Effects of Partially Confined Explosion on Jet Penetration

Interaction of a metal-explosive assembly with a normally-incident shaped chare jet has been investigated with radiographic and oscillographic technique. Some of the significant effects associated with this interaction like detonation of explosive by impact of jet, expansion of covering metal plates, disturbance in coherence and reduction in penetration of the jet have been observed. It is found that the jet penetration in stack of mild steel plates is reduced to 30% of its blank penetration. The disturbance in the jet commences 12.3 μs after initiation of explosive and it remains for about 25 μs in the present set up.     

Spaced Armor Effects on Shaped Charge Jet Penetration

Spaced armor has a simple structure and is easily produced with low cost. Previous authors calculated how a jet penetrates spaced armor; but, this study provides both a theoretical calculation method describing the interaction of a jet with spaced armor and experimental data which agree well with the theoretical values. The effects of several factors were explored using LS‐DYNA such as the distance between the first plate and the second plate as well as layer thickness on the interaction between the jet and the target. A method for simulating the protection afforded by spaced armor and supporting the design of spaced armor is presented.     

Depth of Penetration of a Gas Jet into a Granular Medium

Theoretical Foundations of Chemical Engineering -     

A Discussion on Minimum Spout Velocity and Jet Penetration Length

The similarity and difference between the flat‐bottom and cone‐bottom cylindrical spouted beds, conical spouted beds and vertical upward jets in fluidized beds have been analyzed in this paper based on the effects of geometrical parameters on the minimum spouting velocity and operating stabilities of the spouted beds. The effect of angle on minimum spouting velocity was found to be only significant within the range of 30 to 60 degrees cone angles. Minimum spouting velocity in deep cylindrical spouted beds was proportional to the square root of the static bed height, but was proportional to the static bed height in conical spouted beds and large cylindrical spouted beds with small height‐to‐diameter ratio. The relationship between the minimum spouting velocity and the static bed height was consistent with that between jet velocity and the vertical jet penetration length in jetting fluidized beds.     

带侧边微孔射流扰动火焰结构特性

In this paper, an innovative jet lifted flame with side micro-jets has been proposed and its effects on the flame structure have also been investigated. Due to the changes of the initial combustion conditions, mixing and aerodynamics which resulted from the perturbation of the side micro-jets, such a lifted jet flame has different flame structure compared with the common premixed flame. Results demonstrate that use of the micro-jets can control, to a certain extent, the flame structure, including the flame length, lift-off distance and blow-off limit. With the same fuel and air flow rate, the flame length with the side micro-jets will decrease about 5%-40% as the air volume ratio α increases from 58%-76%. Compared with the common diffusion flame, the jet flame with the side micro-jets demonstrates to be easier to be a momentum-dominated flame. The flame length with 2 micro-jets is about 5% less than with 6 micro-jets under the same fuel and air flow rate. With the same α, the fewer number of the controlled jets lead to the flame with relatively shorter length, not easier to be blown off and higher NOx emission. With cer-tain fuel flow rate, the critical air volume ratio is largest for the flame with 3 micro-jets, which is more difficult to be blown off than the cases with 2, 4 or 6 micro-jets.     

Behavior of an Inclined Jet after Penetration in a Contact Surface

Experimental facts show that when the direction of a metallic jet is inclined to the target surface, the penetration length may be decreased enormously. In this paper, the author proves this phenomena by a theoretical analysis. The conclusion could also be used in the respect of anti-hollow charge warheads.     

Study on Rubber Composite Armor Anti‐Shaped Charge Jet Penetration

The process of rubber composite armor anti‐shaped charge jet (SCJ) penetration was divided into four parts based on jet deformation that occurred when the SCJ penetrated the rubber composite armor. Results on the interference speed interval, interference frequency, and surplus penetration capability of the SCJ with the rubber composite armor were derived based on the stress wave and the Kelvin‐Helmholtz instability theory. The effects of rubber layer thickness and obliquity of the armor for the composite armor anti‐SCJ penetration were studied through theoretical, X‐ray, and depth of penetration experiments. The results showed that when the obliquity was at 60° and the rubber layer thickness was in the range of 3 mm to 3.5 mm, the rubber composite armor seriously disturbed the stability of the SCJ. Thus, the rubber composite armor was found to have the best protection capability under these specifications.     

