The diesel fuel consumption affects the costs of transport in a significant manner. All measures leading to its minimization are therefore important. The proper formation of the transport combinations is one of such measures, i.e. selecting the power traction means to the trailer whose engine will run in the optimum working regime most of the time in the course of the transport operation, when its specified fuel consumption achieves low values. Vitlox and Michot (2005) dealt with the effect of the rated engine power utilization on the specific fuel consumption when cultivating soil with rotary harrows. They found that, when using rotary harrows with the 3 m engagement and 4 km/h working speed, the input power was 24 kW and the specific fuel consumption was 330 g/kWh. If the working speed increased to 7 km/h and the engagement to 4.5 m while all other parameters remained unchanged, the input power was 65 kW, however, the fuel consumption decreased to 242.5 g/kWh.Bauer et al. (2006) give an example of an engine running in two regimes at the same 150 kW power output, but at different speeds. In the first regime, the engine runs at 2000 min -1 and the fuel consumption is 230 g/kWh, in the second regime, it runs at 1770 min -1 and the fuel consumption is 210 g/kWh. The difference in the hourly consumption between both regimes is therefore 3.7 l/h. With the diesel fuel price of CZK 27 per litre, the difference is 100 CZK/h in fuel costs. MATERIAL AND METHODSThe goal of this work was the determination of how the change of the tractor engine rated power in a transport combination affects the diesel fuel consumption related to the unit of the transport output (l/tkm) and the transport performance (t/h) in the conditions of a mountainous region.First, a theoretical analysis of the diesel fuel consumption was carried out according to the available literature references when using different engine power in the tractor-trailer working combinations.The measurement was carried out in the territory of the Šumava Nicov farm which is situated in the sloping Abstract: The authors of this paper determined in a field measurement how the change of the tractor engine power in a tractor-trailer combination affects the diesel fuel consumption related to the unit of transport output (l/tkm) and the transport performance (t/h) in the conditions of a mountainous region. Transport combinations (tractor -trailer) were compared that were formed by a tipping trailer connected to three tractors with different engine powers when passing allong a route with the gradient of 0°-5.5°. It is obvious from the results of these measurements that the diesel fuel consumption differed by up to 27% in individual combinations. The lowest specific consumption on the measured route was found in the combination with the tractor with the engine rated power of 50 kW (0.037 to 0.077 l/tkm), the highest consumption with the tractor with the rated engine power of 114 kW (0.056 to 0.093 l/tkm). The lowest transport performance on the measured route was found in the...

Abstract:The elementary simulation mathematical models presented in this article are related with the sub-system Crop production of the expert system for the decision support in technological and working processes management and their optimisation. Along with this sub-system, the expert system also involves the sub-systems Livestock production and Material handling which is further divided into the parts transport and storage. The boundary between the individual parts of the expert system is usually a short-term or long-term material storage. The relative individual subsystems are mutually connected through the information flow. For each of the sub-systems, specific simulation models are created. The simulation models in the expert system investigated replace the complex of general standards and norms used in other expert systems. The simulation models allow to take into consideration the concrete natural and production conditions (area, plots shape and inclination, soil type, transport routes length and surface, fertilisers doses, crops yields etc.) and also the technological systems utilised during the realisation of operations in working processes (technical, exploitation, energy, economical or energy means, attached vehicles, machines and equipment and method of their work) and the calculation of the parameters utilised. The simulation models also allow the creation of suitable working, and transport sets to choose their optimal variants for the given conditions. In comparison with the utilised standards and norms, the parameters computed through the simulation models significantly improve the data which represent the output from the expert system.

In the second half of the past century, technological progress changed dramatically the performance of agricultural machines. The consequences were both positive and negative. The positive aspect is the stable and abundant production of food, the negative aspect is a larger dependence on fossil fuels and a lower energy efficiency (GIAMPIETRO, PIMENTEL 1994). The consumption of fuels is the main part of all the consumed energy not only during crop production, but also in the entire agriculture sector. In the past time, the consumption of fossil fuels and energy ranks among the most closely monitored issues all over the world. The reason is that the economical development of each country depends to a certain degree on the level of fuel and power resources, the ability of continuous supplying, when these energy resources are limited and can only be obtained with increasing difficulties. The increasing disproportion between energy consumption and the possibility of its providing makes a current issue from the necessity to rationalize all forms of energy use. The solution of the problem of the rationalization of the diesel fuel consumption during crop production is the main part of the rationalization of the consumption of all the energy of an agricultural plant (ONDŘEJ 1985).Depending on the type of fuel and the amount of time a tractor or machine is used, fuel and lubricant costs will usually represent at least 16 percent to over 45 percent of the total machine costs (SIEMENS, BOWERS 1999). The maximization of the engine fuel efficiency, maximization of the efficiency of the traction mechanism and the selection of the optimum working speed of the traction set (GRISSO et al. 1999) effects the efficiency of tractors. Apart from the construction parameters of the engine used, the fuel consumption per hour depends on the degree of the use of the engine output and the fraction of the running time with respect to the overall operational time (PASTOREK et al. 2002). The energy intensity of individual operations depends not only on the technical parameters of the machine set used, method, depth and intensity of work, the manner of using the machine set, but depends to a considerable extent also on the variability of the physical and mechanical properties of the processed material, land size, its regularity, slope, fraction conditions and other parameters.In the Research Institute of Agricultural Engineering in Prague, the effect of the factors was analyzed that influence the implementation of operational steps, considered primarily from the point of achieved performances, rated energy consumption, primarily of diesel fuel and the unit direct costs. It is obvious that the greatest influence on performing operational steps from the point of view of exploitation, economical and energy criteria has the size and shape of land units (SYROVÝ et al. 2002). This influence is caused by the number of turns at the headland, when the operational capacity of the machine is not used. During agricultural operations, ABSTRACT:The goal of ...