Experimental study of hydrogen-rich/oxygen-rich gas-gas injectors

Five types of coaxial injectors were investigated experimentally using hot hydrogen-rich gas and oxygen-rich gas, which were respectively provided by a GH2/GO2 hydrogen-rich perburner and a GH2/GO2 oxygen-rich preburner. The injectors were the shear coaxial injector, the oxidizer post expansion coaxial injector, the fuel impinging coaxial injector, the central body coaxial injector, and the shear tri-coaxial injector. The characteristic velocity efficiency and the combustor＇s wall temperatures were obtained for different design parameters through the experiments. It can be con- cluded that angles of the oxidizer post expansion and the fuel impinging have little influence on the combustion performance and the wall temperatures. The contact area between fuel and oxidizer and the mass flow rate have significant impacts on the combustion performance. The shear tri-coaxial injector has the best combustion performance but also the highest wall temperatures among the five types of injectors.     

高温风洞收集口喷水降温数值仿真研究

针对高温风洞中扩压器前段壁面防热问题，提出对高温气流外缘喷水降温的方法。通过在收集器入口与喷管出口间安装喷水环，利用液态水汽化吸热对高温气流进行降温，使扩压器壁面形成低温保护层。为了解该方法降温效果，本文利用DPM、组分输运等模型的耦合建立了超声速两相流CFD模型，对向超声速热气流喷水进行降温的过程进行了数值计算，计算结果表明，扩压器启动后有显著的降温保护效果。同时，为探索风洞排气背压和喷水量对风洞流场和壁面降温效果的影响，通过计算得出了变排气背压、变喷水量与降温效果之间的关系，为高温风洞收集口喷水降温装置的优化设计提供了参考。     

共轴高速直升机振动载荷计算分析模型

共轴高速直升机上下旋翼之间存在强烈的气动干扰现象,这对旋翼的气动特性影响较大。本文根据这一特点并考虑气弹耦合计算效率,利用单旋翼自由尾迹模型的尾迹几何和固定尾迹计算的初始诱导速度分布作为共轴双旋翼预定尾迹模型的初始迭代值。与Leishman-Beddoes非定常动态失速模型、Pitt-Peters动态入流模型、共轴直升机上下旋翼桨叶全本征动力学方程及弹性桨叶与变距轴承边界约束条件等计算模块相结合,建立了一种考虑上下旋翼之间气动干扰及耦合迭代的共轴双旋翼振动载荷计算模型。为验证本分析模型的计算精度,以西科斯基公司的验证机XH-59A为研究对象,与国外风洞试验结果进行了对比,两者吻合较好。     

间隙位置和几何对端壁冷却性能的影响

采用数值求解三维雷诺平均Navier-Stokes(RANS)方程和k-ω湍流模型,研究了间隙位置和几何对燃气轮机叶片端壁冷却性能的影响。在验证数值方法正确性的基础上,研究了3种间隙位置对端壁气膜冷却性能的影响,并提出了3种渐缩梯形间隙结构,分析了渐缩间隙结构对端壁流动和冷却特性的影响。结果表明,间隙距叶片前缘距离的增大会降低叶片前缘附近马蹄涡影响区域的气膜有效度,但是,当质量流量比大于1.0%时,端壁气膜有效度分布均匀性提高。在质量流量比为0.5%时,间隙位于距叶片前缘0.1倍轴向弦长位置时,会发生主流入侵的现象。相比于原始间隙,3种渐缩梯形间隙均能够显著提高端壁气膜有效度。特别是质量流量比为1%时,3种渐缩梯形间隙使得端壁平均气膜有效度最大增大了105.36%。此外,渐缩梯形间隙还防止了在质量流量比为0.5%时,主流入侵的发生。     

W波段FMCW SAR系统实现与试验

与C波段、X波段和Ka波段相比,W波段的调频连续波(FMCW)合成孔径雷达(SAR)系统因具有更高的分辨率,更易实现低功耗与小型化而备受关注。W波段波长短,因此该波段的FMCW SAR更适用于短距离成像。提出一种W波段FMCW SAR系统的设计方案,根据提出的系统方案与指标,实现W波段FMCW轨道SAR系统的样机研制。该系统分辨率可达5 cm。系统样机试验在上海交通大学的多功能船模拖拽水池完成。设置不同目标进行成像试验,最终得到多组有效试验数据,并基于改进的RD算法进行数据处理,得到理想的SAR图像。经分析可知,系统实际分辨率优于5 cm。试验结果证明了W波段FMCW SAR系统的可行性与有效性。     

