In place of silicon, which is normally used in microelectronics, organic materials offer the opportunity to produce devices on large area, low-cost and plastic planar substrates. These materials are attracting increased attention also in the field of electronic-textiles (e-textiles) because they show an interesting combination of electronic and mechanical properties that can be favourably exploited in smart textiles. A key step for the integration of mass production of e-textiles is to combine electronic production with textile manufactures. In the last years, progress has been achieved in the development of fibers and their processing for application in e-textiles. The application ranged from fabric integrated light sources to low cost solid state lighting for protection and security. Here research results are presented regarding the integration of encapsulated glass OLEDs and additionally OLEDs fabricated on flexible high barrier substrates which were integrated into textiles. On the other hand, the first results concerning the realization of an OLED on cylindrical surfaces based on solution processed technologies which is a first step in the direction of low cost processing will be discussed. A simple, inverted planar construction prepared from solution was realized. This preliminary work was the precondition for the development of a fiber based OLED. In addition, OLEDs that were prepared using glass fibers as substrates and solution processed active and hole-transport layers will be shown.

This paper presents the numerical results of a code for computing the unsteady transonic viscous flow in a two-dimensional cascade of harmonically oscillating blades. The flow field is calculated by a Navier–Stokes code, the basic features of which are the use of an upwind flux vector splitting scheme for the convective terms (Advection Upstream Splitting Method), an implicit time integration, and the implementation of a mixing length turbulence model. For the present investigations, two experimentally investigated test cases have been selected, in which the blades had performed tuned harmonic bending vibrations. The results obtained by the Navier–Stokes code are compared with experimental data, as well as with the results of an Euler method. The first test case, which is a steam turbine cascade with entirely subsonic flow at nominal operating conditions, is the fourth standard configuration of the “Workshop on Aeroelasticity in Turbomachines.” Here the application of an Euler method already leads to acceptable results for unsteady pressure and damping coefficients and hence this cascade is very appropriate for a first validation of any Navier–Stokes code. The second test case is a highly loaded gas turbine cascade operating in transonic flow at design and off-design conditions. This case is characterized by a normal shock appearing on the rear part of the blades’s suction surface, and is very sensitive to small changes in flow conditions. When comparing experimental and Euler results, differences are observed in the steady and unsteady pressure coefficients. The computation of this test case with the Navier–Stokes method improves to some extent the agreement between the experiment and numerical simulation.

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Experimental investigations of the aerodynamic damping of compressor blades are usually performed by forcing the blades externally to a motion that is similar to a given mode shape and inter-blade phase angle (IBPA) while measuring the motion-induced unsteady pressure distribution. Evaluating this to an aerodynamic work entry from the fluid to the blade, at least a local contribution to the flutter (in-)stability can be determined. Test rigs are usually non-rotating linear or rotating annular cascade wind tunnels. In the latter case, besides measuring in and transmitting data out of the rotating system, the excitation of the blades themselves is still a challenge. In the present case a blisk rotor with realistic fan blade geometries and flow conditions was investigated aeroelastically. For the excitation of the 1st bending (1F) mode shape of the blading a sector of five blades was chosen. In this sector the natural vibration of the blading, represented by constant vibration amplitudes and a given IBPA should be simulated. Therefore the blades were equipped with Macro Fiber Composites (MFC). These foils of piezoelectric material expand and contract due to the applied high voltage. A control system was developed to adjust the amplitude and the IBPA of the blade vibration. For the transmission of the high voltage, a separate data transmission system on the base of liquid metals was chosen. The blade vibration was measured by strain gauges and additionally monitored by a specific rig system. The aeroelastic investigations were carried out in the compressor test facility M2VP of the DLR Institute of Propulsion Technology in Cologne. During the measurement, the MFCs were able to excite the blades to a certain extent. The paper will present the technique to excite the blades of a compressor blisk by means of MFCs as well as achieved vibration amplitudes and limitations under engine-like operating conditions.

A parametric study which investigates the influence of viscous effects on the damping behavior of vibrating compressor cascades is presented here. To demonstrate the dependence of unsteady aerodynamic forces on the flow viscosity, a computational study was performed for a transonic compressor cascade of which the blades underwent tuned pitching oscillations while the flow conditions extended from fully subsonic to highly transonic flow. Additionally, the reduced frequency and Reynolds number were varied. In order to check the linear behavior of the aerodynamic forces, all calculations were carried out for three different oscillation amplitudes. Comparisons with inviscid Euler results helped identify the influence of viscous effects. The computations were performed with a Navier-Stokes code, the basic features of which are the use of an AUSM upwind scheme, an implicit time integration, and the implementation of the Baldwin-Lomax turbulence model. In order to demonstrate the possibility of this code to correctly predict the unsteady behavior of strong shock-boundary layer interactions, the experiment of Yamamoto and Tanida on a self-induced shock oscillation due to shock-boundary layer interaction was calculated. A significant improvement in the prediction of the shock amplitude was achieved by a slight modification of the Baldwin Lomax turbulence model. An important result of the presented compressor cascade investigations is that viscous effects may cause a significant change in the aerodynamic damping. This behavior is demonstrated by two cases in which an Euler calculation predicts a damped oscillation whereas a Navier-Stokes computation leads to an excited vibration. It was found that the reason for these contrary results are shock-boundary-layer interactions which dramatically change the aerodynamic damping.