2008 Vol. 28, No. 1

Display Method:
Gas-liquid Like Phase Transition in Granular Gases Under Zero Gravity
HOU Meiying, LIU Rui
2008, 28(1): 1-5. doi: 10.11728/cjss2008.01.001
Abstract(2137) PDF 1494KB(1192)
Granular systems are intrinsically far from equilibrium for their many-body and dissipative nature.Driven by external foroes,they can behave like that of solids,liquids,or gases.In dilute granular gases,clusters usually form due to dissipation,which leads to inhomogeneous density distributions.Such a local condensation shows spontaneous symmetry-breaking instability and negative compressibility,just sa droplets form in vapor.In this paper,a three-dimensional model for granular gases under zero gravity is investigated,and calculations predict such a gas-liquid like phace transition.Molecular dynamics simulations show good agreements with the theoretical results.The numerical results shall provide detailed experimental parameters for the further related space exteriments.
Preparation of Cu-Pb Alloy in Ground Simulating Microgravity Condition and Research of Microstructure and Friction Performance of the Alloy Samples
WANG Xiaoyong, DA Dao'an
2008, 28(1): 6-11. doi: 10.11728/cjss2008.01.006
Abstract(2113) PDF 3060KB(2399)
With electro-magnetic simulating equipment established on the ground Cu-Pb binary immiscible alloy are produced successfully,and microstructure and friction performance of the alloy samples are analyzed and tested.The analyzed results of microstructure show the alloy specimens produced on electro-magnetic simulating microgravity condition overcome severe phase separation due to gravity,the minority phase of simulating samples are well distributed in matrix,the lower contents of the minority phase is,the smaller size of dispersive phase is and the better it are distributed;test results of friction performance show friction performance of simulating samples is evidently better than the matrix metal,friction factor become small and wear properties rapidly reduce first and slowly increase later with increase of the minority phase contents.Simultaneously the test results are analyzed and discussed briefly.
Experimental Study on the Coupling of Thermocapillary Convection and Evaporation Effect in a Liquid Layer
Zhu Zhiqiang, Ji Yan, Liu Qiusheng, Yan Jiaping, Xie Jingchang
2008, 28(1): 12-16. doi: 10.11728/cjss2008.01.012
Abstract(2129) PDF 2373KB(1199)
There has been a variety of applications for therm ocapillary convection and evaporation,such as t1iin-film evaporators, boiling teclinologies and heat pipes. And the stab ilities of therm ocapillary convection in a fluid layer subjected to a liorizontal temperature gradient have been experimentally and nulnerically analyzed by many scientists. While tlie inter I : acia I flow with evaporation,whic1i is a classical physical phenomenon, is absent of comp re1iensive understanding. Recently, many theoretical and experimental researcbes have found that evaporation plays a very important role inthe instabilities of therm ocapilllary convection. In our experiment, we study the coupling of the omcapillary convection and evaporation effect Ilor 0.65 cst Silicone Oil as the experimental liquid in a recta ngitlar cavity which has the I engtli of 0.08 m and width of 0.04 m. The temperature gradientalong the liquid layer, which induces t1ie therm ocapillary convection, is the dominate parameter. The temperature at the interface and the evaporating rate are measured by a thermocouple and a laser co focal displacement meter, respectively. The PIV metbod is applied for flow visualization, and the flow pattern transforms from a steady unicellular flow to a steady multicellular fiow, to a turbulent flow ultimately with the temperature difference along the interface increases from 2o C to l4o C . For discussion, the experimental results are compared wit1i linear stability analysis.
Experimental Study on Two-Phase Flow and Power Performance of DMFC
Utilizing the Drop Tower Beijing
Zhao Jianfu, Guo Hang, Ye Fang, Wan Shixin, Wei Minggang, Wu Feng, Lu Cuiping, Ma Chongfang
2008, 28(1): 17-21. doi: 10.11728/cjss2008.01.017
Abstract(1867) PDF 1604KB(1304)
Utilizing the Drop Tower Beijing/NMLC, the characteristics of two-phase gas-liquid flow and power performance of a direct methanol fuel cell (DMFC) are studied experimentally in normal and microgravity conditions. It's found that CO2 bubbles in anode channels of DMFC move much slowly in microgravity, and that their shapes change from ellipsoid to globosity and their sizes increase with time, even block the whole channel and then the flow pattern changes into slug flow gradually. Larger current density, more easily is it to block the channel. It's also shown in the power curves that there exists an evident influence of gravity in the regime of the concentration polarization. The diminution of the power performance of DMFC in microgravity increases with the degree of the concentration polarization.
