The aerodynamics of centrifugal compressors is a topical issue, as the vibrations and noise reduce the comfort of people who are in proximity to the compressor. The current trend in rotating machinery research is therefore not only concerned with performance parameters but also increasingly with the effect on humans. An analysis of aerodynamic noise based on external acoustic field measurements may be a way to assess the nature of aerodynamic excitation. In this research, the experimental measurements at 20 operating points covered the entire characteristic operating range of the selected centrifugal compressor. The dominant noise arising at blade-passing frequency (BPF) was identified at all the operational points, and the dominant effect of the buzz-saw noise was identified at the maximum rotor speed. The determination of the total sound pressure level $L_{\mathrm{P}}\left(\mathrm{A}\right)$ showed a trend towards an increasingly higher rotor speed and compressor surge line. In the amplitude-frequency characteristics, the sound pressure was found to be dependent on the rotor speed for BPF. On the other hand, non-monotonicity was detected between the operational points at given speed lines, confirming the complexity of the aerodynamics of rotating machines. The metric chosen to identify prominent tones determined by the tonality of individual tones in the frequency spectrum showed a clear effect of integer multiples of the rotational frequency on the overall noise. Thus, the results presented here confirm the dominant influence of BPF in terms of the psychoacoustic impact on humans.

High level of mechanical efficiency is exacted from internal-combustion engines. The reduction of friction losses of crankshaft main bearings can significantly contribute to the enhancement of this efficiency. For this purpose, an innovative design of a crankshaft is developed. The potential of computational modelling during the development of this innovative crank train is described in the article. The dynamics of the whole crank train is solved by using a multi-body system software, where flexible finite-element bodies along with hydrodynamic bearings are incorporated. Regarding the simulation results, attention is paid to the torsional vibration and its analysis, including concept design of a torsional damper, because a reduction of friction losses is associated with the improvement of torsional vibration in this case.

Currently, multibody dynamics simulations are moving away from issues exclusive to dynamics to more multiphysical problems. Most mechanical systems contain contact pairs that influence the dynamics of the entire mechanism, such as friction loss, wear, vibration and noise. In addition, deformation often affects the interaction between the contact bodies. If that is the case, this effect must be considered. However, a major disadvantage arises in that it leads to an increase in the number of degrees of freedom and the computational time. Often, the general-purpose multibody dynamics software does not take into account advanced phenomena, such as a lubricated contact pair. This paper can serve as a guide to implementing the elastohydrodynamic lubrication of rough surfaces into general-purpose multibody dynamics software (in this case MSC Adams), which remains challenging. In this paper, the deformation shape reconstruction of the reduced flexible bodies is described, as well as a solution to the increase in the computational speed issues thereby caused. To alleviate this burden, advanced sensitivity analysis techniques are used. In this paper, parallel computing has been employed. The proposed method leads to reasonable computational times for the multibody dynamics simulations, including elastohydrodynamic lubrication. The proposed method is applied to the multibody dynamics simulation of the piston–liner interaction of an internal combustion engine.

The article describes the development and a subsequent application of a computational model for effective and fast simulations of the turbocharger rotordynamics in time domains. The simulation tool consists of two basic models which are described in the article. The rotor is modelled as a flexible structure based on the nonlinear beam approach suitable for an effective solution in the time domain. The computational model also incorporates radial and axial bearing models. Theoretical background of the inovative journal bearing computational models, based on the numerical solution of the Reynolds equation, is presented. The capabilities of the simulation and sample results are demonstrated on a middle size turbocharger rotor supported by fully floating ring bearings.