共查询到20条相似文献,搜索用时 62 毫秒
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High-speed air breathing propulsion systems have many attractive military and civil applications. The high propulsive efficiency of these systems allows the exploitation of speed, distance, and bigger payloads, or any combination of the three. The severe operating conditions of these systems require particular attention to overall thermal management of the engine/air-frame. Fuel-cooling the engine structure is a viable way of maintaining thermal balance over a range of flight conditions. Air Force applications have focused on using endothermic hydrocarbon fuels to address this issue because of their compatibility with the military operations. Recent ground tests of scramjet engines have demonstrated adequate performance utilizing state-of-the-art technology in materials. This progress has paved the way for an expendable flight test vehicle in the near future. In order to take full advantage of the capabilities of this propulsion system, advances in fuel-cooled structures, high temperature un-cooled materials, and increased heat capacity of hydrocarbon fuels will be needed to enable expendable systems to reach higher Mach numbers. An additional benefit would be realized in future reusable systems. 相似文献
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Simultaneous measurements of multiple flow parameters for scramjet characterization using tunable diode-laser sensors 总被引:1,自引:0,他引:1
This paper reports the simultaneous measurements of multiple flow parameters in a scramjet facility operating at a nominal Mach number of 2.5 using a sensing system based on tunable diode-laser absorption spectroscopy (TDLAS). The TDLAS system measures velocity, temperature, and water vapor partial pressure at three different locations of the scramjet: the inlet, the combustion region near the flame stabilization cavity, and the exit of the combustor. These measurements enable the determination of the variation of the Mach number and the combustion mode in the scramjet engine, which are critical for evaluating the combustion efficiency and optimizing engine performance. The results obtained in this work clearly demonstrated the applicability of TDLAS sensors in harsh and high-speed environments. The TDLAS system, due to its unique virtues, is expected to play an important role in the development of scramjet engines. 相似文献
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One of the major reasons coatings are used in internal combustion engines is to enhance the oxidation/corrosion resistance in contaminated corrosive environments. Such atmospheres are often encountered in diesel and utility gas turbines. Aircraft gas turbines are usually subjected to simple oxidation conditions, since the environment is generally cleaner and the operating temperatures higher than in ground-based engines. The primary source of corrosive species (sulfur, vanadium and even sodium) is in the fuel; but airborne salts are a concern, particularly for those engines operating close to to ocean. Diesel engines in ships may run on fuels containing up to 5% S, 400 ppm V, and 100 ppm Na. 相似文献
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The capabilities of the computing complex developed at the Institute for Problems in Mechanics of the Russian Academy of Sciences are studied by the example of an external hypersonic flow over a model of an unmanned experimental aircraft X-43 of complex configuration. The program complex includes a generator of the unstructured surface and volumetric computational meshes and a series of computer codes that implement the integration of the closed system of Euler and Navier-Stokes equations using the method of splitting by physical processes on an unstructured mesh. The results of application of the developed numerical method on the generated unstructured computational meshes for three-dimensional modeling of the aerothermodynamics of the complex hypersonic aircraft X-43 are presented. The flow field and heat transfer processes in the entire region of the flow from the bow wave to the far wake are investigated. The configuration of the shock waves generated in the flow over a hypersonic flying vehicle (HFV) is studied. The effect of the angle of attack and free stream on the flow flown and the aerodynamic and thermal characteristics of the HFV surface is studied. The integral aerodynamic characteristics of X-43, lift coefficients C L , and drag coefficients C D are calculated for each regime of the flow. The HFV lift-drag ratio K dependences on the Mach number and angle of attack are found. The data of the X-43 flight and wind-tunnel tests are compared with the results of numerical modeling. 相似文献
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A data recorder was utilized to record in‐flight vibration of a twin engine turbo propeller (feeder) aircraft. The data recorded produced power spectral density (PSD) profiles which are currently used in laboratory settings to drive vibration tables in order to simulate a particular vehicle type. Overall Grms values were averaged and compared to previous research studies. The data collected from this research study could be utilized for packaging research when developing products and packages that will pass through a distribution cycle which includes transportation via a feeder aircraft. One example of this type of distribution cycle is the small parcel shipping environment. The PSD profiles which were analyzed from this research could simulate in‐flight aircraft vibration of the aircraft chassis in a laboratory environment. This will enable further research in the air transport environment. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
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M.N Šarevski 《International Journal of Refrigeration》1996,19(6):382-389
Comparison of the main geometrical and operating parameters of centrifugal compressors working with various refrigerants is realised in this paper. The interdependence between the centrifugal compressor pressure ratio, compression work, impeller peripheral speed, Mach number, compressor capacity, impeller diameter and width, speed of rotation, and refrigerant molecular mass, normal boiling temperature and specific volumetric cooling capacity for various refrigerants are shown and discussed. The flow phenomena in the turbocompressor flow field, caused by high Mach number and high pressure ratio, are analysed. Some theoretical observations for the influence of the substitute of the refrigerant on the turbocompressor performance characteristics are presented. The possibilities for the replacement of the refrigerant in the existing refrigerating machines are discussed. 相似文献
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The flight control system of a launch vehicle is the result of the right tradeoff between different objectives, such as the
interaction between the control, guidance and performance aspects of a mission with specified end conditions and the analysis
of the mission trajectories and vehicle systems under a variety of normal and failure modes. Hence an evaluation of the design
and performance of such a system is not feasible through purely analytical means even with simplified models. This, together
with the necessity for step-by-step refinement of the models used for the vehicle and its environment, calls for the computer
simulation approach. The various considerations involved in developing and selecting the simulation model and implementing
it on a computer are discussed. To illustrate the approach, a hybrid simulation evaluation of the performance of the first
stage control system of a satellite launch vehicle and that of the controlled vehicle under different operational modes is
presented. 相似文献
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Tandem Configurations for Automated Guided Vehicle Systems and the Analysis of Single Vehicle Loops 总被引:1,自引:0,他引:1
Automated Guided Vehicle (AGV) systems continue to play a significant role in many low to medium flow manufacturing operations, including Flexible Manufacturing Systems (FMS) and other applications. The relatively inexpensive guidepath, coupled with the high degree of flexibility and control offered in vehicle routing, has made AGV systems a proven and viable handling technology for the 90's.
