Ulf Håll

VALIDATION OF A THROUGHFLOW TIME-MARCHING FINITE-VOLUME SOLVER FOR TRANSONIC COMPRESSORS

An improved throughfiow method to treat transonic viscous flows with shocks, using a finite-volume time-marching solver, is presented. Effects due to deviation, secondary losses, endwall skin friction and spanwise mixing are modelled. An alternative blade blockage is used to better take into account the effect of the blade on the transonic passage flow. A theoretical and numer- ical study of the rucisymmetric shock showed that it is treated as a normal blade passage shock by the blade row model. Two different techniques to solve the numerical problems associated with the leading edge singularity due to incidence are investi- gated. The computation of an entire speed-line for a three stage transonic fan has been conducted in order to further calibrate and validate the various models. The validation showed that the solver is capable of giving a reasonable meridional picture of the transonic flow field for different operating points.

Large-scale low-speed facility for investigating intermediate turbine duct flows

This paper presents the design of a large-scale, low-speed experimental facility for the investigation of the flow in intermediate turbine ducts. For the design, classical low-speed wind tunnel design procedures were used and CFD calculations were performed. In order to generate realistic inlet conditions (i.e. incoming unsteady wakes), a high-pressure turbine stage was designed and placed upstream of the intermediate duct.

Evaluation of Higher-Order Terms in the Throughflow Approximation Using 3D Navier-Stokes Computations of a Transonic Compressor Rotor

Two three-dimensional Reynolds-averaged Navier-Stokes solutions of the Nasa 67 transonic compressor rotor with tip clearance, computed at near-peak efficiency and near-stall flow conditions, have been circumferentially averaged in order to evaluate the circumferential spatial fluctuation terms such as u′u′, u′v′, u′w′, etc. The three-dimensional distribution of these fluctuations is presented and physically interpreted for the two flow conditions. Then, the meridional distributions of the tangential average of each of these fluctuation terms, the so-called perturbation stresses, are described and interpreted for the two flow conditions. A meridional throughflow computation for which all stresses were included has been performed for the near-peak efficiency flow condition using a time-marching finite-volume solver. The calculation proved to be in good agreement with the tangentially averaged 3D solution. Moreover, the relative importance of the perturbation and viscous stresses has been investigated. The influence of the viscous stresses on the meridional flow was not found important whereas the perturbation stresses were identified as significant contributors to the blade passage losses and to the spanwise mixing phenomenon. Furthermore, the relative effects of each perturbation term on the meridional flow prediction have been investigated for the near-peak efficiency case. The Display Formulau′w′~, Display Formulav′w′~, Display Formulau′v′~ and Display Formulau′u′~ stresses proved to exert a significant influence on the prediction of blade design key parameters such as flow angles and losses in the tip region, essentially.Copyright