A. Della Torre

A New Integrated Approach for the Prediction of the Load Independent Power Losses of Gears: Development of a Mesh-Handling Algorithm to Reduce the CFD Simulation Time

To improve the efficiency of geared transmissions, prediction models are required. Literature provides only simplified models that often do not take into account the influence of many parameters on the power losses. Recently some works based on CFD simulations have been presented. The drawback of this technique is the time demand needed for the computation. In this work a less time-consuming numerical calculation method based on some specific mesh-handling techniques was extensively applied. With this approach the windage phenomena were simulated and compared with experimental data in terms of power loss. The comparison shows the capability of the numerical approach to capture the phenomena that can be observed experimentally. The powerful capabilities of this approach in terms of both prediction accuracy and computational effort efficiency make it a potential tool for an advanced design of gearboxes as well as a powerful tool for further comprehension of the physics behind the gearbox lubrication.

A Nonlinear Quasi-3D Approach for the Modeling of Mufflers with Perforated Elements and Sound-Absorbing Material

Increasing demands on the capabilities of engine thermo-fluid dynamic simulation and the ability to accurately predict both performance and acoustics have led to the development of several approaches, ranging from fully 3D to simplified 1D models. The quasi-3D approach is proposed as a compromise between the time-demanding 3D CFD analysis and the fast 1D approach; it allows to model the acoustics of intake and exhaust system components, used in internal combustion engines, resorting to a 3D network of 0D cells. Due to its 3D nature, the model predicts high-order modes, improving the accuracy at high frequencies with respect to conventional plane-wave approaches. The conservation equations of mass and energy are solved at cell centers, whereas the momentum equation is applied to cell connections including specific source term to account for the of sound-absorbing materials and perforated elements. The quasi-3D approach has been validated by comparing the predicted transmission loss to measured data for a number of standard configurations typical of internal combustion engine exhaust systems: a reverse-flow chamber and series chambers with perforates and resistive material.

Modeling the Unsteady Flows in I.C. Engine Pipe Systems by Means of a Quasi-3D Approach

Increasing demands on the capabilities of engine simulation and the ability to accurately predict both performance and acoustics has lead to the development of several numerical tools to help engine manufacturers during the prototyping stage. One dimensional simulation tools are widely used during this phase and they allow the simulation of several engine configurations within a short time. Certain components, however, such as the intake and exhaust manifolds, exhibit a high degree of geometric complexity, which cannot be accurately modelled by ID codes, unless equivalent ID models are adopted. The need of achieving good accuracy, along with acceptable computational runtime, has given the spur to the development of a geometry based quasi-3D approach. This is designed to model the acoustics and the fluid dynamics of both intake and exhaust system components used in internal combustion engines. Models of components are built using a network, or grid, of quasi-3D cells based primarily on the geometry of the system. The solution procedure is an explicitly time marching pseudo staggered grid approach, where the equations of mass and energy are solved at cell centers while the momentum equation at cell connections or boundaries. The quasi-3D approach has been fully integrated into a ID research code in order to study the behavior of intake and exhaust devices under real engine pulsating flow conditions. This approach was mainly developed to model the acoustic behavior of complex shape silencers, however, in this work it has been extended and applied to the prediction of the fluid dynamic behavior of intake and exhaust systems. The validation was carried on a high performance V4 motorbike engine. In particular, the silencer and the air box have been modeled resorting to a quasi-3D reconstruction. Calculated results of instantaneous pressure traces and volumetric efficiency have been compared to measured data, highlighting a good capability in capturing dynamic effects with a computational runtime much lower than the one required by the integration of fully 3D models with the ID.Copyright

CFD framework for the modeling of aftertreatment systems: Application to the study of an electrically heated DOC for Diesel e

In this work, a state-of-the-art 48 V electrical heated catalyst is considered to investigate its effect in increasing the abatement efficiency of a standard DOC. The electrical heating device considered is based on a metallic support, arranged in a spiral layout, and it is heated by the Joule effect due to the passage of the electrical current. As a result of the spiral arrangement, the distribution of the heat source on the heating section is not uniform, determining a certain spatial distribution of the temperature of the gas entering the DOC section. To simulate the after-treatment system, a suitable CFD framework has been implemented on the basis of the open-source OpenFOAM code. Firstly it is validated resorting to experimental data. Then, it is applied for the investigation of the effects of the electrical heating on the pollutant abatement, with particular focus on the effects of the non-uniform temperature distribution related to different layouts of the heating spirals.