Microgravity Smoldering Combustion Experiments Aboard the China Recoverable Satellite S J-8
Wang Shuangfeng, Yin Yongli
2008, 28(1): 22-27. doi: 10.11728/cjss2008.01.022
Abstract(1917) PDF 2082KB(1129)
The present space experiments have been conducted aboard the China recoverable satellite SJ-8 to investigate the smoldering characteristics of flexible polyurethane foam with a forced oxidizer flow velocity of 3.1 mm/s. They are unique in that a combination of mixed flow opposed and forward smolder was investigated at specific ambient pressure. The results show that in the 21% O2 case, the microgravity opposed flow smolder reaction is not strong enough to progress through the foam sample and eventually extinguishes, whereas the forward smolder propagates along the entire sample length. In the 35% O2 case, both two types of smolder reaction exhibit a self-sustained propagation. Particular important is the discovery that, there is a transition from smoldering to flaming near the sample end in the opposed smolder, and it seems to be caused by the strong acceleration of smoldering reaction. This transition serves to initiate a vigorous, forward-propagating, oxidation reaction in the char left behind by the smolder reaction. The secondary char oxidation reaction propagates through the sample and consumes most of the remaining char. The study provides additional information of %practical interest in fire safety for manned spacecraft. At the same time, the data obtained in microgravity experiments can be used for the verification and development of smolder theory.
Study on Fire Initiation of Wire Insulations on Board the Satellite
KONG Wenjun, WANG Baorui, LAO Shiqi, AI Yuhua
2008, 28(1): 28-32. doi: 10.11728/cjss2008.01.028
Abstract(1819) PDF 2162KB(1031)
The damage and overheating of wire insulation is the main ignition source in the fire incidents of the manned spacecraft in microgravity. Anyway, until now the study on wire insulation flammability in microgravity is limited. Thus the study on fire initiation of wire insulation in microgravity is of importance for fire safety in spacecraft. The experimental hardware was developed to perform the experiments of fire initiation of wire insulation caused by overload on board the SJ-8 China recoverable satellite. In the experiments, the fire initiation characteristics including the temperature and radiation characteristics of the wire insulations were presented. The temperature histories of the wire insulation in microgravity and the low-pressure environment in normal-gravity were obtained. Effects of overloaded currents on the fire initiation were investigated for different wire coiled states. The results indicate that the natural convection almost vanished and the heat loss of the electric components decreased in the microgravity environment. It might cause overheat of the electric components and then results in fire, and thus the fire risks of wire in the microgravity condition are much more dangerous than that in normal-gravity under the condition of overload.
Marangoni Instability in Vertically Inhomogeneous Porous Media
Zhao Sicheng, Liu Qiusheng
2008, 28(1): 33-37. doi: 10.11728/cjss2008.01.033
The surface-tension-driven instability in a vertically inhomogeneous porous media has been discussed in this paper. The system is heated from below. The upper surface is free without any deformation. Therefore, the vertical temperature gradient which can lead the Marangoni-Bernard convection is formed. The linear function and the trigonometric function are chose to describe the distribution of the porosity, and Brinkman-Forchheimier equations are for linear instability analysis. Chebyshev-tau approximation is used for general eigenvalue problem correspondingly, and the neutral instability curves, i.e. the critical Marangoni number against dimensionless wavenumber, are obtained. The influence of the distribution and its gradient of porosity on the instability of the system and streamline patterns are also analyzed. Finally, the new characteristics of the convection instability in vertically inhomogeneous porous media are discovered.
Origin of Thermocapillary Convection in Pool Boiling
LI Zhendong, ZHAO Jianfu, LU Yanghui, LI Jing
2008, 28(1): 38-43. doi: 10.11728/cjss2008.01.038
Abstract(2735) PDF 827KB(1146)
The phenomenon of boiling heat transfer is broadly exists in many nature and technology fields, covering from human daily life to the manned space flight. The study of the phenomenon of boiling heat transfer is one of the most important research fields in science and engineering. In the present paper, different view-points on the origin of thermocapillary convection are discussed for the case of one component liquid pool boiling phenomenon in microgravity. It's pointed out that the key problem is how to model the temperature jump condition across the vapor-liquid interface with phase change. Therefore, some existed correlations on the temperature jump condition across the vapor-liquid interface with phase change are reviewed in detail. It's found that the non-equilibrium of phase change will result in an obvious temperature gradient at the interface and then thermocapillary convection around the vapor bubble is driven by the surface tension gradient due to the temperature gradient. However, both the mechanisms and the predictions of these models are very different from each other, and no one can be generally recognized up to now, further study is needed.
