Numerical and experimental investigations have been carried out in order to study the effect of the poppet geometry on the flow-pressure characteristic of a direct acting pressure relief valve, which is equipped with a flow deflector for flow force compensation. A dynamic 3D-CFD model was built in ANSYS Fluent™, which is capable of simulating the interaction between the fluid flow and the poppet dynamics by means of mesh deformation and of a user-defined function (UDF). This model was applied to predict the flow-pressure characteristics of the valve for different spring preload settings and deflector geometries. The simulated curves were validated using experimental data acquired at FPRL (Fluid Power Research Laboratory) at the Politecnico di Torino, and an excellent agreement was found. The CFD model was then used to predict the effect of geometric parameters of the poppet, such as the cone angle and the position of the deflector. Finally, a 0D model has been developed in order to predict the flow forces; this model requires very few calibration points using 3D-CFD simulations, and can easily be implemented in lumped parameter simulation tools. It was found that this model leads to a satisfactory prediction of the flow-pressure characteristic of the valve.

A real-time combustion model was assessed and applied to simulate BMEP (Brake Mean Effective Pressure) and NO_x (Nitrogen Oxide) emissions in an 11.0 L FPT Cursor 11 diesel engine for heavy-duty applications. The activity was carried out in the frame of the IMPERIUM H2020 EU Project. The developed model was used as a starting base to derive a model-based combustion controller, which is able to control indicated mean effective pressure and NO_x emissions by acting on the injected fuel quantity and main injection timing. The combustion model was tested and assessed at steady-state conditions and in transient operation over several load ramps. The average root mean square error of the model is of the order of 110 ppm for the NO_x simulation and of 0.3 bar for the BMEP simulation Moreover, a statistical robustness analysis was performed on the basis of the expected input parameter deviations, and a calibration sensitivity analysis was carried out, which showed that the accuracy is almost unaffected when reducing the calibration dataset by about 80%. The model was also tested on a rapid prototyping device and it was verified that it features real-time capability, since the computational time is of the order of 300–400 µs. Finally, the basic functionality of the model-based combustion controller was tested offline at steady-state conditions.