多级压气机中可控扩散叶型研究的进展与展望 第二部分 可控扩散叶型的实验与数值模拟

目前 ,大量的可控扩散叶型 (CDA)已设计应用于多级轴流压气机中。通过亚音、跨音叶栅实验 ,证明了在可比的气动设计条件下 ,CDA叶栅可以达到更高的临界马赫数、更大的冲角范围和更高的负荷。通过单级或多级测试 ,CDA提供了更高的效率、更高的负荷、且易于进行级间匹配 ,并最终减少研发费用 ,提高喘振裕度 ;由于 CDA叶型具有增厚的前缘和尾缘 ,这为压气机寿命的提高提供了保证     

基于中弧线曲率控制的压气机叶型优化

为提高压气机叶型优化设计水平,基于中弧线曲率控制方法编写了压气机叶片造型程序,将中弧线曲率控制参数作为优化变量,结合粒子群寻优算法对传统可控扩散叶型(CDA)进行了优化研究。结果表明:基于中弧线曲率控制的叶片造型程序能够对CDA叶型进行较好的拟合,拟合叶型的气动性能与设计要求较符。优化叶型在设计点的总压损失降低了约6.34%,优化叶型总压损失随攻角变化较为平缓。在一定攻角范围内,叶型中弧线曲率峰值的前移能够将吸力面马赫数峰值前移,提高叶型吸力面的扩压能力,降低总压损失。在大攻角工况下,改进的中弧线曲率分布能够显著降低叶型总压损失。将中弧线曲率控制参数作为优化变量进行CDA叶型的优化是可行的。     

基于DSP BUILDER的数字下变频器设计

介绍利用DSP BU ILDER设计基于FPGA的数字下变频器的方法,研究使用专用乘法器的NCO设计、半波带滤波器多相抽取处理结构和FIR滤波器的分布式算法,同时给出实际应用的设计方案和仿真分析结果。     

Silkworms culture as a source of protein for humans in space

This paper focuses on the problem about a configuration with complete nutrition for humans in a Controlled Ecological Life Support System (CELSS) applied in the spacebases. The possibility of feeding silkworms to provide edible animal protein with high quality for taikonauts during long-term spaceflights and lunar-based missions was investigated from several aspects, including the nutrition structure of silkworms, feeding method, processing methods, feeding equipment, growing conditions and the influences on the space environmental condition changes caused by the silkworms. The originally inedible silk is also regarded as a protein source. A possible process of edible silk protein was brought forward in this paper. After being processed, the silk can be converted to edible protein for humans. The conclusion provides a promising approach to solving the protein supply problem for the taikonauts living in space during an extended exploration period.     

Minimizing energy utilization for growing strawberries during long-duration space habitation

Strawberry is a candidate crop for space that is rich in protective antioxidants and could also have psychological benefits as a component of crew diets during long-duration space habitation. Energy for electric lighting is a major input to a controlled-environment crop-production system for space habitation. Day-neutral strawberry cultivars were evaluated at several different photoperiods to determine minimum lighting requirements without limiting yield or negatively impacting fruit quality. The cultivars ‘Tribute’, ‘Seascape’, and ‘Fern’ were grown at 14, 17, or 20 h of light per day, and fruit yield was evaluated over a 31-week production period. This amounted to a difference of 2418 kWh m⁻² in energy usage between the longest and shortest photoperiods. All cultivars produced similar total fresh weight of fruit regardless of photoperiod. Volunteer tasters rated organoleptic characteristics including sweetness, tartness, texture, and overall appeal as measures of fruit quality. Generally, organoleptic attributes were not affected by photoperiod, but these attributes were somewhat dependent upon cultivar and harvest time. Cultivars under different photoperiods varied in their production of fruit over time. ‘Seascape’ was the most consistent producer, typically with the largest, most palatable fruit. ‘Seascape’ plants subsequently were grown at 10-, 12-, or 14-h photoperiods over a treatment period of 33 weeks. Photoperiod again had no significant effect on total fruit weight, although there were periodic flushes of productivity. Fruit under all photoperiods had acceptable approval ratings. A large-fruited, day-neutral strawberry cultivar such as ‘Seascape’ remains productive under shortened photoperiods, allowing reductions in energy and crew labor while maintaining flexibility for mixed-cropping scenarios in space.     

