An outlook for radical aero engine intercooler concepts
Paper i proceeding, 2016

A state of the art turbofan engine has an overall efficiency of about 40%, typically composed of a 50% thermal and an 80% propulsive efficiency. Previous studies have estimated that intercooling may improve fuel burn on such an engine with a 3-5% reduction depending on mission length. The intercooled engine benefits stem firstly from a higher Overall Pressure Ratio (OPR) and secondly from a reduced cooling flow need. Both aspects relate to the reduced compressor exit temperature achieved by the intercooler action. A critical aspect of making the intercooler work efficiently is the use of a variable intercooler exhaust nozzle. This allows reducing the heat extracted from the core in cruise operation as well as reducing the irreversibility generated on the intercooler external surface which arises from bypass flow pressure losses. In this respect the improvements, higher OPR and lower cooling flow need, are achieved indirectly and not by directly improving the underlying thermal efficiency. This paper discusses direct methods to further improve the efficiency of intercooled turbofan engines, either by reducing irreversibility generated in the heat exchanger or by using the rejected heat from the intercooler to generate useful power to the aircraft. The performance improvements by using the nacelle wetted surface to replace the conventional intercooler surface is first estimated. The net fuel burn benefit is estimated at 1.6%. As a second option a fuel cooled intercooler configuration, operated during the climb phase, is evaluated providing a net fuel burn reduction of 1.3%. A novel concept that uses the rejected heat to generate additional useful power is then proposed. A secondary cycle able to convert rejected intercooler heat to useful thrust is used to evaluate three possible scenarios. The two first cases investigate the impact of the heat transfer rate on the SFC reduction. As a final consideration the geared intercooled engine cycle is re-optimized to maximize the benefits of the proposed heat recovery system. The maximum SFC improvement for the three cycles is established to 2%, 3.7% and 3%.

Författare

Olivier Petit

Chalmers, Tillämpad mekanik, Strömningslära

Carlos Xisto

Chalmers, Tillämpad mekanik, Strömningslära

Xin Zhao

Chalmers, Tillämpad mekanik, Strömningslära

Tomas Grönstedt

Chalmers, Tillämpad mekanik, Strömningslära

Proceedings of ASME Turbo Expo 2016: Turbine Technical Conference and Exposition, Seoul, South Korea, Jun 13-17, 2016

Vol. 3

Styrkeområden

Transport

Ämneskategorier

Rymd- och flygteknik

Strömningsmekanik och akustik

Infrastruktur

C3SE (Chalmers Centre for Computational Science and Engineering)

Drivkrafter

Innovation och entreprenörskap

DOI

10.1115/GT2016-57920

ISBN

978-079184974-3

Mer information

Skapat

2017-10-08