Hypersonic Window Cooling with Throttled Two-Phase Flow
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Solution Overview
Problem
Current window materials for hypersonic vehicles face challenges in surviving extreme temperatures and maintaining electromagnetic transparency, leading to performance degradation due to thermal issues and structural limitations, especially in high-speed flight environments where heat fluxes and pressure variations cause significant problems.
Innovation Solution
The implementation of internally cooled windows using two-phase flow in channels with hydraulic diameters less than 0.118 inches, combined with throttling devices to manage pressure drops and flow stability, allows for uniform temperature maintenance and reduced mass flow rates, while the passage design can be optimized for non-transmissivity in IR sensors and adjustable transmissivity in RF sensors to enhance performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If window materials are used for hypersonic vehicles, then electromagnetic transparency is achieved, but thermal survival capability deteriorates under extreme temperatures
Solution Approach 1:
The window assembly is segmented into multiple functional layers: an outer window layer for electromagnetic transparency, an intermediate cooling layer with internal passages, and an inner window layer. This segmentation allows each layer to perform its specific function without compromising the others, enabling the window to maintain electromagnetic transparency while surviving extreme temperatures through active cooling.
Solution Approach 2:
A cooling fluid (intermediary substance) is introduced into internal passages within the window assembly to act as a thermal mediator. The coolant absorbs heat from the window structure and transports it away, preventing thermal degradation while maintaining the window's electromagnetic transparency. This intermediary cooling mechanism resolves the contradiction between thermal survival and electromagnetic functionality.
2Temperature
If cooling passages are added to the window assembly, then thermal control capability is improved, but device complexity increases
Solution Approach 1:
The cooling passages are merged directly into the window assembly structure itself, rather than being separate external components. The intermediate layer incorporates internal passages that are integral to the window's construction, combining the structural and thermal management functions into a single integrated assembly. This reduces overall device complexity while maintaining effective thermal control.
Solution Approach 2:
The intermediate layer serves multiple functions simultaneously: it provides structural support, contains the cooling passages for thermal management, and facilitates heat transfer. This multi-functionality reduces the need for separate dedicated cooling components, thereby improving thermal control capability without proportionally increasing device complexity.
3Temperature
If internal cooling passages are implemented, then heat transfer efficiency is improved, but manufacturing difficulty increases
Solution Approach 1:
The cooling passages are formed within the intermediate layer during the manufacturing process itself, before final assembly. Molds or mandrels are used to create the passage structures upfront, allowing coolant channels to be integrated into the window assembly in a single manufacturing step. This preliminary formation of cooling passages improves heat transfer efficiency without requiring complex post-manufacturing operations.
Solution Approach 2:
The intermediate layer is designed with a porous or cellular structure that inherently provides cooling pathways. This porous architecture naturally facilitates heat transfer through capillary action and increased surface area, achieving high heat transfer efficiency while using standard manufacturing techniques for creating porous materials, thereby reducing manufacturing difficulty.
4Stability of the object's composition
If throttling devices are added to manage pressure drops, then flow stability is improved, but device complexity increases
Solution Approach 1:
Throttling features are implemented locally at specific positions within the cooling passages, such as at entrances or critical flow sections, rather than requiring system-wide control mechanisms. These localized throttling elements (such as restricted openings or constricted passages) provide flow stability where most needed while keeping the rest of the system simple, thus improving flow stability without proportionally increasing overall device complexity.
Solution Approach 2:
The cooling passage design incorporates self-regulating throttling features that automatically adjust flow characteristics based on local pressure and temperature conditions. For example, variable area passages or elastic seals that respond to thermal expansion provide flow stability without requiring external control systems, improving flow stability while avoiding additional complexity from active control mechanisms.
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 solution effectively maintains window integrity and electromagnetic transparency under extreme conditions, reducing thermal distortion and pressure variations, and allows for smaller system size with improved heat transfer coefficients, thereby enhancing the performance and durability of hypersonic vehicle windows.
Implementation Method 1
The throttling device may be a porous medium through which the coolant flows
Implementation Method 2
The coolant may flow through the passages in a two-phase flow regime
Implementation Method 3
maintain a uniform temperature across the window
Data Source
AI summary
A window assembly heat transfer system is disclosed in which a window member has a selected transparency to monitored or sensed electromagnetic wavelengths. One or more passages are provided in the window member for flowing a single-phase or two-phase heat transfer fluid. A mechanism allows either evaporation or condensation of the fluid and/or balancing of a flow of the fluid within the passages. In one embodiment, the window assembly can be made by producing passages in a top surface of a first single plate, optionally producing passages in a bottom surface of a second single plate and bonding the top surface of the first plate to a bottom surface of a second single plate to form the window member with the passage or passages. In another embodiment, the window assembly can be made by providing a core around which the window member material is grown and thereafter removing the core to produce the passage or passages.