共查询到18条相似文献,搜索用时 62 毫秒
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脉冲爆震发动机进气道气动性能的数值研究 总被引:4,自引:0,他引:4
采用有限体积法计算了脉冲爆震发动机某轴对称超音速进气道在3种
不同出口条件(单个正弦扰动压力、某脉冲爆震发动机爆震室头部表压和进气道出口堵塞)
下的进气道内结尾正激波的运动情况,得出了进气道内结尾正激波运动特性和不同出口条件
的关系. 在计算中,采用了多块结构化网格,控制体积的界面无黏通量采用三阶迎风格
式插值获得,同时采用了minmod通量限制器以确保在激波处的解的物理特性;扩散通量采
用二阶中心差分格式插值获得. 定常计算采用当地时间步法,非定常计算采用双时间步法.
离散的代数方程采用交替方向迭代法求解。 相似文献
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采用简化的脉冲爆轰推进装置模型,利用热循环效率分析方法,推导了包含进气道总压恢复系数的热循环效率公式. 并在特定来流条件下,考察了一个爆轰循环中进气道总压恢复系数和燃烧室初始温度对热循环效率和比冲的影响. 研究发现,降低来流总压损失有助于提高热循环效率,而提高燃烧室初始温度能更有效地提高热循环效率. 据此,提出了多级重起爆脉冲爆轰发动机概念,利用在突扩截面上解耦的爆轰波的前导激波去再次压缩工质,进一步提高工质的热力学参数,从而提高脉冲爆轰装置的热循环效率. 推导了此种构型PDE的热循环效率计算公式,并对多级重起爆脉冲爆轰发动机进行了原理性论证. 研究结果表明,多级重起爆方法提高了燃烧室的爆前温度,从而有效地提高脉冲爆轰发动机热循环效率. 最后,关于出口工质的非完全膨胀的情况,做了定性的阐述,认为只有降低工质的出口压力,才能更有效增加工质的出口动能,从而提高热循环效率. 相似文献
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脉冲爆轰发动机是一种新概念引擎,具有热循环效率高的显著优点。介绍了脉冲爆轰发动机的基本工作原理、优点和军用、民用上的广阔前景;综述了脉冲爆轰最新的实验研究进展;讨论了单循环爆轰的工作过程以及试验研究脉冲爆轰的主要难点。 相似文献
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爆轰燃烧具有释热快、循环热效率高的特点. 斜爆轰发动机利用斜爆轰波进行燃烧组织, 在高超声速吸气式推进系统中具有重要地位. 以往研究主要关注斜爆轰波的起爆、驻定以及波系结构等, 缺少从整体层面出发对斜爆轰发动机开展推力性能分析. 本文将斜爆轰发动机内的流动和燃烧过程分解成进气压缩、燃料掺混、燃烧释热和排气膨胀4个基本模块并分别进行理论求解, 建立了斜爆轰发动机推力性能的理论分析模型. 在斜爆轰波系研究成果的基础上, 选取了过驱动斜爆轰、Chapman?Jouguet斜爆轰、过驱动正爆轰和斜激波诱导等容燃烧等4种燃烧模式来描述燃烧室内的燃烧释热过程, 并对比分析了不同燃烧模式对发动机比冲性能的影响. 此外, 还获得了不同来流参数、燃烧室参数和进排气参数等对发动机推力的影响规律, 发现来流马赫数和尾喷管的膨胀面积比是发动机理论燃料比冲的主要影响因素. 最后, 结合以往关于受限空间内斜爆轰波驻定特性等方面的研究成果, 提出了斜爆轰发动机燃烧室的设计方向. 相似文献
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偶件表面粗糙度对碳纤维增强尼龙复合材料摩擦学性能的影响 总被引:14,自引:6,他引:8
在栓-盘摩擦磨损试验机上考察了干摩擦条件下偶件表面粗糙度对碳纤维增强尼龙(PA1010)复合材料摩擦学性能的影响,采用不迩显微镜观察分析了偶件表面转移膜的形貌。结果表明,碳纤维能够明显提高PA1010的耐磨性能,当碳纤维增强相的质量分数为10%和20%时,增强PA1010复合材料的磨损率比非增强PA1010的降低3~6倍。这是由于碳纤维起到了承载作用并具有较强的抗犁削能力所致,磨损表面形貌光学显微分析表明:磨损前后偶件表面形貌发生了明显的变化;当偶件表面粗糙度Ra处于0.11~0.13um范围内时,复合材料的摩损率最低;随Ra值的增大或减小微切削和转移膜疲劳脱落加剧致使复合材料的磨损率快速增大。 相似文献
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Effect of scale on the onset of detonations 总被引:6,自引:0,他引:6
S.B. Dorofeev V.P. Sidorov M.S. Kuznetsov I.D. Matsukov V.I. Alekseev 《Shock Waves》2000,10(2):137-149
Critical conditions for onset of detonations are compared at (1) two significantly different scales, (2) for a range of -air mixtures diluted with C, O, and (3) for two types of geometry – one a long obstructed channel and the other a room with a relatively small aspect ratios.
