高陡度光学非球面高效制造的探讨

分析了计算机控制光学表面成形法、计算机控制应力盘抛光、磁流变抛光制造光学非球面元件的几项先进技术,探讨了光学元件的高速、高效加工,提出了高陡度光学非球面的固着磨料研磨加工。     

吸力面翼刀对压气机叶栅内二次流的影响

1引言在叶轮机械叶栅内流动控制中,可以通过在叶片吸力面、端壁上安装翼刀或隔片,控制二次流的发展,降低二次流损失,其中将翼刀加装在吸力面上的控制方式即为吸力面翼刀控制技术。吸力面翼刀主要是通过阻断端壁附面层和叶片吸力面附面层近端壁处低能流动沿吸力面的展向迁移来对     

能谱变硬后的X射线对Ly12铝破坏效应的研究

用数值模拟方法讨论了X射线的能谱向短波方向变化后,对Ly12铝破坏效应的影响,对所得结果进行了分析和解释。     

燃烧室头部进气规律对煤粉燃烧效率的影响

用实验方法研究了火焰筒式煤粉燃烧室头部进气规律对燃烧效率的影响。通过对6种结构的头部配气方案的分析比较,得出了煤粉燃烧室合理的头部配气方案,为今后煤粉燃烧室的设计和工作状态的选择提供了重要的实验依据。     

Aerodynamic performance enhancement for flapping airfoils by co-flow jet

Introducing active flow control into the design of flapping wing is an effective way to enhance its aerodynamic performance. In this paper, a novel active flow control technology called Co-Flow Jet (CFJ) is applied to flapping airfoils. The effect of CFJ on aerodynamic performance of flapping airfoils at low Reynolds number is numerically investigated using Unsteady Reynolds Averaged Navier-Stokes (URANS) simulation with Spalart-Allmaras (SA) turbulence model. Numerical methods are validated by a NACA6415-based CFJ airfoil case and a S809 pitching airfoil case. Then NACA6415 baseline airfoil and NACA6415-based CFJ airfoil with jet-off and jet-on are simulated in flapping motion, with Reynolds number 70,000 and reduced frequency 0.2. As a result, CFJ airfoils with jet-on generally have better lift and thrust characteristics than baseline airfoils and jet-off airfoil when C_μ is greater than 0.04, which results from the CFJ effect of reducing flow separation by injecting high-energy fluid into boundary layer. Besides, typical kinematic and geometric parameters, including the reduced frequency and the positions of the suction and injection slot, are systematically studied to figure out their influence on aerodynamic performance of the CFJ airfoil. And a variable C_μ jet control strategy is proposed to further improve effective propulsive efficiency. Compared with using constant C_μ, an increase of effective propulsive efficiency by 22.6% has been achieved by using prescribed variable C_μ for NACA6415-based CFJ airfoil at frequency 0.2. This study may provide some guidance to performance enhancement for Flapping wing Micro Air Vehicles (FMAV).     

Three-dimensional numerical analysis on combustion performance and flow of hybrid rocket motor with multi-segmented grain

This paper presents the combustion characteristics in hybrid rocket motors with multi-segmented grain through three-dimensional numerical simulations. Multi-segmented grain is composed of several thin grains with two or more ports. The numerical model consists of Navier-Stokes equations with turbulence, solid fuel pyrolysis, chemical reactions, a fluid–solid coupling model and a regression rate model. The simulations adopt 90% Hydrogen Peroxide (HP) and PolyEthylene (PE) as the propellant combination. The effects of the rotation, port number, fuel grain segment number and mid-chamber length on the flow field and combustion performances are analyzed. The results indicate that the multi-segmented grain configuration can strengthen the flow field, and the regression rate and combustion efficiency are enhanced. Take the cases with two grain segments and three ports for example, the regression rate is increased by 32.4%−45.1% and the combustion efficiency increases by 6%−8.6% in different rotation angles.     

