The study of non-axisymmetric fuel dispersal and detonation can provide reference for the prevention of industrial cloud explosion accidents and the design of fuel air explosive(FAE).The concentration and detonation f...The study of non-axisymmetric fuel dispersal and detonation can provide reference for the prevention of industrial cloud explosion accidents and the design of fuel air explosive(FAE).The concentration and detonation fields of 85 kg cylindrical and fan-shaped fuel are investigated by experiments and numerical simulations.A dynamic model of the whole process for fuel dispersal and detonation is built.The concentration distribution of fuel is used as the initial condition to calculate the detonation stage,thus solving the initial value problem of detonation field.The phase and component changes of fuel cloud at different locations are compared.The fuel cloud is divided into directions of 0°,90°,135°and 180°.The results show that the maximum cloud radius is 20.94 m in 135°and the minimum is 12.04 m in 0°.The diameter of the detonation fireball is 53.6 m,and the peak temperature is 3455 K.The highest peak overpressure is 3.44 MPa in 0°and the lowest is 2.97 MPa in 135°.The proportion of liquid phase in 0°is22.90%,and the fuel loss is 11.8% and 9% higher than that in 135°and cylindrical charge,respectively.The stable propagation distance of blast wave in 135°is 42.50% longer than 0°and 28.37% longer than cylindrical charge.展开更多
The stratification phenomenon resulting from differences in the physical properties of solid-liquid components seriously affect the final combustion and explosion characteristics of mixed fuel under the action of osci...The stratification phenomenon resulting from differences in the physical properties of solid-liquid components seriously affect the final combustion and explosion characteristics of mixed fuel under the action of oscillation.The effects of oscillation on the physical stability of mixed fuel with two solid-liquid ratios and three liquid component distribution ratios have been investigated using a self-designed experimental system at oscillation frequencies of 60-300 r/min.The explosion characteristics of mixed fuel before and after oscillation are gained from a 20 L spherical explosion container system.When the mass ratio of liquid components is controlled at 66.9%,64.7%,62.6%the final explosion characteristics are stable,with a maximum difference of only 0.71%.The volume of liquid fuel precipitation increases with increasing oscillation frequency when the mass ratio of liquid components reaches 71.7%,69.6%,67.7%.The fuel explosion overpressure after oscillation decreases with increasing liquid precipitation volume,and the repeatability is poor,with a maximum standard deviation of 82.736,which is much higher than the ratio without stratification.Properly controlling the mass ratio of liquid components of the mixed fuel can effectively combat the impact of oscillation on the physical state and maintain the stability of the final explosion characteristics.展开更多
Wind data were collected during the 2011 typhoon Meari at heights of 10, 20, 30, and 40 m above the ground using a 40 m high anemometer tower in the coastal area near Shanghai Pudong International Airport. Wind speeds...Wind data were collected during the 2011 typhoon Meari at heights of 10, 20, 30, and 40 m above the ground using a 40 m high anemometer tower in the coastal area near Shanghai Pudong International Airport. Wind speeds and directions, turbulence intensities, gust factors, and peaks were analyzed using the time records of wind speed. The results show that turbulence intensity components in longitudinal, lateral, and vertical directions decrease with mean wind speed, regardless of elevations, and the turbulence intensities are in a linear relationship with mean wind speeds. The ratios of three turbulence intensity components(i.e. Iu, Iv, Iw) at heights of 10, 20 and 40 m were calculated and equal to be 1:0.88:0.50, 1:0.84:0.57, and 1:0.9:0.49, respectively. In addition, the gust factors in three directions exhibit a reduction with increasing mean wind speed. The peak factors at different heights show a similar trend and slightly decrease with mean wind speed; average peak factors for all 10-min data from Typhoon Meari are 2.43, 2.48, and 2.47, respectively.展开更多
The dynamic characteristic analysis model of antenna structures is built,in which the structural physical parameters and geometrical dimensions are all considered as unascertained variables.And a structure dynamic cha...The dynamic characteristic analysis model of antenna structures is built,in which the structural physical parameters and geometrical dimensions are all considered as unascertained variables.And a structure dynamic characteristic analysis method based on the unascertained factor method is given.The computational expression of structural characteristic is developed by the mathematics expression of unascertained factor and the principles of unascertained rational numbers arithmetic.An example is given,in which the possible values and confidence degrees of the unascertained structure characteristics are obtained.The calculated results show that the method is feasible and effective.展开更多
The central buckle, which is often used in a suspension bridge, can improve bridges' performance in the actual operation condition. The influence of the central buckle on natural vibration characteristics and brid...The central buckle, which is often used in a suspension bridge, can improve bridges' performance in the actual operation condition. The influence of the central buckle on natural vibration characteristics and bridge-deck driving comfort of a long-span suspension bridge is studied by using a case study of Siduhe Suspension Bridge in China. Based on the finite element software ANSYS and independently complied program, the influence of the central buckle on the structure force-applied characteristics of a long-span suspension bridge has been explored. The results show that the huge increases of natural frequencies can result in the presence of central buckles because of the increases of bending and torsional rigidities. The central buckle basically makes the stiffening girders and cables within the triangular area covered as a relatively approximate rigid area. Hence, the central buckle can reduce the torsional displacement of the main girder. However, the increases of bending and torsional rigidities have little influence on the impact factor, which is obtained by using vehicle-bridge coupled vibration analysis. This means that the central buckle has little effect on the comfort indices. In addition, it is found that the central buckle can enhance the bridge deck's driving stability due to the decrease of the torsional displacements of the main girder.展开更多
基金supported by the National Key Research and Development Program of China (Grant No.2021YFC3001204)。
文摘The study of non-axisymmetric fuel dispersal and detonation can provide reference for the prevention of industrial cloud explosion accidents and the design of fuel air explosive(FAE).The concentration and detonation fields of 85 kg cylindrical and fan-shaped fuel are investigated by experiments and numerical simulations.A dynamic model of the whole process for fuel dispersal and detonation is built.The concentration distribution of fuel is used as the initial condition to calculate the detonation stage,thus solving the initial value problem of detonation field.The phase and component changes of fuel cloud at different locations are compared.The fuel cloud is divided into directions of 0°,90°,135°and 180°.The results show that the maximum cloud radius is 20.94 m in 135°and the minimum is 12.04 m in 0°.The diameter of the detonation fireball is 53.6 m,and the peak temperature is 3455 K.The highest peak overpressure is 3.44 MPa in 0°and the lowest is 2.97 MPa in 135°.The proportion of liquid phase in 0°is22.90%,and the fuel loss is 11.8% and 9% higher than that in 135°and cylindrical charge,respectively.The stable propagation distance of blast wave in 135°is 42.50% longer than 0°and 28.37% longer than cylindrical charge.
