Fred1982 From United States of America, joined Sep 2001, 17 posts, RR: 0
Reply 1, posted (11 years 7 months 3 weeks 5 days 6 hours ago) and read 1500 times:
The GE 90 engine with the cone uses that cone to straighten and smooth the exhaust gases to extract the greatest possible thrust. The RB211 uses a intergrated nozzle which mixes the exhaust gases and fan bypass air prior to exit from the engine. This helps to reduce noise. As far as the GE engines on the 747 I believe those are the CF-6's. Those have a smaller cone inside of the exhaust nozzle which does not extend beyond the end of the nozzle. I went to school for an aircraft mechanic still working on getting my license's only have to take my Oral and Practical. More to come when I look into my books on this. Fred
BA From United States of America, joined May 2000, 11154 posts, RR: 58
Reply 2, posted (11 years 7 months 3 weeks 5 days 6 hours ago) and read 1477 times:
It all has to do with different methods of thrust that come out of the back. Engines with these different designs are high-bypass engines which means the engine creates most of its thrust from a large fan located in the front that is connected by a shaft from the turbine.
Fred explained them to you pretty well.
Also, all of the 777 engines have the cone design. The Pratt & Whitney PW4000s are pictured below: