Computation of the flow and heat transfer in a high-pressure compressor stage

Citation

Seire, O. (2003), "Computation of the flow and heat transfer in a high-pressure compressor stage", Aircraft Engineering and Aerospace Technology, Vol. 75 No. 4. https://doi.org/10.1108/aeat.2003.12775daf.004

Computation of the flow and heat transfer in a high-pressure compressor stage

Computation of the flow and heat transfer in a high-pressure compressor stage

Keywords: Computation, Jet engines, Compression

Over the last few years, cost reduction has become a major concern for jet engine manufacturers. At the same time, growing quality and performance standards have driven the search for new ways to improve the design and development process, vital parts of which are suitable for investigation methods and tools. In the last decade, CFD has proven to be one such tool.

At MTU Aero Engines, a supplier of sub-systems such as high-pressure compressors and high- and low-pressure turbines for commercial and military engines, CFD is commonly employed in areas such as blade design. A further and increasingly crucial application of CFD is in the computation of flow and heat transfer in the multiple rotating cavities of the secondary air system of an engine. Indeed, the growing performance requirements have emphasised the importance of precise strain and rotor tip clearance predictions, which in turn demand accurate knowledge of the thermal behaviour of the rotor discs. For this, the flow and heat transfer mechanisms inside the rotor drum have to be known as precisely as possible. At MTU Aero Engines, CFX-TASCflow from AEA Technology has been chosen for computing such challenging flows, which are usually difficult to simulate due to their complexity and the lack of information about their characteristics.

In order to demonstrate that CFX- TASCflow is able to provide reliable results, a typical high-pressure compressor stage and secondary air system has been modelled. The computational domain, which extends from the annulus down to the rotor drum, consists of one upstream rotor blade, two stator vanes and a calming region downstream of the stage. Also included are the rotor-stator cavities with labyrinth seals (stator wells). These are connected by a bleed hole to a rotating chamber inside the rotor, at the bottom of which is an outlet where flow is tapped off for turbine disc cooling purposes. The rotating and stationary components are connected using CFX-TASCflows multiple-frame-of-reference facility.

The agreement has been found to be quite satisfactory. For instance, the mass flow into the bore hole was predicted as within 10 per cent of the experimental value. Furthermore, some typical flow features observed in previous experimental investigations, for example typical vortex formations, have been reproduced here too. The simulation has also provided useful information about the repartition of inflow and outflow from the axial rim seals, the generation of windage heating and the location of potential hot spots, where overheating is liable to compromise the safety of components.

Briefly, the investigation with CFX- TASCflow has shown that it can reliably simulate phenomena as complex as these cavity flows. Moreover, the extent of the insight provided by the simulations cannot be obtained with experimental methods. This positive experience will pave the way for further applications of CFD, including cavity optimisation studies.

Details available from: AEA Technology plc. Tel: +44 (0)1235 832347; Fax: +44 (0)1235 448001; E-mail: cfx.aeat.co.uk; Web site: www.cfxaeat.com

Olivier SeireMTU Aero Engines, Germany