Improving efficiency is a general task in the design process of high-speed journal bearings. A specific fixed-pad bearing geometry featuring reduced pad length and additional design measures with the intention of reducing frictional power loss is investigated, experimentally and theoretically, for a journal diameter of 500 mm up to surface speeds of 94 m/s and unit loads of 5.0 MPa. To model fluid flow in the bearing outside the lubricant gap, an extension to Elrod’s cavitation algorithm based on assuming the inertia of fluid flow is proposed. Validation of the extended thermo-elasto-hydrodynamic lubrication (TEHL) model shows good agreement between measurement and prediction in wide operating ranges, however, with systematic tendencies of the remaining deviations. Furthermore, measured local pressure and film thickness distributions indicate a complex formation of cavitation with an influence of axial flow that is not covered by pure Couette-flow in the cavitation region. Measured as well as predicted data prove increased bearing efficiency for high rotor speeds. To provide understanding on the impact of the applied design measures improving efficiency, their combination is separated into the individual ones. Reduced axial and peripheral pad length both contribute almost equally to the reduction in power loss and improve its value by 37% compared to the standard design. Finally, further steps to deeper identify the behavior of the bearing are comprehensively discussed.

Linearized dynamic bearing parameters and models are of essential interest for rotordynamic analyses in machine design. This paper experimentally studies the impact of pad preload and pivot offset on the frequency-dependent characteristics of dynamic stiffness (K) and damping coefficients (C) of a KC-model for tilting-pad journal bearings. For this purpose, two four-pad test bearing configurations (preload $m=0.17$, pivot offset 0.5 and preload $m=0.47$, pivot offset 0.6) that differ highly with respect to the pad design parameters are investigated. Contributing effects on the results due to geometric differences are excluded as far as possible, as only one aligning ring and one pivot support design is used. The tests are conducted on a high-performance test rig for surface speeds up to 140 m/s and excitation frequencies of 500 Hz. Significant deviations between the two bearings are identified that generally match theoretically predicted differences and, therefore, contribute to the validation of dynamic bearing modeling.

Thermal loads induced by internal fluid friction significantly influence the operating behavior of high-speed journal bearings. These loads increase on average if critical Reynolds numbers are exceeded. This paper presents a detailed thermo-elasto-hydrodynamic (TEHD) analysis of a large five-pad tilting-pad journal bearing operating up to surface speeds of 94 m/s. The structure mechanical analysis is conducted by a FE-Code that is implemented as a submodule of the bearing code to improve computational efficiency. The nonlinear structure model includes the pads, their aligning ring, and the housing while the journal's thermal expansion is approximated analytically. The contact of pads and ring is modeled with a contact algorithm. Validation with test data from literature indicates the relevance of structure model's complexity. Besides the pad deflection, in particular, the consideration of the ring and housing thermal expansion is decisive in predicting the effective clearance properly. Furthermore, comparisons between measurement and simulation show that the experimentally identified nonlinear speed-dependent characteristic of minimum film thickness that features an increase due to turbulent flow is well predicted by the theoretical model. Generally, results provide an insight on the impact of the different effects dominating the behavior of the bearing in the respective speed ranges, and therefore, improve the understanding of complex bearing systems. Finally, the quality of results of approximation formulas that are easier to implement and more time efficient than the complex FE-code is investigated.

Aim: The purpose of this article is to present the structure, functioning, and results of the EMPACT platform in the field of cybercrime, which has a prominent role in international criminal cooperation and is now a permanent EU instrument.Methodology: The Author collected knowledge about the EMPACT platform by examining the available EU legislation and by performing in practice the tasks of a former expert in the cyber-attacks priority and the current deputy national EMPACT coordinator.Findings: In the fight against serious and organized crime, the Member States, and countries with close links to the EU can carry out their tasks effectively by working together and making the greatest possible use of legal, technical, and educational resources. The permanent EU instrument provides both operational and strategic support for the participants.Value: The study provides a comprehensive overview of this area of international criminal cooperation, which will help law enforcement and judicial authorities to gain a deeper insight into the practical implementation of the task, and will provide interested parties with contextualised answers about the steps and processes involved. Cél: Az írás célja a nemzetközi bűnügyi együttműködésben kitűntetett szerepet betöltő és már állandó uniós eszköznek számító EMPACT platform struktúrájának, működésének, eredményeinek bemutatása a kiberbűnözés vonatkozásában.Módszertan: A szerző az EMPACT platformmal kapcsolatos ismereteket az elérhető uniós szabályozások áttanulmányozásával, valamint a kibertámadások prioritásban korábban betöltött szakértői, valamint a jelenleg ellátott nemzeti EMPACT koordinátor helyettesi feladatok gyakorlati végrehajtásával gyűjtötte.Megállapítások: A súlyos és szervezett bűnözés elleni küzdelem területén az egyes tagállamok, valamint az Európai Unióval szoros kapcsolatban lévő országok egymással együttműködve, a jogi, technikai, támogatási, képzési lehetőségek legteljesebb kihasználásával tudják megfelelő hatékonysággal ellátni feladataikat. Az állandó uniós eszköz részben operatív, részben stratégiai támogatást nyújt a résztvevőknek.Érték: A tanulmány átfogó képet kíván mutatni a nemzetközi bűnügyi együttműködés ezen területéről, amelynek segítségével a bűnügyi és igazságügyi hatóságok munkatársai mélyebb betekintést kaphatnak a gyakorlati feladatvégrehajtással kapcsolatban, illetve az érdeklődők összefüggéseiben is értelmezett válaszokat kaphatnak az egyes lépésekről, folyamatokról.

The frequency-dependent dynamic coefficients of tilting-pad bearings are significantly influenced by the pad pivot elasticity. In addition to the elasticity of the pivot, there is also the flexibility of the structure that predominantly leads to a bending of the pad. For the calculation of the dynamic coefficients, it is common to describe the structural stiffness by a support stiffness in series with the lubricant film. For this purpose, the stiffness according to Hertz's theory is widely used. This approach only allows the rigid body motion of the pad in the theoretical model. However, the elasticity of the pad leads to a film thickness characteristic, which cannot be represented with a pure rigid body motion. Additionally, the structural elasticity already includes the stiffness of the contact between the pad and the support, and therefore the elasticity according to Hertz cannot simply be added. This paper investigates the influence of dynamic pad deformation on dynamic bearing coefficients considering the contact boundary conditions and examines whether it can be replaced by a suitable support stiffness. A three-dimensional finite element model provides the eigenmodes for calculating the dynamic coefficients by perturbed Reynolds equations within a thermo-elasto-hydrodynamic bearing analysis. The model is validated with measurement data.

Dynamic analyses of vertical hydro power plant rotors require the consideration of the non-linear bearing characteristics. This study investigates the vibrational behavior of a typical vertical machine using a time integration method that considers non-linear bearing forces. Thereby, the influence of support stiffness and unbalance magnitude is examined. The results show a rising influence of unbalance on resonance speed with increasing support stiffness. Furthermore, simulations reveal that the shaft orbit in the bearing is nearly circular for typical design constellations. This property is applied to derive a novel approximation procedure enabling the examination of non-linear resonance behavior, using linear rotor dynamic theory. The procedure considers the dynamic film pressure for determining the pad position. In addition, it is time-efficient compared to a time integration method, especially at high amplitudes when damping becomes small.