Computational Study of the Flow in an Axial Turbine with Emphasis on the Interaction of Labyrinth Seal Leakage Flow and
This paper presents a numerical study of the flow in a 1.5 stage lowspeed axial turbine with a straight labyrinth seal on the rotor blade and focuses on the interaction of the leakage flow with the main flow. The influence of the leakage flow on the flow
- PDF / 1,520,020 Bytes
- 12 Pages / 439.32 x 666.12 pts Page_size
- 112 Downloads / 211 Views
1
Introduction
Tip leakage flow can account for considerable parts of the total losses in performance of turbomachinery. The loss of performance due to leakage flow in turbomachinery with unshrouded blades has been intensively studied over the last decade. Much less work has been done on leakage flow over shrouded blades. The most obvious way to minimize losses caused by tip clearance flow in turbomachinery with shrouded blades is to reduce the leakage flow. Thus, up to now the research activities have concentrated on optimizing the sealing efficiency of labyrinth seals, such as the work of Stoff [18], Rhode et al. [13], Waschka [22], Rhode und Johnson [14] and Storteig [19]. In these references, isolated labyrinth seals and their sealing efficiency are considered. However, the influence of leakage flow on the main flow was not examined. One of the first investigations on overall losses in turbomachinery with shrouded blades reported were performed by Kacker and Okapuu [8]. Later Denton [2] derived a theory for tip leakage losses of shrouded blades. These publications provide global correlations for losses caused by leakage flow, but they do not take into account that leakage flow effects not only result in entropy generation due to mixing but also can induce losses in subsequent stators due to the change of the flow field. E. Krause et al. (eds.), High Performance Computing in Science and Engineering '01 © Springer-Verlag Berlin Heidelberg 2002
364
J.E. Anker, J.F. Mayer, and H. Stetter
Wallis et al. [21] and Korschunov and Dahler [9] have studied the interaction of the leakage flow and the main flow in turbomachinery in detail. While the first paper concentrates on reducing aerodynamic losses by turning the leakage flow using bladelets on the shroud of the rotor in a four stage turbine, in the second paper the effect of an artificially produced jet (which simulates leakage flow) entering the main flow at different angles on a following linear cascade is studied. In a project partly funded by European turbomachinery industry, Lehrstuhl fUr Dampf- und Gasturbinen (DGT), Ruhr-Universitiit Bochum and Institut fur Thermische Stramungsmaschinen und Maschinenlaboratorium (ITSM), University of Stuttgart, are collaborating to study the influence of the leakage flow in a 1.5 stage axial turbine with a labyrinth seal on the periphery of the moving row experimentally and numerically. First experimental and numerical results from this project were published by Peters et al. [12]. While their paper concentrates on experimental results and how the tip leakage flow changes the secondary flow in the turbine, this paper focuses on the numerical modeling and on the leakage flow interaction directly behind the outlet gap of the labyrinth seal.
2
Test Rig and Measurement Data
The turbine considered in this paper is a 1.5 stage axial low-speed air turbine. It is operated in a test rig at the Ruhr-Universitiit Bochum where extensive steady-state measurements have been carried out [17]. The turbine stage consists of two identic
Data Loading...
