Thermal Gradient on Hybrid Composite Propellant Tank Materials at Cryogenic Temperatures

2016 ◽  
Author(s):  
Raudel O. Avila ◽  
Md S. Islam ◽  
Pavana Prabhakar
Keyword(s):  
Thermal Gradient ◽  
Computational Models ◽  
Hybrid Composites ◽  
Textile Composites ◽  
Liquid Oxygen ◽  
Large Temperature ◽  
Cryogenic Temperatures ◽  
Composite Wall ◽  
Propellant Tank ◽  
Combustible Liquids

Cryogenic tanks are devices that are commonly used to store extremely low temperature fluids, usually in their liquid state. Cryogenic fuel tanks carry cryogenic propellants such as liquid oxygen, liquid methane or liquid hydrogen, at subfreezing temperatures in its condensed form in order to generate highly combustible liquids. This type of tank is exposed to an extremely cold temperature in its interior and to ambient temperature on its external surface resulting in large temperature gradient across the thickness of the wall. In this paper, hybrid textile composites with carbon and Kevlar® fabric are explored as means to reduce the influence of thermal gradient in order to enhance the material performance when cryogenic propellant fuels are stored in spacecraft applications. Previous initial studies of tensile and flexural tests have indicated that carbon and Kevlar® textile composites are suitable materials for cryogenic temperatures. The pristine mechanical properties of carbon composites changed within a maximum of 3–4% after initial cryogenic exposure during the fueling stage, while 17% for Kevlar® composites. Computational models of hybrid carbon-Kevlar® composites were subjected to cryogenic temperature (77 K) to investigate the effect of exposure for extended periods and to aid in the design of optimum layups for the same. Six optimal combinations were selected that resulted in low interface stresses and lower number of peak stresses through the thickness of the laminate. These layups were deduced to perform better compared to other layups due to lesser susceptibility to delamination type failure upon cryogenic exposure. Experimental investigation of the chosen hybrid composites has revealed few optimum combinations for use in tanks. As a next step, computational analysis of cryogenic exposure to only one surface of hybrid composites was performed to simulate the composite wall containing the liquid fuel. Based on the suggestions from the computational models, experiments to determine optimum designs of the composite wall were conducted. An ABS plastic insulating holder was computationally designed and 3D printed to hold the specimens such that only one surface is exposed to LN2. A total of eight composite layups were exposed to liquid nitrogen using the plastic holder to study their response to thermal gradient cryogenic exposure. Based on the results obtained computationally and supported by experiments, optimum hybrid layups of composites to sustain cryogenic exposure were determined.

Thermo-structural analysis of cryogenic tanks with common bulkhead configuration

2021 ◽  
pp. 095441002110247
Author(s):  
S Sumith ◽  
R Ramesh Kumar
Keyword(s):  
Structural Analysis ◽  
Temperature Gradient ◽  
Thermal Gradient ◽  
Load Transfer ◽  
Thermal Analyses ◽  
Positive Margin ◽  
Heat Transfer Analysis ◽  
Liquid Oxygen ◽  
Launch Vehicles ◽  
Element Analysis

In launch vehicles, cryogenic propulsion stages store liquid oxygen (LOX) at 76 K and liquid hydrogen (LH2) at 20 K, generally in two separate insulated tanks connected through tubular truss components. Consequently, load transfer from the LH2 tank to the LOX tank is very much localized, resulting in a nonoptimal design. This article presents an alternative single tankage design using a common bulkhead (CBH) to enhance the payload capability, which enables maintaining LH2 temperature within a specified temperature when exposed to a temperature gradient. A sandwich insulator using aramid honeycomb embedded with polyimide foam keeps the LH2 temperature within 20 ± 1 K is proposed, based on transient heat transfer analysis for 1000 s. The foam-filled honeycomb core is treated as equivalent foam in the analysis as the thermal conductivity of the core and the foam is quite close. The efficacy of the insulator is established by an experiment to measure the back wall temperature when liquid nitrogen is loaded on the top skin of the panel, and the insulator maintains a temperature gradient of 123 K for 1000 s. A good agreement is obtained between the transient finite element analysis results with experimental data. An externally insulated LOX tank configuration with an optimum length of the skirt–cylinder where the temperature reaches 80 K is arrived at based on slosh, buckling, and thermal analyses. No thermal gradient is found across the thickness of the skirt, while the thermal gradient is observed along the length of the skirt as anticipated. An integrated thermo-structural analysis of the cryo-system is carried out considering temperature-dependent material properties. A positive margin for the skirt is obtained. A payload gain of 366 kg is estimated based on the present study for the new design option with a CBH and skirt as compared to the traditional tubular truss arrangements.

