Dynamic Behaviour of EHD-contacts using a regularised, mass conserving Cavitation Algorithm

The paper deals with the holistic simulation of systems supported in journal bearings, which is demonstrated using the example of a conrod’s big end bearing. For that purpose, primarily the interactions of multibody-, structureand hydrodynamics have to be described. Based on the time integration of the global equations of motions, the non-linear bearing forces in the fluid film and the elastic deformation of the bearings surfaces have to be modelled adequately concerning their mutual influence. The implementation of the elastic structure is carried out by means of a hierarchised, IRS–based1modal reduction in order to represent its eigenbehaviour as realistic as possible and to fulfil the requirement of low computational costs by reducing the number of degree of freedoms. Additionally, the journal bearing is considered by an online solution of the Reynolds equation, whereat the cavitation is handled by a transient acting, mass-conserving algorithm. This is based on the classical Elrod algorithm, but was extended by a regularisation, which enables a faster and more stable solution. Due to the general approach, both mechanical and tribological output quantities are accessible. This provides the possibility to draw a comparison with simpler approaches and to emphasize the benefit of the described procedure

Nurses' perceptions of aids and obstacles to the provision of optimal end of life care in ICU

Contains fulltext : 172380.pdf (publisher's version ) (Open Access

Dynamische Abgasmessung mit Diodenlasern.

We report on a fast exhaust gas analysis system, based on infrared spectroscopy of a single absorption line by pulse-operated diode lasers and a newly designed gas sampling system. Otto and Diesel engines in dynamic test beds were investigated. A rise time smaller than 3 ms and detection limits of 100 ppm for NO and 20 ppm for CO were obtained with resolution of dynamic engine operation changes. For time resolution of a single stroke the exhaust gas sample point should be close to the exhaust valve. Unexpected fast variations in NO and CO content were observed even behind the catalyst with regular engines under stationary conditions. Concentration changes occuring faster than 100 ms were detected and are attributed to oscillations of the engine control system. First applications of the system have shown it to be important for the analysis and optimization of modern engines

SIMULATION VON SCHWIMMBUCHSENLAGERUNGEN IN ABGASTURBOLADERN

Der Beitrag behandelt die Berechnung eines vollständigen Hochlaufs der Turboladerwelle auf Betriebsdrehzahl zur Untersuchung der Stabilität der Lagerung. Aus der Schwimmbuchsenlagerung resultieren zum einen spezielle Randbedingungen, die zur Kopplung von innerem und äußerem Schmierfilm führen. Zum anderen ist dadurch der Rotor in der Lage sich derart schiefzustellen, dass die Berechnung der hydrodynamischen Schmierfilmdrücke unter Annahme eines Parallelspalts nicht mehr gerechtfertigt ist. Die Modellierung erfolgt daher innerhalb eines Mehrkörpersystems(MKS), wobei die Reynolds Differentialgleichung in jedem Zeitschritt unter Verwendung der Finiten-Elemente-Methode gelöst wird. Abschließend erfolgt ein Vergleich zwischen gemessenen Daten und numerischer Simulation. Dabei wird der Einfluss der Berücksichtigung der Wellenschiefstellung sowie der Kommunikationsbohrungen bei der Lösung der Reynolds DGL auf die Ausbildung des instabilen Bereichs diskutiert.This paper deals with the calculation of a full-dynamical run-up of a turbocharger shaft up to operating speed to investigate the stability of the bearing. Due to the full floating ring bearings special boundary conditions result, which lead to a coupling of outer and inner lubrication film. Furthermore the rotor is able to take a skew position in such a way, that for the solution of Reynolds equation the simplistic assumption of a parallel gap isn’t longer valid. Therefore the modeling is done in a multi-body-system(MBS), whereat the finite element method is used for the calculation of hydrodynamic pressures in every timestep. Concluding a comparison is done between measured data and numerical simulation. Thereby the development of the instable region is discussed by the influence of shaft inclination as well as thecommunication drill-holes

Simulation von schwimmbuchsenlagerungen in Abgasturboladern

Der Beitrag behandelt die Berechnung eines vollständigen Hochlaufs der Turboladerwelle auf Betriebsdrehzahl zur Untersuchung der Stabilität der Lagerung. Aus der Schwimmbuchsenlagerung resultieren zum einen spezielle Randbedingungen, die zur Kopplung von innerem und äußerem Schmierfilm führen. Zum anderen ist dadurch der Rotor in der Lage sich derart schiefzustellen, dass die Berechnung der hydrodynamischen Schmierfilmdrücke unter Annahme eines Parallelspalts nicht mehr gerechtfertigt ist. Die Modellierung erfolgt daher innerhalb eines Mehrkörpersystems (MKS), wobei die Reynolds Differentialgleichung in jedem Zeitschritt unter Verwendung der Finiten-Elemente-Methode gelöst wird. Abschließend erfolgt ein Vergleich zwischen gemessenen Daten und numerischer Simulation. Dabei wird der Einfluss der Berücksichtigung der Wellenschiefstellung sowie der Kommunikationsbohrungen bei der Lösung der Reynolds DGL auf die Ausbildung des instabilen Bereichs diskutiert.This paper deals with the calculation of a full-dynamical run-up of a turbocharger shaft up to operating speed to investigate the stability of the bearing. Due to the full floating ring bearings special boundary conditions result, which lead to a coupling of outer and inner lubrication film. Furthermore the rotor is able to take a skew position in such a way, that for the solution of Reynolds equation the simplistic assumption of a parallel gap isn’t longer valid. Therefore the modeling is done in a multi-body-system (MBS), whereat the finite element method is used for the calculation of hydrodynamic pressures in every timestep. Concluding a comparison is done between measured data and numerical simulation. Thereby the development of the instable region is discussed by the influence of shaft inclination as well as the communication drill-holes