Is the bleed air passengers breathe tapped from the engines before or after it comes in contact with fuel?...
Passengers are often surprised to hear that the air they breathe comes from inside the engines.
This sounds unhealthy. Can you explain, why it is not ?
Is bleed air tapped (for cabin pressurization) before or after it comes in contact with fuel inside turbofan engines on passenger airliners ?
And what is the reason for either choice ?
Specifically where is the location in this diagram ? (diagrams in answers would be very welcome)
scope: This question is about the air breathed by humans inside the plane. Q11917 is about de-icing. Neither the question nor the answers in Q11917 deal with the aspect of whether the air would be safely breathable for passengers and crew. This aspect is very well dealt with in the comments and answers below. As such, these questions should remain separate.
airliner engine turbofan engine-design bleed-air
asked Dec 9 '18 at 18:16
summerrain
1,1911620
|
show 1 more comment
Passengers are often surprised to hear that the air they breathe comes from inside the engines.
This sounds unhealthy. Can you explain, why it is not ?
Is bleed air tapped (for cabin pressurization) before or after it comes in contact with fuel inside turbofan engines on passenger airliners ?
And what is the reason for either choice ?
Specifically where is the location in this diagram ? (diagrams in answers would be very welcome)
scope: This question is about the air breathed by humans inside the plane. Q11917 is about de-icing. Neither the question nor the answers in Q11917 deal with the aspect of whether the air would be safely breathable for passengers and crew. This aspect is very well dealt with in the comments and answers below. As such, these questions should remain separate.
airliner engine turbofan engine-design bleed-air
asked Dec 9 '18 at 18:16
summerrain
1,1911620
9
Think about this for a second - if it comes after the air is in contact with the fuel and it's being used for cabin pressurization, that would mean you'd be building up a fuel-air mixture in the cabin - which would be toxic in the best scenario, and explosive in the worst.
– FKEinternet
Dec 10 '18 at 1:04
I'm asking because cabin air sometimes smells of kerosene.
– summerrain
Dec 10 '18 at 9:16
3
I'd guess cabin air smelling of kerosene has to do with standing on the ground before takeoff amid kerosene being used --- by other planes, by own idling engines, wafting from just-released fuel truck nozzle, ... --- so whatever outside air is taken in must carry the smell (via the open doors everyone just entered through, if from a staircase; or any air intake point).
– user3445853
Dec 10 '18 at 14:06
2
Possible duplicate of Why is bleed air taken from some stage of the compressor used for de-icing? Why not e.g. exhaust gas?
– fooot
Dec 12 '18 at 20:15
1
@fooot I don't see how it's a duplicate of that. Cabin air isn't taken from the exhaust because the passengers need oxygen; it isn't taken after fuel injection because the passengers need a cabin full of no jet fuel.
– David Richerby
Dec 13 '18 at 12:22
|
show 1 more comment
Passengers are often surprised to hear that the air they breathe comes from inside the engines.
This sounds unhealthy. Can you explain, why it is not ?
Is bleed air tapped (for cabin pressurization) before or after it comes in contact with fuel inside turbofan engines on passenger airliners ?
And what is the reason for either choice ?
Specifically where is the location in this diagram ? (diagrams in answers would be very welcome)
scope: This question is about the air breathed by humans inside the plane. Q11917 is about de-icing. Neither the question nor the answers in Q11917 deal with the aspect of whether the air would be safely breathable for passengers and crew. This aspect is very well dealt with in the comments and answers below. As such, these questions should remain separate.
airliner engine turbofan engine-design bleed-air
asked Dec 9 '18 at 18:16
summerrain
1,1911620
Passengers are often surprised to hear that the air they breathe comes from inside the engines.
This sounds unhealthy. Can you explain, why it is not ?
Is bleed air tapped (for cabin pressurization) before or after it comes in contact with fuel inside turbofan engines on passenger airliners ?
And what is the reason for either choice ?
