气-气推进剂氧喷嘴出口型面对特征效率的影响

通过对气氢/气氧为推进剂的同轴剪切喷嘴进行研究,分析同轴剪切结构喷嘴出口型面变化和厚度对特征效率的影响.结果表明:氧喷嘴出口处能形成小尺度的回流区,起到火焰稳定器的作用;带扩口的氧喷嘴使氧产生径向速度,使回流区受到干扰,使推进剂特征效率较低;直口的喷嘴有利于推进剂火焰的稳定,而达到高的特征效率;而不同氧出口厚度对特征效率的影响不大.

燃烧加热脉冲风洞气动/推进一体化试验研究

吸气式高超声速飞行器的机体与超燃冲压发动机高度耦合,使得一体化气动性能预测非常困难,但是能够开展一体化带动力试验的地面设备很少。中国空气动力研究与发展中心(CARDC)研制了一种氢氧燃烧加热高焓脉冲风洞,其有效试验时间大大超过长时间激波风洞,采用模型-天平一体化设计实现了在几百毫秒内进行高精度测力,重复性测力误差小于2%。结合数值计算进行了支架干扰、来流污染凝结、壁温等影响及试验数据修正研究。典型升力体高超声速飞行器气动/推进一体化试验结果表明:在燃烧加热脉冲设备的300~600ms有效试验时间内,能够有效获得飞行器的升力、阻力(推力)和力矩特性,试验数据与CFD计算结果基本吻合。

考虑气水界面推进的底水凝析气藏直井见水时间预测

预测底水凝析气藏见水时间通常不考虑气水界面推进的影响,预测结果存在一定偏差。文中在综合考虑气水界面推进、凝析油析出、水质点舌进等基础上,分析了底水凝析气藏气水界面运移规律,并基于物质平衡与渗流理论,建立了底水凝析气藏直井见水时间预测公式;运用单因素分析法研究了气藏厚度、采气速度及水侵速度对见水时间的影响。结果表明:文中建立的公式能准确地预测见水时间;见水时间随气藏厚度的增加而增加,且气藏厚度越大,气水界面推进对见水时间的影响越大;见水时间随采气速度的增加而减少,且采气速度越大,气水界面推进对见水时间的影响越小;见水时间随水侵速度的增加而减少。

常规潜艇发展的一个里程碑——世界第一艘不依赖空气推进潜艇服役

常规潜艇一般在水面或通气管状态航行时采用柴油机推进,在水下航行时使用蓄电池作为动力源。虽然常规潜艇至今已发展到第三代,甚至第四代,各方面性能都有了很大提高,但蓄电池仍采用传统的铅酸电池,能量有限,潜艇必须经常浮到水面在柴油机推进的同时,给蓄电池充电。这样不但使潜艇的最大潜航时间只有3～4天,而且大大增加了潜艇暴露的危险性。为此,从第二次世界大战起,许多国家就一直致力于不依赖空气推进(AIP)的潜艇非核推进系统的研究。目前这项研究已取得突破性进展。其中瑞典研制的斯特林(Stiring)发动机和都国研制的燃料电池这两种新型AIP系统已达到实用阶段。

气溶胶推进剂CFC替代技术

一、由于使用CFC(氟氯碳、氟利昂)造成的危害: 由于大气的结构,地球上的生命得以生存。上层大气中的臭氧层保护我们免受紫外线辐射的伤害,而同时让可见光通过,支持各种植物的生长构成食物链的基础。其它微量气体起着调节气温的作用。

Application of Pyrolysis-Gas Chromatography in Explosive and Propellant Analysis

Applications of pyrolysis-gas chromatography and pyrolysis capillary gas chromatography in explosive and propellant analysis are reviewed, including the identification of explosives and propel- lants, the investigation of the thermal decomposition of nitrocellulose (NC), cyclotetramethylene tetranitramine (HMX)and cyclotrimethylene trinitramine (RDX), and the study of the wear- reducing mechanism of polyurethane additive in propellant gain.

