Fan drive for gas turbine - has first turbine rotor driving fan via reduction gear and second rotor driving it directly

摘要

Gas turbine has at least a first turbine rotor (16) and a second turbine rotor (17). The first rotor drives the fan (21) via a reduction gear (24, 25, 27) whilst the second rotor provides direct drive for the fan. The first rotor may be the low-pressure turbine rotor (16) or the freely rotating turbine (17). The second rotor may be the high-pressure turbine rotor (15) or the freely rotating turbine (17). The transmission from the first rotor may be via a planetary gear whilst the drive from the second rotor is direct via the radially outward turbine blade tips in a section of the housing containing the fan.