Specifically where is the location in this diagram ? (diagrams in answers would be very welcome)
scope: This question is about the air breathed by humans inside the plane. Q11917 is about de-icing. Neither the question nor the answers in Q11917 deal with the aspect of whether the air would be safely breathable for passengers and crew. This aspect is very well dealt with in the comments and answers below. As such, these questions should remain separate.
airliner engine turbofan engine-design bleed-air
airliner engine turbofan engine-design bleed-air
asked Dec 9 '18 at 18:16
summerrain
1,1911620
asked Dec 9 '18 at 18:16
summerrain
1,1911620
edited Dec 13 '18 at 12:55
asked Dec 9 '18 at 18:16
summerrain
1,1911620
asked Dec 9 '18 at 18:16
summerrain
1,1911620
asked Dec 9 '18 at 18:16
summerrain
1,1911620
1,1911620
9
Think about this for a second - if it comes after the air is in contact with the fuel and it's being used for cabin pressurization, that would mean you'd be building up a fuel-air mixture in the cabin - which would be toxic in the best scenario, and explosive in the worst.
– FKEinternet
Dec 10 '18 at 1:04
I'm asking because cabin air sometimes smells of kerosene.
– summerrain
Dec 10 '18 at 9:16
3
I'd guess cabin air smelling of kerosene has to do with standing on the ground before takeoff amid kerosene being used --- by other planes, by own idling engines, wafting from just-released fuel truck nozzle, ... --- so whatever outside air is taken in must carry the smell (via the open doors everyone just entered through, if from a staircase; or any air intake point).
– user3445853
Dec 10 '18 at 14:06
2
Possible duplicate of Why is bleed air taken from some stage of the compressor used for de-icing? Why not e.g. exhaust gas?
– fooot
Dec 12 '18 at 20:15
1
@fooot I don't see how it's a duplicate of that. Cabin air isn't taken from the exhaust because the passengers need oxygen; it isn't taken after fuel injection because the passengers need a cabin full of no jet fuel.
– David Richerby
Dec 13 '18 at 12:22
|
show 1 more comment
9
Think about this for a second - if it comes after the air is in contact with the fuel and it's being used for cabin pressurization, that would mean you'd be building up a fuel-air mixture in the cabin - which would be toxic in the best scenario, and explosive in the worst.
– FKEinternet
Dec 10 '18 at 1:04
I'm asking because cabin air sometimes smells of kerosene.
– summerrain
Dec 10 '18 at 9:16
3
I'd guess cabin air smelling of kerosene has to do with standing on the ground before takeoff amid kerosene being used --- by other planes, by own idling engines, wafting from just-released fuel truck nozzle, ... --- so whatever outside air is taken in must carry the smell (via the open doors everyone just entered through, if from a staircase; or any air intake point).
– user3445853
Dec 10 '18 at 14:06
2
Possible duplicate of Why is bleed air taken from some stage of the compressor used for de-icing? Why not e.g. exhaust gas?
– fooot
Dec 12 '18 at 20:15
1
@fooot I don't see how it's a duplicate of that. Cabin air isn't taken from the exhaust because the passengers need oxygen; it isn't taken after fuel injection because the passengers need a cabin full of no jet fuel.
– David Richerby
Dec 13 '18 at 12:22
9
9
Think about this for a second - if it comes after the air is in contact with the fuel and it's being used for cabin pressurization, that would mean you'd be building up a fuel-air mixture in the cabin - which would be toxic in the best scenario, and explosive in the worst.
– FKEinternet
Dec 10 '18 at 1:04
Think about this for a second - if it comes after the air is in contact with the fuel and it's being used for cabin pressurization, that would mean you'd be building up a fuel-air mixture in the cabin - which would be toxic in the best scenario, and explosive in the worst.
– FKEinternet
Dec 10 '18 at 1:04
I'm asking because cabin air sometimes smells of kerosene.
