Design and Development of the Inter-Turbine Structure and Power Turbine for MTR390-E Turboshaft Engine

Abstract

The MTR390-E is a turboshaft engine of 1000 kW class developed for the TIGER European helicopter. The project was launched back in 2004 and was certified in 2011. The engine is based on the previous MTR390-2C engine but redesigned for 14% more power at high and hot conditions. ITP is the design authority of the inter-turbine duct (ITD) and structure (IC) and the two stages Power Turbine (PT) as part of the MTRI European consortium (MTU, Turbomeca, RR, ITP) for the design and development of the Enhanced engine. The requirement of higher power, while maintaining the physical envelope of the engine for avoiding changes in the helicopter, led to higher mass flow and turbine inlet temperature. Consequently, the Mach number along the ITD and the PT was increased. A local increase in the flowpath around the area of the ITD and the NGV1 maximum thickness is introduced to avoid high peak Mach numbers and to reduce the flow diffusion. The PT aerofoils feature higher flow velocities leading to transonic Mach numbers at the suction side. The increase in temperature drove the introduction of internal cooling on the ITD and the NGV1 to maintain similar materials while avoiding risk of melting at Super Emergency Conditions (SUP). Due to the high shaft rotation speed and high operating temperatures the blades are subject to very high mechanical demanding conditions. Single crystal materials are used in both stages where also tip shroud cut outs were introduced to reduce centrifugal stresses. Life requirements were met in both statics and rotating parts. A complete development test plan was performed to achieve certification and qualification with 7 development engines and 4 flight proto engines. Performance was demonstrated at sea level and altitude conditions. Successful mechanical condition of parts was obtained after the 150-hrs Type Test plus additional SUP shots. Also good conditions were obtained after sand ingestion test. Good mechanical robustness was proved all along the development programme.