Abstract:

In this study, the air flow resistance acting on scaled agricultural tractor models using a wind tunnel was determined experimentally. Tractor models have the same shape, but three different designs were tried on the operator platform section. These are the platform surrounded by the cab, the sunshade platform and the platform with the protection bar to protect the user in case of overturning. Thus, depending on the design of the user section, the air resistance changes that the tractors are exposed to in on-road transportation are determined experimentally for the first time. Tractor models used in the wind tunnel were prepared in a ratio of 1:13 according to geometric similarity principles. In wind tunnel tests, kinematic and dynamic similarity cannot be achieved, but Reynolds number independence can be obtained. A Reynolds number range was surveyed by performing experiments at different air velocities in the wind tunnel air flow rate range. In this range, the aerodynamic resistance forces acting on the models and the air flow-induced pressure distributions in the symmetry axis of the tractors were measured. Dimensionless aerodynamic drag coefficient and pressure coefficient values were calculated from the measurements obtained. According to the calculations, the use of the cabin increases the aerodynamic resistance in the range of 3-15%. While the percentage of resistance increase due to cabin usage is high at low speeds, it decreases at high speeds. As a result of the use of the cabin, the tractor front projection area perpendicular to the flow increases. However, the increase in aerodynamic drag is one order lower than the increase in the frontal projection area. Considering the benefits of cabin use in terms of occupational safety, it is understood that the increase in aerodynamic resistance due to cabin use is an acceptable cost. It is expected that the results of the study will contribute to the separation of energy consumption in on-road transportation with agricultural tractors.

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