Influence of the axial turbine design parameters on the stator–rotor axial clearance losses

A. Grönman, T. Turunen-Saaresti, P. Röyttä, A. Jaatinen-Värri. Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy August 2014 vol. 228 no. 5 482-490.


The drive towards lower emissions in aerospace engines promotes more efficient and physically smaller engines. One way to decrease the size of the axial turbine is to minimize the distance between successive stator and rotor rows. This can usually have either a positive or negative influence on the turbine performance. The reasons for this behaviour are not currently fully understood. In this study, a novel approach is taken to find new insights into this design question by analysing the influence of different design parameters on the turbine efficiency behaviour. Several different turbines are analysed using the literature. For the first time, the performed analysis reveals the design parameters, which correlate with the different efficiency curve shapes. The correlating parameters are the stator–rotor axial clearance, stator pitch to axial chord ratio, turning velocity Mach number and rotor aspect ratio. The mechanisms behind the found correlations are further analysed to connect the physical phenomena with the design parameters.


The authors thank Dr Dongil Chang from the University of Ottawa for providing additional information about their work. The authors also thank the Academy of Finland and Lappeenranta University of Technology. Professor Jari Backman is also acknowledged for giving the opportunity to complete this study.

Authors and Affiliations

  • Aki Grönman, Institute of Energy, Lappeenranta University of Technology, Lappeenranta, Finland.
  • Teemu Turunen-Saaresti, Institute of Energy, Lappeenranta University of Technology, Lappeenranta, Finland.
  • Pekka Röyttä, Computational Engineering and Design, Fraunhofer Chalmers Centre, Chalmers Science Park, Gothenburg, Sweden.
  • Ahti Jaatinen-Värri, Institute of Energy, Lappeenranta University of Technology, Lappeenranta, Finland.

Photo credits: Nic McPhee