In the internal air system of gas turbine engines or generators, a large variety of different types of annular channels with rotating cylinders are found. Even though the geometry is very simple, the flow field in such channels can be completely three-dimensional and also unsteady. From the literature it is well-known, that the basic two-dimensional flow field breaks up into a pattern of counter-rotating vortices, as soon as the critical speed of the inner cylinder is exceeded. The presence of a superimposed axial flow leads to a helical shape of the vortex pairs, which are moving through the channel. For the designer of cooling air systems there are several open questions. Does the formation of a Taylor-vortex flow field significantly affect the convective heat transfer behaviour of the channel flow? Is there a stability problem even for high axial Reynolds-numbers and where is the location of the stability boundary? After all, the general influence of rotation on the heat transfer characteristics has to be known. By the results of flow field and heat transfer measurements, the impact of rotation and the additional influence of Taylor-vortex formation on the heat transfer characteristics in annular channels with axial throughflow will be discussed. The flow field was investigated by time-dependant LDA-measurements, which revealed detailed information about the flow conditions. By a spectral analysis of the measured data, the different flow regimes could be identified. Based on these results, the heat transfer from the hot gas to the rotating inner shaft was determined with a steady-state method. Thus, the influence of the different physical phenomena such as rotation with and without Taylor-vortex formation or the flow development could be separated and quantified. Finally, correlations of the measured results were derived for technical applications.

Heat transfer and leakage loss measurements were obtained for compressible flows in typical straight-through labyrinth seals with high rotational speeds. The experiments are an extension of our earlier measurements in a stationary test facility. In order to ensure direct comparisons to the original experiments, the principal dimensions of the test facility and gas dynamic parameters of the hot gas were kept similar. The new study encompasses a wide range of Taylor numbers, Reynolds numbers and clearances between the rotating annular fins and the stationary shroud. Heat transfer coefficients are determined for the stator as well as for the rotor. Temperature measurements along the cooled rotor were performed utilizing a high accuracy telemetric system. Continuous clearance control was achieved by employing specially designed gauges. Detailed pressure and temperatur measurements in the axial as well as in the circumferential direction were performed. Heat transfer coefficients and loss parameters are presented and compared with those obtained under steady state conditions.

The discharge behaviour of a “direct-transfer” pre-swirl system has been investigated experimentally. The influences of the pressure ratio and the swirl ratio as well as the influence of the receiver and stator geometry were investigated. The discharge coefficients of the pre-swirl nozzles are given in the absolute frame of reference. The definition of the discharge coefficient of the receiver holes is applied to the rotating system in order to consider the work done by the rotor. Numerical calculations carried out for a free expansion through the stationary pre-swirl nozzles show very good agreement with experimental data.

The influence of Reynolds number and pressure ratio on the operating characteristics of a stepped labyrinth seal was experimentally determined. The geometries investigated represent designs of a stepped labyrinth seal typical for modern jet engines. Heat transfer and discharge measurements were obtained for two plane models with various seal clearances. The experiments covered a range of Reynolds numbers and pressure ratios. Independent variation of Reynolds number and pressure ratio was obtained by adjusting the back pressure at the seal exit for a given pressure ratio. Dimensionless discharge coefficients, describing the sealing performance, were derived from the measured leakage rates. Pressure ratio, Reynolds number, tip geometry and seal clearance all affected the sealing performance. Finite element calculations were employed to calculate the local heat transfer coefficients from the measured wall and gas temperatures. Averaging of the local values yielded mean heat transfer coefficients and mean Nusselt numbers. The heat transfer was mainly determined by the Reynolds number. Compressibility effects on the heat transfer were observed to be very small.

This paper describes an experimental investigation initiated to determine the threedimensional flow field inside the rim seal cavity of a double-shrouded rotor-stator system. Thereby, the effects caused by perturbances in the rotor wall were additionally examined. The objective of this work is to provide detailed information about the mechanisms that can promote elevated temperature levels in the high pressure section of a gas turbine. Both ingested hot gas and windage heating generated at the rotor-stator interface can severely affect the material temperatures and thus considerably increase the thermal load of the rotating parts.The flow velocities were measured by means of an advanced LDV system capable of providing phase-resolved data. The flow field was determined for two different rotorstator combinations. One of the rotor disks contained small rectangular cavities, located at the disk rim and arranged uniformly in’ the circumferential direction. These elements are referred to as the shank cavities of the rotor disk.The mechanical torque was measured to demonstrate the influence of these elements on the windage power. The measurements were performed at operating conditions that are typical for aero-engines. It is shown that a perturbed rotor surface can raise the drag notably. The experiments were conducted in a high speed test rig at rotational Reynolds numbers up toReϕ≈4.2*106. The data were plotted as the dimensionless moment coefficientcMand correlated withReϕand the dimensionless cooling flow ratecw.