On the analysis of experimental data for external gear machines and their comparison with simulation results

This paper deals with the simulation of hydraulic gear machines, focusing on the validation of simulation models and on the comparison between numerical results and experimental data, concerning both steady and unsteady conditions. First authors give a brief overview on the simulation tool HYGESim, which has been presented and discussed in several previous papers. Afterwards, the attention shifts on the analysis of the simulation results for the case of a stock gear pump. Regarding steady state characteristics, the paper shows how HYGESim is able to accurately reproduce the operation of the analyzed pump, in terms of flow, pressures and efficiency maps. Regarding unsteady simulations, namely the delivery pressure ripple, the paper highlights the significant effort done by the authors in order to achieve experimental data clear and suitable for the comparison with simulation results. In fact, the peculiarities of common measuring systems (in particular of the load apparatus and the sampling methods) are often difficult to reproduce numerically: frequently different acceptable assumptions in the numerical model lead to remarkable discrepancies in simulated results. For this purpose, the authors developed a measuring device mainly focused on the easy reproducibility in the simulation environment. Furthermore, an original technique for processing unsteady data (pressure and flow ripples) is proposed, allowing to achieve comparable data indifferently of the adopted sampling method and of the data origin (experimental or numerical). In the final part of the paper, pressure ripple simulations and test results (obtained with the described measuring system and analyzed with the described technique) are presented and compared