A PART OF MARELLI
The last decade has been marked by the development and continuous improvement of technologies for the numerical representation of physical processes, by means of numerical simulation assisted by computer and advanced 3D graphic representation techniques.
This has made the use of advanced calculation techniques for computer-assisted design of components and systems efficient and reliable, thus allowing the execution, already in the conceptual processing phase and with no physical specimens available, of most of the functional performance verifications for a specific product of human engineering.
Terms such as “Virtual Prototyping” and “Virtual Analysis” were thus coined: Magneti Marelli has always been actively engaged and at the vanguard in these fields, employing the most modern technologies available and possessing significant specialized skills and application experience.
Magneti Marelli commonly employs the most modern modelling and analysis techniques available, from the more simple ones known as “concentrated parameters” up to the most complex three-dimensional techniques, capable of representing highly complex phenomena (interaction between fluids and solid structures, mixing of different types, chemical reactions, changes in the state of materials, etc).
Specifically, in the three-dimensional area, we are talking about Finite Element Modelling (FEM) and Finite Element Analysis (FEA) mainly in the structural, magnetic and thermal area of solid components, and Computational Fluids Dynamics (CFD) in the field of fluids mechanics.
The main objective of all these analyses is to obtain information on the response of physical systems to certain set conditions, commonly indicated as boundary conditions and/or loads.
Through the extensive use of these forecast analysis tools, a Development Team can verify whether the proposed project will be able to comply with the customer’s specification before a prototype is even built.
At Magneti Marelli, mathematical models are used both for the design/definition of the product/project, and for its certification.
During the design phase, many numerical analyses are usually carried out. Design engineers compare and classify alternative projects in accordance with the customer’s objectives. During the certification phase, the project is reviewed in order to verify that the final project complies with all the set requirements.
The most frequently requested and used analyses are:
Structural Analysis: used to determine the level of stress and deformation in a component, structure or kinematic motion. It is based on linear calculation models and non-linear models.
Linear models assume that deformations and geometric displacement are of small entity (“geometric” linearity) and that the material does not deform plastically (“material” linearity).
Non-linear models consist of taking into account large displacements/deformations and/or subjecting the material to stresses beyond its elastic limit.
Vibrational Analysis: used to predict the intrinsic vibrational characteristics of a component or structure (“modal” analysis) and the vibrational response modes of such component or structure to oscillatory or impulsive type stresses (“harmonic” analysis).
Heat Transmission Analysis: used to identify, within components and structures, the distribution of temperatures and the entity and transmission routes of heat, when such components and structures are in proximity to heat sources. They can be stationary or transitory analyses, in other words representing situations stable over time or describing the evolution of the phenomenon as it evolves.
Noise, Vibration and Harshness Analysis (NVH): this is an extension of vibrational analysis in the field of pressure changes transmitted to the acoustic means (air). It is used to represent the acoustic field present in proximity to a vibrating component and to illustrate in detail its spatial distribution in terms of both intensity and spectrum (frequencies present). These analyses are crucial for the design of mechanical components that guarantee adequate acoustic and vibrational comfort.
Magnetic Analysis: used to estimate the distribution of magnetic flows and the forces associated to such flows with regards to a component, structure o group. This analysis can also be based on linear and non-linear models, this time considered such from an electromagnetic standpoint.
Fluid Dynamics Analysis: used to predict the spatial motion field of a fluid (velocity, pressure, temperature, etc.) when subjected to changes in pressure or temperature. It can be “internal”, in other words aimed at analyzing motions that develop inside specific environments (volumes, conduits, etc.) or “external”, aimed at analyzing motions that develop outside specific structures (aerodynamics of a vehicle, field of motion of air around a radiator, etc.)
Coupled Analysis: this type of analysis is basically a simultaneous analysis, which takes into account mutual interactions, of one or two types of analyse (for example: fluid-structure interaction (FSI), thermo-structural analysis, coupled magnetic-thermal analysis, etc.)
This type of analysis is used extensively in analyzing components for hybrid systems (HEC), to predict heat transfer and air flow inside and around electronic equipment, from the individual component or card up to the complete system.
Engine analysis: there are three classes of numerical models that can be used in simulating the operation of an internal combustion engine. For a quick calculation of the engine, simple zero-dimensional models are used. These models do not include a spatial resolution and only describe general processes, with no information on local phenomena. They are used to quickly calculate the torque and power that can be obtained from an engine based on macro characteristics such as bore, stroke, overall dimensions of the intake and exhaust circuits, etc.
The second class of models consists of phenomenological models, which take into account certain types of quasi-spatial resolution of the combustion chamber and use more detailed sub-models to describe the relevant processes, such as blend formation, ignition and combustion. These one-dimensional phenomenological models can be used to predict with reasonable accuracy the main engine parameters (volumetric yield, torque, power, noise at the air intake mouth, etc.)
The third class of models are the CFD three-dimensional models. In the CFD-3D calculation codes, more detailed models are used and all sub-processes of interest can be solved.
For example, in an in-depth “cylinder interior” analysis, in the case of blend formation, the sub-processes such as injection, break-up and evaporation of liquid drops, with relevant collisions and impingement on the cylinder walls can be calculated point by point inside the combustion chamber represented in its three-dimensional entirety. This class of models is the most sophisticated one in terms of solutions employed and the engineering skills requested of the users, as well as the most expensive one with regards to the necessary calculation time and power.