文摘The stratification phenomenon resulting from differences in the physical properties of solid-liquid components seriously affect the final combustion and explosion characteristics of mixed fuel under the action of oscillation.The effects of oscillation on the physical stability of mixed fuel with two solid-liquid ratios and three liquid component distribution ratios have been investigated using a self-designed experimental system at oscillation frequencies of 60-300 r/min.The explosion characteristics of mixed fuel before and after oscillation are gained from a 20 L spherical explosion container system.When the mass ratio of liquid components is controlled at 66.9%,64.7%,62.6%the final explosion characteristics are stable,with a maximum difference of only 0.71%.The volume of liquid fuel precipitation increases with increasing oscillation frequency when the mass ratio of liquid components reaches 71.7%,69.6%,67.7%.The fuel explosion overpressure after oscillation decreases with increasing liquid precipitation volume,and the repeatability is poor,with a maximum standard deviation of 82.736,which is much higher than the ratio without stratification.Properly controlling the mass ratio of liquid components of the mixed fuel can effectively combat the impact of oscillation on the physical state and maintain the stability of the final explosion characteristics.
基金Projects(51378396,51678452,51708074,2014M560706)supported by General Program of National Natural Science Foundation of ChinaProject(2014M560706)supported by the China Postdoctoral Science Foundation
文摘Wind data were collected during the 2011 typhoon Meari at heights of 10, 20, 30, and 40 m above the ground using a 40 m high anemometer tower in the coastal area near Shanghai Pudong International Airport. Wind speeds and directions, turbulence intensities, gust factors, and peaks were analyzed using the time records of wind speed. The results show that turbulence intensity components in longitudinal, lateral, and vertical directions decrease with mean wind speed, regardless of elevations, and the turbulence intensities are in a linear relationship with mean wind speeds. The ratios of three turbulence intensity components(i.e. Iu, Iv, Iw) at heights of 10, 20 and 40 m were calculated and equal to be 1:0.88:0.50, 1:0.84:0.57, and 1:0.9:0.49, respectively. In addition, the gust factors in three directions exhibit a reduction with increasing mean wind speed. The peak factors at different heights show a similar trend and slightly decrease with mean wind speed; average peak factors for all 10-min data from Typhoon Meari are 2.43, 2.48, and 2.47, respectively.
基金the National Defense Science and Technology Research Projects of China (51421060505DZ0155)the National Science Foundation of Shaanxi Province of China (2005A009)
文摘The dynamic characteristic analysis model of antenna structures is built,in which the structural physical parameters and geometrical dimensions are all considered as unascertained variables.And a structure dynamic characteristic analysis method based on the unascertained factor method is given.The computational expression of structural characteristic is developed by the mathematics expression of unascertained factor and the principles of unascertained rational numbers arithmetic.An example is given,in which the possible values and confidence degrees of the unascertained structure characteristics are obtained.The calculated results show that the method is feasible and effective.
基金Project(2015CB057701)supported by the National Basic Research Program of ChinaProjects(51308071,51378081)supported by the National Natural Science Foundation of China+2 种基金Project(3JJ4057)supported by the Natural Science Foundation of Hunan Province,ChinaProject(12K076)supported by the Open Fund of Innovation Platform in Hunan Provincial Universities,ChinaProject(2015319825120)supported by the Traffic Department of Appliced Basic Research,China
文摘The central buckle, which is often used in a suspension bridge, can improve bridges' performance in the actual operation condition. The influence of the central buckle on natural vibration characteristics and bridge-deck driving comfort of a long-span suspension bridge is studied by using a case study of Siduhe Suspension Bridge in China. Based on the finite element software ANSYS and independently complied program, the influence of the central buckle on the structure force-applied characteristics of a long-span suspension bridge has been explored. The results show that the huge increases of natural frequencies can result in the presence of central buckles because of the increases of bending and torsional rigidities. The central buckle basically makes the stiffening girders and cables within the triangular area covered as a relatively approximate rigid area. Hence, the central buckle can reduce the torsional displacement of the main girder. However, the increases of bending and torsional rigidities have little influence on the impact factor, which is obtained by using vehicle-bridge coupled vibration analysis. This means that the central buckle has little effect on the comfort indices. In addition, it is found that the central buckle can enhance the bridge deck's driving stability due to the decrease of the torsional displacements of the main girder.
