高空活塞发动机2级涡轮增压系统匹配分析

为满足无人机高性能动力要求,改进了某型涡轮增压活塞式发动机2级涡轮增压系统。根据发动机工作过程模拟计算原理,利用CFD软件建立了该型发动机1级涡轮增压模型,并验证了该模型的准确性;确定了2级涡轮增压参数及高、低压气机的压比分配,讨论了2级增压器和中冷器的布置方案,分析了2级涡轮增压的高空特性,为2级涡轮增压系统选配了合适的增压器。     

基于P-ε-N曲线整体推断的涡轮盘寿命可靠性分析

疲劳寿命符合对数正态分布,并且对数寿命的标准差随弹性应变幅和塑性应变幅的减小而增大。采用基于异方差回归分析的整体推断方法在现有低循环疲劳试验数据的基础上,得到了航空发动机涡轮盘材料GH4133在温度250℃下的P-ε-N曲线;利用P--εN曲线对某涡轮盘进行低循环疲劳寿命可靠性分析,得到置信度0.95,可靠度0.998 7的轮盘寿命为1 866次循环,合683飞行小时,与涡轮盘疲劳试验分析得到的技术寿命接近。整体推断得到的P-ε-N曲线精度较高,利用P-ε-N曲线进行轮盘寿命可靠性设计分析具有计算简便、节约试验成本的优点。     

多功能显示系统中的矢量字符构成方法

介绍了航电多功能显示系统(MFDS)中字符的构造方法,具体阐述了一种用于MFDS的矢量字符构造方法。     

Vegetable production facility as a part of a closed life support system in a Russian Martian space flight scenario

A Manned Mars Mission scenario had been developed in frame of the Project 1172 supported International Science & Technology Center in Moscow. The Mars transit vehicle (MTV) supposed to have a crew of 4–6 with Pilot Laboratory compartment volume of 185 m³ and with inner diameter of 4.1 m. A vegetable production facility with power consumption up to 10 kW is being considered as a component of the life support system to supply crew members by fresh vegetables during the mission. Proposed design of conveyor-type plant growth facility (PGF) comprised of 4-modules. Each module has a cylindrical planting surface and spiral cylindrical LED assembly to provide a high specific productivity relative to utilized onboard resources. Each module has a growth chamber that will be from 0.7 m to 1.5 m in length, and a crop illuminated area from 1.7 m² to 4.0 m². Leafy crops (cabbage, lettuce, spinach, chard, etc.) have been selected for module 1, primarily because of the highest specific productivity per consumed resources. Dietitians have recommended also carrot crop for module 2, pepper for module 3 and tomato for module 4. The maximal total PGF light energy estimated as 1.16 kW and total power consumption as about 7 kW. The module 1 characteristics have been calculated using own experimental data, information from the best on ground plant growth experiments with artificial light were used to predict crop productivity and biomass composition in the another modules. 4-module PGF could produce nearly 0.32 kg per crew member per day of fresh edible biomass, which would be about 50% of recommended daily vegetable supplement. An average crop harvest index is estimated as 0.75. The MTV food system could be entirely closed in terms of vitamins C and A with help of the PGF. In addition the system could provide 10–25% of essential minerals and vitamins of group B, and about 20% of food fibers. The present state of plant growth technology allows formulating of requirements specification for the flight-qualified modules.     

基于最小二乘支持向量机的工具误差分离与折合

制导工具误差分离与折合是导弹精度评定中的重要问题,提出了利用支持向量机方法获得工具误差系数估计和进行弹道误差折合的新方法,由于支持向量机综合考虑了结构风险和经验风险,使得模型的泛化能力增强。仿真计算表明,与最小二乘和主成分方法相比,最小二乘支持向量机获得的误差系数估计与真值更加接近,折合得到的全程弹道遥外差更加准确。     

速度矢量滚转的运动学及气动力分析

速度矢量滚转定义为飞机在保持定常迎角的情况下,围绕其瞬时速度矢量所产生的无侧滑、速度保持为常值的旋转运动。对于典型的战术飞机,最大俯仰力矩是飞机方位的函数,在水平轨迹中出现在倾斜90°的情况,此时飞机的滚转速率达到峰值,迎角超过45°。最大滚转力矩依赖于滚转模态时间常数。对于较小的滚转时间常数（快速响应）,最大滚转力矩出现在最大滚转加速度、零迎角,基本与飞机的方位无关;对于较大的滚转时间常数,最大滚转力矩出现在最大滚转速率、迎角最大、倾斜角180°的水平飞行中。最大的航向力矩出现在最大滚转加速度、迎角最大时,基本与飞机的方位无关。     

