Combustion modeling in a model combustor

The flow-field of a propane-air diffusion flame combustor with interior and exterior conjugate heat transfers was numerically studied.Results obtained from four combustion models,combined with the re-normalization group(RNG) k-ε turbulence model,discrete ordinates radiation model and enhanced wall treatment are presented and discussed.The results are compared with a comprehensive database obtained from a series of experimental measurements.The flow patterns and the recirculation zone length in the combustion chamber are accurately predicted,and the mean axial velocities are in fairly good agreement with the experimental data,particularly at downstream sections for all four combustion models.The mean temperature profiles are captured fairly well by the eddy dissipation(EDS),probability density function(PDF),and laminar flamelet combustion models.However,the EDS-finite-rate combustion model fails to provide an acceptable temperature field.In general,the flamelet model illustrates little superiority over the PDF model,and to some extent the PDF model shows better performance than the EDS model.      

对下一代卫星操作控制的系统研究

自1975年发射首颗ETS-1卫星以来,总计已发射了28颗NASDA(日本空间局)卫星。关于卫星的操作,NASDA已经开发了实时遥测/遥控处理系统,可通用于不同类型卫星。目前第三代系统已投入使用。而卫星操作的最新发展趋势则是更加复杂,例如正在出现采纳CCSDS建议的卫星,而且计算机技术也发展的相当迅速。 此外,NASDA在卫星操作中的任务正从主要是卫星星体操作发展为实验/整个卫星任务操作。根据这些情况,NASDA已经开始研究适于操作未来卫星的下一代操作系统。研究中考虑到以下几点: ·任务支持的要求 ·卫星设计的趋势 ·计算机环境的进展 本文是该研究的阶段性报告。     

热载荷下轻质复合结构件的应力和应变分析

复合结构件在固化和其它使用环境条件中,均受到热载荷的作用。这类结构的横向热膨胀系数(CTEs)大,刚度低;但平面的刚度高,热胀系数小。本文分析了典型的复合结构件,即空间天线反射器的曲面薄壳,由温度引起的应力和变形。     

EUVE卫星的GPS测轨

1992年夏,随着极紫外探测卫星(EUVE)一起发射了一台单频GPS接收机。EUVE卫星轨道低,并在星体上直接安装了二个天线,可用来研究误差源,以及未来卫星可达到的定轨精度。利用GDPSY—OASLSⅡ软件处理了几段GPS教据。从EUVE来的数据和从全球GPS接机网来的数据相结合,消除了SA的影响。研究了几种消除单频数据中电离层延时误差以及利用简化动力学法求解轨道的方法。通过内符合检验并与哥达德航天中心产生的GTDS轨道解作比对,鉴定了GPS测轨精度。利用GPS的测轨精密度和准确度在一米量级。     

使用新型磁路的宽带电源噪声滤波器

1 引言 本文阐述了一种用于交流电源滤波器的新型磁路。这种设计在一个宽的频带内具有高的衰减。对交流电源滤滤器来说,如果不是很好地接地或者将其装到没有接地端的设备中时,很少能在宽频带内较强地衰减共模感应噪声。从结构上来说,造成这种性能较差的原因有两个,原因之一是这种广泛使用的圆环形线圈输入输出端之间的寄生电容很大,高频噪声容易通过。另一个原因是滤波器接地电容不能正常工作,除非接地端真正接地。     

Novel laboratory approaches to multi-purpose aquatic bioregenerative closed-loop food production systems

Based on the construction principle of the Closed Equilibrated Biological Aquatic System (C.E.B.A.S.) two novel combined animal-plant production systems were developed in laboratory scale the first of which is dedicated to mid-term operation in closed state up to two years. In principle both consist of the "classic" C.E.B.A.S. subcomponents: animal tank (Zoological Component), plant cultivators (Botanical Component), ammonia converting bacteria filter (Microbial Component) and data acquisition/control unit (Electronical Component). The innovative approach in the first system is the utilization of minimally three aquatic plant cultivators for different species. In this one the animal tank has a volume of about 160 liters and is constructed as an "endless-way system" surrounding a central unit containing the heat exchanger and the bacteria filter with volumes of about 1.5 liters each. A suspension plant cultivator (1 liter) for the edible duckweed Wolffia arrhiza is externally connected. The second plant cultivator is a meandric microalgal bioreactor for filamentous green algae. The third plant growth facility is a chamber with about 2.5 liters volume for cultivation of the "traditional" C.E.B.A.S. plant species, the rootless buoyant Ceratophyllum demersum. Both latter units are illuminated with 9 W fluorescent lamps. In the current experiment the animal tank contains the live-bearing teleost fish Xiphophorus helleri and the small pulmonate water snail Biomphalaria glabrata because their physiological adaptation to the closed system conditions is well known from many previous C.E.B.A.S. experiments. The water temperature is maintained at 25 degrees C and the oxygen level is regulated between 4 and 7 mg/l by switching on and off the plant cultivator illuminations according to a suitable pattern thus utilizing solely the oxygen produced by photosynthesis. The animals and the microorganisms of filter and biofilm provide the plants with a sufficient amount of carbon dioxide. Oxygen concentration, pH value, temperature and redox potential are on-line recorded. Ion concentrations and numbers of living germs in the system water are determined twice monthly in the laboratory from samples taken from a special "sample removal module"; the sample volume is automatically replaced from an reservoir container. A rotatory pump produces a water flow of about 38 l/min. For a similar smaller test system with approx. 10 l volume developed from the C.E.B.A.S.-MINI-MODULE a novel indirect solar energy supply is tested which has a buffer capacity to maintain the system for 7 days in darkness under central European climate conditions also in winter. It contains only a single plant cultivator which is operated with Wollfia arrhiza. This lemnacean plant is able to produce large amounts of plant biomass in a short time by vegetative reproduction via daughter fronds. This easy-to-handle apparatus is dedicated to be operative more than 4 month. The experimental animals and microorganisms are the same as in the large system. The paper provides detailed information on the system construction principles and the biological, physical and chemical data of the initial phase of the test runs of both systems with the main focus on the large one.