– summerrain
Dec 10 '18 at 9:16
I'm asking because cabin air sometimes smells of kerosene.
– summerrain
Dec 10 '18 at 9:16
3
3
I'd guess cabin air smelling of kerosene has to do with standing on the ground before takeoff amid kerosene being used --- by other planes, by own idling engines, wafting from just-released fuel truck nozzle, ... --- so whatever outside air is taken in must carry the smell (via the open doors everyone just entered through, if from a staircase; or any air intake point).
– user3445853
Dec 10 '18 at 14:06
I'd guess cabin air smelling of kerosene has to do with standing on the ground before takeoff amid kerosene being used --- by other planes, by own idling engines, wafting from just-released fuel truck nozzle, ... --- so whatever outside air is taken in must carry the smell (via the open doors everyone just entered through, if from a staircase; or any air intake point).
– user3445853
Dec 10 '18 at 14:06
2
2
Possible duplicate of Why is bleed air taken from some stage of the compressor used for de-icing? Why not e.g. exhaust gas?
– fooot
Dec 12 '18 at 20:15
Possible duplicate of Why is bleed air taken from some stage of the compressor used for de-icing? Why not e.g. exhaust gas?
– fooot
Dec 12 '18 at 20:15
1
1
@fooot I don't see how it's a duplicate of that. Cabin air isn't taken from the exhaust because the passengers need oxygen; it isn't taken after fuel injection because the passengers need a cabin full of no jet fuel.
– David Richerby
Dec 13 '18 at 12:22
@fooot I don't see how it's a duplicate of that. Cabin air isn't taken from the exhaust because the passengers need oxygen; it isn't taken after fuel injection because the passengers need a cabin full of no jet fuel.
– David Richerby
Dec 13 '18 at 12:22
|
show 1 more comment
3 Answers
3
active
oldest
votes
The bleed will be tapped from one or two of the 3rd, 4th, 5th or 6th High Pressure Compressor stages. Usually there are two bleed ports. The highest pressure port will supply really hot air for things like anti-icing. The lower pressure port farther upstream will supply air for air conditioning/pressurization and other pneumatics. Some systems combine the two ports into one system and draw from the low pressure or high pressure one as required.
The air has to come from the compressor, not after combustion, mainly because it needs to be clean ambient air free of kerosene combustion byproducts, and it's plenty hot enough anyway and taking it from the turbine would be way too hot. The discharge in the last stages of the HP compressor can be upwards of 700-800F at takeoff thrust.
If the aircraft uses a high temperature "evaporative" anti-icing system, it will tap air from hotter stages of the compressor than if there is a non-evaporative system (Evaporative = anti-iced skin temperatures above the boiling point of water. The leading edge will be over 100 C, like the surface of a steam iron.)
Even if it is taking "clean" air, the bleed flow will have all sorts of charred bits of things from the atmosphere in it; pollen, bits of bugs, that collect and get everything dirty in the ducting and components (at lower altitudes). Combusted air would be ten times worse, not to mention the carbon monoxide poisoning the passengers and being way too hot to be usable in the first place.
answered Dec 9 '18 at 19:00
John K
14k11543
1
7th stage bleed is also possible on some engines.
– Daniel Kiracofe
Dec 9 '18 at 20:13
6
Anti-deicing sounds like a terrorist plot :-0
– TonyK
Dec 9 '18 at 22:59
A secondary reason for multiple bleed ports is to keep the compressor stable. Unlike turbines, compressors are potentially unstable devices, and the overall flow conditions need to be controlled to avoid stall or surge. The bleed ports are in effect part of that control system.
– alephzero
Dec 9 '18 at 23:35
1
"not to mention the carbon monoxide poisoning the passengers" let's not quibble over small details :-)
– summerrain
Dec 10 '18 at 5:55
1
@DevSolar "Clean" from the perspective of a massive jet engine differs quite a bit from "clean" from the perspective of our fragile little human lungs. Even if the combustion is almost perfectly complete, the sheer amount going on would quickly bring ambient CO to lethal concentrations.
