Том 34, № 3 (2024)

Introduction. The low purity of combing flax seed balls with flax harvesters is a problem for the technological operation when harvesting fibre flax. The analysis of the comb designs of the combing units made it possible to identify the main disadvantages that do not fully meet the agrotechnical requirements for harvesting fiber flax. An innovative design of a removable comb for single-rotor drum-type harvesters is proposed.

Aim of the Study. The study is aimed at determining the purity of combing the standing fiber flax stems using a single-rotor comb-dresser with removable combs.

Materials and Methods. There has been made an experimental setup to simulate the process of combing standing fiber flax plants with combs of a single-rotor comb dresser. During the period from 2018–2023, the design parameters and operating modes of the combing unit were investigated and justified. There has been developed a technique for conducting a multifactorial experiment to determine the purity of combing fiber flax using a combing drum-type unit with removable combs.

Results. The results of laboratory studies on the separating flax balls from the standing fiber flax stems by removable combs are presented to determine the combing quality. It has been found that the purity of combing fiber flax plants is up to 99.2%.

Discussion and Conclusion. When studying the technological process of combing Nadezhda standing fiber flax plants the with single-rotor drum removable combs, the physico-mechanical properties of the flax stems were studied in laboratory conditions, the optimal operating modes of the combing drum were determined, which ensure the purity of the stems above 98% that meets the agrotechnical requirements for flax combines.

Introduction. The performance of precision seeders depends on many factors, including the functionality of their dosing systems, the modernization of which is possible only on the basis of patterns, which allows forecasting the indicators of single seed placing into a furrow.

Aim of the Study. The study is aimed at analyzing the influence of the diameter of the suction holes of seed-placing units and the rarefaction created in them on the characteristics of placing seeds of the main row crops.

Materials and Methods. The results of the study were obtained based on a series of experiments on sowing corn and sunflower seeds using an MS-8 seeder, the operation principle of which can be considered typical for vacuum seed-placing units.

Results. There have been obtained empirical dependences of the particular features of zero and group placing seeds of such row crops as corn and sunflower on the area of the suction holes and the rarefaction in the vacuum chamber.

Discussion and Conclusion. The quantitative estimates obtained may differ for seeds of the same crop, but having different technological properties. The general factor is that the frequency of missing seeds is proportional to the suction force magnitude in the working plane of the metering element, regardless of its area. At the same time, the probability of double seed placing depends on the area of the metering ports with a constant suction force, a decrease in their diameter leads to a decrease in the frequency of double seed placing. The data obtained allow considering joint variations in the magnitude of the rarefaction in the vacuum chamber and the diameter of the suction holes as effective tools for improving the seed placing quality.

Introduction. The operation of eco friendly and high-efficiency internal combustion engines is not possible without deep and comprehensive study of using new types of fuels. That is why, forecasting the indicators of injecting and spraying in a diesel engine running on a mixed alcohol-containing fuel, which have a direct effect on the combustion and formation of toxic components and, as a result, on efficiency and eco friendliness, is an urgent scientific task. 
Aim of the Study. The study is aimed at developing a theoretical basis for calculating the characteristics of injecting and spraying methanol-containing fuel into diesel engine cylinders that allows optimizing its processes.
Materials and Methods. There are considered the characteristics of injecting and spraying alcohol-containing fuel in a diesel engine modified to operate on a mixed methanol-containing fuel. There were used the well-known A.S. Lyshevsky dependencies, which fairly reliably reflect the processes of injecting and spraying in diesel engines.
Results. The in-depth studies of the basic principles for evaluating the indicators of injecting and spraying standard fuel made it possible to adapt them for fuels of mixed methanol-containing composition and to investigate the dynamics of changes in the duration and speed of injection, the Weber criterion values, the boundaries between the areas of fuel jet forming, droplet size and spraying angle.
Discussion and Conclusion. There has been developed a theoretical basis for calcu­lating the characteristics of injecting and spraying methanol-containing fuel that makes it possible to optimize the operation of a diesel engine running on mixed fuel and, as a result, improve its efficiency and eco friendliness. The presented numerically information on the change in the boundaries of the fuel jet forming areas, the size of the droplets and the angle of the spraying cone allows us to reliably determine the basic parameters of spraying of the used mixed methanol-containing fuels, determine the vector of optimization of the mixing processes and gives insight into the promising directions in designing the geometry of combustion chambers, intake ducts, etc.

Introduction. Plastic deformation and electric current, acting separately, usually have opposite effects on the deformation behavior and flow stresses in electrically conductive materials. In the case of the combined action of plastic deformation and applied electric current, the result is not pre predictable. The study of the synergistic effect of deformation and electric current can be used for metal forming.
Aim of the Study. The study is aimed at demonstrating the existence of impulse current threshold parameters at which the athermal electroplastic effect manifests itself in various materials.
Materials and Methods. Tensile tests were performed at various current modes, which exclude the increased contribution of the thermal effect to the reduction of flow stresses – current density and duty cycle. The fractographic features of the fracture surface were studied using raster scanning microscopy. There were found the threshold values of current parameters at which stress jumps associated with the electroplastic effect occur.
Results. The influence of the density and duty cycle of the impulse current on the manifestation of the electroplastic effect is shown. Both parameters have threshold values, above which the electroplastic effect becomes observable (at density j > jкр ) or athermal (at duty cycle Q > Qкр). All types of tension are accompanied by a viscous fracture and void formation, which is most intensively formed, when current is injected.
Discussion and Conclusion. In alloys with low electrical resistance, the threshold impulse current density corresponding to the occurrence of the electroplastic effect is higher than in alloys with high electrical resistance. Increasing the duty cycle of the impulse current reduces the temperature of the deformed sample that allows considering the electroplastic effect as athermal.

Introduction. Optical fibers are widely used for high-bandwidth transmitting communication signals over long distances. The key feature enabling this performance is signal low attenuation, that is  signals experience minimal power loss propagating along the optical fiber. One of the factors influencing power loss during information transmission is the fiber bending. Bending can increase the signal transmission power loss of an optical fiber because of both macrobending and microbending. Studying the dependence of signal power losses when bending on waveguide parameters makes it possible to control the signal power losses of an optical fiber during information transmission. 
Aim of the Study. The study ia aimed at evaluating the effect of microbending on the field and energy of a weakly guiding optical fiber with a gradient refractive index profile in a single-mode regime.
Materials and Methods. From the equations for the fields of straight and curved sections of weakly guiding fiber for an arbitrary gradient profile of the refractive index with the help of the subsequent solution of inhomogeneous Helmholtz equations by the Green’s function method, there were obtained expressions for relative energy: the ratio of the field energy of the fiber curved section to the field energy of the fiber straight section (in the first approximation for a single-mode regime).
Results. The obtained expression for the relative energy depends on two parameters: the waveguide parameter and the ratio of the optical fiber radius to the radius of curvature. For the quadratic case of a power-law profile, as the closest to the actually used one, numerical calculations were used to construct the dependences of the relative energy on the parameter characterizing the bending for different values of the waveguide 
parameter.
Discussion and Conclusion. It has been shown that in the case of microbending, the longer the wavelength or the smaller the fiber radius, the lower the losses. The results obtained can be used in calculating optical fiber profiles designed to operate in a bent state and eliminate expensive experimental modeling of light guides and in designing waveguides to solve specific applications, in particular, to increase energy efficiency, reliability and performance of the measuring instruments.