炸高对乳化炸药聚能射流侵彻深度的影响

利用半球型药型罩,对乳化炸药进行聚能装药,讨论了炸高对乳化炸药聚能射流侵彻深度的影响,通过聚能射流侵彻铝板的深度来表征对乳化炸药的侵彻能力,并从机理上进行了分析和讨论,得出在本实验条件下聚能射流的最佳炸高为9 cm左右,这对认识乳化炸药的聚能作用效应具有一定的实际意义。     

Adaptive Sampling of Dynamic Systems for Generation of Fast and Accurate Surrogate Models

For economic nonlinear model predictive control and dynamic real-time optimization fast and accurate models are necessary. Consequently, the use of dynamic surrogate models to mimic complex rigorous models is increasingly coming into focus. For dynamic systems, the focus so far had been on identifying a system's behavior surrounding a steady-state operation point. In this contribution, we propose a novel methodology to adaptively sample rigorous dynamic process models to generate a dataset for building dynamic surrogate models. The goal of the developed algorithm is to cover an as large as possible area of the feasible region of the original model. To demonstrate the performance of the presented framework it is applied on a dynamic model of a chlor-alkali electrolysis.     

Calculation of Depth and Crater Diameter for the Supersonic Penetration of Shaped Charge Jet into Concrete

Considering that the sound velocity of concrete is lower than that of metal, this study discusses the effect of stationary shocks and compression during the process of shaped charge jet penetration into concrete when the penetration velocity is greater than sound velocity. The linear relationship between shock velocity and particle velocity is used to describe concrete materials. The state parameters of concrete under shock loading are calculated using Rankine‐Hugoniot jump conditions. Moreover, a combination of these relations with the Bernoulli equation yields a supersonic penetration equation across the shock. A cavity growth equation based on the Szendrei‐Held equation is presented when supersonic penetration occurs. Predictions from the supersonic penetration model are in good agreement with the depth and cavity diameter of experimental results for shaped charge jet penetration into concrete for charge diameters of 60, 142, 200, and 400 mm.     

基于虚拟原点概念的连续射流侵彻计算

对于沿射流长度方向具有线性分布速度的连续射流，经典的基于虚拟原点理论的射流侵彻关系式能很好的描述其侵彻行为。但对于非线性速度分布的连续射流，存在的虚拟原点不是唯一的。本文从对非线速度分布的射流的有限段线性近似和射流的应变率两个方面出发，讨论了虚拟原点概念在具有非线性速度分布的连续射流对目标侵彻深度计算中的推广问题。     

Influence of Drift Velocity and Distance Between Jet Particles on the Penetration Depth of Shaped Charges

The penetration depth of shaped charge jet into target is strongly affected by the stand‐off. The penetration process terminates even when the jet velocity is still high, and the penetration capability of jet particles degrades after jet breakup at a large stand‐off. This work presents an analytical model to describe the radial drift velocity and distance between jet particles, which leads to decreased penetration depth. The results show that jet particles with low drift velocity impact the crater wall easily. Furthermore, the jet particles cannot reach the crater bottom to increase depth because the crater diameter generated by the jet is quite small. Moreover, the distances between jet particles also play an important role in penetration depth under the influences of strain hardening of target, as well as tumbling and dispersion of jet particles. The radial drift velocity and distance between jet particles are investigated by applying the model to non‐precision charge and precision charge penetrations into target at different stand‐offs. The cutoff jet velocity and cutoff penetration velocity also are determined based on the analytical model. With increased stand‐off, the cutoff jet velocity increases, and the cutoff penetration velocity is almost constant. This result is proven by a number of experiments. The stand‐off curves of two charges are also calculated, and results are in good agreement with experiments. The stand‐off curve can be determined with only two or three experiments using the proposed method. Notably, jet particles should have a slow drift velocity and great penetration capability after breakup for suitable shaped charge.     

