Theoretical research into the power and energy performance of agricultural tractors

Abstract

The widespread use of a great number of different types and manufacturer brands of tractors in agricultural use raises several important questions. These all concern the implementation of the criteria which may be involved in making the right choice in regard to a particular power unit that is capable of delivering the required result during the subsequent course of that unit’s service life. Even more importantly, the result should be an economically sound one. Despite the fact that tractor theory offers a sufficient number of scientifically grounded criteria that characterise agricultural power units with respect to their particular properties, the engine power rating remains the most widely used and decisive figure – and the factor which defines the ultimate choice of power unit. Meanwhile, the traction properties of tractors, especially in case of wheeled tractors, should be of prime importance as these properties determine the maximum measures that can be taken in relation to efficiency levels in power units as parts of various unitised agricultural machines. Currently, in most areas around the world, the traction and energy performance of wheeled tractors is determined using the same common method, one which is based upon the tractor’s power balance. But when taking into account the ever-increasing requirements for protecting the soil, the aforementioned method needs corresponding upgrading with respect to the destructive effect of the wheeled running gear of agricultural tractors on the soil’s structure. The aim of this study is to develop a new method of determining the minimum required engine power rating for an agricultural wheeled tractor, as well as its operating mass and energy saturation rate when considering the linear type of dependence for its running gear slipping due to the tractive force being generated. The research utilises standard tractor theory and numerical computation methods. The completed study resulted in several updated and new analytical dependences, all of which can be used to define the tractive power of a wheeled tractor, taking into account the linear type of relationship between wheel slip, operating mass, and energy saturation rate. The data that is obtained through computational methods show that the classification of various wheeled tractors with regard to their traction or their traction and power category using the new method will subsequently allow more accurate calculations to be effected when it comes to unitising various agricultural machines, which should help to ensure an improvement in their overall performance levels.