maintaining constant contact surfaces, either through convex bearing surfaces on the pin or inner convex bushings in the bores, preventing edge contact and stress concentration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the pin diameter is increased to strengthen it and prevent wear, then the pin strength and wear resistance are improved, but the weight of the jet engine increases
Solution Approach 1:
The invention applies different geometric properties to different parts of the pin. The bearing surfaces are made convex (spherical or conical) to distribute contact stresses, while the shaft portion remains cylindrical for rotational function. This localized differentiation allows the pin to withstand high stresses without requiring an overall increase in diameter, thus avoiding weight increase.
Solution Approach 2:
The invention introduces convex (spherical or conical) surfaces at the bearing areas of the pin instead of flat cylindrical surfaces. This curvature allows the pin to maintain contact over an area rather than at a point or line, distributing stresses and reducing wear. The convex surfaces act as stress-distributing elements that prevent coating stripping and extend pin lifetime without increasing overall pin dimensions.
2Ease of manufacture
If the pin bearing surfaces are made cylindrical for simple manufacturing, then the manufacturing ease is improved, but the contact surface distribution deteriorates under bending loads causing edge contact and high stresses
Solution Approach 1:
The invention replaces the cylindrical bearing surfaces with convex (spherical or conical) surfaces. This geometric change ensures that under bending loads, the contact occurs over a distributed area on the convex surface rather than concentrating at sharp edges. The curved geometry naturally adapts to bending moments while maintaining uniform stress distribution.
Solution Approach 2:
The invention applies convex surfaces specifically at the bearing contact zones while keeping the shaft portion cylindrical. This localized application of non-cylindrical geometry provides the stress-distribution benefit where needed (at bearing surfaces) without complicating the overall manufacturing process, as only specific zones require precision convex surfacing.
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 design extends the lifespan of the pin, reduces the risk of nozzle seizing, and lowers maintenance and manufacturing costs by ensuring continuous stress distribution and eliminating the need for protective coatings.
Implementation Method 1
the pin, the bores of the braces and the bores of the fasteners are arranged so that the contacts between the pin with the bore walls of the braces and with the bore walls of the fasteners are made over convex surfaces
Data Source
AI summary
The jet engine of the invention comprises an exhaust nozzle of variable section, comprising at least one flap pivot mounted about a pin, the pin being joined to the fixed structure of the jet engine via two braces each comprising a bore for housing the pin, the flap being pivot commanded by an actuating cylinder, connected to two fasteners which each comprise a bore through which the pin passes and about which they rotate. The jet engine is characterized by the fact that the pin, the bores of the braces and bores of the fasteners are arranged so that the contacts between the pin with the bore walls of the braces and with the bore walls of the fasteners are made over convex surfaces. Therefore, when in operation, in the event of pin bending the contact surfaces follow this convex shape and are suitably distributed.