Vol 88, No 2 (2021)

Alternative motor fuel is a mixture of various hydrocarbons and their compounds. Motor fuel is based on naphthenic, paraffinic and aromatic hydrocarbons. The performance characteristics of the fuel depend on its composition. When developing methods for monitoring the characteristics of fuels, the main problem is their multicomponent nature, since each component contributes to the operational characteristics. The operational characteristics are: cetane number, sulfur content, water-soluble acids and alkalis, lower heat of combustion and some others. To determine them, the combustion of diesel fuel (DF) and the subsequent analysis of the combustion products are carried out. The disadvantage of the existing method is the fact that it is impossible to quickly control the fuel at the place of operation, at a tank farm, a gas station, a process pipe or a vehicle fuel tank. When designing analyzers and measuring instruments the correlation dependences, which link the value of the operational property of the fuel with its physicochemical characteristics, are used. Taking into account the use of various types of alternative fuels (AT) with a wide range of their operational properties, the problem of a quick and accurate preliminary assessment of these properties arises. Along with diesel fuel, it is proposed to use similar physicochemical methods to assess the flammability of alternative fuels.

The pneumatic seat suspension is one of the most important, and in some situations, one of the key components of the vibration protection system for the human operator of the vehicle. At the present stage of scientific and technical activities of most developers, great emphasis is placed on controlled seat suspension systems, as the most promising systems. This article analyzes the methods of controlling the elastic damping characteristics of the air suspension of a vehicle seat. Ten different and fairly well-known methods of changing the shape and parameters of elastic damping characteristics due to electro-pneumatic valves, throttles, motors, additional cavities, auxiliary mechanisms and other actuators were considered, the advantages, application limits and disadvantages of each method were analyzed. Based on the results of the performed analytical procedure, as well as the recommendations known in the scientific and technical literature on improving the vibration-protective properties of suspension systems, the authors proposed and developed a new method for controlling the elastic-damping characteristic, which is implemented in the proposed technical solution for the air suspension of a vehicle seat. The method differs in the thing that it implements a cyclic controlled exchange of the working fluid between the cavities of the pneumatic elastic element and the additional volume of the receiver on the compression and rebound strokes, forming an almost symmetric elastic damping characteristic, and partial recuperation of vibrational energy by a pneumatic drive, presented in the form of a rotary type pneumatic motor. In addition, the method does not require an unregulated hydraulic shock absorber, while still having the advantage of improved vibration-proof properties of the air suspension of a vehicle seat over a wide range of operating influences.

Today, soil cutting tools are mainly made from carbon steels, which are heat treated to provide high hardness and strength. However, at present, the durability of such a hardened soil-cutting tool of both domestic and foreign manufacturers is far from perfect. One of the reasons for the insufficient resistance to abrasive wear of a soil-cutting tool subjected to hardening by heat treatment may be its heating by frictional force in contact with the soil. As a result of such heating, the steel undergoes additional tempering, which leads to a decrease in the surface hardness of the cutting edge of the tool by almost 2 times - 49-50 HRC to 22-34 HRC, depending on the intensity of metal heating. This circumstance was established during metallographic studies of samples cut from the shares of the KB-01 body of the PBS-4 plow. One of the ways to solve this problem is to obtain a wear-resistant layer on the surface of the soil-cutting tool, which is not subject to the negative effects of reheating during operation, for example, from alloyed white cast iron by the method of plasma-powder surfacing. Metallographic studies showed that the deposited layer has a hardness of more than 62 HRC. At the same time, such types of heat treatment as hardening, normalization or annealing do not have a noticeable effect on the hardness of the deposited layer. Metallographic studies of the deposited metal after operation also showed the absence of noticeable changes in its microstructure and hardness. This indicates that reheating from the action of friction forces does not have a significant effect on the properties of a soil-cutting tool strengthened by plasma-powder surfacing, which contributes to an increase in its duration of operation.

The article presents a brief analysis of the technology of harvesting grain crops and technical means, from which it follows that one-section threshing-separating decks structurally look as follows. The “sockets” for their installation in the combine are fixed on the side cheeks, which, in turn, are rigidly connected to the transverse strips, installed between them at a uniform interval along the entire length of the deck, and the transverse strips with their inner side are located on a cylindrical surface with a certain drum wrap angle. At the same time, to increase the rigidity of the transverse strips and the entire deck as a whole, below the surface of the bar tier, the transverse strips are interconnected by rectangular ribs curved along a concentric circle of a larger radius than the radius of the working surface of the separating grid. All decks are installed on the combine with respect to the outer diameter of the drum beaters, not along a concentric circle, but with an offset. Therefore, the principal disadvantages of single-drum single-section decks are the high levels of under-threshing, loss of free grain in the coarse heap through straw walkers, and especially crushing. In this connection, there is a need for its improvement, as well as the need to modernize the threshing-separating device with an improvement in the operation of the air-sieve cleaning. On the basis of prospecting studies, a single-section threshing deck protected by the RF patent was proposed. The deck consists of at least three zones. In the first zone of threshing and separation the separating grid is made two-tier, with a variable distance between the tiers by means of a variant installation under the main tier of removable bars of the grid, located on the transverse slats with a step t larger on radii than those of the main tier, passing in the middle of the step bars of the main upper tier with intervals from 0.75 to 1.25t. In the second zone of separation and threshing the separating grid with a length of 5 to 12 intervals between the transverse strips is single-tier, but the step between the grid bars located on the continuation of the tier of the first zone on the transverse strips of the zone is at least 1.5t of the step. In the third zone of final threshing and separation with a length of no more than 6 intervals between the transverse slats, a single-tier grating is a continuation of the upper tier of the first zone with a bar pitch from 0.5 to 1.5t of the first zone pitch. This solution has practical significance and perspective for implementation by installing them on self-propelled grain harvesters.