Thermal Shroud Research Articles

Conceptual design of a compact multipurpose space simulation system

One of the biggest challenges in space systems engineering is simulating the space environment when developing and testing various components, subsystems and entire satellites prior to a mission. Therefore, a space simulation system is needed to reproduce the vacuum of space, the intense solar radiation and the extreme temperature variations. Such a facility can be extremely complex and expensive. One way to reduce costs is working with small-sized systems and implementing a compact facility capable of fulfilling multiple applications. The system must be useable as a space simulator, a thermal-vacuum chamber or a standard vacuum chamber, all the while allowing a quick and easy transition between operational modes. This requires the implementation of a removable thermal shroud capable of reaching −150 °C and +150 °C. First, the thermal shroud geometry is defined and the nitrogen flow and temperature requirements are calculated. The second step is a steady-state heat transfer and structural analysis, performed using the software Ansys in order to obtain the temperature, stress and deformation. The last step is the virtual integration of the thermal shroud and vacuum chamber using the software Catia V5.

Design and Test of the Removable Thermal Shroud for Prevention Residual Gas Condensation on the Laser Entry Hole Windows on Cryogenic Inertial Confinement Fusion Targets

Design and Test of the Removable Thermal Shroud for Prevention Residual Gas Condensation on the Laser Entry Hole Windows on Cryogenic Inertial Confinement Fusion Targets

진공 챔버 내 저온 환경 모사를 위한 스테인리스 스틸 튜브-구리 플레이트 타입 열 쉬라우드 제작 및 테스트

진공 챔버 내부의 저온 환경 구현을 위한 쉬라우드는 다양한 재질과 형태로 제작될 수 있다. 두 개의 플레이트를 접합하여 내부에 냉각물질을 채우는 방식의 쉬라우드는 냉각 효율이 좋지만, 큰 사이즈로 제작하기에는 제작 난이도가 높고 비용도 높다. 본 연구에서는 스테인리스 스틸 튜브와 구리 플레이트를 접합한 형태의 쉬라우드를 제안하였으며 이는 제작이 쉽고 열 전도성이 우수한 장점이 있다. 제안된 쉬라우드의 제작성과 냉각성능을 확인하기 위해 샘플 쉬라우드를 제작하여 소형 진공 챔버에서 냉각 테스트를 수행하였다. 냉각 테스트 결과 목표성능인 쉬라우드의 표면온도 -190°C, 온도 균일도 10°C 이내 조건을 만족하였으며, 열 사이클링 테스트와 누설 테스트를 통해 쉬라우드의 제작 안정성을 확인하였다. 이를 통해 제안된 형태의 대형 쉬라우드 제작에 대한 적합성을 확보하였다.

열진공 챔버용 폐회로 열제어시스템 설계 및 성능평가

A closed loop thermal control system simulates space thermal environment to verify the satellites` functionality in extremely cold/hot temperature. It is composed of a cryogenic blower, thermal shroud, heater, cryogenic valves. This paper presents an overview of closed loop thermal control system`s design parameter and test results for control parameter. A capacity of blower is calculated through energy balance equation and an advantage/disadvantage for a shroud material and a type was analysed. The thermal control system is controlled by a constant density of fluid in the system. A requested performance of closed loop thermal control system was verified by measuring a homogeneity and stability of shroud through control parameter such as density and RPM of blower.

동흡진기를 이용한 포신의 진동감쇠에 대한 연구

Advanced tanks in the future combat system are expected to have the trends of large caliber, high explosive shell and light weight for destructive power and improvement in mobility. Their guns are required to have longer barrels to meet increased muzzle exit velocities. However, as the length of the barrel is extended, the vibrations induced by the breech forces in fire and the terrain lead to increased muzzle pointing errors. Therefore, the fire-induced and terrain-induced vibrations must be attenuated. A method to reduce these vibrations without the significant increase of the gun mass is to use the forward thermal shroud as part of a tuned mass damper. In this study, the dynamically-tuned-shroud using this shroud and leaf springs is introduced and its effectiveness on the vibration attenuations of the barrel are verified. The parametric studies on the stiffness of these leaf springs are performed and the analytical results are verified using the experimental model of the dynamically-tuned-shroud.

