Numerical study of fragments from cylindrical casing with one of end caps fully constrained

In order to study the process and characteristic of the fragments in the warhead with one end cap under full constraint condition, we established a cylindrical casing with two end caps which one of them was fully constrained using the simulation analysis. The result showed that the fragmentation of cylindrical casing with one end full constrained has its own characteristic. The Mach stem was generated when the detonation wave propagated to the fully constrained end cap under the condition of one end detonation, working on unreactive explosives and causing the nearby fragment subjected to nearly 2.5 times the normal pressure to obtain a higher speed. The cylindrical casing first ruptured at the contact surface with the fully constrained end, and then at the end cover of the initiating end, and then the rupture extends to the whole cylindrical casing. The detonation products started to leak out from the rupture. driving fragments to fly, and forming two dense flying areas. The analysis of this paper can provide a reference for the optimal design of this kind of warhead.

Analysis of features of the design of a screw feeder for the purpose of improving its work

Feeders are an integral part of the modern technological process, they establish and regulate the pace of production, ensure its rhythm, contribute to increased productivity and increase output. The aim of the article is to investigate and analyze the types of feeders, in particular the design features of a screw feeder, to determine its advantages and disadvantages. In order to increase the efficiency of the screw feeder, to propose a way to improve its design based on the modernization of the screw. The types of feeders are considered in the article, and the main attention is paid to the study of the advantages and disadvantages and design features of the screw feeder most common in technological processes of various industries as the simplest in design and often structural features of screw feeders in modern sources, which showed that the issue of the screw configuration screw feeders are not adequately studied in terms of uptime and the factors affecting this aspect indicate relevance. Currently, in the works of modern domestic authors and in the industries of various industries, waste-free screw feeders are considered. The article describes in detail these feeders developed by TechTron in two versions - the gutter and pipe. Today, there are also studies of a screw conveyor with additional blades on the spirals of the screw, in which the relationship between its structural and functional parameters is established. An analysis of the considered design features of existing screw feeders in modern sources has shown that issues of design features, namely the configuration of screws of screw feeders, have not been studied enough in terms of uptime and factors affecting this aspect, indicating the relevance of this issue to solve a specific problem of increasing work efficiency. The advantages of screw (screw) feeders compared to other types of feeders, such as continuity of supply, tightness, simplicity of design, the ability to create excess pressure at the outlet of the screw, the ability to aggregate with other equipment in industrial plants, have led to their widespread use in many industries in various technological processes.The main disadvantage of screw feeders is the low productivity due to the communication of the auger blade of the transported material, not only translational motion, but also rotational, which leads to turning the material together with the auger. Also a disadvantage of screw feeders is the rapid operation of the screw and the loading pipe due to overloads. To increase the efficiency of the screw feeder and eliminate one of its most important shortcomings - sensitivity to overload, resulting in accumulation of material inside the chute, stopping the feeder and reducing its performance and operational reliability, screw configurations were changed. Namely, the advanced screw was divided into two zones A - the loading zone, B - the main zone of the screw. Such a structure has a spiral surface and a cylindrical casing of smaller diameter D1 in the loading zone than the diameter of the spiral surface and a cylindrical casing in the main zone D2 of the screw feeder. The advanced design of the screw feeder works as follows. During loading of the feeder, the bulk material fills the entire space under the loading device with a continuous flow, including the spiral surface D1 of the screw. When the screw is rotated, the material completely filled the cylindrical casing with a diameter of D1, having a fill factor of j1 = 1, moves in a continuous flow through section A. When approaching the material to section B, by increasing the diameter of the spiral surface to D2, the fill coefficient decreases to j2, which ensures the operation of the screw feeder without accumulation of material and increases its operational reliability.

Real-time calculation of the initial angle of projection for fragments in cylindrical warheads

This paper presents an improvement in the speed and accuracy of calculating the initial angle of projection of fragments for exploding cylindrical shells. It is a fast tool that can be used by designers, where existing approaches, such as computationally intensive Finite Element Analysis, are preventively slow. An enhanced Taylor equation is presented using available experimental data and the effect of the changing shape of the warhead’s cylindrical casing on the fragment’s initial projection angle. The resulting equation is computationally fast as it uses uncomplicated equations and provides improved accuracy for estimating a fragment’s initial angle of projection in comparison to existing work.