Flow mechanism between purge flow and mainstream in different turbine rim seal configurations

The rim seal is used to prevent mainstream ingestion to the gap between the vane of a turbine and its blade. In this article, the dolphin lip with a hook configuration and a large seal cavity with hook structures are designed based on the high-pressure turbine datum single shark lip rim seal configuration. The sealing effect and parameters of the flow field are measured by an experiment method and a numerical simulation is used to explain the mechanism. For three configurations, the effect of the leakage slot vortex on the efficiency of the seal and the influence of leakage vortex, generated by the interaction between purge flow and mainstream flow, are discussed in depth. The result shows that the reverse vortex formed by the dolphin lip rim seal with hook structure will increase the sealing efficiency. The seal configuration with a large cavity improves sealing efficiency to a greater extent than the datum structure. At different purge flow rates and with unequal seal structures, the purge flow produces three types of leakage vortices in the passage. Besides, the seal configuration with dolphin lip produces a Kelvin-Helmholtz instability at the interface of the purge and the mainstream flows at a low purge flow rate to induce new leakage vortex branches in the passage of the blade.     

Experimental study on plasma jet deflection and energy extraction with MHD control

This paper presents an integrated research scheme for vector deflection and energy extraction in a gas plasma jet under Magneto-Hydrodynamic (MHD) control. A MHD-controlled thrust-vector test rig was used to conduct the experimental research. A gas plasma was obtained by injecting ionization seeds of Cs₂CO₃ into the combustion chamber via artificially forced ionization. The effects of the gas temperature and ionization seed mass fraction on the plasma jet deflection and energy extraction were experimentally verified under an applied magnetic field. The experimental results were analyzed theoretically. The results showed that the deflection amplitude of the gas plasma jet and the extracted voltage signal intensity increased with increasing gas temperature and the ionization seed mass fraction. The extracted dynamic voltage signals proved that the ionization seeds of Cs₂CO₃ induced gas ionization at 1173 K. The experiment verified that it is feasible to simultaneously achieve jet deflection and extract energy under the action of an external magnetic field.     

Grinding temperature and energy ratio coefficient in MQL grinding of high-temperature nickel-base alloy by using different vegetable oils as base oil

Vegetable oil can be used as a base oil in minimal quantity of lubrication(MQL). This study compared the performances of MQL grinding by using castor oil, soybean oil, rapeseed oil, corn oil, sunflower oil, peanut oil, and palm oil as base oils. A K-P36 numerical-control precision surface grinder was used to perform plain grinding on a workpiece material with a high-temperature nickel base alloy. A YDM–III 99 three-dimensional dynamometer was used to measure grinding force,and a clip-type thermocouple was used to determine grinding temperature. The grinding force, grinding temperature, and energy ratio coefficient of MQL grinding were compared among the seven vegetable oil types. Results revealed that(1) castor oil-based MQL grinding yields the lowest grinding force but exhibits the highest grinding temperature and energy ratio coefficient;(2) palm oil-based MQL grinding generates the second lowest grinding force but shows the lowest grinding temperature and energy ratio coefficient;(3) MQL grinding based on the five other vegetable oils produces similar grinding forces, grinding temperatures, and energy ratio coefficients, with values ranging between those of castor oil and palm oil;(4) viscosity significantly influences grinding force and grinding temperature to a greater extent than fatty acid varieties and contents in vegetable oils;(5) although more viscous vegetable oil exhibits greater lubrication and significantly lower grinding force than less viscous vegetable oil, high viscosity reduces the heat exchange capability of vegetable oil and thus yields a high grinding temperature;(6) saturated fatty acid is a more efficient lubricant than unsaturated fatty acid; and(7) a short carbon chain transfers heat more effectively than a long carbon chain. Palm oil is the optimum base oil of MQL grinding, and this base oil yields 26.98 N tangential grinding force,87.10 N normal grinding force, 119.6 °C grinding temperature, and 42.7% energy ratio coefficient.     

供热系统集约化运行的能耗监测及节能调节问题探讨

对我校供热系统的现状进行了分析；指出了锅炉热效率及能耗监控方面的不足，并针对锅炉热效率提高和二次网循环泵变频调节进行了节能分析计算；同时根据我校实际情况对循环泵设备配置及控制进行了分析，提出了要加强技术指标量化考核和能耗监测，提高效率、节能降耗，实现供热系统的科学化、集约化运行。