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1.
基于混沌理论的室内轰燃判据   总被引:2,自引:0,他引:2  
陈爱平  宋飞 《爆炸与冲击》2010,30(6):622-627
根据混沌理论,在研究大量小规模室内火灾实验结果的基础上,得到了一种新的、通过温度变化率 表征的轰燃判据;利用大规模室内火灾的实验结果,对该判据的实用性进行了初步验证。结果表明:这一判据 可以应用于预测大规模实际室内火灾中轰燃的发生。  相似文献   

2.
固体火箭冲压发动机补燃室沉积数值模拟   总被引:1,自引:0,他引:1  
考虑液态颗粒碰撞和聚合过程、液态颗粒和壁面碰撞过程,建立了固体火箭冲压发动机补燃室沉积数值计算模型,对模型发动机补燃室内颗粒之间碰撞、沉积的相互作用过程进行了数值模拟,得到了颗粒沿轴向和沿出口平面径向方向的分布情况,并计算得到了补燃室壁面不同段的沉积层厚度值。将计算结果与试验结果进行对比,最大误差为0.8mm,表明该计算模型具有较高的计算精度。  相似文献   

3.
介绍了首腔电子反轰的二维数值模拟结果。计算中略去了空间电荷效应和尾场效应,使用了射频基波场方程和电子的动量方程及能量守恒方程。  相似文献   

4.
为了探究热刺激作用下泄压结构对熔铸炸药点火时间及点火前内部物理场变化的影响,设计了有/无泄压结构烤燃弹的内部多点测温慢烤对比试验。基于炸药通用烤燃模型(universal cookoff model, UCM),建立了炸药熔化后受浮升力驱动流动,反应速率随压力、反应进程等变化的B炸药烤燃计算模型,对有/无泄压结构烤燃弹的炸药在升温过程中的温度场及内部压力变化等情况进行了数值模拟,并与试验结果进行比较。结果表明:慢烤条件下,烤燃弹内部压力呈先缓后急上升趋势;有泄压结构烤燃弹在结构作用前的压力变化趋势与无泄压结构的一致,泄压结构的作用会使炸药自热反应速率骤然降低,炸药内部温度下降,自热反应速率降低和产物气泡驱动的对流共同导致了点火时间的延后;由于对流的作用,炸药点火点都在弹体顶部区域。  相似文献   

5.
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   

6.
中压开关设备内部短路燃弧爆炸对设备、建筑物以及工作人员的安全带来了严重威胁。为提出合适的数值计算方法对短路爆炸引起的压力效应进行计算,对开关设备内部短路燃弧的能量平衡机制进行了分析;通过分析燃弧过程的热-力效应,提出了基于CFD法的间接耦合分析方法,并开展了实际封闭容器内部短路燃弧实验验证了算法的可行性。研究结果表明:实验测量与模拟计算获得的平均压强仅相差2%左右;电弧尺寸对压力升的影响较小;封闭容器内部压力升随电弧能量的增大近似线性增大;安装负压室后燃弧室的压强可降低60%左右,因此,增设负压室可有效抑制开关设备内部短路爆炸引起的压力升。  相似文献   

7.
针对某高氯酸铵/端羟基聚丁二烯(AP/HTPB)推进剂固体火箭发动机,采用两步总包反应描述AP/HTPB的烤燃过程,建立了考虑发动机空腔自然对流的二维轴对称烤燃模型,对加热速率分别为3.6、7.2和10.8 K/h时火箭发动机的慢速烤燃行为进行了数值预测,研究了该火箭发动机的热安全性问题。结果表明,固体火箭发动机空腔内的自然对流对AP/HTPB推进剂的着火温度、着火延迟期和着火位置有一定影响,在热安全性精确分析中不可忽略。3种加热速率下,AP/HTPB推进剂的最初着火位置均出现在药柱肩部的环形区域内,3种加热速率对应的着火延迟期、着火温度及着火时壳体温度分别为30.71、20.06、18.68 h,526.52、528.10、530.64 K,和479.56、496.82、508.77 K。随着加热速率的增大,烤燃响应区域向推进剂与绝热层交界处移动,着火位置的二维截面由椭圆形变为半椭圆形。  相似文献   

