Impulse Density Measurements after the Held Method

The introduction shows the importance of the impulse on damage, if the high explosive amount is smaller than 1000 kg.     

Blast Impulse at Very Near Distance

Steel cubes and steel spheres were propelled in radial directions by a detonating cylindrical high explosive charge at scaled distances of 0.05–0.25 m kg^−1/3. The analysed velocities can be simply transferred to momenta, to energies and analysed impulse densities. A little surprising result is that the cubes with the larger area mass achieved remarkably higher velocities compared to the spheres. This is definitely a result caused by different air drag coefficients.     

Replacing the Equations of Fano and Fisher for Cased Charge Blast Impulse – III – Yield Stress Method

Previous papers by the author [1–3] pointed to a discovery by Fisher [4] that an equation by Fano [5], when used to predict blast impulse from cased munitions, did not fit the available data. These previous papers showed that an alternative equation for casing‐modified blast impulse could be derived directly from an equation by Gurney [6] for the kinetic energy balance between the mass of casing metal and the mass of explosive gases. However, this equation was derived for very ductile casings that are accelerated to their ideal Gurney velocity before they fracture. A previous paper [3] showed how the finite fracture strain of real casing metal can be taken into account in determining the relative blast impulse from a cased charge. This paper shows how, based on previous work by Taylor [7], the equation in [2] can instead be modified to allow for the yield stress of the casing metal and provides validation for this further equation from available experimental data.     

Radial Blast Prediction for High Explosive Cylinders initiated at Both Ends

This paper presents experimental results for the double ended initiation of cylindrical, explosive charges. Bare cylindrical charges of PE4 (RDX/binder 88/12 %) were used with length to diameter ratios of 1/3.7 to 5.75/1 and masses of 0.25 to 0.45 kg. Pressure measurements were taken at distances of 1 to 3.5 m in the radial direction. It was found that it was possible to predict the peak overpressure in the radial direction using P=K′ M(L/D)^1/3R⁻³. M is the mass of explosive, L the length of the explosive charge, D the diameter of the explosive charge, and R the distance from the charge. For PE4, K′=2251 kPa m³ kg⁻¹ for all length to diameter ratios. The double ended initiation gives a peak overpressure 1.6 times that for single ended initiation. The impulse for double ended initiation was found to be the same as for single ended initiated charges.     

Replacing the Equations of Fano and Fisher for Cased Charge Blast Impulse‐II‐Fracture Strain Method

Previous papers by the author [1, 2] pointed to a discovery by Fisher [3] that an equation by Fano [4], when used to predict blast impulse from cased munitions, did not fit the available data. These previous papers showed that an alternative equation for casing‐modified blast impulse could be derived directly from an equation by Gurney [5] for the kinetic energy balance between the mass of casing metal and the mass of explosive gases. However, this equation was derived for very ductile casings that are accelerated to their ideal Gurney velocity before they fracture. Many real casings, even under high dynamic strain rates, fracture before they can receive the full drive available from the explosive gases. This paper shows how the equation in reference [2] can be modified to allow for casing fracture at finite dynamic strain and provides validation for this modified equation from previously unpublished AWE archive experimental data.     

The Effect of the Relief Wave on the Uniformity of an Air Blast Load

In most blast loading structure analyses, it is assumed that the load acts uniformly on a target area. For the rationable design, it is useful to have a quantitative criterion to determine at which maximum distance the standoff can be placed to assume a uniform pressure distribution. Surprisingly, no standard criterion was found in the literature and the effect of blast wave clearing was not considered as well. In this paper, pressure histories applied on structures are calculated considering the non‐uniform loading characteristic as well as pressure relief from the edges. Additionally, the effects of various parameters on uniformity of impulse distribution are investigated. The results have shown that the effect of pressure relief on impulse uniformity is very important, especially when the blast wave is attenuated. This phenomenon leads an optimum distance at which impulse distribution is the most uniform.     

Comparison of Rectangular and Round Momentum Gauges for Blast Impulse Measurements

Measuring the blast contour method of the horizontal displacement of momentum gauges made of cylinders with 70 mm diameter and 50 mm, respectively 100 mm length or rectangular cross section of 25 mm width and 50 mm height with the Held momentum method gives very well corresponding results with regard to the measured impulse densities in the four selected radii of 0.25 m, 0.5 m, 0.75 m and 1.00 m. This confirms the validity of the selected test method.     