Analysis and Test of a Robust Sector Thrust Bearing for a Cryogenic Turboalternator

2001 ◽  
Vol 123 (4) ◽  
pp. 768-776
Author(s):  
G. F. Nellis ◽  
M. V. Zagarola ◽  
H. Sixsmith
Keyword(s):  
Thrust Bearing ◽  
Large Temperature ◽  
Cryogenic Temperatures ◽  
Inertial Effects ◽  
Test Results ◽  
Viscous Effects ◽  
Reliable Operation ◽  
Restoring Force ◽  
Thrust Bearings ◽  
Leakage Flows

The miniature turboalternator associated with a reverse-Brayton cryocooler requires geometrically simple, self-acting thrust bearings capable of reliable operation over a large temperature range and insensitive to secondary leakage flows. In order to meet this need, a robust sector thrust bearing has been developed. This thrust bearing is different from a classic stepped sector thrust bearing in that the restoring force at cryogenic temperatures originates primarily from inertial effects while at higher temperatures its restoring force is related primarily to viscous effects. This paper describes the analysis and initial test results for a prototypical robust sector thrust bearing.

scholarly journals Energy Harvesting Using Thermocouple and Compressed Air

Sensors ◽  
2021 ◽  
Vol 21 (18) ◽  
pp. 6031
Author(s):  
Robert Bayer ◽  
Jiří Maxa ◽  
Pavla Šabacká
Keyword(s):  
Gas Flow ◽  
Temperature Drop ◽  
Compressed Air ◽  
Large Temperature ◽  
Physical Analysis ◽  
Cryogenic Temperatures ◽  
Head Shape ◽  
Available Energy ◽  
Thermoelectric Voltage ◽  
Gas Expansion

In this paper, we describe the possibility of using the energy of a compressed air flow, where cryogenic temperatures are achieved within the flow behind the nozzle, when reaching a critical flow in order to maximize the energy gained. Compared to the energy of compressed air, the energy obtained thermoelectrically is negligible, but not zero. We are therefore primarily aiming to maximize the use of available energy sources. Behind the aperture separating regions with a pressure difference of several atmospheres, a supersonic flow with a large temperature drop develops. Based on the Seebeck effect, a thermocouple is placed in these low temperatures to create a thermoelectric voltage. This paper contains a mathematical-physical analysis for proper nozzle design, controlled gas expansion and ideal placement of a thermocouple within the flow for best utilization of the low temperature before a shockwave formation. If the gas flow passes through a perpendicular shockwave, the velocity drops sharply and the gas pressure rises, thereby increasing the temperature. In contrast, with a conical shockwave, such dramatic changes do not occur and the cooling effect is not impaired. This article also contains analyses for proper forming of the head shape of the thermocouple to avoid the formation of a detached shockwave, which causes temperature stagnation resulting in lower thermocouple cooling efficiency.

Design and Manufacture of Liquid Oxygen Propellant Tank for University Rocket

2017 ◽  
Author(s):  
Neil Benkelman ◽  
Russell Berger ◽  
Alex Farias ◽  
Francesca Frattaroli ◽  
Weldon Peterson ◽  
...  
Keyword(s):  
Liquid Oxygen ◽  
Propellant Tank ◽  
Design And Manufacture

Investigations of Thermal Stresses and Deformations in Laser Microwelding Processes

Manufacturing ◽  
2003 ◽  
Author(s):  
Wei Han ◽  
Ryszard J. Pryputniewicz
Keyword(s):  
Laser Welding ◽  
Heat Affected Zone ◽  
Computational Models ◽  
Thermal Stresses ◽  
Contact Process ◽  
High Stress ◽  
Weld Strength ◽  
Large Temperature ◽  
Machining Processes ◽  
Laser Microwelding

