Vol 89, No 1 (2022)

AIMS: Evaluation of the effectiveness of converting diesel engines used in agricultural self-propelled vehicles to fully or partially natural gas (methane) fueled engines.

METHOD: Is analytical.

RESULTS: In agriculture up to 25% of operating expenses are fuel costs. However, the only number of the concomitant objective and subjective factors allow us to estimate expedience and efficiency of converting diesel engines used in agricultural self-propelled vehicles for full or partial supply of natural gas (methane). On the one hand, the price of an equivalent amount (in terms of work performance) of natural gas is more than 2 times lower than the price of diesel fuel. At the same time, natural gas is the most environmentally friendly hydrocar-bon fuel. But, on the other hand, the underdeveloped refueling infrastructure is obvious, and the environmental friendliness of natural gas itself is not a guarantee of the environmental friendliness of the engine itself. Also, the safety of gas equipment operation under high pressure is an important matter.

CONCLUSIONS: Firstly, the use of natural gas instead of diesel fuel requires taking into account the difference in the physicochemical characteristics of these fuels, which determines both the requirements for the organization of the working process and the advantages and disadvantages of such replacement. Secondly, the combustion process of natural gas, compared to diesel fuel, is characterized by in-creased formation of water leading to more intensive watering of lubricating oil, although it re-duces carbon dioxide emission into the atmosphere. Safety of natural gas equipment operation plays an important role, and first of all, it is concern of cylinders that are filled at pressure of 20.0…25.0 MPa.

BACKGROUND: Trucks, as a rule, have a significate difference between the kerb and gross weights. Usual spring or leaf suspensions do not allow to have acceptable values of static running and suspension stiffness at different machine loading, and pneumatic elastic elements, despite their relative simplicity, are mainly implemented only on overseas technology samples, and designers do not pay attention to pneumatic elastic elements with counterpressure. One of determinants of truck users is the acceptable vibration loading of the driver’s seat. Trucks with a carrying capacity comparable or even overestimated to their kerb weight, when they move without cargo on public roads, especially with a dirt surface, have significant levels of vibration acceleration at using the metal elastic.

AIMS: The purpose of the present work is to reduce the vibration loading of the driver’s seat due to rational choice of parameters of the cushioning system with pneumatic elastic elements with backpressure, that ensures the non-zero static travel and saticfactory stiffness of suspension in the kerb and loaded state.

METHODS: Using the regorous mathematical tools of Mechanics, Pneumatics and Thermodinamics, scientific-based theoretical prerequisites as well confirm the validity and reliability of the presented dependencies for characteristics calculation, conclusions and recommendations.

RESULTS: According to the method developed and proposed in this article, effective characteristics of the pneumatic elastic elements with a single-level stiffness and backpressure for a KAMAZ-53215 Selkhoznik truck were obtained. At the kerb weight, the static stroke of the front and rear suspensions is approximately 0.06 m; at a gross weight it is of 0.12 m and 0.24 m, respectively. The period of normal vertical vibrations decrease by 25% versus a gross vehicle weight and by 31% at absence of backpressure, however, it occurs in the allowable range.

CONCLUSIONS: The proposed method allows to determine the base design parameters of the pneumatic elasticity of the suspension elements of wheeled vehicles, providing an acceptable periods for a normal vertical oscillations of the cushoining body with maintaining the non-zero static stroke to a large weight range.

BACKGROUND: Intensive development of the transport sphere and the extension of the fleet of tractors and cars, as well as the tightening of standards and requirements in the field of exhaust gas emissions have resulted in increased requirements for the combustion process. This problem can be solved by improving the working process in the engine by preheating the fuel to 300 °C in the high pressure fuel supply system. Under external thermal influence, the conditions of mixture formation are improved, an increase in the rate of preflame reactions and a positive change in the dynamics of the combustion process are observed. When potential energy of hydrocarbon molecules increases in the activated complex system, energy is redistributed among active molecules. Along with this, the rate coefficient of a chemical reaction increases due to the concentration of foci of hydrocarbon molecules that have reached the energy barrier.

The object of research is the process of diesel fuel combustion at preliminary external influence on it.

