Bleedless engines

Alistairbastian · Post by **Alistairbastian** » 20 Mar 2005, 17:57

Knowing that from the current engines

Engine bleed is used to pressurize the pneumatic system. That system does several things. To name a few, but not all inclusive, provides air for cabin heating/cooling and pressurization via the air con packs, wing and engine anti ice, pressure to water system, head pressure on hydraulic resevoirs.

Heard that the B787 will be using bleedless engines
bleedless engines

is one that doesn't supply air from the internal flow of the engine to the pneumatic system of the aircraft. All of the air entering a bleedless engine will be used to create thrust, excepting a small amount of air for internal cooling and engine stability.

CAn anybody throw more light on bleedless engines ... any planes that have used it in the past and even if the claim that the B787 will using such an engine how will cabin pressure and other functions of bleed air be taken care of

SN30952 · Post by **SN30952** » 20 Mar 2005, 18:05

Bleed air

Avro · Post by **Avro** » 20 Mar 2005, 18:26

The engines of the B787 will be the very first bleedless engines in history. No other aircraft is currently using such engines.

The advantage of bleedless engines is that the engines will weigh less, need less maintenance (or less complicated maintenance) since their will be less valves and ducts inside the engine ad finally since less air will be taken out of the compressor the engine will have a higher efficency.

The bleed air which was used to pressurize the cabin and for other tasks, will be replaced by electrically driven pneumatic systems in the plane which will be more efficient than bleed air.

Chris

Advisor · Post by **Advisor** » 20 Mar 2005, 20:49

Interesting post Alistair. Keep up the good work. Make India and Luchtzak proud.

In commercial aircrafts, BLEEDLESS ENGINES primary use is to provide hot air for heating the inside of the plane (since at cruising altitude, the ambient temperature is around -50°C), as well as for providing pressure for the cabin.

Also as per the links submitted by Hon. Fons and update by Avro, bleed air is used to keep critical parts of the aircraft (such as the wing leading edges) ice-free.

EBAW_flyer · Post by **EBAW_flyer** » 22 Mar 2005, 15:06

In commercial aircrafts, BLEEDLESS ENGINES primary use is to provide hot air for heating the inside of the plane

The opposite, the engines with bleed air have this use, bleedLESS engines have the purpose of just taking it from elsewhere. My question is, how do they pressurise and heat the air of it doesn't come from from the engine?

brakes_78 · Post by **brakes_78** » 22 Mar 2005, 16:29

Does a bleedless engine mean that there will be more electrical parts as most of the fuel related functions will be lessened and thereby reducing load on the engine?

Avro · Post by **Avro** » 22 Mar 2005, 19:06

EBAW_flyer wrote: My question is, how do they pressurise and heat the air of it doesn't come from from the engine?

As far as I know, it will be done thanks to electrical systems and electrically driven pneumatic systems.

Chris

Alistairbastian · Post by **Alistairbastian** » 22 Mar 2005, 19:26

The main advantage of a a bleedless engine

efficiency . A lot of hot air is dumped overboard in the process of supplying pneumatic functions to an aircraft. Now this is wasted energy.The electrical pneumatic systems that will replace bleed air systems will be much more efficient.

and that what we will have to wait and see. Now if the engines are just used for thrust purposes and no secondary duties then fuel efficiency of an engine increases and yes even if 10% of better efficiency means whole lot of money that can be saved . With Fuel prices @ $ 57 a barrel .

The other advantage i can see is that the valves and ducting will be mostly eliminated.Weight may also be saved by eliminating these components.

The respected Advisor who is GURU on fuel can surely help better the efficiency approach

Alistairbastian · Post by **Alistairbastian** » 22 Mar 2005, 20:13

some statements by boeing on their 787 which we assume will be using the bleedless engines. No wonder they state 20 % lower fuel consumption than other airplanes its size

see link below

http://www.newairplane.com/en-US/787Dre ... cient.html

EBAW_flyer · Post by **EBAW_flyer** » 22 Mar 2005, 23:11

As far as I know, it will be done thanks to electrical systems and electrically driven pneumatic systems.

But how do you heat the air? You can't heat that amount of air from -56° to 25° in such time with an electrical system

Avro · Post by **Avro** » 23 Mar 2005, 21:49

My guess is the air will be heated with the help of smaller compressors driven by electrical power. Those compressors will be small and optimized for the heating of the air.

But it's just a guess.

Chris

Knight255 · Post by **Knight255** » 23 Mar 2005, 23:04

My only concern with bleedless engines is that the newer pressurization, anti-ice, a/c, and hydraulic pressurization won't be as redundant. You have at least two engines providing bleed air for those systems on normal airplanes. I hope they will provide reliable redundancy for these systems with the newer bleed-less engines.

Alistairbastian · Post by **Alistairbastian** » 23 Mar 2005, 23:52

EBAW_flyer wrote:
As far as I know, it will be done thanks to electrical systems and electrically driven pneumatic systems.
But how do you heat the air? You can't heat that amount of air from -56° to 25° in such time with an electrical system

the above pointed by EBAW is good . Even though we see weight reduction by eliminating some valves and ducts

but wouldn't the electric motors and the pneumatic systems to carry out the task of bleed air incrase aircraft weight

Avro · Post by **Avro** » 24 Mar 2005, 19:16

Of course it will increase the weight, but I don't think the main purpose of bleedless engines is to reduce the weight.

The most important part is the less costly and less heavy maintenance on the engines and the better efficiency which can be obtained by separating both systems from each other.

Chris

Advisor · Post by **Advisor** » 24 Mar 2005, 19:28

Full marks to Avro on the direct identification for the less heavy maintenance on the engines.

And about efficiency,
Alistair

Now if the engines are just used for thrust purposes and no secondary duties then fuel efficiency of an engine increases and yes even if 10% of better efficiency means whole lot of money that can be saved .

Need i say more

HorsePower · Post by **HorsePower** » 24 Mar 2005, 23:55

10% of efficiency!! I think it is closer to 2 or 3 % (at best).

Regards

Seb.

Avro · Post by **Avro** » 25 Mar 2005, 13:21

10% seems a lot to me too. Let's first see the results on the first prototype.

Chris

Advisor · Post by **Advisor** » 31 Mar 2005, 09:45

Which is this engine

brakes_78 · Post by **brakes_78** » 01 Apr 2005, 13:03

I do not know about the engine but yes they are high velocity gases.

mrocktor · Post by **mrocktor** » 01 Apr 2005, 21:05

As far as I know, the fuel efficiency gain by not extracting bleed air is expected to be in the vicinity of 2% as Horse Power stated.

All the electrical equipment that will have to be installed (and the increase in electrical power generation and distribution systems) will most likely be very close to weight neutral with the removal of all the bleed air ducting (which is heavy).

On the other hand, the elimination of bleed air ducting means one less fire hazard (a big annoying one at that), the associated fire detectors and warning system.

In all its a good move in my opinion.

mrocktor