Numerical analysis of fan drive technologies for agricultural tractors

Cooling systems play a fundamental role in ensuring the reliability and performance of agricultural tractors, while at the same time contributing to the overall energy demand of the vehicle. Among the various components of the cooling system, the engine cooling fan represents a significant source of parasitic power absorption, as it is continuously driven to ensure adequate heat rejection under a wide range of operating conditions. The power required by the fan directly affects engine load and, consequently, fuel consumption, making the fan drive system a relevant aspect in the pursuit of improved tractor efficiency. In conventional tractor architectures, the cooling fan is mechanically driven by the engine through belts and pulleys, resulting in a fan rotational speed that is strictly proportional to engine speed. This configuration does not account for the actual thermal demand of the cooling system and can lead to inefficient operation when full cooling capacity is not required. Alternative fan drive technologies, such as hydraulic fan drives, offer the possibility of decoupling fan speed from engine speed and enabling a more flexible control strategy based on cooling requirements. This technological difference motivates a detailed investigation of the impact of fan drive architectures on power absorption and fuel consumption. The objective of this thesis is to perform a numerical analysis of different fan drive technologies for agricultural tractors, with a specific focus on the comparison between mechanically driven and hydraulically driven fan systems. The study aims to evaluate how the choice of fan drive architecture influences the power absorbed by the cooling fan and how this power demand translates into engine fuel consumption. The analysis is carried out under predefined and representative operating conditions, selected to ensure a consistent and repeatable comparison among the considered configurations. A CFD-0D simulation-based methodology was adopted using the AMESim® environment. Detailed numerical models of the fan drive systems were developed, including the mechanical transmission elements and the hydraulic components required for variable-speed fan operation. The models were used to simulate the fan behavior and to calculate the power absorbed by the fan for each configuration under the selected operating conditions. Particular attention was paid to ensuring a consistent modeling approach, allowing differences in power demand to be attributed solely to the fan drive technology. Once the fan power absorption data were obtained from the simulations, these values were used as input for the evaluation of engine fuel consumption. The contribution of the fan drive to fuel consumption was quantified by employing the engine Brake Specific Fuel Consumption (BSFC) map, which relates engine operating conditions to fuel usage. By linking the fan power demand to the engine BSFC characteristics, the analysis provides a systematic method for translating fan drive power requirements into corresponding fuel consumption values.