共查询到19条相似文献,搜索用时 612 毫秒
1.
室内轰燃预测方法研究 总被引:10,自引:0,他引:10
回顾总结了目前常用的室内轰燃预测方法 ;提出了一种预测轰燃的新方法轰燃综合预测法 ,对这一方法的有效性进行了试验验证。结果表明 :由于室内火灾受建筑材料热惯性、开口通风因子、燃料释热速率和房间内部尺寸等多种因素影响 ,传统轰燃预测方法存在多方面的局限性 ,而轰燃综合预测法预测的结果与试验结果比较吻合。 相似文献
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中庭建筑天井内火灾烟气运动特性的盐水实验模拟 总被引:1,自引:0,他引:1
本文运用盐水实验模拟方法研究了中庭建筑天井内的火灾烟气运动特性,实验模拟了天井内的烟气流态,即烟气羽流和并存的烟气环流,并定性分析了环流产生的机理。通过理论分析和实验结果,推导了天井内的羽流速度和决定环流起始方向的判据。同时,通过研究天井结构和侧室源强对流态的影响,给出了一种估算天井内不出现烟气环流时天井极限高度的方法 相似文献
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基于燃料可燃界限研究建筑火灾中的回燃现象 总被引:4,自引:0,他引:4
为了研究回燃产生的临界条件和细水雾抑制回燃产生的可行性及其抑制机理 ,建立了一套小尺寸回燃实验装置 ,并进行了一系列的实验 ;实验结果表明腔体内未燃烧燃料的质量分数是回燃产生的决定性参数 ,而细水雾确实能抑制回燃的产生 ,并且其抑制机理是降低腔体内未燃烧燃料的质量分数。最后利用燃料可燃界限图进行了实验结果的定性验证及分析。 相似文献
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建筑物内火灾烟羽流和顶蓬射流诱发的空气运动盐水模拟实验研究 总被引:3,自引:0,他引:3
盐水在清水中的扩散与火灾烟气在空气中的蔓延相似,因而可用盐水的扩散来模拟火灾烟气的蔓延;同样地,由于盐水的扩散而导致的环境清水的运动也可用来模拟烟气蔓延诱发的空气运动。基于这一原理,本文用实验的方法,研究了建筑物内初起火灾产生的烟羽流和顶蓬射流所诱发的空气运动,并对走廊空气层生长规律和运动特性进行了初步的测量和分析。所得结果基本合理,对建筑物通风排烟及疏散通道设计有帮助,从而为建筑火灾环境空气的运动的实验研究开辟了新的思路,也为火灾区域模拟提供了实验依据 相似文献
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为了探究受外部不同温度影响下带壳JH-14C传爆药的响应特性,设计了一套慢速烤燃下可测量JH-14C传爆药温度变化和壳体应变的实验装置,获取了不同升温速率下弹体内部温度随时间变化曲线、慢烤响应过程中装药壳体径向应变历程曲线,揭示了带壳JH-14C传爆药的慢速烤燃响应特性,将烤燃实验中弹体径向应变测试结果和炸药反应烈度相关联,提出了一种弹药烤燃实验反应等级的判定方法;基于热力学和装药化学反应,建立了带壳装药烤燃热传导模型和Arrhenius模型,采用BP神经网络反演了JH-14C传爆药热的热反应参数,对不同升温速率下弹体内部的温度场进行了研究。结果表明:升温速率越低,装药的响应温度越高,响应越剧烈;随着升温速率的降低,炸药的点火区域从炸药两端外缘逐渐向炸药内部转移。 相似文献
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Rodney A. Bryant 《Experiments in fluids》2009,47(2):295-308
Flow fields encountered in full-scale enclosure fires are highly three-dimensional and span a large spatial extent. Stereoscopic
particle image velocimetry (SPIV) was applied to provide a large-scale planar interrogation of the flow of air available to
a series of fires burning inside an enclosure. Time-averaged velocity fields across the doorway of the enclosure are presented.
