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ANALYSIS AND TESTING OF THE VULCAIN 2 LOX TURBINE BLADES FOR PREDICTION OF HIGH CYCLE FATIGUE LIFE

This paper describes the design approach used for high cycle fatigue (HCF) life predictions of the turbine blades of the liquid oxygen (LOX) turbopump for the Vulcain 2 engine, powering the main stage of the Ariane 5 launcher. The Vulcain 2 LOX turbine is a two-staged supersonic/transonic impulse type turbine, working in a gas generator cycle, see Figure 1. At 12660 rpm, turbine power output is 5130 kW using a pressure ratio of 12.0. Its rotor with bearings is arranged as an overhang turbine designed to work at subcritical speeds. The rotor concept is based of shrouded blades with firtree attachments. The development of the Vulcain 2 engine began in 1995 and its first flight is scheduled for late 2001. Figure 1 Vulcain 2 TPO, pump and turbine arrangement The main procedures are: • Unsteady force predictions using CFD tools and measurements in air test rig. • Damping evaluation of the blades in air rig using different damper configurations. • Alternating stress predictions of the blades using FE analysis and strain measurements at test. • HCF life evaluation. The objective has been to obtain a more accurate prediction of turbine blade dynamic response for reliably predicting high cycle fatigue failure.