– forest
Dec 10 '18 at 10:10
|
show 2 more comments
To add to what John K already posted, cooling requirements prevent any bleed air being taken in the combustor and high pressure turbine sections. In these sections, thin film cooling is preformed where a small amount of air is injected around the surfaces to prevent the hot combustion products from touching them. Even if the bleed air was being taken for a non-human contact purpose such as active flow control, the air is simply too hot to handle at this point.
answered Dec 10 '18 at 7:19
XRF
2455
add a comment |
I have found a diagram showing the location where the bleed air is tapped (red arrow).
As can be seen in the image, the location is upstream of the combustion chambers, which means that bleed air is tapped before it comes into contact with fuel:
answered Dec 12 '18 at 19:25
summerrain
1,1911620
add a comment |
Your Answer
StackExchange.ifUsing("editor", function () {
return StackExchange.using("mathjaxEditing", function () {
StackExchange.MarkdownEditor.creationCallbacks.add(function (editor, postfix) {
StackExchange.mathjaxEditing.prepareWmdForMathJax(editor, postfix, [["$", "$"], ["\\(","\\)"]]);
});
});
}, "mathjax-editing");
StackExchange.ready(function() {
var channelOptions = {
tags: "".split(" "),
id: "528"
};
initTagRenderer("".split(" "), "".split(" "), channelOptions);
StackExchange.using("externalEditor", function() {
// Have to fire editor after snippets, if snippets enabled
if (StackExchange.settings.snippets.snippetsEnabled) {
StackExchange.using("snippets", function() {
createEditor();
});
}
else {
createEditor();
}
});
function createEditor() {
StackExchange.prepareEditor({
heartbeatType: 'answer',
autoActivateHeartbeat: false,
convertImagesToLinks: false,
noModals: true,
showLowRepImageUploadWarning: true,
reputationToPostImages: null,
bindNavPrevention: true,
postfix: "",
imageUploader: {
brandingHtml: "Powered by u003ca class="icon-imgur-white" href="https://imgur.com/"u003eu003c/au003e",
contentPolicyHtml: "User contributions licensed under u003ca href="https://creativecommons.org/licenses/by-sa/3.0/"u003ecc by-sa 3.0 with attribution requiredu003c/au003e u003ca href="https://stackoverflow.com/legal/content-policy"u003e(content policy)u003c/au003e",
allowUrls: true
},
noCode: true, onDemand: true,
discardSelector: ".discard-answer"
,immediatelyShowMarkdownHelp:true
});
}
});
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
StackExchange.ready(
function () {
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2faviation.stackexchange.com%2fquestions%2f57892%2fis-the-bleed-air-passengers-breathe-tapped-from-the-engines-before-or-after-it-c%23new-answer', 'question_page');
}
);
Post as a guest
Required, but never shown
3 Answers
3
active
oldest
votes
3 Answers
3
active
oldest
votes
active
oldest
votes
active
oldest
votes
The bleed will be tapped from one or two of the 3rd, 4th, 5th or 6th High Pressure Compressor stages. Usually there are two bleed ports. The highest pressure port will supply really hot air for things like anti-icing. The lower pressure port farther upstream will supply air for air conditioning/pressurization and other pneumatics. Some systems combine the two ports into one system and draw from the low pressure or high pressure one as required.
The air has to come from the compressor, not after combustion, mainly because it needs to be clean ambient air free of kerosene combustion byproducts, and it's plenty hot enough anyway and taking it from the turbine would be way too hot. The discharge in the last stages of the HP compressor can be upwards of 700-800F at takeoff thrust.
If the aircraft uses a high temperature "evaporative" anti-icing system, it will tap air from hotter stages of the compressor than if there is a non-evaporative system (Evaporative = anti-iced skin temperatures above the boiling point of water. The leading edge will be over 100 C, like the surface of a steam iron.)
Even if it is taking "clean" air, the bleed flow will have all sorts of charred bits of things from the atmosphere in it; pollen, bits of bugs, that collect and get everything dirty in the ducting and components (at lower altitudes). Combusted air would be ten times worse, not to mention the carbon monoxide poisoning the passengers and being way too hot to be usable in the first place.
answered Dec 9 '18 at 19:00
John K
14k11543
1
7th stage bleed is also possible on some engines.
– Daniel Kiracofe
Dec 9 '18 at 20:13
6
Anti-deicing sounds like a terrorist plot :-0
– TonyK
Dec 9 '18 at 22:59
A secondary reason for multiple bleed ports is to keep the compressor stable. Unlike turbines, compressors are potentially unstable devices, and the overall flow conditions need to be controlled to avoid stall or surge. The bleed ports are in effect part of that control system.
– alephzero
Dec 9 '18 at 23:35
1
"not to mention the carbon monoxide poisoning the passengers" let's not quibble over small details :-)
– summerrain
Dec 10 '18 at 5:55
1
@DevSolar "Clean" from the perspective of a massive jet engine differs quite a bit from "clean" from the perspective of our fragile little human lungs. Even if the combustion is almost perfectly complete, the sheer amount going on would quickly bring ambient CO to lethal concentrations.
– forest
Dec 10 '18 at 10:10
|
show 2 more comments
The bleed will be tapped from one or two of the 3rd, 4th, 5th or 6th High Pressure Compressor stages. Usually there are two bleed ports. The highest pressure port will supply really hot air for things like anti-icing. The lower pressure port farther upstream will supply air for air conditioning/pressurization and other pneumatics. Some systems combine the two ports into one system and draw from the low pressure or high pressure one as required.
The air has to come from the compressor, not after combustion, mainly because it needs to be clean ambient air free of kerosene combustion byproducts, and it's plenty hot enough anyway and taking it from the turbine would be way too hot. The discharge in the last stages of the HP compressor can be upwards of 700-800F at takeoff thrust.
If the aircraft uses a high temperature "evaporative" anti-icing system, it will tap air from hotter stages of the compressor than if there is a non-evaporative system (Evaporative = anti-iced skin temperatures above the boiling point of water. The leading edge will be over 100 C, like the surface of a steam iron.)
Even if it is taking "clean" air, the bleed flow will have all sorts of charred bits of things from the atmosphere in it; pollen, bits of bugs, that collect and get everything dirty in the ducting and components (at lower altitudes). Combusted air would be ten times worse, not to mention the carbon monoxide poisoning the passengers and being way too hot to be usable in the first place.
answered Dec 9 '18 at 19:00
John K
14k11543
1
7th stage bleed is also possible on some engines.
– Daniel Kiracofe
Dec 9 '18 at 20:13
6
Anti-deicing sounds like a terrorist plot :-0
– TonyK
Dec 9 '18 at 22:59
A secondary reason for multiple bleed ports is to keep the compressor stable. Unlike turbines, compressors are potentially unstable devices, and the overall flow conditions need to be controlled to avoid stall or surge. The bleed ports are in effect part of that control system.
– alephzero
Dec 9 '18 at 23:35
1
"not to mention the carbon monoxide poisoning the passengers" let's not quibble over small details :-)
– summerrain
Dec 10 '18 at 5:55
1
@DevSolar "Clean" from the perspective of a massive jet engine differs quite a bit from "clean" from the perspective of our fragile little human lungs. Even if the combustion is almost perfectly complete, the sheer amount going on would quickly bring ambient CO to lethal concentrations.
– forest
Dec 10 '18 at 10:10
|
show 2 more comments
The bleed will be tapped from one or two of the 3rd, 4th, 5th or 6th High Pressure Compressor stages. Usually there are two bleed ports. The highest pressure port will supply really hot air for things like anti-icing. The lower pressure port farther upstream will supply air for air conditioning/pressurization and other pneumatics. Some systems combine the two ports into one system and draw from the low pressure or high pressure one as required.