Traditionally, AGV systems have been implemented and analyzed assuming that every vehicle is allowed to visit any pick up/deposit point in the system. We introduce a conceptually simple and intuitive approach where the system is decomposed into non-overlapping, single-vehicle loops operating in tandem. In this paper, we also develop an analytical model to study the throughput performance of a single vehicle loop. The resulting expressions are the first closed form analytical expressions that have been obtained to determine the throughput capacity of a single vehicle operating under a specific dispatching rule in a non-deterministic environment. 相似文献
Traditionally, AGV systems have been implemented and analyzed assuming that every vehicle is allowed to visit any pick up/deposit point in the system. We introduce a conceptually simple and intuitive approach where the system is decomposed into non-overlapping, single-vehicle loops operating in tandem. In this paper, we also develop an analytical model to study the throughput performance of a single vehicle loop. The resulting expressions are the first closed form analytical expressions that have been obtained to determine the throughput capacity of a single vehicle operating under a specific dispatching rule in a non-deterministic environment. 相似文献
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以凝胶注模技术制备的固相含量为40%、45%、50%(质量分数,下同),孔隙率高达65.24%、63.26%、61.19%的多孔氮化硅天线罩材料作为研究对象。将测得的材料性能参数作为有限元分析模拟的数据支撑,构件模型载体选择正切尖拱形,使用FLUENT模拟流场,结构场采用ANSYS软件,热力耦合得到不同固相含量的材料在不同马赫数下流-热-固耦合后的热应力强度,对其力学特性进行分析。结果表明,较高马赫数下的飞行构件的尾部连接端是受热应力最大的部位,也是失稳较为严重的部位。飞行构件的结构稳定性需通过加固尾部连接端来提高;气动热是引起天线罩构件失稳的首要问题,解决结构失稳的关键在于解决气动热,可通过在天线罩构件外增加耐热隔层,使其免受气动热;多孔氮化硅材料的孔隙率与失稳时对应的马赫数成正比,热导率是影响多孔氮化硅天线罩构件在较高马赫数下受到热应力大小的关键因素。 相似文献
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Dr. rer. nat. B. Schmitt-v. Schubert 《Acta Mechanica》1995,111(3-4):161-170
Summary Slip boundary conditions are deduced for the Navier-Stokes equations describing the flow of a mixture of gases along a wall. Chemical reactions and changes of the internal energy at the wall are taken into account. A simplified approximation is introduced for a special case of the flow of a binary mixture consisting of atoms and molecules, which can be used as a model in treating the high-altitude flight of a space vehicle. The resulting conditions are compared with those given by other authors. 相似文献
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K. C. SHARMA 《国际生产研究杂志》2013,51(3):247-261
The present study relates to a transport organisation operating a fleet of aircraft and aims at determination of the optimal spare float of engines. The flow of the engines is viewed as a queueing problem in a closed loop system with variable demand and supply. The servicing facility consists of three stations in tandem. Two cases of the servicing facility operation are investigated, first when no inter-stage queue is permitted, and second when a queue length of one unit is allowed between the first and second stations. The solution is obtained by the Monte Carlo Simulation technique. The results are compared with those obtained from a reliability theoretical approach and conclusions are drawn. 相似文献
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O. M. I. Nwafor 《Sadhana》2002,27(3):375-382
This paper investigates the combustion knock characteristics of diesel engines running on natural gas using pilot injection
as means of initiating combustion. The diesel engines knock under normal operating conditions but the knock referred to in
this paper is an objectionable one. In the dual-fuel combustion process we have the ignition stage followed by the combustion
stage. There are three types of knock: diesel knock, spark knock and knock due to secondary ignition delay of the primary
fuel (erratic knock). Several factors have been noted to feature in defining knock characteristics of dual-fuel engines that
include ignition delay, pilot quantity, engine load and speed, turbulence and gas flow rate 相似文献
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微束等离子喷涂Al2O3陶瓷涂层特性 总被引:2,自引:0,他引:2
采用轴向中心送粉式微束等离子喷涂系统在2kW级的小功率条件下制备了Al2O3陶瓷涂层.研究了电弧功率、工作气体流量和喷涂距离对粒子速度与涂层组织结构和性能的影响.采用光学显微镜观察涂层的组织结构,采用X射线衍射分析涂层的相结构,采用磨粒磨损质量损失表征涂层的性能,用热辐射粒子速度温度测量系统测试工艺参数对喷涂粒子速度的影响.结果表明,电弧功率、工作气体流量和喷涂距离对粒子速度的影响都比较明显,粒子速度随着电弧功率和工作气体流量的增加而增加,随着喷涂距离的增加而下降.涂层的磨粒磨损质量损失随电弧功率的增加而减少,而随工作气体流量和喷涂距离的增加而增加.分析表明粒子的温度对涂层磨粒磨损质量损失有较大的影响.采用微束等离子喷涂可以制备磨粒磨损性能与传统等离子喷涂在38kW下制备的涂层相当的Al2O3涂层. 相似文献
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