The Effects of Yield Stress and Casing Thickness on Blast Impulse and Fragment Velocity

A previous paper by the author [1] showed how his equation [2], based on the model first proposed by Gurney [3] for the blast impulse from cased munitions, can be modified to allow for the yield stress of the casing metal. This paper [1] also provided validation for this further equation from available experimental data. Further issues regarding the many smaller but significant interactions between the fracturing casing and the expanding gases need to be investigated before it can be said that a complete theory of blast impulse and fragment initial velocity is in place. In this paper, an approximate evaluation will be made of the potential effect and significance of kinetic energy losses, due to dissipation by means of casing strain energy dissipation. As expected, these losses are found to be most significant for thick, low density, high yield stress casings. The effect of finite casing thickness, also not previously considered, has been found to be small.     

穿孔机顶头设计的ActiveX Automation方法

介绍了穿孔机顶头设计方法的现状和ActiveX Automation技术。利用VB6．0基于ActiveX Automation技术开发了穿孔机顶头专用设计计算程序,并调用AutoCAD给出了设计图形结果,是快速进行顶头设计的良好方法。     

国产脉冲填料性能研究

在直径为262 mm有机玻璃塔内,用空气一水体系对国产50 mm陶瓷脉冲填料进行了流体力学性能的测试,得出了干、湿填料压降,载、泛点气速关联式。以Na_2SO_3溶液在钻离子催化下用空气氧化法测定了液相传质系数和有效表面,并对有效表面、载点气速提出了新的关联式。试验结果表明,国产脉冲填料与西德产脉冲填料一样,具有良好的流体力学性能和传质性能。     

Characterization of Residence Time Distribution in a Plug Flow Reactor

One of the biggest advantages of plug flow reactors lies in their narrow residence time distribution. The pulse experiment, as a common method on acquiring that distribution, relies on the tracer injection being a perfect pulse. A deviation from a perfect pulse leads to erroneous results if not taken into account. With a numerical analysis of experimental data, this effect is quantified in turbulent and laminar flow regime and the results are compared to an analytical method. Significant deviations occur mostly in the turbulent regime, which has the greatest technical relevance.     

Optical Characterization of Large Caliber Muzzle Blast Waves

High‐speed, 1,600 Hz, visible imagery of the blast wave from 147 firings of a 152 mm howitzer were observed for three different propellant charges. Blast wave trajectories were determined at 0.5–13 m from the muzzle exit, yielding initial velocities of Mach 3–4 that decayed to near acoustic within the imager field of view. A piecewise treatment of the Taylor‐Sedov point blast model was sufficient to describe the trajectories with an average error of 0.1 m. The trajectories were consistent with a three‐dimensional expansion and constant rate of energy release. A Constant Breech Pressure gun model was used to estimate total energy of the muzzle flow, and the efficiency of depositing energy into the blast wave was 18–24 %. Plume temperatures of approximately 980–1,210 K were estimated by partitioning energy and were correlated with likelihood of plume combustion. Classification of charge type based on energy deposition rate was modest, characterized by a ratio of between‐class to within‐class variance of 1.3, for the very similar events.     

Predicting the Impulse from the Curved Surface of Detonating Cylindrical Charges

TNT (Trinitrotoluene) equivalency depends on knowing the relative strength of different explosives compared to TNT. However, the current values for TNT equivalency mostly depend on work on spherical charges, whereas most military ammunition is cylindrical in shape. Cylindrical charges are known to give an enhanced blast close in when compared to that of spherical charges. A previous paper looked at predicting the peak pressure perpendicular to the curved side of a cylinder. This paper examines impulse data for the curved surface of cylindrical charges from the literature for Composition B and Pentolite and then describes experimental work carried out on cylindrical PE4 charges. Analysis of the free air experimental and literature data shows that it is possible to predict the impulse using a linear relationship, though it is not possible to decide on the best fit based on the current data. The fits for both I=K_IM^0.5/R and I= M^2/3/R give very similar correlation coefficients, where M is the charge mass and R the distance from the charge and K_I and are constants characteristic of the explosive. Values of K_I and have been fitted to literature and current experimental data for Composition B, Pentolite and PE4. Whichever of these two relationships is used, it should be possible to develop a method of determining TNT equivalency for the curved surface of cylindrical charges by using TNT equivalency=K_{I explosive}/K_{I TNT}, provided that data for TNT cylinders is obtained.     

