Архив рубрики 'Articles' summaries'

Assessment of model adequacy of the process of grain impurities separation from the fraction of light waste in settling chamber to experimental results

    V.E. Saitov (1), DSc in Engineering
    A.N. Suvorov (2), PhD in Engineering

    (1) N.V. Rudnitskiy Zonal Research Institute of Agriculture of the North-East, Kirov, Russia, vicsait-valita@e-kirov.ru
    (2) Center for Distance Education of Children, Kirov, Russia, suvorov-alex@mail.ru

Abstract
The fullest utilization of harvested grain is an important task of agricultural production. During separation of seed grain from grain heap a large amount of grain impurities (feeble and crushed grain) being a valuable animal feed is lost. One of the effective methods of separation of grain impurities from light waste is the fractionation on aerodynamic properties. When developing and improving the devices for fractionation of light waste by means of airflow, it is necessary to carry out a large number of experiments, which is associated with time, energy and material consumption. Mathematical modeling allows to minimize the number of experiments. Before applying a mathematical model in designing of technical devices, it is necessary to assess its adequacy. The article presents the assessment of adequacy of the results of mathematical modeling of light waste fractionation process to the experimental results. Qualitative assessment of adequacy is carried out by determining whether the results of mathematical modeling are within the tolerance range of experimental data; quantitative assessment is carried out by means of statistical hypotheses testing. The results of theoretical calculations draw one sample, the results of experiments draw another. Two statistical hypotheses are considered. Each of the hypotheses is tested at 0.05 of significance level. The hypothesis that both of received samples belong to the same parent population is tested with the use of the sign test. As a result of research, the hypothesis is accepted on the selected significance level. Then a regression model is developed for each of the samples, and using the Chow test the hypothesis about the coincidence of constructed regression models is tested. As a result of research, the second hypothesis is also accepted at 0.05 of significance level. The considered mathematical model can be used in the design of technical devices for fractionation of light waste.

Keywords:
grain material; airflow; settling chamber; pneumatic separator; grain-cleaning machine; aspirating channel; statistical hypothesis; parent population.

Influence of the shape of disk knife on the pinching of material

    I.D. Kobyakov (1), DSc in Engineering
    A.V. Evchenko (1), PhD in Engineering
    E.V. Demchuk (2), PhD in Engineering

    (1) P.A. Stolypin Omsk State Agrarian University, Tara branch, Tara, Russia, doc-kid@yandex.ru
    (2) P.A. Stolypin Omsk State Agrarian University, Omsk, Russia, demchykev@mail.ru

Abstract
During the primary cultivation by means of general-purpose ploughs, the circular disk knives do not provide a reliable cutting; with that, the traction resistance of plough is increased, productivity and quality of its work are reduced. The purpose of the research is to increase the operational efficiency, the quality of soil cultivation and to reduce the energy intensity of general-purpose ploughs equipped with disc knives. Different designs of knives are studied in order to find the optimal shape providing a reliable pinching of plant and straw mass. A formula for determining the angle of pinching of a polygonal disc depending on the cultivation depth and number of angles in the polygon is given. The studies show that the hexagonal disk knives have the minimum angle of pinching, thus this shape is rational. The operating conditions are defined, in which the stalks of straw mass do not slip out of the knife blade when cutting. Motion paths of blades of hexagonal and circular knives at different positions of the instantaneous center of disk rotation are studied graphically. An empirical formula is obtained; dependences of pinching coefficient on the position of instantaneous center of disk rotation are constructed. It is found that with decreasing of nominal diameter of a knife the pinching coefficient is increased, and the quality of pinching of crop materials is improved. As a result of the research, the dependences are obtained showing that the areas of reliable pinching and cutting linearly depend on the kinematic parameter. With the cultivation depth of 0.08-0.12 m, the efficiency of pinching of hexagonal knife is increased by 1.8-2 times compared to the circular one.

Keywords:
primary cultivation; plough; angle of pinching; pinching coefficient; hexagonal knife.

Basics of safe drying of seeds

    A.V. Golubkovich, DSc in Engineering

    All-Russian Research Institute of Agricultural Mechanization, Moscow, Russia, tel. +7 (499) 1748818

