| 摘要 |
A variable cycle gas turbine engine (10) includes first and second compressors (18,16), combustion apparatus (20) and first and second turbines (22,24) operable to drive the first and second compressors (18,16) respectively via interconnecting shafts. The capacity of one of the turbines (24) may be varied, for example by means of guide vanes (32) which can be adjusted to reduce or increase a throat area (40) through which air leaves the guide vanes to impact the turbine. The capacity of the turbine may be increased at low engine speeds, to reduce the pressure ratio across the turbine and across the compressor (16) which it drives, thereby improving the surge margin of the compressor.
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