The air has to come from the compressor, not after combustion, mainly because it needs to be clean ambient air free of kerosene combustion byproducts, and it's plenty hot enough anyway and taking it from the turbine would be way too hot. The discharge in the last stages of the HP compressor can be upwards of 700-800F at takeoff thrust.
If the aircraft uses a high temperature "evaporative" anti-icing system, it will tap air from hotter stages of the compressor than if there is a non-evaporative system (Evaporative = anti-iced skin temperatures above the boiling point of water. The leading edge will be over 100 C, like the surface of a steam iron.)
Even if it is taking "clean" air, the bleed flow will have all sorts of charred bits of things from the atmosphere in it; pollen, bits of bugs, that collect and get everything dirty in the ducting and components (at lower altitudes). Combusted air would be ten times worse, not to mention the carbon monoxide poisoning the passengers and being way too hot to be usable in the first place.
answered Dec 9 '18 at 19:00
John K
14k11543
The bleed will be tapped from one or two of the 3rd, 4th, 5th or 6th High Pressure Compressor stages. Usually there are two bleed ports. The highest pressure port will supply really hot air for things like anti-icing. The lower pressure port farther upstream will supply air for air conditioning/pressurization and other pneumatics. Some systems combine the two ports into one system and draw from the low pressure or high pressure one as required.
The air has to come from the compressor, not after combustion, mainly because it needs to be clean ambient air free of kerosene combustion byproducts, and it's plenty hot enough anyway and taking it from the turbine would be way too hot. The discharge in the last stages of the HP compressor can be upwards of 700-800F at takeoff thrust.
If the aircraft uses a high temperature "evaporative" anti-icing system, it will tap air from hotter stages of the compressor than if there is a non-evaporative system (Evaporative = anti-iced skin temperatures above the boiling point of water. The leading edge will be over 100 C, like the surface of a steam iron.)
Even if it is taking "clean" air, the bleed flow will have all sorts of charred bits of things from the atmosphere in it; pollen, bits of bugs, that collect and get everything dirty in the ducting and components (at lower altitudes). Combusted air would be ten times worse, not to mention the carbon monoxide poisoning the passengers and being way too hot to be usable in the first place.
answered Dec 9 '18 at 19:00
John K
14k11543
edited Dec 10 '18 at 3:36
answered Dec 9 '18 at 19:00
John K
14k11543
answered Dec 9 '18 at 19:00
John K
14k11543
answered Dec 9 '18 at 19:00
John K
14k11543
14k11543
1
7th stage bleed is also possible on some engines.
– Daniel Kiracofe
Dec 9 '18 at 20:13
6
Anti-deicing sounds like a terrorist plot :-0
– TonyK
Dec 9 '18 at 22:59
A secondary reason for multiple bleed ports is to keep the compressor stable. Unlike turbines, compressors are potentially unstable devices, and the overall flow conditions need to be controlled to avoid stall or surge. The bleed ports are in effect part of that control system.
– alephzero
Dec 9 '18 at 23:35
1
"not to mention the carbon monoxide poisoning the passengers" let's not quibble over small details :-)
– summerrain
Dec 10 '18 at 5:55
1
@DevSolar "Clean" from the perspective of a massive jet engine differs quite a bit from "clean" from the perspective of our fragile little human lungs. Even if the combustion is almost perfectly complete, the sheer amount going on would quickly bring ambient CO to lethal concentrations.
– forest
Dec 10 '18 at 10:10
|
show 2 more comments
1
7th stage bleed is also possible on some engines.
– Daniel Kiracofe
Dec 9 '18 at 20:13
6
Anti-deicing sounds like a terrorist plot :-0
– TonyK
Dec 9 '18 at 22:59
A secondary reason for multiple bleed ports is to keep the compressor stable. Unlike turbines, compressors are potentially unstable devices, and the overall flow conditions need to be controlled to avoid stall or surge. The bleed ports are in effect part of that control system.
