Design of a Counter-Rotating Turbo-Fan with a Counter-Rotating Booster

Abstract

Abstract In DLR, alternative engine drafts are receiving increasing attention to meet demands of the future air traffic. That is, first of all, conservation of the mobility with much lower consumption of resources. One of the expected future successful concepts is the consistent application of counter-rotating compressors and turbines. Such an engine would be based on the classical cyclic process. The moreover one modern simulation method in the areas of aero-dynamic, mechanic, elastic and acoustic as well as the construction simulation is probably laid and evaluated in sufficient dimensions for counter-rotating turbomachines. At the moment first researches on counter rotating Fans are being performed on high-bypass engines. Considering these boundary conditions, the existing Know-How can be used for the interpretation of turbomachines with the concept we have to examine here. Simultaneously, there is a chance of designing an engine which has clear advantages for thrust/weight ratios and engine length without losses of efficiency. The goal of this project is to design a new counter-rotating fan (two fan rotors) with a counter-rotating booster. Our design is based on two references: The first one is the CRTF from the EU-VITAL project, a project between the DLR, the SNECMA and other partners. It is still in studies. The second reference is the BR715 from Rolls Royce, a real existing engine. The first part of this report is devoted to basic studies about the concept of counter-rotating compressors and the adaptation to turbo-fans with counter-rotating booster. Some basic ideas on the link between loading parameter, loss level and velocity triangles are presented. After that, the design of the core part, that is to say the part with the booster, is performed. Only the two first but important steps of the design cycle are discussed up to this point. In the second part, the complete study of our concept, that is to say the complete design cycle for the entire compressor (core and bypass parts) is performed: Definition of a flowpath, profile design, creation of 3-D blades, creation of 3-D mesh, 3-D Navier-Stokes simulation and post-processing. The results of the report show that counter-rotating turbomachines promise a higher efficiency in a compact and therefore light aircraft engine but further research work is necessary.