Evolution and Progress of the Cryogenic Target Shroud Remover Prototypes Developed for the LMJ Facility

The Laser Mégajoule (LMJ) cryogenic target is protected from ambient thermal radiation by a thermal shroud. When the cryotarget, held by the cryotarget positioner, is at the LMJ chamber center, the thermal shroud has to be removed just before the shot to allow the laser beams to reach the laser entrance hole of the cavity.The shroud remover, PET, will have to disconnect the thermal shroud from the cryogenic target base without disturbing the target base temperature regulation (˜18 K ± 2 mK), which guarantees the needed cryogenic target conditions to reach the ignition.The shroud withdrawal is divided into two successive phases: a slow withdrawal for the thermal disconnection between shroud and target base and a fast withdrawal for a quick extraction of the shroud out of the laser beamways pointing onto the cavity. The slow shroud withdrawal must be handled within 30 min to respect laser pointing stability. After the final target alignment at the chamber center, the shroud must be ejected 0.5 m away from the source point in <0.1 s before the shot.To cope with all these issues, a prototype of the shroud remover, PPET, has been first built and developed at CEA-Grenoble, at INAC/SBT, before being tested at CEA-CESTA on the DEMOCRYTE setup, a prototype of the cryogenic target charger and holder.The experimental results mainly obtained at CEA-CESTA in 2008 and 2009 on two generations of target bases and shrouds are presented in this paper.

Cryogenic systems for LMJ cryotarget and HiPER application

AbstractFor the future, we have to develop new sources of energy. These new sources may be based on nuclear fusion with magnetic confinement (as with the ITER experiment) or with a new concept based on inertial confinement. The European community plans to build a facility (HiPER project) which is dedicated to reaching high gain with cryogenic targets, and to test the concepts of target mass production and rep rate shots. The cryogenic system for the 1stphase experiments in HiPER is based on the cryogenic system developed for the French facility Laser MegaJoule (LMJ). The latter must be modified and upgraded for direct drive targets. In particular the target must be protected from the radiation flux from the vacuum vessel by a thermal shroud. In addition, the LMJ system must be equipped with a thermal system to allow layering of the fusion fuel to take place. The new developments concern a leak tightness thermal shroud for direct drive and a fast shroud retractor able to allow the laser shot within few milliseconds.

Development of a Cryogenic Target Delivery System for HiPER

For the future, we have to develop new sources of energy. These new sources may be based on nuclear fusion with magnetic confinement (as with the ITER experiment) or with a new concept based on inertial confinement. The European community plans to build a facility (HiPER project) which is dedicated to reaching high gain with cryogenic targets, and to test the concepts of target mass production and rep rate shots. The cryogenic system for the 1st phase experiments in HiPER is based on the cryogenic system developed for the French facility Laser MegaJoule (LMJ). The latter must be modified and upgraded for direct drive targets. In particular the target must be protected from the radiation flux from the vacuum vessel by a thermal shroud. In addition, the LMJ system must be equipped with a thermal system to allow layering of the fusion fuel to take place.

Noise Reduction of High-pressure Common-rail Engine and the Impact of the Engine Performances on the Noise

The noise of high-pressure common-rail engine and the impact of engine performances on the noise are studied. The overall noise of the prototype is measured and sound sources are identified through acoustic scan, and it is found that the front-end face, the intake side, the exhaust side and the top of the engine are the main sources of noise. So, clad steel plate is installed on the gear room, and the heat baffle of exhaust pipe and the thermal shroud of turbine shell all use noise reduction parts. These measures are very effective. Then the impact of economy and power performances of the engine on the noise is studied by adjusting the parameters of high-pressure common-rail system, and it is found that increasing the fuel consumption and reducing the torque can reduce the noise. Research results show that the engine performances have great influence on the engine noise, and the noise can be reduced at the expense of a certain percentage of economy and power performance.

Cryogenic systems for inertial fusion energy

AbstractThe Low Temperatures Laboratory of CEA/Grenoble (France) is involved in the development of cryogenic systems for inertial fusion since a ten of years. A conceptual design for the cryogenic infrastructure of the Laser MegaJoule (LMJ) facility has been proposed. Several prototypes have been designed, built and tested like for example the 1500 bars cryo compressor for the targets filling, the target positioner and the thermal shroud remover.The HIPER project will necessitate the development of such equipments. The main difference is that this time, the cryogenic targets are direct drive targets. The first phase of HIPER experiments is a single shot period. Based on the experience gained the last years, not only by our laboratory but also by Omega and G.A teams, we could design the new HIPER equipments for this phase.Some experimental results obtained with the prototypes of the LMJ cryogenic system are given and a first conceptual design for the HIPER single shot cryogenic system is shown.

Target manufacturing and delivery for HiPER

For the future, we have to develop new sources of energy. These new source are based on the nuclear fusion by magnetic confinement as with the ITER experiment or with a new concept based on the inertial confinement. The European community plan to build a facility (HiPER project) which is dedicated to prove the capability to reach a high gain with cryogenic targets, to test the concept of target mass production and the rep rate shot. The cryogenic system for 1st phase experiment is based on the cryogenic system developed for the French facility Laser Mega Joule (LMJ). The latter has to be modified and upgraded for direct drive target. In particular the target has to be protected by a thermal shroud from the radiation flux from the vacuum vessel and it is equipped with a thermal system which allows the core layering.