– alephzero
Dec 9 '18 at 23:35
1
"not to mention the carbon monoxide poisoning the passengers" let's not quibble over small details :-)
– summerrain
Dec 10 '18 at 5:55
1
@DevSolar "Clean" from the perspective of a massive jet engine differs quite a bit from "clean" from the perspective of our fragile little human lungs. Even if the combustion is almost perfectly complete, the sheer amount going on would quickly bring ambient CO to lethal concentrations.
– forest
Dec 10 '18 at 10:10
1
1
7th stage bleed is also possible on some engines.
– Daniel Kiracofe
Dec 9 '18 at 20:13
7th stage bleed is also possible on some engines.
– Daniel Kiracofe
Dec 9 '18 at 20:13
6
6
Anti-deicing sounds like a terrorist plot :-0
– TonyK
Dec 9 '18 at 22:59
Anti-deicing sounds like a terrorist plot :-0
– TonyK
Dec 9 '18 at 22:59
A secondary reason for multiple bleed ports is to keep the compressor stable. Unlike turbines, compressors are potentially unstable devices, and the overall flow conditions need to be controlled to avoid stall or surge. The bleed ports are in effect part of that control system.
– alephzero
Dec 9 '18 at 23:35
A secondary reason for multiple bleed ports is to keep the compressor stable. Unlike turbines, compressors are potentially unstable devices, and the overall flow conditions need to be controlled to avoid stall or surge. The bleed ports are in effect part of that control system.
– alephzero
Dec 9 '18 at 23:35
1
1
"not to mention the carbon monoxide poisoning the passengers" let's not quibble over small details :-)
– summerrain
Dec 10 '18 at 5:55
"not to mention the carbon monoxide poisoning the passengers" let's not quibble over small details :-)
– summerrain
Dec 10 '18 at 5:55
1
1
@DevSolar "Clean" from the perspective of a massive jet engine differs quite a bit from "clean" from the perspective of our fragile little human lungs. Even if the combustion is almost perfectly complete, the sheer amount going on would quickly bring ambient CO to lethal concentrations.
– forest
Dec 10 '18 at 10:10
@DevSolar "Clean" from the perspective of a massive jet engine differs quite a bit from "clean" from the perspective of our fragile little human lungs. Even if the combustion is almost perfectly complete, the sheer amount going on would quickly bring ambient CO to lethal concentrations.
– forest
Dec 10 '18 at 10:10
|
show 2 more comments
To add to what John K already posted, cooling requirements prevent any bleed air being taken in the combustor and high pressure turbine sections. In these sections, thin film cooling is preformed where a small amount of air is injected around the surfaces to prevent the hot combustion products from touching them. Even if the bleed air was being taken for a non-human contact purpose such as active flow control, the air is simply too hot to handle at this point.
answered Dec 10 '18 at 7:19
XRF
2455
add a comment |
To add to what John K already posted, cooling requirements prevent any bleed air being taken in the combustor and high pressure turbine sections. In these sections, thin film cooling is preformed where a small amount of air is injected around the surfaces to prevent the hot combustion products from touching them. Even if the bleed air was being taken for a non-human contact purpose such as active flow control, the air is simply too hot to handle at this point.
answered Dec 10 '18 at 7:19
XRF
2455
add a comment |
To add to what John K already posted, cooling requirements prevent any bleed air being taken in the combustor and high pressure turbine sections. In these sections, thin film cooling is preformed where a small amount of air is injected around the surfaces to prevent the hot combustion products from touching them. Even if the bleed air was being taken for a non-human contact purpose such as active flow control, the air is simply too hot to handle at this point.
answered Dec 10 '18 at 7:19
XRF
2455
To add to what John K already posted, cooling requirements prevent any bleed air being taken in the combustor and high pressure turbine sections. In these sections, thin film cooling is preformed where a small amount of air is injected around the surfaces to prevent the hot combustion products from touching them. Even if the bleed air was being taken for a non-human contact purpose such as active flow control, the air is simply too hot to handle at this point.
answered Dec 10 '18 at 7:19
XRF
2455
answered Dec 10 '18 at 7:19
XRF
2455
answered Dec 10 '18 at 7:19
XRF
2455
answered Dec 10 '18 at 7:19
XRF
2455
2455
add a comment |
add a comment |
I have found a diagram showing the location where the bleed air is tapped (red arrow).
