e

Downprevious published experience has been discussed in Part I and so will not be repeated here. The objective of the project was firmly focused on the re-design of the engine compressors and this had an influence on the ap-proach taken throughout the work. The compressors to be re-designed were existing engine machines that were well under-stood. In particular, the high pressure ~HP! compressor was in use in the Trent 700 and 800 engines. It was decided that the basic axial and radial matching and vortex design of the compressor would not be altered as part of the redesign because these were deemed acceptable in the existing machine. The objective was to improve the efficiency without reducing the stability margin or operating range of the compressor. It was also decided to re-design the engine compressor blading in two steps. In the first, the stator blade rows were redesigned and this was followed by a re-design of the rotor blade rows. The designs were also con-strained to be back-compatible with the existing blading so that it would not be essential to have all the 3-D-designed blade rows in the compressor. A mixed set of blading, with some rows being unchanged from the original 2-D design, would be an option if so desired. This would allow some improvements to be made to the engine compressor even if particular 3-D blade rows were not successful. The possible design space for the 3-D designs was thus designs, which would not be available from the engine compres-sor tests. The low-speed designs were conducted at Rolls-Royce in parallel with the high-speed engine design activity. The tests were carried out at Cranfield University on the low-speed four-stage test facility. A description of the rig is available in other publications ~e.g., Howard et al