Design Optimization of Condensers in a CO2 Two-Phase Thermal Control System for Space Detector Application
HUANG Zhencheng, MO Dongchuan, LU Shushen, HE Zhenhui, A. Paul, J.E. Van
2008, 28(1): 44-48. doi: 10.11728/cjss2008.01.044
Abstract(2747) PDF 2312KB(1229)
The silicon Tracker, a charge particle core detector in the Alpha Magneto- spectrometer, requires a cooling system to provide a working condition. This cooling system must be small in size, strong for its cooling ability and temperature control precision, even in the complex thermal, and microgravity environments on the international space
station. In this paper, the attempt of design optimization of the condenser in the CO$_2$ two-phase thermal control system for such purpose is introduced, by employing thermal simulation analysis with SINDA/FLUINT. Because of the specific radiator, different design of the configurations of condenser inlet are investigated, by contacting the inlet at 1st, 2nd, 5th heat pipe and out of all heat pipes on the radiator. The result shows that with different configurations, the inlet part will have different effect on the heat transfer part of the condenser, which will cause the outlet temperature of the condenser different. It also tells that contacting the inlet at the 2nd heat pipes shows a best result for either reducing the anti-freezing power in cold case or guaranteeing enough subcooling of the pump inlet in the hot case.
Analysis of Disturbance in the Measurement of the Residual Acceleration of the Drop Capsule With the Laser Interferometry
QU Shaobo, YAN Qizhong, TIAN Wei, WU Shuchao
2008, 28(1): 49-54. doi: 10.11728/cjss2008.01.049
Drop tower is an important facility to obtain microgravity environment. For the scientific experiments which will be performed in drop tower, it is quite important to know the residual acceleration of the drop capsule. Laser interferometry is a new method for measuring the residual acceleration of the drop capsule. The basic principle of this method can be described as following: a reference object falling in the drop capsule can fall more freely than the drop capsule itself because the outer air drag acts on the latter, so there is a difference of acceleration between the reference object and the drop capsule. The difference of the acceleration can be obtained according to the relative displacement which can be measured by laser interferometry. The main disturbance of this method is discussed in details. The total error caused by the main disturbance is 1.2 x 10-7 g, less than the estimated microgravity of 10-4~10 -6 g, so the laser interferometry is a suitable method for measuring the residual acceleration of the drop capsule.
Method for Spectral Analysis of Electrostatically Suspended Accelerometer Noise Data
XUE Datong
2008, 28(1): 55-63. doi: 10.11728/cjss2008.01.055
The signification of discrete Fourier transform formulae with different coefficient is analyzed and the formula proper for engineering analysis is screened out. There are more ways to make the sample amount fit integral power of 2 for using fast Fourier transform. The strongpoint and the shortcoming of these ways is discussed. The applied objects of various frequency spectra are analyzed, the power spectral density is suitable for the noise of the electrostatically suspended accelerometer and the corresponding coefficient of window method should be selected. The correcting which must be used when the power spectral density is calculated by commercial software "Origin 5.0/7.0" of OriginLab Corporation is presented. The difference measurement of the noise of the electrostatically suspended accelerometers is required to bate the influence of environment noise in Ground. It is demonstrated that the differential method should be as follows: the noise of twin accelerometers in time domain, from which already deducted the average value, is subtracted mutually, whereafter is divided by sqrt{2}.
Image Feedback Control System in the Space Drop Evaporation Experiment
YU Qiang, NING Qiao, ZHU Zhiqiang, YUAN Zhangfu
2008, 28(1): 64-68. doi: 10.11728/cjss2008.01.064
Abstract(2269) PDF 1865KB(1153)
In this paper, a method to measure the drop evaporation velocity by image feedback control system is presented. The system is constituted of 3 parts: image acquisition, image processing, and feedback control. Analyzing drop pictures from the CCD camera, the physical features of the drop could be obtained, and evaporating volume could be calculated
from the geometry differences between two pictures. To maintain the drop volume, drive the injector to inject dynamically. The evaporation velocity could be calculated by the evaporating volume per unit time. In order to determine the accurate contour of the dynamically changed drop, the contour approach principle is investigated and some numerical algorithms such as Laplace equation, Newton-Raphson method and Runge-Kutta method are introduced. Based on the drop contour determined from the contour approach, the volume and the surface area of drop could be calculated by numerical integral. The software structure and hardware structure of the system are described, an experiment result is given finally. The system is developed for the liquid experiment in SJ-10 recoverable satellite.
Numerical Simulation of Liquid-Vapor Interface Tracking in Tank of Spacecraft
LI Zhangguo, LIU Qiusheng, JI Yan, HOU Hui
2008, 28(1): 69-73. doi: 10.11728/cjss2008.01.069
Abstract(2142) PDF 2394KB(1195)
This paper presents a comprehensive analysis of the transport processes of propellant in tank of spacecraft in different gravity. The motion of the liquid-vapor interface of propellant in the tank of on-orbit spacecraft is investigated numerically by solving the incompressible Navier-Stokes equations using the VOF method coupled with the surface tension effect under micro-gravity environment. The objectives of this study are to examine the robust method of controlling the interface transformation of the two phase flow by comparing and analyzing the effects of gravity and contact angle as the typical parameters. Results show that, the gravity effect plays a dominant role in determining the shape of gas-liquid interface and the relative location of the gas-liquid phase in the tank at large Bond number; when the Bond number is small enough, the wettability effect exert a great influence.
