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Quoting JAAlbert (Thread starter): Any chance the new 777X will have non bleed engines? |
Quoting JAAlbert (Thread starter): ny chance the new 777X will have non bleed engines? |
Quoting JAAlbert (Thread starter): is there any data showing the non-bleed engines are more efficient or otherwise more desirable than traditional bleed engines? |
Quoting mandala499 (Reply 4): Yes, just look at the manuals of any jets... bleeds = more engine power required for a given thrust... more engine power = more fuel burn. Just look at take off numbers for example. |
Quoting JAAlbert (Thread starter): - is there any data showing the non-bleed engines are more efficient or otherwise more desirable than traditional bleed engines? |
Quoting TristarSteve (Reply 5): Taking the bleed away from the engine has been replaced with an electrical load. I expect the electrical load is smaller than the bleed load, but not by much |
Quoting TristarSteve (Reply 5): Taking the bleed away from the engine has been replaced with an electrical load. I expect the electrical load is smaller than the bleed load, but not by much. |
Quoting TristarSteve (Reply 9): Agreed, but I believe that the fuel saving from the change to electric systems has not been as great as Boeing originally expected. |
Quoting okie (Reply 7): Steve we use the ratio of 8hp of energy to produce 1hp of work in industrial applications of air vs electrical as far as efficiency is concerned. |
Quoting bueb0g (Reply 6): it reduces cabin air contamination |
Quoting Stitch (Reply 8): We are looking at the first generation of this technological application, however. The expectation by Boeing is that as the application of this technology advances, that load will reduce and efficiency will increase. |
Quoting TristarSteve (Reply 9): Agreed, but I believe that the fuel saving from the change to electric systems has not been as great as Boeing originally expected |
Quoting ferpe (Reply 10): There is a pretty good discussion on this in one of the earlier A350 prototypes threads where CM (who was in a senior position on the project) concluded that the efficiency gains were there but not the weight gains advertised (not yet, you need liquid cooling for the conversion electronics and that is a weight downer). In sum more efficient frame but no gain in weight |
Quoting airmagnac (Reply 11): The cabin air on a bleedless aircraft is still sucked in from outside and conditioned by passing through machinery, so it can still be contaminated |
Quoting airmagnac (Reply 11): The cabin air on a bleedless aircraft is still sucked in from outside and conditioned by passing through machinery, so it can still be contaminated. And it is still not clear whether these issues can be scientifically substantiated, or if they are more matters of perception. If it's a perception problem, the architecture change will likely only have a temporary effect |
Quoting okie (Reply 13): which can easily be contaminated from the bleed air |
Quoting bueb0g (Reply 14): the scope for contamination - especially by dangerous toxins - is far lower |
Quoting bueb0g (Reply 14): Germanwings A319 event |
Quoting airmagnac (Reply 15): The information on that one is quite vague and fragmented, but as far as I remember, no one in the cabin noticed anything abnormal, not even a smell. Supposing that's true, and as the air provided to both cabin zones and cockpit comes through the same mixer unit and trim air main duct, I don't see how the contamination could come from the air system and yet affect only the cockpit. So it may have been some kind of local source of contamination. I guess we'll never know for sure. |
Quoting airmagnac (Reply 15): |
Quoting Jetlagged (Reply 12): |
Quoting bikerthai (Reply 17): The real question for me is whether there is anything in the low pressure/high pressure compressor of the engine that might introduce contamination into the air. I'm talking about burning oil . . . |
Quoting Kuja (Reply 18): Did the 707 and DC-8 also did not take cabin air through the engines? |
Quoting larshjort (Reply 16): I believe the cockpit recieves 100% "fresh" air, while the cabin air is mixed 50% "fresh" and 50% from the cabin |
Quoting bikerthai (Reply 17): filtered for particle contamination. |
Quoting bikerthai (Reply 17): The real question for me is whether there is anything in the low pressure/high pressure compressor of the engine that might introduce contamination into the air. I'm talking about burning oil . . . I don't think we can avoid the air floating around the tarmac, I just don't want any extra contaminate that may be coming directly from the engine compressor stages. |
Quoting airmagnac (Reply 21): Not quite, here is the system functional diagram |
Quoting airmagnac (Reply 21): So you're right, the whole question is whether particules from the downstream parts of the engine can flow back to the compressor and enter the bleed valves. |
Quoting Tristarsteve (Reply 22): Note that this is a diagram. The item referred to as a mixer unit looks like a round dustbin. The way the pipes are connected to it means that the flight deck receives the majority of their air from the Nbr 1 pack. There are no valves in there, it is just the way it is constructed. This unit is at the rear of the fwd freight hold. Get someone to show you next time you see an aircraft in the hangar. |
Quoting Reply 23): Also note, an unmentioned benefit of a bleedless system is the reduced amounts of components inside the aircraft itself. No longer having ducts/valves/bleed fed anti-ice systems...etc. It is a substantial amount of weight reduced. Weight = fuel = well, you know... |
Quoting Reply 23): Also note, an unmentioned benefit of a bleedless system is the reduced amounts of components inside the aircraft itself. No longer having ducts/valves/bleed fed anti-ice systems...etc. It is a substantial amount of weight reduced. Weight = fuel = well, you know... |
adiru777 wrote:So is the 777X going to be bleedless or NOT?
hivue wrote:adiru777 wrote:So is the 777X going to be bleedless or NOT?
NOT, I think. The 777 is a legacy airframe and was not originally designed for bleedless.
adiru777 wrote:Okay thanks, so far to say the 737MAX will be using bleed as well?
adiru777 wrote:But I heard that 737 MAX will be using FBW, which previously only the 777 had.
adiru777 wrote:So if the 737 can go FBW, can't the 777X go bleedless or is that more of a change in the aircraft?
Jetlagged wrote:Before the VC-10, in the era of piston power, air compressors were the norm for cabin pressurisation.
wingscrubber wrote:Meanwhile, engine inlet anti-ice on 787 is still not bleedless... so, they have capability to use bleed air after all. Might be why A350 didn't bother?
wingscrubber wrote:787 architecture is to drive a generator, and then with the power from the generator, drive a compressor, which pressurises the cabin. Better for fume events, but more energy conversions means more losses, which means overall, it is less efficient... but the trend in industry is inexorable, you can do trade studies all day long which disagree, but more electric = more better!
wingscrubber wrote:It is happening in landing gear too, deletion of hydraulics. What seems to be desired is to have new aircraft power a generator, which powers a motor which powers a pump, why not just power a pump?
wingscrubber wrote:drive a generator, and then with the power from the generator, drive a compressor, which pressurises the cabin. more energy conversions means more losses
kitplane01 wrote:Jetlagged wrote:Before the VC-10, in the era of piston power, air compressors were the norm for cabin pressurisation.
Is this true? For modern piston planes (Cessna, Beech, Piper) the air for pressurization is tapped off the compressor side of the turbo where it is then conditioned and sent into the cabin. Was this not true back then?
Googling does not provide an obvious answer.