一种新型M形顶部结构药型罩的设计及形成射流的侵彻能力分析

在锥角药型罩结构基础上通过改变其顶部结构设计了一种新型M形顶部结构药型罩,并分析了其射流头部的形成机理;采用有限元软件ANSYS/LS-dyna对在爆轰波作用下M形顶部结构药型罩射流的形成过程,以及对45号钢板的侵彻过程进行了数值模拟,并与锥角药型罩、平顶药型罩形成射流的头尾部速度、拉伸长度、杵体大小以及对45号钢板的侵彻能力进行了对比。结果表明,M形顶部结构药型罩的M形顶部结构在爆轰波作用下经二次汇聚形成了射流头部,相同装药条件下,其形成射流的头部速度相比锥角药型罩形成射流的头部速度提高约9.10%,比平顶药型罩形成的射流头部速度提高约5.56%;其侵彻深度比锥角药型罩提高约10.4%,比平顶药型罩提高约7.28%。     

间隔靶对射流侵彻能力影响极限的实验研究

利用实验方法对间隔靶影响射流侵彻能力的极限值进行了确定。通过实验，获得间隔靶间隔值与射流侵彻深度的关系曲线，得出间隔靶对射流侵彻能力的降低极限为5．5％左右，即当间隔靶间隔值为最不利于射流侵彻的间隔值时，每个间隙使射流的侵彻能力下降5．5％左右。通过对实验现象的观察，发现射流在间隔靶之间的飞溅是降低射流侵彻能力的一个主要因素。     

Mathematical Model of Ignition of Condensed Systems by a High-Temperature Supersonic Underexpanded Jet

An approximate mathematical model is constructed and characteristics are calculated of ignition of a reactive plane infinite obstacle by a high-temperature nonstationary axisymmetric supersonic jet of combustion products escaping from the igniter. The approximate model data are compared with the results of numerical calculations using the system of equations of motion of an ideal gas, nonstationary equations of heat conduction and chemical kinetics, and conditions of conjugate heat exchange at the gas–condensed medium interface. The suggested approximate model adequately describes the ignition process and can be used for proximate evaluation of ignition time and temperature. Key words: ignition, jet, gas dynamics, supersonic flow, mathematical simulation.     

底喷式等离子体发生器射流的输出特性

通过自行设计的可以综合评定等离子体射流速度、温度、压力分布等特性的实验装置,研究了底喷式等离子体射流特性。采用压电测量装置、光电测量装置和数字高速摄影研究了射流在一定距离上的压力分布特性、射流速度及射流形貌特征。结果表明,该发生器所产生等离子体射流随着距射流中心位置距离的增大迅速衰减,等离子体射流速度约500m/s,射流运动过程可分为两个阶段:第一阶段是电爆炸丝产生高温、高压等离子体射流;第二阶段是消融管消融所产生的射流。     

Hypoalbuminemia as Surrogate and Culprit of Infections

Hypoalbuminemia is associated with the acquisition and severity of infectious diseases, and intact innate and adaptive immune responses depend on albumin. Albumin oxidation and breakdown affect interactions with bioactive lipid mediators that play important roles in antimicrobial defense and repair. There is bio-mechanistic plausibility for a causal link between hypoalbuminemia and increased risks of primary and secondary infections. Serum albumin levels have prognostic value for complications in viral, bacterial and fungal infections, and for infectious complications of non-infective chronic conditions. Hypoalbuminemia predicts the development of healthcare-associated infections, particularly with Clostridium difficile. In coronavirus disease 2019, hypoalbuminemia correlates with viral load and degree of acute lung injury and organ dysfunction. Non-oncotic properties of albumin affect the pharmacokinetics and pharmacodynamics of antimicrobials. Low serum albumin is associated with inadequate antimicrobial treatment. Infusion of human albumin solution (HAS) supplements endogenous albumin in patients with cirrhosis of the liver and effectively supported antimicrobial therapy in randomized controlled trials (RCTs). Evidence of the beneficial effects of HAS on infections in hypoalbuminemic patients without cirrhosis is largely observational. Prospective RCTs are underway and, if hypotheses are confirmed, could lead to changes in clinical practice for the management of hypoalbuminemic patients with infections or at risk of infectious complications.     

Jet printing

Ink jet printers, some capable of producing a full colour gamut, are now widely used as output devices for computer-generated design work. Some advances have been made in the application of these ink jet paper printing technologies to textile printing, mainly for carpets. This review describes the principal jet systems that have been developed commercially for both textile and reprographic uses, and indicates areas in which the ink jet principle appears to have future potential. The physical and chemical requirements of the inks used in the different systems, as well as the possible pretreatment of the substrate to improve ink receptivity and the durability of the print, are also discussed.