Improved SMB speckle filtering of polarimetric SAR data with synergistic use of orientation angle compensation and spatial majority rule

The scattering-model-based(SMB)speckle filtering for polarimetric SAR(Pol SAR)data is reasonably effective in preserving dominant scattering mechanisms.However,the efficiency strongly depends on the accuracies of both the decomposition and classification of the scattering properties.In addition,a relatively weak speckle reduction particularly in distributed media was reported in the related literatures.In this work,an improved SMB filtering strategy is proposed considering the aforementioned deficiencies.First,the orientation angle compensation is incorporated into the SMB filtering process to remedy the overestimation of the volume scattering contribution in the Freeman-Durden decomposition.In addition,an algorithm to select the homogenous pixels is developed based on the spatial majority rule for adaptive speckle reduction.We demonstrate the superiority of the proposed methods in terms of scattering property preservation and speckle noise reduction using L-band Pol SAR data sets of San Francisco that were acquired by the NASA/JPL airborne SAR(AIRSAR)system.

Numerical simulation of bubble chaotic motion in a cavitating water jet

A computational fluid dynamics (CFD) method is developed to investigate the radical motion of single cavitating bubble in the oscillating pressure field of a cavitating water jet. Regarding water as a compressible fluid, the simulation is performed at different oscillating frequencies. It is found that the bubble motion presents obvious nonlinear feature, and bifurcation and chaos appear on some conditions. The results manifest the indetermination of the cavitating bubble motion in the oscillating pressure field of the cavitating water jet.

The Potentially Dangerous Asteroid （99942） Apophis

This paper computed the newest impact solutions of the potentially dangerous asteroid （99942） Apophis based on 4,138 optical observations from March 15.10789 UTC （Universal Time Coordinated）, 2004 to February 28.089569 UTC, 2014 and 20 radar observations from January 27, 2005 through March 15, 2013, as of June 20, 2014. Using the freely available the OrbFit software Package, this paper followed its orbit forward in the searching for close approaches with the Earth and possible impacts up to year 2116. With the different A2 non-gravitational parameter in the motion of the asteroid （99942） Apophis, this paper computed possible impact solutions using the JPL DE405 （Jet Propulsion Laboratory Development Ephemeris） and 25 additional massive perturbed asteroids. Additionally, this paper used weighing and selection methods adopted in the OrbFit software as prepared by the NEODyS （Near Earth Objects--Dynamical Side） Team. Moreover, this paper used method of computing the orbit of Apophis taking into account star catalog debiasing and an error model with assumed astrometric errors RMS （root mean square）, deduced from the observational material of the given observatories. JPL＇s Sentry and NEODyS＇s CLOMMON2, two automatic monitoring systems routinely scanning for possible impacts in the next hundred years. Only for several dangerous asteroids presented results are computed with the non-gravitational parameters. This paper detected possible impacts of the asteroid （99942） Apophis only with the non-gravitational parameter, A2 〉 0. It was appeared that impacts in 2068, 2087, 2105 and in 2111 were possible only when Apophis rotated in prograde direction.

未来常规潜艇技术发展展望

20世纪90年代以来,随着世界政治格局的变化,以及常规潜艇技术的飞速发展,适合近岸环境作战的常规潜艇的地位日益凸现:担任战略威慑、反舰、秘密作战和侦察等广泛的作战任务,可望与核潜艇平分秋色,成为海战的主要力量。

The State of Arts of Hall Thruster

Electric propulsion is broadly defined as the acceleration of a working fluid for propulsion by electrical heating and/or by electric and magnetic body forces. Compared with chemical propulsion, electric propulsion has the characteristic of higher specific impulse, lower thrust, lighter weight and longer lifetime. So electric propulsion is generally suitable for satellite attitude control, the orbit transfer and raising, orbit correction, resistance compensate, position keeping, reposi- tion, space exploration and interplanetary flight.

RESEARCH ON SCHEME OF HIGH-SPEED ROTOR／WING TRANSITION HELICOPTER RD15

To analyze the existing schemes of high-speed rotorcrafts and some new technologies, a new conceptual sketch of the high-speed rotor/wing transition helicopter RD15 is proposed. The overall layout of the RD15 is given out and the transition process from the helicopter mode to the airplane mode is designed. The lift system consists of a circular disk-wing with four retractable blades. The technology of individual blade control is adopted for flight control in hover and low speed flight. The tail is a vectored thrust duct propeller. It can provide the anti-torque in hover, and offer the multi-directional controls and propulsion drive for the airplane mode flight. The aerodynamic characteristics and key technologies in the transition process for this layout, including the nose up angle of disk-wing, the length of the blade, rotation speed, pitch angle and other parameters, are theoretically ana lyzed and experimentally tested. Calculation and experiments show that the shift process of the lift, the power and controls are smooth, and the designed scheme is feasible.

