Vol 90, No 5 (2023)

BACKGROUND: In recent years, there has been a trend of increasing activity towards the development of polar territories. A characteristic feature of the North is negative ambient temperatures that have a negative impact on the condition of piston engines of ground transport, mobile and stationary power plants and labor saving tools. An engine is the least adapted unit for use in such conditions. There is a chain of negative factors that consistently links negative ambient temperatures, in which the equipment is operated, and the condition of the mechanisms and engine systems. The primary link of this chain is condensation processes. The existence of condensation processes during low-temperature operation of the engine has been experimentally proved. The latter takes place when warming up in conditions of negative ambient temperatures. The question «How much water changes the state during the warm-up period?» arises.

AIMS: Development of a mathematical model that makes possible to obtain unbiased information about the activity of condensation processes and to estimate the amount of water that changes the state during the warm-up period.

METHODS: Solving the given tasks is based on classical theories describing operational processes of boilers. The high labor intensity and significant financial costs in organizing such experiments require the search for new research methods. Mathematical models help to solve the task of defining the mass amount of water condensing in a cylinder of a piston engine computationally.

RESULTS: The mathematical model that is characterized by its adaptation to piston engines and is capable of determining the mass amount of water changing the state during the warm-up period iteratively, using the differences in partial pressures and the density of the mass flow of water condensate, has been developed.

CONCLUSIONS: The existence of water has a negative impact on conditions of a piston engine. The information about the amount of water condensing in a cylinder during the warm-up period stimulates to continue studies in the field of motor oils watering, active acids formation and corrosive wear of surfaces of details.

BACKGROUND: Surface tillage is very important in agriculture, because it helps to increase the quantity and quality of the yield. One of the types of surface tillage is packing. It is carried out in order to improve the contact of seeds with the soil, as well as to create optimal soil porosity, in which the pores contain the necessary amount of water and air for good plant development.

AIMS: Improvement the quality of surface tillage based on the development of a highly efficient spring-wave roller, which ensures meeting the agricultural requirements, reducing operating costs and increasing crop yields.

METHODS: The new design of the spring-wave roller capable of packing the soil in compliance with the agrotechnical requirements has been proposed.

RESULTS: As a result of the conducted field studies of the spring-wave roller, a regression equation describing the influence of all independent factors of the packing process on the optimization criterion KPI was obtained. The adequacy of the mathematical model was evaluated according to the Fisher criterion, the calculated value of which was 1.001 with a tabular value of F_t = 2.46, which indicates its adequacy. The analysis of the deviations of the experimental results from the results obtained by calculating the resulting equation showed that at all points of the experimental plan, the data obtained fit into the confidence interval, which indicates the high quality of the experiments.

CONCLUSIONS: The maximum value of the coefficient of approximation to the KPI standard when using the spring-wave roller is 0.81 at the motion velocity v = 11 km/ h, the total force generated by compression springs C = 1750 N and the weight of the ballast m = 70 kg. The maximum KPI value achieved during operation of the commercially produced KKZ-6 roller is 0.57, which is 42.1% better than the proposed spring-wave roller has.

BACKGROUND: Currently, the requirements to energy efficiency of transport vehicles are more and more tightened due to service cost reduction. Energy efficiency is the most relevant for them as it directly influences on the key feature — maximum mileage. Therefore it is necessary to control electric motors in a way to ensure maximal surface grip coefficient excluding propulsors’ slipping, as well as to establish operation modes of motors and switching between the modes to the one having the maximal efficiency. In this case, for effective control, it is necessary to define electromagnetic torque at the shaft of an electric motor and resistance torque at wheels rapidly for generating corresponding control and correcting exposures.

AIMS: Development of the theoretical basis and the law of estimation the electromagnetic torque at the shaft of a traction electric motor of transport vehicles for the sake of efficient control of traction electric drive and its diagnostics.

METHODS: Simulation of the observer of the electromagnetic torque at the shaft of a traction electric motor was carried out in the MATLAB/Simulink software package.

RESULTS: The article provides with theoretical basis of formatting the law of optimal estimation of the electromagnetic torque at the shaft of a traction electric motor of transport vehicles for the sake of efficient control of traction electric drive, its diagnostics, as well as the results of simulation the law of estimation of the electromagnetic torque at the shaft of a traction electric motor obtained in the MATLAB/Simulink.

CONCLUSIONS: Practical value of the study lies in ability of using the proposed observer for development of control system and diagnostics of transport vehicles.

BACKGROUND: When performing plowing operations with modern tractor units equipped with automatic control systems for hitches, various methods of regulating the depth of soil cultivation are used. The main attention should be paid to compliance with agricultural requirements and fuel consumption reduction. However, there is no integrated numerical criterion for joint assessment of these technological process parameters, helping to justify a reasonable regulation method.

AIMS: Development the integral criterion for assessment of the efficiency of plowing unit operation and selection of a reasonable method for adjusting the depth of cultivation for specific soil conditions.

METHODS: Mathematical modeling of a plowing unit including the Belarus 1523 tractor with an electro-hydraulic system for controlling the hitch and with the PLN-4-35 four-furrow mounted plow.