8.
一种新型的大速差同向射流预燃室已经研制成功。本文基于SIMPLE算法,发展了计算这种流场的数值解法。文中介绍了算法、边界条件的详细说明以及计算结果。计算结果证明存在大面积迴流区;呈现了重要的三维特征。本文初步讨论了设计参数对迴流特性的影响。  相似文献   

9.
不同升温速率下复合药柱烤燃实验与数值模拟研究   总被引:3,自引:0,他引:3  
为了研究不同升温速率下复合炸药JO-9159/JB-9014烤燃实验的热反应规律,建立了复合炸药的烤燃模型,利用有限元程序LS-DYNA3D对不同结构的复合药柱在烤燃过程中的热响应情况进行了数值模拟,并利用实验进行了验证,结果显示模拟结果可信。利用已建立的模型对5 K/h、3 K/min和10 K/min等3种不同升温速率下复合药柱烤燃过程进行了数值模拟,结果表明:升温速率和装药结构的不同对复合药柱的点火时间和位置有较大影响,随着升温速率的增大,点火时间变短,点火位置由药柱的中心处逐渐移至药柱的两端边缘,升温速率较小时,复合药柱的热安定性取决于内部高能炸药的特性,升温速率较大时,复合药柱的热安定性与单一钝感药柱性能近似。因此,只有在较大的升温速率下,钝感炸药内部嵌入高能炸药才能既提高整体药柱的威力,又保证其具有较好的热安定性。  相似文献   

10.
炸药装药尺寸对慢速烤燃响应的研究   总被引:8,自引:0,他引:8  
利用自行研制的烤燃实验装置,选用JB-B、TNT、R852三种炸药,研究探讨了炸药装药尺寸对慢速烤燃响应特性的影响,得出了随着炸药装药尺寸的增大炸药慢速烤燃反应的环境温度和发生反应的剧烈程度都会增大的规律,并对结果进行了分析和讨论。  相似文献   

11.
Progress in modelling, predicting and measuring soil-vehicle interaction performance is reviewed. Topics include soil properties, track systems, rigid and lugged wheels, pneumatic tyres and soil working systems. Methods range from the highly theoretical to the largely experimental. Substantial progress has been made in computer modelling methods for predicting the tractive performance of track systems and lugged wheels. A generally accepted method for describing the strength/deformation properties of surface soils has yet to evolve.  相似文献   

12.
A comparison of the performance of 68 void fraction correlations based on unbiased data set (2845 data points) covering wide range of parameters than previous assessments was made. A comprehensive literature search was undertaken for the available void fraction correlations and experimental void fraction data. After systematically refining the data, the performance of the correlations in correctly predicting the diverse data sets was evaluated. Comparisons between the correlations were made and appropriate recommendations drawn. The analysis showed that most of the correlations developed are very restricted in terms of handling a wide variety of data sets. Based on the observations made, an improved void fraction correlation which could acceptably handle all data sets regardless of flow patterns and inclination angles was suggested. It was shown that this correlation has the best predictive capability than all the correlations considered in this study.  相似文献   

13.
The blended-fuel based eddy-dissipation-concept combustion model was newly developed in the FireFOAM framework, and applied to simulate 30 cm×30 cm heptane-ethanol pool fire. Comparison was made of fire height, centerline temperature against experimental measurements, which shows that they match very well with each other. However, further studies are needed to examine the validation of this model in fire simulations with various scales.  相似文献   

14.
Slot-die coating windows have been previously obtained by several researchers for low-viscosity solutions. However, practical applications necessitate the use of relatively high-viscosity (?1 Pa s) non-Newtonian fluids for coating films. Also, earlier theoretical studies predicting coating windows are mainly limited to 2D single-phase studies, and based the prediction of the coating window on the upstream contact angle made by the coating fluid with the substrate. The numerical predictions varied significantly from the experimental findings in most cases due to oversimplification of the model. In the current study, experimental and theoretical methods are used for obtaining the coating window for blackstrap molasses, which is classified as a relatively high-viscosity, shear thinning solution. The coating process is monitored by a microscope connected to a camera placed under the slot-die. Air entrainment is found to occur in a three-step or four-step cycle. In addition, a comprehensive theoretical study is performed by simulating the coating process using a 3D, multiphase, volume of fluid (VOF) method. The simulation is found to predict the coating window within 10% accuracy of experimental results. Also, the model does an excellent job of predicting the formation of air bubbles at high coating speeds.  相似文献   