超跨声速无导叶对转涡轮整流型动叶设计

为了探讨对转涡轮气动设计规律，采用常用于导叶的可控涡法设计对转涡轮上游整流动叶，并配合可控子午成型设计，用以控制对转涡轮内径向压力分布，并与传统涡轮进行了深入对比分析。该方法设计的5．25kg／s小流量模型对转涡轮效率为94．2％。三维数值模拟表明：对转涡轮取消导叶后，在设计自由度减小，参数受到制约条件下，整流动叶采用可控涡设计是调控对转涡轮流场积极有效措施之一。     

用于电控旋翼气弹分析的带襟翼翼型气动力模型

为满足电控旋翼的气弹分析需要,给出了带襟翼翼型的综合时域非定常气动力模型,该模型可以计及襟翼移轴补偿的影响.之后通过与静态、动态风洞吹风数据的比较,验证了该模型的准确性.相关分析表明该模型在翼型未发生失速前具有良好的静、动态气动力预测能力.     

Influence of the interaction between light intensity and CO2 concentration on productivity and quality of spinach (Spinacia oleracea L.) grown in fully controlled environment

The effects of the factorial combination of two light intensities (200 and 800 μmol m⁻² s⁻¹) and two CO₂ concentrations (360 and 800 ppm) were studied on the productivity and nutritional quality of spinach (Spinacia oleracea L.) grown under controlled environment. After 6 weeks within a growth chamber, spinach plants were sampled and analyzed for productivity and quality. There were no statistically significant interactions between the effects of light and CO₂ for all of the variables studied, except for the nitrate and oxalic acid content of the leaves. High light and high CO₂ independently one from the other, promoted spinach productivity, and the accumulation of ascorbic acid, while their interactive effect limited the accumulation of nitrate and oxalic acid in the spinach leaves. The results highlight the importance of considering the effects of the interaction among environmental variables on maximizing production and the nutritional quality of the food when cultivating and modeling the plant response in controlled environment systems such as for bioregenerative life support.     

Sweetpotato vine management for confined food production in a space life-support system

Sweetpotato (Ipomea batatas L.) ‘Whatley–Loretan’ was developed for space life support by researchers at Tuskegee University for its highly productive, nutritious storage roots. This promising candidate space life-support crop has a sprawling habit and aggressive growth rate in favorable environments that demands substantial growing area. Shoot pruning is not a viable option for vine control because removal of the main shoot apex drastically inhibits storage-root initiation and development, and chemical growth retardants typically are not cleared for use with food crops. As part of a large effort by the NASA Specialized Center of Research and Training in Advanced Life Support to reduce equivalent system mass (ESM) for food production in space, the dilemma of vine management for sweetpotato was addressed in effort to conserve growth area without compromising root yield. Root yields from unbranched vines trained spirally around wire frames configured either in the shapes of cones or cylinders were similar to those from vines trained horizontally along the bench, but occupying only a small fraction of the bench area. This finding indicates that sweetpotato is highly adaptable to a variety of vine-training architectures. Planting a second plant in the growth container and training the two vines in opposite directions around frames enhanced root yield and number, but had little effect on average length of each vine or bench area occupied. Once again, root yields were similar for both configurations of wire support frames. The 3–4-month crop-production cycles for sweetpotato in the greenhouse spanned all seasons of multiple years during the course of the study, and although electric lighting was used for photoperiod control and to supplement photosynthetic light during low-light seasons, there still were differences in total light available across seasons. Light variations and other environmental differences among experiments in the greenhouse had more effects on vine length than on root yield. Average vine length correlated positively with total hours of daylight received across seasons, and responses for one plant per container were higher above a threshold duration of solar exposure, suggesting that the vines of two plants per container compete for available light. In addition to the adaptability of sweetpotato to various vine-training architectures and across seasons in terms of maintaining root productivity, the open, interior volumes of the support frames tested in this study will provide future opportunity to enhance sweetpotato root yield in space by adding novel interior lighting, such as from intracanopy arrays of light-emitting diodes. This work was sponsored by NASA grant NAG 5 1286.     

悬停状态电控旋翼桨距控制

针对改进型电控旋翼系统,首先建立了其各控制环节的数学模型,采用串级PID(proportion in-tegration differentiation)控制算法设计了悬停状态下电控旋翼桨距控制律,PID参数根据Ziegler-Nichols方法进行整定.通过仿真计算分析,初步验证了该控制算法对于桨距控制的有效性.以上述控制方法为基础,进一步开展了悬停状态下电控旋翼桨距控制的闭环试验研究,成功的实现了电控旋翼桨距幅值和相位的控制,验证了串级PID电控旋翼桨距控制算法的正确性和有效性.