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Electric vehicles offer cleaner transportation with lower emissions, thus their increased popularity. Although, electric powertrains contribute to quieter vehicles, the shift from internal combustion engines to electric powertrains presents new Noise, Vibration, and Harshness challenges. Unlike traditional engines, electric powertrains produce distinctive tonal noise, notably from motor whistles and gear whine. These tonal components have frequency content, sometimes above 10 kHz. Furthermore, the housing of the powertrain is the interface between the excitation from the driveline via the bearings and the radiated noise (NVH). Acoustic features of the radiated noise can be predicted by utilising the transmitted forces from the bearings. Due to tonal components at higher frequencies and dense modal content, full flexible multibody dynamics simulations are computationally expensive.

With the increasing stringent emissions legislation on ICEs, alongside requirements for enhanced fuel efficiency as key driving factors for many OEMs, there are many research activities supported by the automotive industry that focus on the development of hybrid and pure EVs. This change in direction from engine downsizing to the use of electric motors presents many new challenges concerning NVH performance, durability and component life. This paper presents the development of experimental methodology into the measurement of NVH characteristics in these new powertrains, thus characterizing the structure borne noise transmissibility through the shaft and the bearing to the housing. A feasibility study and design of a new system level test rig have been conducted to allow for sinusoidal radial loading of the shaft, which is synchronized with the shaft’s rotary frequency under high-speed transient conditions in order to evaluate the phenomena in the system.

Elastohydrodynamic (EHD)-simulation is a widely applied simulation technique that is used in a very diverse field of applications ranging from the study of vibroacoustics to the calculation of friction power losses in lubricated contacts. In particular, but not limited to, the automotive industry, technical advances and new requirements put current EHD simulation methodology under test. Ongoing trends like downsizing, downspeeding, start-stop and the continuing demand for increasing fuel efficiency impose new demands and challenges also on the simulation methodology. Increasing computational capabilities enable new simulation opportunities on the other hand. In the following, an overview is given on the current state of the art and today’s challenges for the elastohydrodynamic simulation of journal bearings and their wide range of applications from highly loaded main bearings supporting the crank shaft in the ICE to high speed turbocharger bearings.

For vibration and acoustics vehicle development, one of the main challenges is the identification and the analysis of the noise sources, which is required in order to increase the driving comfort and to meet the stringent legislative requirements for the vehicle noise emission. Transfer Path Analysis (TPA) is a fairly well established technique for estimating and ranking individual low-frequency noise or vibration contributions via the different transmission paths. This technique is commonly applied on test measurements, based on prototypes, at the end of the design process. In order to apply such methodology already within the design process, a contribution analysis method based on dynamic substructuring of a multibody system is proposed with the aim of improving the quality of the design process for vehicle NVH assessment and to shorten development time and cost.

The aim of this paper is to present the adjoint equations for shape optimization derived from steady incompressible Navier-Stokes (N-S) equations and an objective functional. These adjoint Navier-Stokes equations have a similar form as the N-S equations, while the source terms and the boundary conditions depend on the chosen objective. Additionally, the gradient of the targeted objective with respect to the design variables is calculated. Based on this, a modification of the geometry is computed to arrive at an improved objective value. In order to find out, whether a more sophisticated approach is needed, the adjoint equations are derived by using two different approaches. The first approach is based on the frozen turbulence assumption and the second approach, which is advanced in this paper, is derived from the near wall k − ζ − f turbulence model.

The reduction of acoustic excitation due to piston slap as well as friction loss power and seizure are main issues when simulating the oil film lubricated piston - cylinder contacts of internal combustion engines. For a correct representation of the contact conditions between a piston skirt and a cylinder liner surface both the dynamics of the contacting flexible bodies, the shape of the contacting surfaces, the amount of available oil and the properties of the lubricant itself play important roles. Besides an appropriate representation of the hydrodynamic load carrying capacity using an averaged Reynolds equation with laminar flow conditions, the simulation has to use an appropriate asperity model to consider the mixed lubrication condition. The lubricant properties are in particular influenced by its thermal conditions.

The objective of the present investigation is to develop a suitable simulation method for dynamic analysis of rotary engines using Finite Element Method (FEM) and for flexible multi-body dynamics using AVL EXCITE. The engine analyzed is the current MAZDA gasoline engine with two rotors. The general approach and the tools applied are well established for reciprocating combustion engines, but the requirements concerning the simulation of rotary engines are very different due to the higher bearing loads, rotor guidance in the housing by a gear and the special requirements for axial movement of the rotor relative to the housing to ensure sealing. Detailed investigations are made for the simulation of the complex dynamics of the moving engine parts with respect to the interaction between flexible models of rotors, eccentric shaft and housing using axial contact between rotors and housing as well as detailed elasto-hydrodynamic bearing models (EHD) for the rotor bearings.

The authors want to introduce a general methodology for the simulation of the dynamics of the piston-liner contact considering a realistic oil film at inner liner wall. Because of the complexity of this problem and in order to minimize computing time a twin model was developed. Firstly, a simplified model is used to compute piston motion trends and piston ring lubrication in minimum simulation time. Secondly a very detailed model simulating multi-body dynamics, surface vibrations and elasto-hydrodynamic contact is applied. Both, the theoretical background of the twin model and the advantages of the coupled simulation procedure given in the wide range of considerable influences are discussed. The result examples focus on interaction effects of piston secondary movement and the influence of the available oil film. Finally, the status of verification of the models using measured results is shown.