500-ton LOX/Kerosene Engine Joint Test Achieved Success

Recently,the first gas generator-turbopump joint test for the 500-ton LOX/kerosene engine was completed with success.The engine developed independently by the Academy of Aerospace Liquid Propulsion Technology（AALPT）will be used for the heavy-lift rocket.The 500-ton LOX/kerosene engine has the thrust of the largest ever developed by China and in the foreseeable future.

Fuel Cell Technology for Propulsion and Power Generation of Ships： Feasibility Study on Ocean Research Vessel Sagarnidhi

Rising fuel prices, increasing emission levels and impending environmental regulations made shipping industry to find an alternate for internal combustion engine in 21st century. Fuel cell is a sustainable, emerging technology with negligible pollution. More significantly for a research ship, emission levels need to be substantially low to have quality measurements. A feasibility study is carried-out First time in the world, to drive an ice class multi-disciplinary ORV （Oceanography Research Vessel） Sagarnidbi, using hydrogen powered fuel cell. Sagamidhi is equipped with special equipments viz., Deep Sea winch, specially designed cranes for Launching and retrieval of ROV （Remotely Operable Vehicle）, DSMC （Deep Sea Mining Crawler）, Tsunami systems, manned/unmanned submersible and ACS （Autonomous Coring System） and other facilities that support research in Indian, International and Antarctic waters. Beside this, the propulsion system along with DP （Dynamic Positioning）, centralized air conditioning and special equipments require enormous electrical power. The combustion of diesel oil in an engine, that coupled with an alternator generates electrical power required, along with NOx （Nitrous Oxides）, SOx （Sulphur Oxides） and PM （Particulate Matter） emissions. Shipping industry is the fourth largest contributor to air pollution and carbon emissions, particularly in coastal areas, and the growth rate makes the problem even more critical. Stringent international air pollution regulation and increasing fuel price paves the way for an alternative ＂green emission technology＂. Various fuel cells were analyzed with different combination of fuel, electrolyte and electrodes. From the analysis, it has been found that SOFC （Solid Oxide Fuel Cell） is most suitable for the present scenario. A fuel cell designed with hydrogen as fuel, zirconium oxides stabilized with yttrium oxide as electrolyte and zirconium electrodes is used for 1.5 MW power output and 0.5 MW through regenerator. Volume required for storage of hydrogen is in line with volume of fuel and a high standard safety measures were taken using sensors. The present system saves 3000 MT/annum of diesel oil costing 3,000,000 USD approximately.

气氧/丙烷小推力发动机设计与实验

为适应小推力发动机无毒、无污染、高性能、低成本的发展趋势,设计了一种以气氧(GO2)/丙烷(C3H8)为推进剂的发动机.采用层板式头部喷注器、利用喷嘴间隙实现电火花点火的独特点火方案、通过边区喷嘴进行气膜冷却,同时设计了发动机实验系统并开展了初步实验研究.实验结果表明:实验系统设计合理;发动机点火方案可靠、燃烧稳定、热防护效果良好,为进一步的研究奠定了基础.

Numerical exploration on jet oscillation mechanism of counterflowing jet ahead of a hypersonic lifting-body vehicle

Numerical investigation of a supersonic jet from the nose of a lifting-body vehicle opposing a hypersonic flow with the freestream Mach number being 8.0 at 40 km altitude was carried out by solving the three-dimensional, time-accurate Navier-Stokes equations with a hybrid meshes approach. Based on the analysis of the flow field structures and aerodynamic characteristics, the behaviours relevant to the LPM jet were discussed in detail, including the drag reduction effect, the periodic oscillation and the feedback loop. The obtained results show that the flow oscillation characteristic of the LPM jet is low-frequency and high-amplitude while that of the SPM jet is high-frequency and low-amplitude. Compared with the clearly dominant frequencies of the LPM jet, the SPM jet exhibits a broad-band structure. The LPM jet can sustain drag reduction effect until the angle of attack is 8°, and the lift-to-drag ratio of the vehicle is effectively improved by 6.95% at angle of attack of 6°. The self-sustained oscillation process was studied by a typical oscillating cycle of the drag force coefficient and the variation of the instantaneous pressure distribution,which reveals an off-axial flapping motion of the conical shear layer. The variation of the subsonic recirculation zone ahead of the vehicle nose strengthens the understanding of the jet behavior including the source of instability in the long penetration mode and the mechanism of the feedback loop. The aim of this paper is to advance the technology readiness level for the counterflowing jet applied as an active control technology in hypersonic flows by gaining a better insight of the flow physics.