二次喷射阀门作动对侧向力的影响

针对潜入式喷管燃气二次喷射推力矢量控制系统,利用AUSM+格式,并结合Realizable k-ε湍流模型,对喷管内二次喷射流场进行数值模拟。主要研究二次喷射阀门作动过程中侧向力的变化规律,分析正弦波、三角波2种作动方式和5、7、10 Hz 3种频率对侧向力的影响规律。结果表明,在阀动过程中侧向力变化与阀门开度变化趋势相同,大体上侧向力随阀门开度增加而增加,随阀门开度减小而减小,但存在一定的时间和空间滞后,侧向力变化滞后于阀门位置变化,最大侧向力出现在半个周期以后,即最大开度出现时刻之后,且阀门重新闭合后,很短时间内仍有侧向力残存,相同开度下,侧向力有如下大小关系:关闭过程大于准稳态,二者又大于开启过程中的侧向力;从最大侧向力出现时刻分析滞后时间τD,在波形上三角波下滞后时间τD要大于正弦波下的τD,在频率上10 Hz下的τD最大,5 Hz下的τD最小;从侧向力相对残存时间τR分析时间滞后,在波形上三角波下的τR要大于正弦波下τR,在频率上7 Hz下的τR最大,5 Hz下的τR最小。     

高超声速飞行器前体/进气道参数重要性测度

针对机体推进高度一体化的吸气式高超声速飞行器前体/进气道相关参数对其性能指标的独立和交互作用问题,基于回归模型和二阶混合中心矩理论,以总压恢复系数为性能指标,提出了参数重要性测度新方法。设计了二维混压楔形前体/进气道变几何构型方案并给出重要性测度模型,定量和定性地对参数重要性进行了对比和分析。研究结果表明:前体/进气道相关参数间具有强的非线性作用,交互作用非常显著,独立作用可以忽略不计,且重要性测度模型易于扩展。     

Plants survive rapid decompression: Implications for bioregenerative life support

Radish (Raphanus sativus), lettuce (Latuca sativa), and wheat (Triticum aestivum) plants were grown at either 98 kPa (ambient) or 33 kPa atmospheric pressure with constant 21 kPa oxygen and 0.12 kPa carbon dioxide in atmospherically closed pressure chambers. All plants were grown rockwool using recirculating hydroponics with a complete nutrient solution. At 20 days after planting, chamber pressures were pumped down as rapidly as possible, reaching 5 kPa after about 5 min and ∼1.5 kPa after about 10 min. The plants were held at 1.5 kPa for 30 min and then pressures were restored to their original settings. Temperature (22 °C) and humidity (65% RH) controls were engaged throughout the depressurization, although temperatures dropped to near 16 °C for a brief period. CO₂ and O₂ were not detectable at the low pressure, suggesting that most of the 1.5 kPa atmosphere consisted of water vapor. Following re-pressurization, plants were grown for another 7 days at the original pressures and then harvested. The lettuce, radish, and wheat plants showed no visible effects from the rapid decompression, and there were no differences in fresh or dry mass when compared to control plants maintained continuously at 33 or 98 kPa. But radish storage root fresh mass and lettuce head fresh and dry masses were less at 33 kPa compared to 98 kPa for both the controls and decompression treatment. The results suggest that plants are extremely resilient to rapid decompression, provided they do not freeze (from evaporative cooling) or desiccate. The water of the hydroponic system was below the boiling pressure during these tests and this may have protected the plants by preventing pressures from dropping below 1.5 kPa and maintaining humidity near 1.5 kPa. Further testing is needed to determine how long plants can withstand such low pressure, but the results suggest there are at least 30 min to respond to catastrophic pressure losses in a plant production chamber that might be used for life support in space.     

氧-乙炔烧蚀试验中热流密度的计算

通过氧-乙炔烧蚀试验中改变氧气与乙炔气流量比值的一系列试验,研究了热流密度随其变化的规律,并利用一元线性回归方法,分区间拟合得到了热流密度与两种气体流量比值的数学关系式,经检验该关系式适用性较好,为防热复合材料在氧-乙炔烧蚀试验中热流密度的变化提供了可靠的计算依据.