New Design of the Reversible Jet Fan

This paper presents two designs of the axial reversible jet fan, with the special focus on the impeller. The intention was to develop a reversible axial jet fan which operates in the same way in both rotating directions while generating thrust as high as possible. The jet fan model with the outer diameter 499.2 ± 0.1 mm and ten adjustable blades is the same, while it is in-built in two different casings. The first construction is a cylindrical casing, while the second one is profiled as a nozzle. Thrust, volume flow rate, consumed power and ambient conditions were measured after the international standard ISO 13350. Results for both constructions are presented for three impeller blade angles: 28°, 31° and 35°, and rotation speed in the interval n = 400 to 2600 rpm. The smallest differences in thrust, depending on the fan rotation direction, as well as the highest thrust are achieved for the first design with the cylindrical casing and blade angle at the outer diameter of 35°. Therefore, it was shown that fan casing significantly influences jet fan characteristics. In addition, the maximum thrust value and its independence of the flow direction is experimentally obtained for the angle of 39° in the cylindrical casing.

Theoretical Analyses of the Number of Backflow Vortices on an Axial Pump or Compressor

This paper presents theoretical analyses of flow fields on an axial pump or compressor, where the main flow enters from one side of the cylindrical casing, whereas an axially reverse and tangentially whirling flow enters from the tip clearance between the casing and the impeller, which sucks in the mixed flow. In this flow field, several secondary vortices exist in the mixing zone across the contact surface between the main and the axially reverse tangentially whirling flow. This type of secondary vortex is called a “backflow vortex.” The backflow vortices are tornado-like, parallel to the casing axis, and periodically distributed on the contact surface; they revolve around the casing axis and rotate around themselves. Regarding the backflow vortices, the relationships between their number (N), revolving diameter (d), revolving angular velocity (ω), and the ratio of the forced vortex region to the distance between the secondary-vortex center and the cylindrical wall (f) were all theoretically investigated. The five major findings are as follows: First, between d, ω, N, and f, any parameter can be determined if the other three are specified. Second, ω decreases, N increases, or f increases when d is increased and the other two are fixed. Third, d decreases, N increases, or f increases when ω is increased and the other two are fixed. Fourth, d increases, ω increases, or f decreases when N is increased and the other two are fixed. Fifth, d increases, ω increases, or N decreases when f is increased and the other two are fixed. To validate these theoretical results, “backflow vortex cavitation,” which occurs around the center of the backflow vortices on a rotating inducer as a representative of axial pumps or compressors, was observed. The backflow vortex cavitation is visible; therefore, d, ω, and N become quantitatively measurable. The test inducer was a triple-threaded helical inducer with a diameter of 65.3 mm and a rotational speed range of 3000–6000 rpm. It was experimentally confirmed that the proposed theoretical analysis is true.

Rapid Evaluation and Analysis of the Deformation of Filled Cylindrical Casing with Deforming Charge Width Based on Self-Compiled MATLAB Program

The casing of deformable warheads warps under the action of deforming charges. The deformation profiles may be concave-, convex-, or D-shaped, but they are all symmetrical. The D-shape is considered the optimal deformation profile. The width of the deformed surface affects the number of fragments in the target area. In order to evaluate the deformable surface width of the cylindrical casing, a criterion α was established and its optimum range was determined as 20 to 30%. Based on our previous theoretical analysis, a MATLAB program that can rapidly evaluate the projectile deformation surface was compiled, which was verified using LS-DYNA and experiments. The laws influencing the deforming charge width on the deformed surface of the filled cylindrical casing were also studied using the MATLAB rapid evaluation program. As the deforming charge width increased, the deformation profile of the casing gradually transferred from “inner-concave” to the “outer-convex”. In addition, a formula that can better reflect the relationship between the deforming charge width φ and the criterion value α was fitted and verified. The conclusions obtained in this paper provide rapid guidance for the structural design of deformable warheads.