These flows are bi-directional and SPIV reveals that the time-averaged height of the region of flow reversal depends on location
within the doorway. The volume flow rate of available air computed from the classical one-dimensional flow approach agrees
well with the numerical integration using the velocity field provided by SPIV. Good agreement between the measured velocities
for SPIV configurations optimized for seed particle displacements along the laser sheet axis and optimized for displacements
perpendicular to the laser sheet demonstrate that large-scale SPIV measurements can be conducted with very good precision. 相似文献
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Francesco Tamanini 《Experimental Thermal and Fluid Science》2010,34(3):404-411
The paper documents the results of an analysis of the effects of ambient conditions, temperature and relative humidity, on the development of large-scale fires during their initial growth. While the study has focused on the behavior of hygroscopic cartoned commodities, because their burning behavior is greatly affected by propensity to absorb ambient moisture, non-hygroscopic materials and their reduced sensitivity to ambient humidity could also be considered. The analysis introduces the heat release rate at the time of first sprinkler activation as a meaningful measure to represent the impact of ambient conditions on the development of a free-burning fire. The next step of estimating the behavior under extinguishment conditions is not possible at this time, though general considerations on expected trends are offered on the basis of the results obtained from another research program. The practical output of the work is in the form of the identification of the desirable range of operating conditions for ambient temperature and relative humidity in large-scale fire testing. 相似文献
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H. R. Baum O. A. Ezekoye K. B. McGrattan R. G. Rehm 《Theoretical and Computational Fluid Dynamics》1994,6(2-3):125-139
An approach to the study of gas phase combustion and convection processes in fires using a combination of mathematical analysis and computer simulation is presented. It seeks to solve the governing equations directly (if approximately) by decomposing the fire into a large-scale convective and radiative transport problem coupled to a small-scale thermal-element model of combustion and radiative emission. The thermal-element model solves the combustion equations in a local Lagrangian coordinate system convected by the large-scale motion, which in turn is driven by the heat released by the combustion processes. The large-scale flow is studied using finite-difference techniques to solve large-eddy simulations of the Navier-Stokes equations. The basic theory behind the methodology is outlined and sample results of both large- and small-scale phenomena are presented. An analytical model of a large eddy is used to show how the simulation can be assembled to yield radiation feedback from a fire plume to a target surface. 相似文献
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We present a numerical method for the computation of shakedown loads of engineering structures with limited kinematical hardening under thermo-mechanical loading. The method is based on Melan’s statical shakedown theorem, which results in a nonlinear convex optimization problem. This is solved by an interior-point algorithm recently developed by the authors, specially designed for lower bound shakedown analysis of large-scale problems. Limited kinematical hardening is taken into account by use of a two-surface model, such that both alternating plasticity and incremental collapse can be captured. For the yield surface as well as for the bounding surface the von Mises criterion is used. The proposed method is validated by two examples, where numerical results are compared to those of literature where available. 相似文献
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V. D. Zimin G. V. Levina S. S. Moiseev S. E. Startsev K. G. Shvarts 《Fluid Dynamics》1996,31(5):647-654
The generation of large-scale structures during turbulent convection in a rotating layer of incompressible fluid heated by internal heat sources is considered. The results of a theoretical and experimental investigation of a physical mechanism of large-scale structure formation which operates under conditions of high-intensity small-scale turbulent convection and low boundary heat transfer are discussed. The theoretical investigation is based on a system of evolutionary equations obtained for the transverse space moments of the physical fields, which describes the motion in thin layers of rotating fluid. The stability of the solution of the mathematical model is studied using the small perturbation method. As a result, a condition of existence of longwave instability of the system and a criterion determining the threshold of its onset are obtained. The theoretical conclusions are confirmed by a series of experiments carried out on a laboratory model. The design of the laboratory apparatus and the experimental technique are described.Moscow, Perm'. Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No. 5, pp. 20–29, September–October, 1996. 相似文献
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舒煌 《应用数学和力学(英文版)》1990,11(8):779-785
On the stability analysis of large-scale systems by Lyapunov functions, it is necessary to determine the stability of vector comparison equations. For discrete systems, only the stability of linear autonomous comparison equations was studied in the past. In this paper, various criteria of stability for discrete nonlinear autonomous comparison equations are completely established. Among them, a criterion for asymptotic stability is not only sufficient, but also necessary, from which a criterion on the function class C
1
is derived. Both of them can be used to determine the unexponential stability, even in the large, for discrete nonlinear (autonomous or nonautonomous) systems. All the criteria are of simple algebraic forms and can be readily used.Projects Supported by the National Natural Science Foundation of China, 1880359. 相似文献
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湍流一般机理及其应用 总被引:2,自引:0,他引:2
本文综述了湍流机理发展中最重要的一些文章,包括:Brown-Roshko的混合剪切层中大尺度涡的发展;Perry和Chong的湍流边界层中A形涡结构的湍流机理;以及笔者提出的关于3维湍流场中涡结构的涡量脉动对流和扩散并存的一般机理。在一般机理基础上建立了判别流场的准则,列举了在固壁边界附近的猝发现象并展望它的未来应用。 相似文献
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J. Sousa 《Experiments in fluids》2002,33(6):854-862
The mean turbulent flow structure around a cube mounted on the surface of an open-surface water channel was studied using a two-dimensional implementation of digital particle image velocimetry (DPIV). The out-of-plane velocity component was obtained by the use of the concept of continuity applied to two-dimensional velocity fields recorded in parallel planes. Various methods were used for the identification and localization of large-scale vortical structures in the three-dimensional flow around the surface-mounted obstacle. The results show the feasibility of its application to three-dimensional PIV data and the superior performance of recent identification techniques (namely swirling strength and normalized angular momentum), over the classical vorticity-based criterion. 相似文献
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为克服圆管截面广义屈服准则不满足比例加载条件,导致采用弹性模量调整法求解该类结构极限承载力时存在计算结果受荷载初值影响、计算精度受损等问题,利用回归分析和最小二乘法研究建立了圆管截面广义屈服函数的齐次多项式,通过误差分析确定了齐次化多项式的阶次;据此定义了圆管截面薄壁构件的单元承载比、承载比均匀度和基准承载比,为高承载比薄壁单元的判别及其弹性模量调整提供了动态判据,进而依据能量守恒准则建立了以单元承载比为基本参数的模量调整公式,结合下限原理提出了圆管截面薄壁结构极限承载力分析的弹性模量缩减法。研究表明,选取齐次化多项式的广义屈服函数能更加准确地考虑各项内力对结构极限承载力的综合影响,具有良好的计算精度和效率,可应用于复杂圆管截面薄壁结构的极限承载力分析中。 相似文献