Orbit determination for Chang'E-2 lunar probe and evaluation of lunar gravity models

The Unified S-Band （USB） ranging/Doppler system and the Very Long Baseline Interferometry （VLBI） system as the ground tracking system jointly supported the lunar orbit capture of both Chang＇E-2 （CE-2） and Chang＇E-1 （CE-1） missions. The tracking system is also responsible for providing precise orbits for scientific data processing. New VLBI equipment and data processing strategies have been proposed based on CE-1 experiences and implemented for CE-2. In this work the role VLBI tracking data played was reassessed through precision orbit determination （POD） experiments for CE-2. Significant improve- ment in terms of both VLBI delay and delay rate data accuracy was achieved with the noise level of X-band band-width syn- thesis delay data reaching 0.2-0.3 ns. Short-arc orbit determination experiments showed that the combination of only 15 min＇s range and VLBI data was able to improve the accuracy of 3 h＇s orbit using range data only by a 1-1.5 order of magnitude, confirming a similar conclusion for CE-1. Moreover, because of the accuracy improvement, VLBI data was able to contribute to CE-2＇s long-arc POD especially in the along-track and orbital normal directions. Orbital accuracy was assessed through the orbital overlapping analysis （2 h arc overlapping for 18 h POD arc）. Compared with about 100 m position error of CE-l＇s 200 kin x 200 km lunar orbit, for CE-2＇s 100 km x 100 km lunar orbit, the position errors were better than 31 and 6 m in the radial direction, and for CE-2＇s 15 km^100 km orbit, the position errors were better than 45 and 12 m in the radial direction. In addi- tion, in trying to analyze the Delta Differential One-Way Ranging （ADOR） experiments data we concluded that the accuracy of ADOR delay was dramatically improved with the noise level better than 0.1 ns and systematic errors better calibrated, and the Short-arc POD tests with ADOR data showed excellent results. Although unable to support the development of an independent lunar gravity model, the tracking data of CE-2 provided evaluations of different lunar gravity models through POD. It is found that for the 100 km x 100 km lunar orbit, with a degree and order expansion up to 165, JPL＇s gravity model LP165P did not show noticeable improvement over Japan＇s SGM series models （100x100）, but for the 15 kmxl00 km lunar orbit, a higher de- gree-order model can significantly improve the orbit accuracy.

Design and optimization of a trajectory for Moon departure Near Earth Asteroid exploration

The lunar probe often has some remaining fuel on completing the predefined Moon exploration mission and may carry out some additional tasks from the Moon orbit using the fuel.The possibility for the lunar probe to escape from the Moon and the Earth is analyzed.Design and optimization of the trajectory from the Moon orbit to the Near Earth Asteroids (NEAs) using the spacecraft's residual fuel is studied.At first,the semi-major axis,inclinations and the phase relations with the Earth of all the numbered NEAs are investigated to preliminarily select the possible targets.Based on the Sun-centered two-body problem,the launch window and the asteroid candidates are determined by calculating the minimum delta-v for two-impulse rendezvous mission and one-impulse flyby mission,respectively.For a precise designed trajectory,a full ephemeris dynamical model,which includes gravities of the Sun,the planets and the Moon,is adopted by reading the JPL ephemeris.The departure time,arrival time,burning time duration and thrust angles are set as variables to be designed and optimized.The optimization problem is solved via the Particle Swarm Optimization (PSO) algorithm.Moreover,two feasible NEA flyby missions are presented.

Hydrogen FBG Sensor Using Pd/Ag Film With Application in Propulsion System Fuel Tank Model of Aerospace Vehicle

The high efficiency hydrogen fiber Bragg grating （FBG） sensor is presented. The sensitive film was a new alliance of palladium-silver （Pd-Ag）. In addition, the titanium （Ti） layer was used as the adhesive layer. The presented sensor showed the resolution of more than 60pm/1%H2, and a fast response time of4s - 5s was guaranteed in the 0.1%H2 - 4%H2 range. Moreover, the life time of the sensor was investigated. The obtained results showed that the sensor had an enhanced life time. Furthermore, the sensor was applied in the propulsion system fuel tank model of the aerospace vehicle. The obtained results indicated that it is a prevention system against the disaster aerospace due to hydrogen leakage.