For the range of scales, mixtures, and initial conditions tested, the detonation cell size was shown to be a reliable scaling parameter for characterization of detonation onset conditions. An experimental correlation
is suggested for the critical detonation onset conditions. This correlation is based on a wide variety of available experimental
data on DDT in mixtures of hydrogen and hydrocarbon fuels with air and on the use of detonation cell size as a scaling parameter characterizing the mixture.
Received 14 November 1999 / Accepted 16 February 2000 相似文献
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A study on jet initiation of detonation using multiple tubes 总被引:1,自引:0,他引:1
A detonator consisting of a dense bundle of small-diameter tubes (4.4–19 mm) is tested experimentally using stoichiometric
mixtures of hydrogen–oxygen and hydrogen–air. Tests are conducted in a 5,200-mm long detonation tube fitted with a schlieren
photograph section and smoked foil to record the deflagration to detonation (DDT) transition. It is confirmed that the flame
jet emanating from the tube assembly causes detonation initiation immediately downstream of the detonator, with little dependence
on the size of the detonation tube. For the fuel–air mixture, the insertion of Shchelkin spirals into each of the smaller
tubes enhances the development of the turbulent flame jet, leading to a shorter DDT distance. Multi-point spark ignition is
also shown to provide a further reduction in the DDT distance compared to single-point ignition.
PACS 47.40.-x; 47.40.Nm; 47.70.Fw; 82.40.-g; 82.40.Fp 相似文献
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Thermal buoyant air inside a modified Rayleigh–Bénard (RB) cavity bounded by a lower flat plate and an inverted‐V upper plate has been investigated numerically using the finite‐volume method. The second‐order‐accurate QUICK and SIMPLE schemes were used for the discretization of the convective terms and the pressure–velocity coupling in the set of conservation equations, respectively. The problem under study is controlled by two parameters: (1) the Rayleigh number ranging from 103 to 106 and (2) the relative height of the vertical sidewalls d. In reference to the latter, it varies from one limiting case corresponding to the standard RB cavity (a rectangle with d = 1) to another limiting case represented by an isosceles triangular cavity where d = 0. The numerical results for the velocity and temperature fields are presented in terms of streamlines, isotherms, local and mean heat fluxes. An additional effort was devoted to determine the critical Ra values characterizing the transition from symmetrical to asymmetrical buoyant airflow responsive to incremental changes in Ra. For purposes of engineering design, a general correlation equation for the Nusselt number in terms of the pertinent Ra and d was constructed using nonlinear multiple regression theory. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
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Influence of the Prandtl Number on the Unsteady Thermo-Fluid Dynamic Field Around a Thick Plate 总被引:1,自引:1,他引:0
The problem of a semi-infinite “thick” plate impulsively accelerated to a constant speed is discussed, considering a compressible laminar boundary layer when the thermo-fluid dynamic field in the flow is coupled with the thermal field in the solid (conjugated heat transfer). Different cases are defined by the boundary condition for the thermal field on the unwetted plate side, A first-order analytical approximation of a more general method of solution is here proposed, with emphasis to the analysis of the effects of the Prandtl number (Pr), when the temperature on the unwetted side of the plate is assumed constant. The comparison with some reference solution available for the limiting conditions of steady flow and plate of infinite length shows a very satisfactory accuracy of the present results in spite of the first order approximation. 相似文献
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壁面对串列双圆柱尾迹影响的实验研究 总被引:1,自引:0,他引:1
为研究壁面对近壁等直径串列双圆柱尾迹特性的影响,用PIV和压力传感器测量尾迹湍流的涡结构及频谱.实验在循环水槽内进行,基于圆柱直径D的雷诺数为1696,壁面边界层厚度为6.6D.影响尾迹流场结构的两个重要的特征参数是T/D和G/D(T为两圆柱中心间的距离,G为圆柱下表面与壁面间的距离),文中主要考察G/D的影响.实验中... 相似文献