Propeller Needle Valve Thermal Insulation via Ceramic Intermediate
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Solution Overview
Problem
Existing thruster designs face challenges in thermal insulation and mechanical integrity due to the high temperatures and thermal conductivity of materials used in the needle and attachment system, which are subjected to extreme heat and mechanical stress during combustion, leading to potential degradation and failure.
Innovation Solution
Incorporating a ceramic intermediate part with thermal insulating properties between the needle and the attachment system, featuring a frustoconical contact surface to reduce thermal conduction and mechanical stress, and optionally including an elastic joint to manage differential expansion, thereby enhancing thermal insulation and mechanical resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a needle made of thermally conductive material is used to control thrust, then the needle can effectively vary the neck section and control combustion pressure, but the needle and attachment system are subjected to extremely high temperatures (above 2000 K) that compromise their integrity
Solution Approach 1:
A ceramic intermediate part is introduced between the metal needle and the attachment system. This intermediate part acts as a thermal barrier, protecting the attachment system from the extreme heat conducted through the needle. The ceramic material has low thermal conductivity, thereby reducing heat transfer to the attachment system while allowing the needle to maintain its thrust control function.
Solution Approach 2:
The attachment system is constructed as a composite structure combining metal components (for mechanical strength and movement) with ceramic components (for thermal insulation). This composite design allows the system to simultaneously withstand mechanical stresses required for needle actuation and thermal stresses from high-temperature combustion gases.
2Device complexity
If the needle is directly connected to the attachment system, then the structure is simple, but the thermal conduction through the thermally conductive needle material causes the attachment system to degrade under extreme heat
Solution Approach 1:
The ceramic intermediate part serves as a thermal mediator that breaks the direct thermal conduction path between the hot needle and the attachment system. While this adds a component to the structure, it significantly improves reliability by preventing thermal degradation of the attachment system.
3Temperature
If the intermediate part is made of ceramic material for thermal insulation, then thermal insulation performance is excellent, but the material must withstand significant mechanical shocks during rapid needle movement
Solution Approach 1:
The intermediate part is designed as a composite structure combining ceramic materials (for thermal insulation) with metallic or polymeric materials (for mechanical strength and shock resistance). This composite construction allows the intermediate part to simultaneously provide excellent thermal barrier properties and withstand the mechanical shocks experienced during rapid needle actuation.
4Ease of manufacture
If the contact surface between the needle and intermediate part is flat, then manufacturing is simple, but thermal conduction and mechanical stress concentration occur at the interface
Solution Approach 1:
The contact surface between the needle and the intermediate part is designed with a frustoconical (truncated conical) shape rather than a flat surface. This curved geometry reduces stress concentration at the interface and distributes thermal and mechanical loads more evenly, improving both thermal management and mechanical durability.
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 solution effectively maintains the integrity of the thruster components by providing excellent thermal insulation and mechanical resistance, allowing operation at temperatures above 2000 K and withstanding significant mechanical shocks, while reducing internal stresses and inert mass.
Implementation Method 1
an intermediate part positioned between the needle and the attachment system, intended to thermally insulate the attachment system of the needle, and at least part of the intermediate part is made of a material having thermal insulating characteristics, of the ceramic type
Data Source
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Figure 5
AI summary
A propulsion system with a thermally stressed connection comprises a combustion chamber (11) for receiving a propellant charge (12), a nozzle assembly (13) consisting of one or more nozzles through which the expansion of combustion gases from the propellant charge (12) occurs after ignition of the propellant charge (12), a needle valve (14) for varying a cross-section (15) of a throat of the nozzle assembly (13), which is thermally stressed by the combustion gases, a mounting system (16) for moving the needle valve (14) within the throat of the nozzle assembly (13), and an intermediate piece (17) positioned between the needle valve (14) and the mounting system (16), designed to thermally insulate the mounting system (16) from the needle valve (14). At least a portion of the intermediate piece is made of a material with thermally insulating properties, such as a ceramic.The intermediate piece (17) at least partially encloses the needle (14), a part of the needle (14) extends longitudinally along a first axis Z, a portion of the part of the needle (14) extending longitudinally along the first axis Z forms a contact surface (18) with the intermediate piece (17), the normal (19) to the contact surface (18) is secant with the first axis Z, and the contact surface (18) is frustoconical in shape.