Vol 83, No 6 (2016)

One of the reasons of poor effectiveness of machines for postharvest grain handling is the difficulty of optimal modes setting under constantly changing input actions. Using of hardware check and technological process control instead of manual adjustment will reduce the costs and improve the quality of postharvest grain handling. A grain loss sensor for device of parameter checkout of technological process of pneumatic systems of grain-cleaning machines is developed. Its operation is based on the analysis of parameters of sound pressure signal, that arises when grains blowing together with impurities are hitting against a wall of settling chamber. The sensor design is developed on the basis of Soho T-1 low-cost piezometric transducer. The sensor is located on the outer side of a wall against which grains are hitting, and lies outside the air stream carrying the impurities and dust. Therefore, the reliability of the sensor increases, and the air stream structure in pneumatic separation system remains steady. The parameters of sound signal arising when grains are hitting against a wall of settling chamber are determined. The researches were conducted with the grains of wheat, rye, oats and barley; the grain moisture content was varied within the range from 12.6 to 35%. The dependencies between the parameters of sound signal arising when grains are hitting against a wall of settling chamber and the grain loss level have been obtained. The operational capability of the sensor was tested on an experimental model of pneumatic separator installed on postharvest grain handling line. The sensor can be adapted for operation in other pneumatic systems of grain-cleaning machines.

The regularities of effective power change of gas-turbine engine (GTD-350T), constant power engine (D-260.4S2) and diesel engine (SMD-62), depending on external load and the coefficient of its variation are investigated. The comparative estimation of efficiency of these engines’ application on tractors in aggregate with soil cultivating machines is carried out; experimental data is received. The methods of mathematical modeling and probabilistic-statistical estimation of the operational parameters of soil cultivating units are applied. The dependencies of extreme values of effective power of abovementioned engines on the shaft torque and coefficient of load variation are obtained. The studies show that the piecewise-linear characteristic of constant power engines is more rational than the piecewise parabolic characteristic of diesel engines. The parabolic characteristic of gas-turbine engines is the most effective one and less sensitive to the fluctuations of external load. The application of gas-turbine engines on tractors meets the technical and technological requirements for agricultural machinery. The gas-turbine engines can improve the competitiveness of domestic tractors by 1.2-1.3 times, reduce the expenditure of labor by 15-20%, increase the productivity of labor on average by 18-22% compared with tractors equipped with diesel engines.

Innovative technologies and technical means of drying which allow to dry the grain efficiently and with minimal costs are very important for development and improvement of grain industry. These technologies include the oscillating modes, the essence of which is that the material is periodically affected by heated and unheated drying agent. These modes provide periodical grain cooling, that allows to increase drying agent temperature and decrease heat losses. However, periodical grain cooling with unheated air often lowers the effect of oscillating mode. Pulse mode, unlike the oscillating one, is characterized only by decreased liquid fuel supply in the dryer, and grain cooling on a value close to theoretical one, which allows to decrease heat losses and increase dryer efficiency. The mathematical methods of calculation of temperature and duration of impact of low-heated drying agent on the grain are suggested. To determine the temperature of low-heated drying agent and its impact duration, the heat and mass transfer equations in layer and caryopsis were composed and solved; the calculated expressions were obtained from them. During acceptance testing of the S-30 dryer, the calculated dependences for determining these parameters were checked. The wet grain was continuously sent into grain dryer, the dried and cooled grain was withdrawn at the same time. The «big fire» nozzle in firebox was periodically enabled and disabled, and the «low fire» nozzle remained in working mode, thus a pulse mode of drying was created. The maximum temperature of heated drying agent was 105 degrees С, while the temperature of low-heated drying agent was 46 degrees С. It was established that curves of changing in temperature and moisture of grain did not differ from the classic curves under oscillating drying mode. The use of pulse drying mode allows to shorten by two times the amplitude of temperature oscillations of drying agent and to reduce heat losses by 10-12%. The temperature of low-heated drying agent should not be below the maximum permissible heating temperature of grain by more than 8-10 degrees C.

From 50 to 70% of failures of working organs and support frames of agricultural machines and implements are accounted for the connections with threaded fasteners. The paper deals with the basic general methodological principles for ensuring the reliability of threaded connections of agricultural machines and implements. The structural scheme of general problem of improving the reliability of threaded connections is proposed. The main ways of improving their reliability are: the development of new designs of threaded connections that meet the above-noticed basic principles; the improvement of the method of calculation of group threaded connections that operate under partial joint opening and contact vibration displacement; the improvement of the method of calculation of group threaded connections that operate under complex loading taking into account the radial and angular contact compliances; the use of numerical methods for calculating of group threaded connections; the improvement of methods of screw retention; the improvement of methods of corrosion protection. The classification of the main factors of fatigue wear failure of threaded connections that operate under complex loading is proposed. The elaboration of fatigue safety factor of connections of agricultural machines is given, depending on the operating conditions, with the use of additional factor which depends on the rate of wear and corrosion. For the expression to determine the degree of fatigue strength on the shear stresses, the uniformity factor of distribution of lateral load between the fasteners is introduced; it depends on the type of connections, constructive gap in the connection and quantity of fasteners. The specified method of calculating the fatigue strength and the proposed basic principles of improving the reliability may be used in the practice of design and repair of agricultural machines.

The increase in productivity of grain crops is possible as a result of production intensification by improvement of cultivation technology, in particular the most important technological operation of sowing, which lays the foundation for growth and development of cultural plants. The purpose of the research concerns the improvement of technology of grain crops sowing, and improvement of working organs of sowing machines. The scheme of technology of soil conservation farming is presented. It is revealed that high-quality sowing is characterized by two components: the uniform distribution of seed material on the feeding area and depth of seeding, and the application of mineral fertilizers lower than the level of seeds of main crop. The form of rational feeding area is determined; the scheme of rational distribution of seeds on the area is given. The issue of joint and dual-level application of mineral fertilizers when sowing is considered. It is established that joint application of seeds and fertilizers leads to a toxic burn of seeds and decrease in productivity, while dual-level application provides gradual perception of nitrate and promotes the accelerated development of root system. The common faults of most of openers are marked, these are the uneven distribution of seeds on the feeding area, and the application of fertilizers together with seeds on the same depth. The design of a dual-level opener is proposed, providing two-tape sowing with a width of tapes up to 40 mm at a distance between them not less than 80 mm. At the same time, the application of mineral fertilizers is carried out lower than the level of seeds of main crop. The use of proposed opener allows to increase the germinating ability of seeds and, as a consequence, the productivity of cultivated crop.