Abstract
In seed-production farms, the temperature of drying agent is often limited by the maximum permissible temperature of heating; the simultaneous moisture removal is 3-6%; seeds are dried to a moisture content that exceeds the normal one by 2-3%; the layer is stirred several times during drying process. All of this increases the process cost and could lead to crop losses. The paper analyzes the essential factors influencing the safe drying of seeds in dense layer. It is found that along with the maximum permissible temperature of heating, account must be taken of the rate of dehydration, the specific surface of seeds, the heat transfer coefficient and the unevenness of moisture of basic material and of a dried-up one. The estimation of parameters for safe drying of seeds is carried out on the basis of mathematical models and well-known empirical expressions of the heat resistance and maximum permissible moisture removal. The article proposes the calculation of drying agent temperature that ensures the complete safety of the process, for breeder seeds also. Permissible temperature of drying agent is calculated by the expression that takes into account the specific surface of grain, the heat transfer coefficient, the heat of vaporization and the coefficient that depends on the permissible rate of dehydration, as well as the maximum permissible temperature of seeds heating. The maximum height of the layer of seeds being dried without stirring depends on the speed of drying agent, the diameter of grain, the porosity of layer, the mass transfer coefficient and the moisture content of drying agent before and after the layer. The maximum permissible temperature of seeds heating should be calculated according to the formula of S.D. Ptitsyn, but the maximum humidity of 10% of weighed portion should be used as a basis.

Keywords:
seeds; safe drying; process intensification; temperature of drying agent.

Simulation of the formation of vibration loading of operator workplace of industrial tractor

    I.Ya. Berezin (1), DSc in Engineering
    Yu.O. Pronina (1), Engineer
    V.N. Bondar’ (1), PhD in Engineering
    L.V. Vershinskiy (2), PhD in Engineering
    P.A. Taranenko (1), PhD in Engineering

    (1) South Ural State University, Chelyabinsk, Russia, proonina@mail.ru
    (2) Chelyabinsk Tractor Plant – URALTRAC, LLC, Chelyabinsk, Russia, verchinskiy_l@chtz.ru

Abstract
The check of compliance with legislative requirements for vibration protection of operators is carried out at the stage of certification testing of new and upgrading products. At this stage, the further development is associated with high time and material costs. The article substantiates the possibility of use of a calculation and experimental method which allows to determine at the development stage the level and frequency content of potentially dangerous sources of vibration; to develop a computer model for the system «excitation source – frame – cab – antivibration seat – operator»; to make out proposals to comply with legislative requirements by means of parametric forecasting. As an example, the problem of vibration in the low frequency range of 2-14 Hz is considered. This vibration is the result of the process of rolling of track rollers on track chain that lies on the yieldable soil foundation. According to biomedical research, the resonance frequencies of critical parts of human body are in this low frequency range, which is displayed in sanitary norms. Based on the analysis of field test results, the kinematic impact of track rollers on tractor frame is represented as stationary narrow-band random processes. Mathematical model of the system is described by a set of differential equations with random input processes. The methods of statistical dynamics are used to implement the model. The simulation results are presented as a set of transfer functions. They represent the distribution of resonance frequencies of angular and heave oscillations of the separate system elements and the spectral density functions. These results allow to obtain the quantitative estimations in the form of mean-square values of the output processes. The use of this approach allows to solve the problems of vibration protection of operator at the stages of design and testing of prototypes of road-building machinery. It is achieved by tuning-out of the system «track assembly – frame – cab – antivibration seat» from resonance phenomena and by introducing some design solutions.

Keywords:
track assembly; supporting branch; random process; mathematical model; transfer functions; spectral density.

Loading of tractor on drawbar test when pulling force is directed at the angle

    K.I. Gorodetskiy (1), DSc in Engineering
    A.M. Lavlinskiy (1), Engineer
    E.M. Alendeev (2), PhD in Engineering

    (1) University of Mechanical Engineering (MAMI), Moscow, Russia, kg1101@yandex.ru
    (2) Research Institute of Steel, PLC, Moscow, Russia, evg9702@gmail.com

Abstract
Foreign methods of tractor drawbar testing do not allow to evaluate the performance capabilities of movers and drive system in general with a number of other common characteristics, because of using a tar makadam as a surfacing. Methods of tractor testing used in Russia provide the experiments on real soils and aiming to a wide variety of the country’s natural environments. But even these tests do not give a full picture of performance of a machine-tractor unit. Tractor is a multipurpose machine that aggregates with a variety of implements that have a wide range of draught resistance. Therefore, during aggregation it is necessary to load tractor’s axles efficiently. Tractor ballasting increases the rolling resistance force that affects negatively on the propulsive efficiency. In most cases, the front ballast is not removed and remains on a tractor permanently, which increases the fuel consumption. There is a search problem for technical solutions that would optimize the tractor performance without using front ballast. For solving this problem, it is proposed to improve the methods of drawbar testing by directing of pulling force at the angle. If this angle is controlled, it is possible to load a front axle without ballast. In this case, the rear axle is loaded, and its trailing weight is decreased. Additional loading of the rear axle is adjusted by adding ballast weights to the rear wheels or on a cross bar of lower arms. For each case of loading by pulling force, it is necessary to provide the proper rational weight distribution to achieve the highest propulsive efficiency.

Keywords:
tractor; pulling force; ground reaction; weight transfer; drawbar test.

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