Thanks to their manufacturing simplicity, robustness, and consolidated design knowledge, external gear pumps are widely adopted in the automotive fields. With the purpose of leading the design procedure of these positive displacement machines, within this work, the authors integrate in a comprehensive tool the salient equations adopted for the design of the major gear pump features. The presented procedure is devoted to the design of multistage external gear pumps characterized by a singular floating driving shaft supported by fluid-dynamic journal bearings. Focusing the attention on the procedure flexibility, it has been structured in three iterative calculation phases. The core section of the methodology concerns the geometrical design of the involute gear tooth profile. It is oriented to ensure a proper volumetric displacement while complying with the space requirement and the tooth manufacturing limitations. Thus, through the analytical pressure loads estimation combined with the operational parameters, the second calculation step provides the design of the driving shaft and the relevant dimensions of the journal bearings. Finally, by means of a power loss approach, the third macrosection of the procedure leads to estimating the clearances between gear tip and housing. The potentials of the methodology are exposed by describing its applications to a case study of multistage gear pump employed in the dry sump lubrication system of an automotive heavy-duty engine. Each calculation step application is outlined with reference to the proposed analytical formulation and the results of the parameters calibration are presented. Within this context, the procedure is assessed by means of a CFD analysis. The results highlight the accuracy of the methodology on the estimation of the required delivery flow rate. Aside from being accurate, flexible, and reliable, the procedure stands out for being an innovative tool within the multistage gear pump framework.

Vehicle dynamics is of primary importance for the determination of the vertical load on wheels and consequently on their traction capability. This is even more true if the vehicle is travelling on an uncompacted soil and influenced by a variable load applied to the hitch, as it is for a ploughing tractor. In this framework, the authors present a comprehensive lumped parameter approach for performance assessment of agricultural tractors in real operating conditions. The proposed methodology integrates in a modular context different numerical models related to the main subsystems of a modern tractor, i.e. diesel engine, hydro-mechanical transmission, full multibody frame and tire mechanics. In particular, the engine and transmission modules reproduce powertrain characteristics and control strategy, the multibody module characterizes the dynamic behaviour of the vehicle detailing the interaction between the tractor rigid bodies, and the tire model predicts tractive capability and resistance to motion on soft soil. It also provides the possibility to properly reproduce real load cycles and their influence on the vehicle setup. The presented lumped parameter model is intended as a powerful simulation tool, capable of considering a large number of phenomena affecting tractor performance, both in terms of fuel consumption and longitudinal response due to load distribution. The predictive capabilities of the proposed modelling approach are presented by simulating a realistic ploughing operation, focusing on tire-soil interaction. Considering the cascade phenomena from the wheel-ground interaction to the engine, passing through the dynamic of vehicle bodies and their mass transfer, numerical results are presented in terms of tractive capability and its effect on fuel consumption.

In this work, the authors present a robust and integrated procedure for the design of multi-stage gear pumps to be used in dry sump system applications. Based on the target delivery flow rate, rotational speed and fluid properties, the developed iterative method enables to directly obtain the geometrical features and the working parameters of the pump components, such as gearpair specifics, shaft and journal bearing dimensions, clearance values. The methodology is then applied to a case study in order to highlight its features and detail the achievable outcomes. Quality of the results is assessed by means of a CFD analysis, demonstrating the capability to obtain the expected volumetric efficiency.

The paper focuses on the development of a predictive numerical tool for the assessment of the filling performance of engine lubrication systems. Filling analyzes are typically carried out by means of multi-phase 3-D CFD models but, despite allowing detailed and reliable results, they require very demanding computational requirements. On this basis, a procedure for the lumped parameter modelling of the fluid domain is proposed, allowing the discretization of complex systems that cannot be straightforwardly attributable to elementary submodels. The presented criteria are then applied to the lubrication system of a heavy-duty engine, for which the filling of the circuit plays a fundamental role. Different temperature conditions are simulated, and the predictive capabilities of the numerical model are presented in terms of flow pattern and filling time of the circuit branches. The same simulations are also carried out by means of a 3-D CFD model, permitting a result comparison. The comparative analysis concerns both the overall distribution of the lubricant over time, and the local phenomena within the oil domain, in order to assess the approximation of the lumped parameter approach with respect to the more accurate three-dimensional models.

Modern agricultural tractors are complex systems, in which multiple physical (and technological) domains interact to reach a wide set of competing goals, including work operational performance and energy efficiency. This complexity translates to the dynamic, multi‐domain simulation models implemented to serve as digital twins, for rapid prototyping and effective pre‐tuning, prior to bench and on‐field testing. Consequently, a suitable simulation framework should have the capability to focus both on the vehicle as a whole and on individual subsystems. For each of the latter, multiple options should be available, with different levels of detail, to properly address the relevant phenomena, depending on the specific focus, for an optimal balance between accuracy and computation time. The methodology proposed here by the authors is based on the lumped parameter approach and integrates the models for the following subsystems in a modular context: internal combustion engine, hydromechanical transmission, vehicle body, and tyre–soil interaction. The model is completed by a load cycle module that generates stimulus time histories to reproduce the work load under real operating conditions. Traction capability is affected by vertical load on the wheels, which is even more relevant if the vehicle is travelling on an uncompacted soil and subject to a variable drawbar pull force as it is when ploughing. The vertical load is, in turn, heavily affected by vehicle dynamics, which can be accurately modelled via a full multibody implementation. The presented lumped parameter model is intended as a powerful simulation tool to evaluate tractor performance, both in terms of fuel consumption and traction dynamics, by considering the cascade phenomena from the wheel–ground interaction to the engine, passing through the dynamics of vehicle bodies and their mass transfer. Its capabilities and numerical results are presented for the simulation of a realistic ploughing operation.