장축 실린더의 열변형 최소화를 위한 차열관 효과 해석 및 실험 연구

A barrel is a high length-to-diameter ratio cylinder that is influenced by environmental factors such as sunlight, precipitation, wind and clouds. Cross-barrel temperature differences caused by uneven heating or cooling lead to thermal deformation that degrades accuracy. Therefore, a barrel is covered by thermal shrouds to minimize the type of thermal deformation, fall-of-shot. In this paper, an analytical and experimental study is presented to design the thermal shrouds for a gun barrel and to evaluate the thermal shroud effect. First, an analytical study on the thermal shroud effect to minimize thermal deformation of a gun barrel by sunlight and wind is performed. The coupled analysis of thermal fluid dynamics of the air flow between a barrel and thermal shrouds and thermal stresses of a barrel Is performed to clarify both the thermal shroud effect and the drift in gun muzzle orientation by thermal deformation. Second, experiments are carried out to test and evaluate the thermal shroud effect on the performance of a gun barrel. The drift in gun muzzle orientation against the solar radiation is confirmed by the experiments, and the results well agree with the analytical estimation. Third, three principal design factors that are presumed to have an effect on the performance of the thermal shrouds are also analyzed; sorts of shroud materials, wall-thickness of thermal shrouds, and distance of the gap between a barrel and thermal shrouds.

Recent Results in Thermal and Hydrodynamic Simulations of Cryogenic Target for LMJ

This paper is an update of the thermal and hydrodynamic simulations of cryogenic target for the laser MegaJoule (LMJ). Depending on the kind of study, 2-D axi-symmetric or 3-D models are used for those numerical simulations with FLUENT, a Computational Fluid Dynamics (CFD) code.Results show the response of the hohlraum assembly and the DT ice layer profile to sinusoidal modulation of the temperature of the cooling rings. aWe have also calculated that no change in the DT ice was observed with variations up to +/-2 mK on thermal shroud. Results of flux absorption during laser alignment are reported here.Taking in account the cavity real geometric configuration, the seven gas-areas cavity appears to be the most effective to counteract convection effects. Other ways to counteract those effects have been explored like heating modulation in the central area on the outer surface of the gold cavity, or uniform heating in this area with auxiliary heating on the lower cooling ring. More, the thermal response of DT ice when it is submitted to a quenching (in order to obtain the LMJ target gas density specification) is shown here.

Examination of the Plenum and Deposition Coupon of the Phebus FPT4 Test by Scanning Electron Microscopy and Photoemission Spectroscopy

Samples of the thoria thermal shroud from the plenum and a deposition coupon from a filter cartridge of the FPT4 test of the Phebus PF project were examined using electron-optical analysis and by photoemission spectroscopy (XPS). The aim was to determine the nature of the fission product deposits formed under conditions of severe nuclear accidents. The plenum had considerable deposits containing Zr, Mo, Ba, Cs, and locally U was found by energy dispersive analysis. The XPS analysis showed that the deposits are mostly in oxidic form, but no U was found in the deposit, although chemical analysis showed considerable amounts present. A possible explanation is that there is layering of the deposit and that U is not released in the early stages. The coupon had very sparse deposits with only occasional U and Re particles; however large, pure Cs particles were observed on the surface that may have come from the filter deposits upstream. Thus an estimate of the deposition behaviour of fission product and fuel dispersed under extreme nuclear accident conditions is built up.

Leak rate measurements for large vacuum chambers

For large vacuum chambers of volume between 50 and 500 m 3, which are required for space simulation and thermal vacuum testing of spacecraft systems and subsystems, a specific method for the determination of the vacuum chamber leak rate is described. The main characteristics of the facility including irradiation, thermal shroud, motion and vacuum subsystem are presented. The outgassing and desorption rates were measured and the functional dependency versus time was evaluated. The specific method of leak rate determination by pressure rise measurement has proven to be very effective and economic.

Low Cost Thermal Vacuum Testing Facility for Electronic Units

A thermal vacuum testing facility for electronic units has been specified, designed, and built. It is fully operational and performs its tasks—thermal vacuum qualification and acceptance testing of electronic units. All performance requirements and design details have been carefully evaluated on a cost-effective basis, resulting in achieving the design goal of low price (purchase, operation, and maintenance) together with ease of operation, maintenance simplicity, and upgrading options. The major cost saving originated from a detailed analysis of thermal vacuum requirements that resulted in low cost substitutes to the common thermal shroud, together with a thermal plate. The plate is actively thermally controlled by a circulating fluid that is temperature regulated by a commercial heating and cooling unit. The high vacuum pumping system includes a diffusion pump with backstreaming holders.