AIMS: The aim is to study the combustion process of a motor-tractor diesel engine upon fuel activation. Development of a scheme of individual phases of the activated diesel fuel combustion of depending on the temperature at heating.

METHODS: Theoretical study and analysis of the combustion process of thermally preprepared fuel for an automotive diesel engine. Theoretical determination of the dependence of the rate of formation and concentration of toxic components and dispersed particles on the rate constant of direct and reverse chemical reactions, as well as on the activation temperature of fuel at emission in exhaust gases.

RESULTS: The actual coefficient of molecular change of the working mixture increases when diesel fuel is activated. The rate of formation of total nitrogen oxides and hydrocarbons increases by 1.79% and 3.66%. The proportion of unburned carbon in the combustion process on activated fuel varies within ± (2…4) %.

CONCLUSIONS: Theoretically, a scheme for changing individual phases of the activated fuel combustion process by time and temperature has been developed. Fuel heating accelerates the pre-flame preparation in the liquid phase, shortens the duration of the rapid gorenje phase. The concentration of toxic indicators depends on the constant of the chemical reaction rate and the activation temperature of the fuel.

BACKGROUND: Theme of this article is actual because issues of the reliable and cost-effective opera-tion of augmented automotive piston engines are still not solved. An important aspect of solving the problem is rational oil supply of the cylinder-piston group.

AIMS: The purpose of this work is the required minimum motor oil level estimation for the hydrodynamic lubrication of the “cylinder-piston skirt” pair. There were set and solved the tasks of determining the volume of motor oil capable of filling: 1) cavities of the flat-topped surface of the cylinder; 2) a raised surface of the piston skirt and 3) the piston skirt clearance. The object of study is an automotive diesel.

METHODS: Three types of analytical determination of the total volume of the cavities of the rough surface and the piston skirt clearance were used as methods for estimation of a motor oil level.

RESULTS: It was found, that the estimation with the well known formula for oil volume (a method 1) gives the overevaluated result of oil level estimation, in comparison with methods 2 and 3, which taking into account the real geometry of cavities and roughness parameters. The advantage of method 3 was determened by criteria of generalization and of simplicity to apply. Using the method 3, the estimated volume of motor oil ensured the hydrodynamic lubrication mode of the “cylinder – piston skirt” pair of the object of study was obtained.

CONCLUSION: The analytical expressions obtained by method 3 can be recommended to optimize the piston engine lubrication systems for reducing the friction and wear losses as well as to minimize a risk of oil starvation and increased oil consumption through burning.

SUBJECT OF THE STUDY: Is the process of preliminary separation of loose grains from combed grain heap on the slatted bottom of the feed elevator of a combine harvester.

AIMS: Is an efficiency evaluation of the combed grain heap separation on the slatted bottom of the inclined chamber of a combine harvester in the field and to compare the degree of crushing of free grain depending on its supply to the threshing device or directly to the cleaning system.

METHODS: All studies were carried out on winter wheat of the Moskovskaya 56 variety with a yield of 30 c/ha. Plant height varied within 0,6–0,9 m with a grain ripeness of at least 98% and a moisture content of 14%. The serial grain header ZHO-5 «OZON» manufactured by PJSC «Penzmash» was aggregated by the Niva-Effect combine harvester with a constant speed of 8 km/h and a stripping cylinder speed of 485 min^-1. The field experiments were divided into two stages. The first series of experiments was devoted to evaluating the efficiency of preliminary separation of combed grain heap on the slatted bottom of the experimental feed elevator. During the second series of the experiment, grain was harvested with a serial feed elevator without its preliminary separation.

RESULTS: According to the results of the first series of studies, it was found that the passage of loose grain through the holes of the slatted bottom of the inclined chamber is 91,6%. At the same time, grain crushing in the feed elevator did not exceed 0,5%, and in the bunker – 1,75%. During the operation of the combine with a serial feed elevator without preliminary separation of the combed grain heap, the crushing of the bun-ker grain was within 5,25%.

CONCLUSION: The practical implementation of such a technical solution makes it possible to 3 times the grain crushing in a bunker by the working bodies of the threshing machine.