Laser microwelding has become a significant industrial process, because there are many outstanding advantages in using laser welding as the bonding method over other widely used bonding technologies. As an alternative to the common adhesives or solders used for the joining process, laser welding offers a number of attractive features such as high weld strength to weld size ratio, reliability, and a minimal heat-affected zone (HAZ). These provide the benefits of low heat distortion, a non-contact process, repeatability, and ability to automate. Therefore, the applications of laser microwelding have been broadened, especially in the microelectronic and packaging industry, in recent past decades. Quality of the laser microwelding, however, depends on a number of parameters such as the characteristics of the laser beam, environmental conditions, and properties of the workpiece. Furthermore, the large temperature gradients occur during laser microwelding process leads to a high stress level, and might result in many undesirable phenomena such as the high level of residual stresses in the vicinity of the heat-affected zone (HAZ) that adversely affect the life time of the component. Numerous studies have been performed on the evaluation and prediction of the thermal stresses in laser microwelding process. However, it is very difficult to measure the thermal stresses, and to predict the magnitude and direction of thermal stress/deformation. Therefore, we develop an optical methodology, based on opto-electronic holography (OEH) technique, to measure and evaluate the thermal stresses/deformations non-destructively. In this paper, the system of OEH measurement of the thermal deformation of the laser welds will be described in details, and representative results will be included. In addition, analytical and computational models will also be developed to simulate the temperature field and thermal stresses/deformations in laser microwelding. Continued work will lead to novel measurement system for monitoring the thermal stresses/deformations during the process of laser microwelding, which will help optimizing efficient and effective laser micro-machining processes for applications in microelectronics and packaging.

Cryogenic atomic force microscopy

1991 ◽  
Vol 49 ◽  
pp. 54-55
Author(s):  
K. A. Fisher ◽  
M. G. L. Gustafsson ◽  
M. B. Shattuck ◽  
J. Clarke
Keyword(s):  
Room Temperature ◽  
Rapid Freezing ◽  
Cryogenic Temperatures ◽  
Soft Or ◽  
Electrically Conductive ◽  
Force Microscopy ◽  
Flexible Molecules ◽  
Advantages And Disadvantages ◽  
Atomic Force ◽  
Chemical Perturbation

The atomic force microscope (AFM) is capable of imaging electrically conductive and non-conductive surfaces at atomic resolution. When used to image biological samples, however, lateral resolution is often limited to nanometer levels, due primarily to AFM tip/sample interactions. Several approaches to immobilize and stabilize soft or flexible molecules for AFM have been examined, notably, tethering coating, and freezing. Although each approach has its advantages and disadvantages, rapid freezing techniques have the special advantage of avoiding chemical perturbation, and minimizing physical disruption of the sample. Scanning with an AFM at cryogenic temperatures has the potential to image frozen biomolecules at high resolution. We have constructed a force microscope capable of operating immersed in liquid n-pentane and have tested its performance at room temperature with carbon and metal-coated samples, and at 143° K with uncoated ferritin and purple membrane (PM).

Fission Gas Bubbles in Fractured UO2

1968 ◽  
Vol 26 ◽  
pp. 286-287
Author(s):  
O. M. Katz
Keyword(s):  
Electron Microscopy ◽  
Thermal Gradient ◽  
Gas Bubbles ◽  
Inert Gas ◽  
Thermal Gradients ◽  
Fission Gas ◽  
Beam Heating ◽  
Limited Application ◽  
Bubble Characteristics ◽  
Electron Beam Heating

The swelling of irradiated UO2 has been attributed to the migration and agglomeration of fission gas bubbles in a thermal gradient. High temperatures and thermal gradients obtained by electron beam heating simulate reactor behavior and lead to the postulation of swelling mechanisms. Although electron microscopy studies have been reported on UO2, two experimental procedures have limited application of the results: irradiation was achieved either with a stream of inert gas ions without fission or at depletions less than 2 x 1020 fissions/cm3 (∼3/4 at % burnup). This study was not limited either of these conditions and reports on the bubble characteristics observed by transmission and fractographic electron microscopy in high density (96% theoretical) UO2 irradiated between 3.5 and 31.3 x 1020 fissions/cm3 at temperatures below l600°F. Preliminary results from replicas of the as-polished and etched surfaces of these samples were published.

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