Energetic Characteristics of HMX‐Based Explosives Containing LiH

The high energy density compound octahydro‐1,3,5,7‐tetranitro‐1,3,5,7‐tetrazocine (HMX) and the strong exothermic compound LiH represent an excellent principal explosive and an active fuel, respectively. Herein, the energetic characteristics of HMX‐based explosives are explored by adding LiH as fuel additive. The detonation parameters of HMX‐based explosives containing LiH were tested with free‐field explosion experiments and compared with those of traditional TNT, HMX, and aluminized explosives. The results show that the explosives exhibit higher energy and present preferable explosion effect when LiH is added as an explosive ingredient. The improvement of impulse is more than 32.8 % at 2 m. The shock wave peak overpressure increases by almost 40 % at a distance of 3 m from detonation center specially for the explosive containing both LiH and Al additives. Elemental H and Li are expected to release tremendous energy to effectively improve the explosives instant damage power, but the detonation duration is shorter than that of Al‐containing mixed explosives, which may limit the advantage over Al in the impulse. Li₂CO₃ powder is the solid product of HMX/LiH, which explains the LiH oxidation during the explosion. The exothermic processes in the formation are the reason for the increased energy of HMX/LiH explosives. These results can provide guidance to a potential energetic system formed by HMX and LiH.     

可取式挤灰桥塞在挤灰作业中的应用与评价

随着油田二次开发阶段的来临,地层剩余油的挖潜成为油田上产稳产的重要措施。因此近年来油田挤封作业工作量呈逐年上升趋势。而现有两大挤封工艺"笼统挤封"和"可钻式桥塞挤封"已不能满足挤封需求。本文提出了可取式挤灰桥塞挤封的技术思路,并阐述了它的技术特点,应用原理以及使用后的效果评价。可取式挤灰桥塞的使用使工序复杂的挤封作业变得容易,有很大的推广价值。     

堵头法在水、蒸汽管道消漏中的应用

介绍了一种简易可行的水、蒸汽管道堵漏方法——堵头法,可在不停水、不停蒸汽及管道正常投用的情况下进行漏点消漏。     

Design and Modeling of Plug Flow Fluid Bed Dryers

Plug flow fluid bed dryers (PFFBD) have been used for drying of particulate solids such as salts, ion exchange resins, grains, and a variety of other products. The present article describes the use of a mathematical model for the scale-up of lab-scale batch fluidization data to design an industrial-scale PFFBD. Axial dispersion theory was used in conjunction with the tanks-in-series model to describe the non-ideal flow. The model was implemented in Matlab 6.5 and it can be used for easily fluidizing particulate materials. The proposed model is capable of analyzing both the exponential falling rate and constant rate drying periods. The model predicts the required dryer dimensions for a given throughput and desired final moisture content. The model can also be used to study the effect of different process parameters such as solids feed rate, inlet air velocity, and temperature on the required dryer dimensions and it can also be used to predict the moisture and temperature profiles along the length of the PFFBD.     

Design and Modeling of Plug Flow Fluid Bed Dryers

Plug flow fluid bed dryers (PFFBD) have been used for drying of particulate solids such as salts, ion exchange resins, grains, and a variety of other products. The present article describes the use of a mathematical model for the scale-up of lab-scale batch fluidization data to design an industrial-scale PFFBD. Axial dispersion theory was used in conjunction with the tanks-in-series model to describe the non-ideal flow. The model was implemented in Matlab 6.5 and it can be used for easily fluidizing particulate materials. The proposed model is capable of analyzing both the exponential falling rate and constant rate drying periods. The model predicts the required dryer dimensions for a given throughput and desired final moisture content. The model can also be used to study the effect of different process parameters such as solids feed rate, inlet air velocity, and temperature on the required dryer dimensions and it can also be used to predict the moisture and temperature profiles along the length of the PFFBD.     

Development of Anti—Creep Andalusite—Based Bricks for Blast Furnace Stove

Secondary mullitization and mineral phase compositions of reacting andalusite of different gain sizes with fine alumina powders are studies. By adopting reasonable process technology to control mullitization behavior during firing, good anti-creep andalusite bricks have been developed.     

Development of a Structure for Blast Wave Mitigation

The internal structure of a blast containment container has been developed and examined by experiments involving the explosion of a high explosive. A steel pipe was selected as an effective structure for blast mitigation, because it dramatically reduces the blast wave in the radial direction near the explosion source. To also reduce the blast wave in the axial direction, two types of model structures consisting of a steel pipe as the main part were examined by both high‐speed photography and pressure measurements of the blast waves. A 0.34‐scale internal structure was constructed by combining these structures. To induce a powerful mitigation effect, the internal structure was filled with a shock‐absorbing material. The peak pressures of C4 explosions in free air were obtained on the basis of the published blast wave data for TNT explosions in free air using an equivalent weight of 1.37. The peak pressures of the blast waves from the structures for all cases were compared with the blast wave data for C4 explosions in free air to estimate the blast mitigation effect. As a result it was estimated that the internal structure not only eliminates the blast pressure in the radial direction but also reduces the blast wave in the axial direction by 36 %. By combining the effects of the internal structure and the shock‐absorbing material, the structure can reduce the peak pressure by 75 %.