Determine the Surface Tension and Contact Angle of Drop by Image Processing Method
NING Qiao, ZHU Zhiqiang, LU Xutao, YU Qiang, YUAN Zhangfu
2008, 28(1): 74-79. doi: 10.11728/cjss2008.01.074
Abstract(2650) PDF 2218KB(1520)
The liquid experiment in space needs intelligence to deal with the surveillance image right away to obtain the goal parameters. A method is investigated to analyze the physical feature of a drop, such as surface tension, contact angle and volume through fitting contour of the drop picture. From the grey picture, generally contour of a drop is obtained by edge detection and segmentation algorithms. Constructed the Laplace equation of the drop, made contour approach process through comparing and using Newton-Raphson method, Runge-Kutta method and coordinate optimizing method. With the help of contour approach, physical feature of the drop is obtained. A new algorithm which nests Newton-Raphson method with One-dimensional optimization is presented. Compared with the original algorithm raised by Ref.\,[1], the new one reached convergence quickly with high accuracy. It is a key technique of the space experimental system for liquid experiment. The method is especially applicable for unmanned environment as well as non-contact measurement in the experiments.
Approach on Flower and Pollen Development of Brassica parachinesis Under Microgravity and Simulated Microgravity
ZHENG Huiqiong, WEI Ning, CHEN Aidi, WANG Liufa
2008, 28(1): 80-86. doi: 10.11728/cjss2008.01.080
Abstract(2103) PDF 1994KB(1053)
Plants have usually evolved under the surface gravity and have acquired the ability to gravistumili to regulate their growth and development. Space experiments show that the plant morphogenesis and growth responses are highly influenced by the gravity level. In the present study, flower and pollen development of {\it Brassica parachinese} under microgravity on board the Chinese SJ-8 recoverable satellite and under simulated microgravity on a 3D clinostat condition, respectively, were studied. Flower opening is due to the rapid growth and the movements of petals, which are accompanied by a high rate of cell expansion. The period of flower bud development and opening in
space were about 18 h significantly increased in comparison with 5 h under 1 g control conditions. The experimental results of the 3D clinostat rotation also showed the similar results, that plants under clinostat rotation produced flowers with smaller petals and shorter stamens in comparison with the usually controlled plants, but no other attributes were apparently affected. In this case, significant reduction of the pollen was also observed in the flowers. The influences of altered gravity on the arrays of microtubules in pollen cells during microspore nuclear migration and the asymmetrical mitosis were also observed. Based on our knowledge, the present space experiment is the first one to use the live imaging analysis to study the influence of the microgravity condition on the flower expansion and opening.
Analysis of Effects of Simulated Microgravity on Signaling Pathways Involved in Osteogenic Differentiation of Human Mesenchymal Stem Cells
HUANG Guoping, ZHENG Qiang, YANG Jinfeng, GUO Chunjuan, SHEN Dan, SHI Dongyan, XU Yulin, PAN Zhijun, WANG Jinfu
2008, 28(1): 87-96. doi: 10.11728/cjss2008.01.087
Abstract(1845) PDF 2855KB(1344)
Microgravity (MG) results in reduction of bone formation. Bone formation is bound up with osteogenic differentiation from human mesenchymal stem cells (hMSC) in bone marrow. We simulated MG to determine its effects on osteogenesis of hMSC and used activators or inhibitors of signaling factors to modulate osteogenic differentiation. Under osteogenic induction, MG reduceds osteogenic differentiation of hMSC and decreaseds the expression of osteoblast gene markers. The expression of Runx2 was likewise inhibited. However, the expression of PPAR$\g$2 increased. MG also decreased phosphorylation of ERK, but increased phosphorylation of p38MAPK. SB203580, a p38MAPK inhibitor, was able to inhibit the phosphorylation of p38MAPK, but not able to reduce the expression of PPARγ2. Bone morphogenetic protein (BMP) increased the expression of Runx2. Fibroblast growth factor 2 (FGF2) increased the phosphorylation of ERK, but did not increase significantly the expression of osteoblast gene markers. The combination of BMP, FGF2 and SB203580 significantly reversed the effect of MG on osteogenic differentiation of hMSC. Our results suggests that simulated MG inhibits the osteogenic differentiation and increases the adipogenic differentiation of hMSC through different signaling pathways. Therefore the effect of MG on the differentiation of hMSC could be reversed by the mediation of signaling pathways.