MODELLING CONTRA-ROTATING TURBOMACHINERY COMPONENTS FOR ENGINE PERFORMANCE SIMULATIONS: THE GEARED TURBOFAN WITH CONTRA-ROTATING CORE CASE

摘要

This paper presents a method of modelling contra-rotating turbomachinery components for engine performance simulations. The first step is to generate the performance characteristics of such components. In this study, suitably modified one-dimensional mean line codes are used. The characteristics are then converted to three-dimensional tables (maps). Compared to conventional turbomachinery component maps, the speed ratio between the two shafts is included as an additional map parameter and the torque ratio as an additional table. Dedicated component models are then developed that use these maps to simulate design and off-design operation at component and engine level. Using this approach, a performance model of a geared turbofan with a Contra-Rotating Core (CRC) is created. This configuration was investigated in the context of the European program NEWAC (NEW Aero-engine core Concepts). The core consists of a seven-stage compressor and a two-stage turbine without inter-stage stators and with successive rotors running in opposite direction through the introduction of a rotating outer spool. Such a configuration results in reduced parts count, length, weight and cost of the entire HP system. Additionally, the core efficiency is improved due to reduced cooling air flow requirements. The model is then coupled to an aircraft performance model and a typical mission is carried out. The results are compared against those of a similar configuration employing a conventional core and identical design point performance. For the given aircraft-mission combination and assuming a 10% engine weight saving when using the CRC arrangement over the conventional one, a total fuel burn reduction of 1.1% is predicted.