Comparative Studies of Alternative HPC Configurations for the NEWAC IRA Engine

Abstract

One of the core configurations being considered under the EU NEWAC (NEWAero-engine Core concepts) programme is for an intercooled recuperative aero-engine (IRA). The IRA concept exploits the heat of the engine exhaust gas and maximises the heat pick up capacity of the combustor inlet air by intercooling in front of the high pressure compressor (HPC). The datum configuration adopted for the HPC is a single stage radial compressor, but comparative design studies into alternative configurations have also been carried out. The ducting arrangements for the HPC in the IRA engine are more complicated than in a conventional turbofan engine, with the inlet flow coming from the intercooler via a C-shaped duct and the outlet flow going to the heat exchangers in the exhaust stream via 8 pipes on the outside of the engine core. A radial compressor fits quite neatly into this configuration, but the size required for a 70,000 lbf (310kN) thrust engine is significantly larger than for existing designs. In addition, the use of intercooling reduces the flow coefficient below the optimum value. By contrast, an axial compressor is likely to achieve higher efficiency, but it will be longer and have considerably more aerofoils. Therefore, preliminary designs for axial, radial and axial-CF configurations have been set up and analysed using CFD and finite element methods to assess their aerodynamic performance and to investigate their mechanical requirements. Each configuration has some advantages and disadvantages, and the results from the current studies quantify these for current levels of compressor technology.