15.
0Introduction Thefracturepropertiesofconcreteandrockmaterials,suchasfracturetoughnessKICand strengthfthavebeenofgreatinterestsformanyyearsbecauseoftheirimportantroleincontrolling thestructuralintegrityofvariousengineeringstructures[1-27].Varioustestingtec…  相似文献   

16.
毛东  唐秋明  高强 《力学学报》2020,52(3):698-706
高压绝缘子在输变电工程中承担着绝缘的重要角色. 由于工业化的飞速发展, 雾霾和沙尘等天气的频繁出现, 污秽颗粒在大气流场的作用下在绝缘子表面沉积, 容易发生污闪事故, 严重影响着电网的安全运行. 将高压绝缘子污闪发生的主要过程-绝缘子的动态积污和表面电场畸变过程进行耦合分析, 探究污闪发生的机理. 建立绝缘子周围的欧拉-欧拉气固两相流模型, 对绝缘子动态积污过程进行数值模拟, 获得绝缘子表面的非均匀积污层分布; 创建其表面导电层单元, 结合有限元方法建立积污绝缘子电场模型, 对非均匀积污层分布的绝缘子串进行电位及电场分析. 研究结果表明: 在积污层非均匀分布情况下, 绝缘子表面积污层周向位置对其电位分布的趋势影响较小, 但对绝缘子表面电场畸变的发生位置影响较大. 随着周向位置的变化, 电场畸变位置的偏移也不同, 且侧风面电场畸变的偏移最大. 随着积污层电导率的增大, 电场强度大于清洁绝缘子表面的场强, 且背风侧的场强畸变最大.   相似文献   

17.
In this paper, a methodology has been developed to accurately predict the elastic properties of multi-constituent particulate composites by accounting for irreversible effects, such as energy loss that arises due to internal friction. The complex dependence on loading density and particle properties (i.e., size, shape, morphology, etc.) is investigated in terms of their effects on the effective elastic modulus of the composite. Confirmed by experimental data from the compression loading of individual Ni and Al particles dispersed in an epoxy matrix, it is believed that this approach captures the effects of internal friction, consequently providing a more accurate and comprehensive representation for predicting and understanding the material behavior of multi-constituent particulate reinforced composites. The present methodology provides a model to directly compare the elastic modulus from an uncomplicated test, such as dual-cantilever beam loading in dynamic mechanical analysis (DMA), to the modulus obtained by other more complex experimental methods such as quasi-static compression. The model illustrates an efficient method to incorporate input data from DMA to represent realistic elastic moduli, hence promising for the characterization and design of particulate composites.  相似文献   

18.
火灾(高温)下索网结构计算的连续化方法   总被引:1,自引:0,他引:1  
李国强  周焕廷 《力学季刊》2007,28(4):638-646
对于火灾(高温)下索网结构的响应,通常基于有限元法利用计算机进行数值模拟,而商用程序的"黑箱"效应不利于对高温下索网结构反应本质的理解.对于单索和索网火灾下的反应,采用温度离散的方法,考虑钢绞线在高温下的力学特性,推导了索结构的高温反应计算式.结果表明,该方法与非线性有限元的计算结果吻合较好.  相似文献   

19.
Measurements have been made by the comparison method for the effective thermal conductivity of dispersed materials which consist of substances with different thermal conductivities. The applicability of existing predicting formulae is discussed in detail as comparing their predicted values with the present data. A new predicting formula is proposed through analyzing the experimental data, the numerical results, and also the data obtained with the electrolytic-bath. It is found that the proposed formula has a wider range of applicability than that of previously reported ones.  相似文献   

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