LMP737 From , joined Dec 1969, posts, RR: Reply 1, posted (9 years 10 months 3 days 17 hours ago) and read 1650 times:
I recently saw a Boeing powerpoint presentation on the 7E7. What they mean by "no-bleed" engines is that the A/C packs will net use bleed air from the engines. Instead they will use four electrically powered turbine compressors. This will help improve reliability. On aircraft such as the 757/767 some of the biggest headaches come from problems with the bleed system.
Bleed air will still be used to start the engines and drive the Air Driven Hydraulic Pumps.
Katekebo From United States of America, joined Apr 2001, 684 posts, RR: 6 Reply 4, posted (9 years 10 months 3 days 11 hours ago) and read 1574 times:
There are several reasons to go with a bleedless engine. The main one is less fuel consumption. Using bleed air for heating is not very efficient from the thermodynamic standpoint. Electrical system is more efficient so it will result in overall better fuel efficiency. The other reason is weight reduction. Less ducts and insulation. There may be other reasons (reliability).
Shenzhen From United States of America, joined Jun 2003, 1706 posts, RR: 2 Reply 7, posted (9 years 10 months 3 days 8 hours ago) and read 1541 times:
The only thing that bleed air will be used for is nacelle anti ice. Everything else will be electric, including the starters and hydraulic pumps. The starters will also be generators, providing power to the electric compressors, which will provide the air to the packs.