高速永磁电机综合设计与分析

高速非晶合金永磁电机设计受电磁、机械、温升的制约,因此高速非晶合金永磁电机的设计是一个多物理场综合设计的过程。针对高速非晶合金永磁电机设计受多物理场制约的问题,基于多物理场的分析方法,分析了非晶合金材料对高速永磁电机电磁性能的影响；研究了内置式永磁转子在高速运行状态下的应力分布,并分析了轴承支撑刚度对转子系统临界转速的影响；针对高速非晶合金永磁电机损耗分布特点研究了其温度场的分布。基于提出的多物理场综合设计方法,设计并制造了一台额定功率15 kW、最高转速30 000 r/min的高速内置式非晶合金永磁电机,并对样机进行了试验,验证了仿真分析与设计方法的可行性,为高速非晶合金永磁电机的设计提供参考。     

三维编织石英纤维热密封材料气密性能研究

引入三维编织石英纤维织物作为热密封材料,对三维四向、三维五向编织结构热密封材料试样进行了不同压缩率下透气性能试验。分析了三维编织结构热密封材料气体渗透量随压缩率、压差及编织工艺参数的变化规律。结果表明,通过优化编织结构,有利于提高试样的气密性能;试样的平均气体渗透量受纤维体积含量影响,随压缩率的增大而降低;在压缩率为10%与20%时,纤维体积含量为50%的三维四向试样相比气密性能更好,平均气体渗透量分别为1.14×10~(-6)、9.29×10~(-7)kg/(s·mm);当压缩率增加到30%时,试样出现明显剪切变形和碎裂,试样失效。通过合理设计,三维编织石英纤维织物可满足密封材料气密性能要求。     

Tolerance of wheat and lettuce plants grown on human mineralized waste to high temperature stress

The main objective of a life support system for space missions is to supply a crew with food, water and oxygen, and to eliminate their wastes. The ultimate goal is to achieve the highest degree of closure of the system using controlled processes offering a high level of reliability and flexibility. Enhancement of closure of a biological life support system (BLSS) that includes plants relies on increased regeneration of plant waste, and utilization of solid and liquid human wastes. Clearly, the robustness of a BLSS subjected to stress will be substantially determined by the robustness of the plant components of the phototrophic unit. The aim of the present work was to estimate the heat resistance of two plants (wheat and lettuce) grown on human wastes. Human exometabolites mineralized by hydrogen peroxide in an electromagnetic field were used to make a nutrient solution for the plants. We looked for a possible increase in the heat tolerance of the wheat plants using changes in photosynthetically active radiation (PAR) intensity during heat stress. At age 15 days, plants were subjected to a rise in air temperature (from 23 ± 1 °C to 44 ± 1 °С) under different PAR intensities for 4 h. The status of the photosynthetic apparatus of the plants was assessed by external СО₂ gas exchange and fluorescence measurements. The increased irradiance of the plants during the high temperature period demonstrated its protective action for both the photosynthetic apparatus of the leaves and subsequent plant growth and development. The productivity of the plants subjected to temperature changes at 250 W m⁻² of PAR did not differ from that of controls, whereas the productivity of the plants subjected to the same heat stress but in darkness was halved.     

基于变速积分的高速电机磁悬浮控制系统设计

针对磁悬浮高速电机的磁轴承-转子系统,设计了基于MCU+FPGA的数字控制系统。为实现转子系统的高转速下稳定控制,在建立了磁轴承-转子闭环控制系统模型的基础上,针对常规PID控制系统的超调振荡问题和PD控制系统的转子位移静差问题,利用变速积分的思想设计了改进的PID控制器。实验表明,在消除了系统静差的同时明显减小了系统的超调量和调节时间,说明设计的控制系统具有很好的动态特性和稳态精度。     

一种负极性直流高压线性电源设计

本文提出了一种基于光耦反馈调整的负极性高压线性电源解决方案，使用NPN型三极管作为功率调整管的前提下，实现了负1200V直流电压输出。本文对提出的电源方案建立了小信号传递函数模型，在传递函数模型的基础上论证了所提出的电源系统具有稳定性高、噪声低等优点。