As can be seen in the image, the location is upstream of the combustion chambers, which means that bleed air is tapped before it comes into contact with fuel:
answered Dec 12 '18 at 19:25
summerrain
1,1911620
add a comment |
I have found a diagram showing the location where the bleed air is tapped (red arrow).
As can be seen in the image, the location is upstream of the combustion chambers, which means that bleed air is tapped before it comes into contact with fuel:
answered Dec 12 '18 at 19:25
summerrain
1,1911620
add a comment |
I have found a diagram showing the location where the bleed air is tapped (red arrow).
As can be seen in the image, the location is upstream of the combustion chambers, which means that bleed air is tapped before it comes into contact with fuel:
answered Dec 12 '18 at 19:25
summerrain
1,1911620
I have found a diagram showing the location where the bleed air is tapped (red arrow).
As can be seen in the image, the location is upstream of the combustion chambers, which means that bleed air is tapped before it comes into contact with fuel:
answered Dec 12 '18 at 19:25
summerrain
1,1911620
answered Dec 12 '18 at 19:25
summerrain
1,1911620
answered Dec 12 '18 at 19:25
summerrain
1,1911620
answered Dec 12 '18 at 19:25
summerrain
1,1911620
1,1911620
add a comment |
add a comment |
Thanks for contributing an answer to Aviation Stack Exchange!
- Please be sure to answer the question. Provide details and share your research!
But avoid …
- Asking for help, clarification, or responding to other answers.
- Making statements based on opinion; back them up with references or personal experience.
Use MathJax to format equations. MathJax reference.
To learn more, see our tips on writing great answers.
Some of your past answers have not been well-received, and you're in danger of being blocked from answering.
Please pay close attention to the following guidance:
- Please be sure to answer the question. Provide details and share your research!
But avoid …
- Asking for help, clarification, or responding to other answers.
- Making statements based on opinion; back them up with references or personal experience.
To learn more, see our tips on writing great answers.
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
StackExchange.ready(
function () {
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2faviation.stackexchange.com%2fquestions%2f57892%2fis-the-bleed-air-passengers-breathe-tapped-from-the-engines-before-or-after-it-c%23new-answer', 'question_page');
}
);
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
9
Think about this for a second - if it comes after the air is in contact with the fuel and it's being used for cabin pressurization, that would mean you'd be building up a fuel-air mixture in the cabin - which would be toxic in the best scenario, and explosive in the worst.
– FKEinternet
Dec 10 '18 at 1:04
I'm asking because cabin air sometimes smells of kerosene.
– summerrain
Dec 10 '18 at 9:16
3
I'd guess cabin air smelling of kerosene has to do with standing on the ground before takeoff amid kerosene being used --- by other planes, by own idling engines, wafting from just-released fuel truck nozzle, ... --- so whatever outside air is taken in must carry the smell (via the open doors everyone just entered through, if from a staircase; or any air intake point).
– user3445853
Dec 10 '18 at 14:06
2
Possible duplicate of Why is bleed air taken from some stage of the compressor used for de-icing? Why not e.g. exhaust gas?
– fooot
Dec 12 '18 at 20:15
1
@fooot I don't see how it's a duplicate of that. Cabin air isn't taken from the exhaust because the passengers need oxygen; it isn't taken after fuel injection because the passengers need a cabin full of no jet fuel.
– David Richerby
Dec 13 '18 at 12:22