PCA will be manning Booth #340 at the ASME Turbo Expo in Glasgow, June 14th to 18th 2010. Chris Robinson, Graham Cox, John Calvert and Mick Casey will be attending the conference and exposition and would be pleased to welcome visitors to the booth. There is a wealth of experience in compressor and turbine aerodynamic design between these engineers, covering both radial and axial machines from a wide range of applications.
PCA staff will present two technical papers: John Calvert will present a paper entitled 'Comparative studies of alternative HPC configurations for the NEWAC IRA engine' in session 26-1 Turbomachinery: Axial Flow Fan and Compressor Aerodynamics: DESIGN, ANALYSIS AND TEST I, at 0830 on Monday June 14th. Mick Casey will present 'The Cordier line for mixed-flow compressors' in session Turbomachinery: Radial Turbomachinery Aerodynamics: CENTRIFUGAL COMPRESSORS IV at 0900 on Wednesday June 16th. Further details of the papers are below.
COMPARATIVE STUDIES OF ALTERNATIVE HPC CONFIGURATIONS FOR THE NEWAC IRA ENGINE
W John Calvert, Ed Swain, Ian Woods, Mark Dempsey (PCA)
Uwe Schmidt-Eisenlohr (MTU Consultant)
One of the core configurations being considered under the EU NEWAC (NEW Aero-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.
THE CORDIER LINE FOR MIXED FLOW COMPRESSORS
Mick Casey (IITSM, University of Stuttgart)
Christof Zwyssig (www.Celeroton.com, Zurich)
Chris Robinson (PCA Engineers Limited)
The specific speed and specific diameter of radial and mixed flow compressors can be plotted in a Cordier diagram, and the best compressors then lie in a narrow band, known as the Cordier line. This line exhibits a distinctive s-shape, and it is shown in this paper that this is due to the variation in the centrifugal effect on the pressure rise of different designs. A new equation for the Cordier line in the mixed flow region based on the pressure rise coefficient is developed and calibrated with data from mixed flow pumps and ventilators. Together with other empirical relationships for the expected efficiency as a function of the specific speed this provides some useful new guidelines for the preliminary design of mixed flow compressors. These guidelines are then examined by carrying out a design of a high-speed mixed flow micro-compressor that is analysed using CFD to justify the approach.