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three-dimensional effect
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  three-dimensional effect
In the present simple manifold, the principal three-dimensional effect is a transfer of flow to the inviscid core region from the high-velocity jets adjacent to the sides which are parallel to the magnetic field.
      
Three-dimensional effect on transonic rectangular cavity flows
      
The use of transparent rotating scans, comparable to a block of glass, generates a three-dimensional effect.
      
Because it accounts for the three-dimensional effect, this model is named as the complete depthaveraged model.
      


A number of analytical studies have so far been conducted on the aero- elastic instability problem of turbomachine blades. Most of them, however, are based upon two-dimensional cascade models, and our knowledge on the three- dimensional effects is far from satisfactory. The three-dimensional effects on the unsteady blade loading involve various aspects, i. e., the annular geometry of real machines [1], spanwise nonuniformity in the amplitude of blade vibration [2], that in the unsteady component...

A number of analytical studies have so far been conducted on the aero- elastic instability problem of turbomachine blades. Most of them, however, are based upon two-dimensional cascade models, and our knowledge on the three- dimensional effects is far from satisfactory. The three-dimensional effects on the unsteady blade loading involve various aspects, i. e., the annular geometry of real machines [1], spanwise nonuniformity in the amplitude of blade vibration [2], that in the unsteady component of the incident flow velocity [4], that in the mean blade loading [5], and the existence of sound-absorbing wall linings [6]. In this paper the attention is focused on the effect of the spanwise variation of the blade geometry, which have never been studied as far as the authors are aware. This paper develops a linearized unsteady three-dimensional flow theory for a supersonic linear cascade of blades with an arbitrary plan form in a uniform mean flow between parallel rigid walls. An integral equation for the unsteady lifting pressure distribution is derived. Two problems have been studied, i. e., vibrating blades and interaction of blades with oncoming periodic gusts. Various aspects of the effect of the blade sweep upon unsteady blade loadings and generated sound waves are demonstrated with numerical examples. Some new discoveries are presented. It is found that local unsteady blade loadings due to vibration with a spanwise uniform amplitude are reduced at forward spans and increased at backward spans by increasing the blade sweep angle. When the sweep angle exceeds the complementary Mach angle, chordwise profiles of unsteady blade surface pressure are substantially deformed, and the unsteady aerodynamic work on blades in torsional vibration is drastically reduced. In the case of interaction with a periodic gust, a higher sweep angle brings about a higher nonuniformity of the gust phase along the blade lead- ing edge, resulting in a wavier unsteady blade loading distribution along the span. Increasing the sweep angle gives rise to the change of the dominant mode of sound waves generated by interaction with a periodic gust, but only a slight decrease in the total sound power.

在线性非定常三元流动分析的基础上,研究了后掠超音速叶栅叶片的后掠角对叶片振动和周期性来流干扰引起的非定常空气动力的影响。发现后掠角增大,叶片由于沿展向等幅振动引起的局部非定常负荷在前伸的半叶高上减小,而在后斜的半叶高上增大。当叶片的后掠角超过马赫角的补角时,叶片表面非定常压差分布有显著的变化,而扭转振动时作用在叶片上的非定常空气动力功激剧地减小。在与周期性来流干扰的情况下,增大后掠角使得叶片非定常负荷沿展向波动起伏次数变多。增大后掠角还使得与周期性来流干涉产生的音响波中占主要地位的波型发生变化,但总的音响能量只略略减小。

Abstract A method,“gross thrust model”,is developed to determine gross thrust of jet engine and afterburning turbofan engine in flight testing.This model is able to determine the gross thrust of modern engines with an acceptable degree of accuracy only by using a few of pressure measurements.The gross thrust model is based on a one dimensional analysis of flows in mixer,afterburner and nozzle.Some correction coefficients are required to account...

Abstract A method,“gross thrust model”,is developed to determine gross thrust of jet engine and afterburning turbofan engine in flight testing.This model is able to determine the gross thrust of modern engines with an acceptable degree of accuracy only by using a few of pressure measurements.The gross thrust model is based on a one dimensional analysis of flows in mixer,afterburner and nozzle.Some correction coefficients are required to account for three dimensional effects,the effects of friction and mass transfer,as well as the effects of the simplifying assumptions used in the theory.The correction coefficients in the model are K,C and E.Both K and C are constants,whereas E varies with engine operating conditions.In order to determine the reasonable coefficients K,C and E,it is necessary to acquire engine testing data in the altitude facility at flight conditions as much as possible.A comparison was made between the data determination from the gross thrust model and the gross thrust measured from the altitude facility for engine J85 GE 21 at H=7620m, Ma 0=0 90.It demonstrates that the accuracy of the gross thrust model is about 3 0 percent and depends on the pressure difference between the total pressure of the turbine discharge and the static pressure of the nozzle inlet.

提出了一种飞机飞行中发动机推力测定的总推力模型。该模型的基本思想是对涡轮后的混合室和加力燃烧室及尾喷管作一元流动分析,用三个修正系数考虑实际流动的三元效应、传热及传质等因素的影响。这三个系数事先由发动机地面台架试验或高空台试验数据优化分析确定。实际飞行中只需要测量涡轮出口截面上的总压p*5,加力燃烧室火焰稳定器后的静压p6,尾喷管进口的静压p7以及外界大气压力p0等少量的气动参数就可求得发动机总推力。这种模型测量简单,计算方便,求得的总推力精度高,适用于现代高性能战斗机的推力测量。

A survery of the development of fracture mechanics is given on the basis of damage tolerant design of structures.The effects of three dimensional stress state on residual strength,fatigue crack propagation life under cnstant-as well as variable-amplitude loading of aircraft structures and cracking resistance of aircraft materials are analyzed in detail.Some ideas on solving the roblems are proposed and some new results worked out by the author are presented.A brief discussion is made on three dimensional...

A survery of the development of fracture mechanics is given on the basis of damage tolerant design of structures.The effects of three dimensional stress state on residual strength,fatigue crack propagation life under cnstant-as well as variable-amplitude loading of aircraft structures and cracking resistance of aircraft materials are analyzed in detail.Some ideas on solving the roblems are proposed and some new results worked out by the author are presented.A brief discussion is made on three dimensional effects upon fatigue and fracture resistance of materials at elevated temperatures and in corrosion environments,durability of airframe,etc.Finally,a list of three dimensional problems is proposed,which must be solved to improve the techniques of damage tolerant design of aircraft structures.

在对三维断裂问题研究的基础上,对航空结构损伤容限评定中的三维问题进行了综合评述。详细分析了现行损伤容限分析的断裂力学基础、剩余强度评定、材料抗裂性能确定、常幅及谱载荷下寿命预测等重要环节中三维应力状态的作用,提出了解决问题的初步设想,给出了一些最新结果。并对介质、温度环境和载荷共同作用下材料失效中的三维问题等做了简述。最后提出了实现高可靠性损伤容限设计必须解决的三维问题

 
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