RESULTS: When using the positional method of adjusting the soil cultivation depth, the total fuel consumption per shift is mp = 28.18 kg with a variation of the cultivation depth Va = 9.99%, when using the power method — mp = 29.74 kg and Va = 5.25%, when using the height method — mp = 29.78 kg and Va = 3.23%, and when using combined methods of adjustment, such as positional-power or height-power, the fuel consumption is mp = 28.94 kg, Va = 5.01% and mp = 29.58 kg, Va = 2.63% respectively.

CONCLUSIONS: The comparative analysis of the research results shows that, given the force and kinematic disturbances from the soil on the plowing unit, the preferred method of adjusting the soil cultivation depth is the height-force method with a mixing coefficient of α = 0.5. With this method, the value of the integral criterion is respectively 1.4 and 1.2 times lower than with force and height adjustment methods.

BACKGROUND: Methods of mathematical modelling are widely used in vehicle development. In order to study vehicle dynamics, stability and handling, as well as to accelerate and to reduce the cost of on-board software development, it is necessary to build a digital twin which contains description of special motion of a vehicle with models of units and subsystems as parts of the vehicle.

AIMS: Development and verification of a virtual prototype of a vehicle.

METHODS: Development of the virtual prototype and vehicle modelling were done in the MATLAB/Simulink software package. Main derivation of the equations necessary to build the models of vehicle’s units and subsystems is given. Verification testing was conducted using special measuring equipment.

RESULTS: The vehicle virtual prototype containing description of combined dynamics of bodyframe, transmission elements, suspension and wheels was developed. Comparison of results of field and virtual testing was made in order to confirm operability and adequacy of the virtual prototype. Main graphs showing dynamics of real and virtual vehicles are presented.

CONCLUSIONS: Practical value of development and study lies in ability of using a virtual prototype in vehicle dynamic studies and development of on-board control systems.

BACKGROUND: During the operation of transport and technological machines and equipment, the most frequent failure is loose running of connecting rod liners of a crankshaft. Previous studies on tractor, locomotive and automotive diesel engines did not sufficiently disclose the reasons for loose running of liners.

AIMS: Study of the stress-strain state of the steel base of connecting rod liners as the initial and developing factors of the process leading to failure.

METHODS: The research is based on the analysis of numerous works devoted to the study of the causes of loose running of connecting rod liners of various internal combustion engines. The methods and results on the operational and bench studies of the stress state and shape changing of connecting rod liners for the KAMAZ-740 (8Ch 12/12) engine obtained by the team of authors are used as the basic data.

RESULTS: The process of change in stress state and consequent change in geometric parameters of the steel base, accompanied by change in the shape of connecting rod liners of the KAMAZ-740 engines has been revealed. It is established with the study that the occurrence of failure is not sudden. The process proceeds according to a certain pattern in three stages. The first stage is characterized by the appearance of deformation of a liner due to excessive stress state; the second stage is caused by development of obtained deformations up to critical values; the third stage is loose running of a connecting rod due to obtained deformations and violations of liner’s hydrodynamics conditions. The main result is justification of requirements and conditions for ensuring stability of parameters and shape of liners during long-term operation of engine.

CONCLUSIONS: Knowledge of the process leading to the change in shape of crankshaft bearing liners makes it possible to develop design and technological solutions and recommendations to eliminate failures by optimizing the parameters of liners.

BACKGROUND. In modern vegetable growing, mainly in conditions of small forms of management, low-cost technical means adapted to different agrotechnical and production conditions are the most in demand. Such a technical means, in particular, is a multivariate cabbage harvester of block design developed at the Chuvash State Agrarian University.

AIMS – identification of the features of the technology of harvesting cabbage with the use of a new cabbage harvester and its economic evaluation by use cases.

MATERIALS AND METHODS. The layout of a multivariate cabbage harvester is provided in three versions with the ability to clean cabbage heads according to various technological schemes: shipment of cabbages in bulk to the body of the vehicle; shipment of cabbages to containers installed in the body of a tractor transport unit; shipment of cabbages first on a flexible flooring or on the web of a belt conveyor installed in the body of a tractor trolley over containers; distribution the flow of heads along the body of a tractor vehicle using longitudinal conveyors of the lower or upper location and with the subsequent transfer of heads from them to containers manually. It is proposed to choose the named technological schemes of cabbage harvesting with the use of a multivariate combine harvester on the farm based on the prevailing agrotechnical and production conditions, taking into account labor, direct and reduced costs, given in the work by calculation.

RESULTS AND DISCUSSION. Based on the results of economic calculations, labor costs, operating costs and reduced costs are established according to the proposed schemes for harvesting cabbage with the use of a multivariate combine. The proposed cabbage harvesting options are economical in terms of labor costs, operating costs and reduced costs compared to the basic option (in-line harvesting).

CONCLUSIONS. It is recommended to apply a specific scheme for harvesting cabbage using a multivariate combine based on the agrotechnical and production conditions in the farm, taking into account the results of the economic assessment.