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 ACM Press/Temp Graph.
 VC-10 From United Kingdom, joined Oct 1999, 3720 posts, RR: 32Posted Mon Dec 31 2001 14:09:08 UTC (13 years 11 months 2 days 7 hours ago) and read 4737 times:

 In response to Essential Power's request that I explain where the energy comes from as illustrated in the P/T graph below I submit the following. The bleed air enters the pack with the pressure & heat energy given to it by engine combustion. As can be seen in the graph this illustrated by the entry P/T of 2.6 bar/190 degs. The air flow now passes through the primary heat exchanger where some of the press & temp energy is lost and enters the ACM centrifugal compressor at 2.5bar/90 degs. The ACM impellor adds energy by accelerateing the air flow while the compressor diffusor converts this kinetic energy into pressure/temp energy. The air leaving the compressor at 3.6bar/140degs. The air now enters the main heat exchanger and water extractor where more heat/pressure energy is lost by radiation & conduction so by the time it enters the ACM turbine the P/T is 3.55bar/40degs. As the air passes through the turbine and has to do work in accelerating the airflow in the compressor plus overcomeing internal frictional losses further energy is lost resulting in the pack outlet P/T being 1.1bar/-10 degrees C. So overall the energy lost through the air cond pack amount to a 200 deg C drop in temp and a 21 psi drop in pressure. Now to answer your other points. 1. "So prior to that you weren't even aware of the concept of the bypass, or what it was for". 2. "and your ignorance of it, greatly reduces your credibility." I refer you to:- 2001-11-06 21:16:31 One point you omitted was that the airflow doesn't have to go through the compressor on system start up. There is a by-pass valve that by-passes the air around to comp, then, as the turbine spins up and turns the compressor, the comp. delivery air back pressure closes the by-pass valve. Which you agreed later was before you brought it up. Furthermore during that long post you seem to have fogotten that there were times when you were asking for my support. Finally may I wish all my readers a happy new year.
 44 replies: All unread, showing first 25:
 Delta-flyer From United States of America, joined Jul 2001, 2676 posts, RR: 6 Reply 1, posted Sat Jan 5 2002 06:32:11 UTC (13 years 10 months 3 weeks 6 days 14 hours ago) and read 4577 times:

 Way-to-go, VC -- I could really use the P/T diagram you provided. Do you by any chance know the mass flow of air in this process during normal operation, and how many packs are working at a time to provide an "average" cabin atmosphere? Thanks Pete
 VC-10 From United Kingdom, joined Oct 1999, 3720 posts, RR: 32 Reply 2, posted Wed Jan 9 2002 22:27:20 UTC (13 years 10 months 3 weeks 1 day 22 hours ago) and read 4560 times:

 Delta-flyer, Sorry for the delay in getting back to you, I had to wait untill I was back in at work the get the data. I haop the following is what you are after. QT= Total fresh airflow to pressurised fuselage QF/D= Fresh a/flow to Flt Dk QC= Fresh airflow to pax cabin QR= Recirc a/flow fron two recirc fans. Normally both packs are used. If the a/c is dispatched under the MEL with a singel pack operational there is an alt restriction of 31,000 Ft. Nml 100% flow = 2.558 Kg/s on Grnd - 1.9 Kg/s at Cruise alt. With one pack off 60% of nml flow is avail at Crz Alt.
 Delta-flyer From United States of America, joined Jul 2001, 2676 posts, RR: 6 Reply 3, posted Thu Jan 10 2002 05:25:10 UTC (13 years 10 months 3 weeks 1 day 15 hours ago) and read 4552 times:

 VC-10, Yes, that's exactly what I was looking for -- THANKS!! I am printing this out so I can study it in more detail - there is a ton (tonne) of data here. Thanks again Pete
 EssentialPowr From United States of America, joined Sep 2000, 1820 posts, RR: 1 Reply 4, posted Thu Jan 10 2002 06:00:53 UTC (13 years 10 months 3 weeks 1 day 15 hours ago) and read 4550 times:

 I asked you to describe where the energy comes from. All you have did above is read the chart...Isn't that why those values are charted in the first place? Save some typing... But I asked about enthalpy, remember??? Btw- You should pay more attention to what you type. 2001-11-06 21:16:31 was posted by Airplay... So Sorry....
 EssentialPowr From United States of America, joined Sep 2000, 1820 posts, RR: 1 Reply 5, posted Thu Jan 10 2002 06:14:51 UTC (13 years 10 months 3 weeks 1 day 15 hours ago) and read 4540 times:

 REf above to VC10 Btw-If you are LATENTLY "willing to concede" a bypass existed after going UNRECOGNIZED in your OWN NOTES...and took weeks just to read what a PT chart clearly shows...and finally, accuse me of something I clearly did not say, maybe you should just leave it alone, or present something with a scrap of legitimacy. Yeay, yeah you'll respond. So, 1. Describe where the energy comes from 2. Accurately identify who you are quoting 3. And as I have, apologize when necessary Otherwise, your credibility is worse now than it was, b/c all you have proven up to this moment is that you like to argue - poorly.
 EssentialPowr From United States of America, joined Sep 2000, 1820 posts, RR: 1 Reply 6, posted Thu Jan 10 2002 08:00:54 UTC (13 years 10 months 3 weeks 1 day 13 hours ago) and read 4533 times:

 VC10, One final comment as I reviewed the ACM topic. Why would you ref 11-06 21:16:31, and then vascillate such that finding the bypass per 11-14 01:59:28 was a revelation, and then were finally "willing to concede" the existance of the bypass 11-15 06:16:37? Why were you "willing to concede" in the first place? Did you not agree with the statement 11-06 21:16:31? You do now, but didn't then? From those contradictory statements, you didn't make a point either way. I did ask for your input, but you ignored that request, so exactly what did you prove in any case? Try to admit to learning one thing: That PT graph doesn't prove where "the energy comes from". It only shows pressure and temp values through the cycle. I offerred an explantion for you in the ACM post, you ignored it, and now come back to explain that the A340 comp inlet press is around 2.5 bars @ around 90C? That's not an explanation. That's reading a graph.
 VC-10 From United Kingdom, joined Oct 1999, 3720 posts, RR: 32 Reply 7, posted Thu Jan 10 2002 08:11:25 UTC (13 years 10 months 3 weeks 1 day 13 hours ago) and read 4535 times:

 Yawn.........
 VC-10 From United Kingdom, joined Oct 1999, 3720 posts, RR: 32 Reply 8, posted Thu Jan 10 2002 12:28:57 UTC (13 years 10 months 3 weeks 1 day 8 hours ago) and read 4534 times:

 FDXmech From United States of America, joined Mar 2000, 3251 posts, RR: 31 Reply 9, posted Thu Jan 10 2002 13:57:43 UTC (13 years 10 months 3 weeks 1 day 7 hours ago) and read 4528 times:

 The bypass valve if incorporated, primary function isn't ACM startup. Any incidental or accidental function is purely unintentional or coincidental....at best. As VC10 stated, the energy originates from the compressor of the engine.
 You're only as good as your last departure.
 Airplay From , joined Dec 1969, posts, RR: Reply 10, posted Thu Jan 10 2002 19:56:35 UTC (13 years 10 months 3 weeks 1 day 1 hour ago) and read 4517 times:

 EP, You are demonstrating some disturbing obsessive behaviour. You're really beginning to ramble. It's difficult, if not immposible to accurately figure out "who said what and when" in the original post without re-reading the entire thread each time. We should really take the focus off of that. It seems to me that VC-10 is just offering some supplementary information that he promised to supply. Of course according to you, all the manufacturers are idiots and the information they provide, including the subject graph is wrong, or incomplete, or has some other deficiency. Read the graph and learn...or ignore it and remain ignorant. Nobody cares anymore. Try to put your energy into something else. You'll feel better and we'll be able to let this "dead horse" rest in peace.
 EssentialPowr From United States of America, joined Sep 2000, 1820 posts, RR: 1 Reply 11, posted Fri Jan 11 2002 01:27:00 UTC (13 years 10 months 3 weeks 19 hours ago) and read 4505 times:

 VC10- 1. You started this entire thread, and have the audacity to call me obsessive? 2. So, exactly what were you willing to Concede? What was your point? Why the contradiction? You still didn't even know what was in your own notes, fail to concede that fact, and blame me for your lack of clarity? 3. Glad you finally learned something from a physics text. A PV diagram doesn't really address enthalpy, does it? That was the hint I originally offerred. More directly, for the Brayton Refrigeration cycle: The refrigeration effect Qdot (in) = h1-h4 where: Qdot(in) = Specific heat transfered off turbine h1 = enthalypy @ compressor inlet h4 = enthalpy @ turbine outlet h1 and h4 are of course, the beginning and end states of this cycle. THAT is "where the energy comes from"; THAT is the ACM equation, and THAT, therefore, is the correct answer to my question for you.
 EssentialPowr From United States of America, joined Sep 2000, 1820 posts, RR: 1 Reply 12, posted Fri Jan 11 2002 01:34:14 UTC (13 years 10 months 3 weeks 19 hours ago) and read 4501 times:

 Airplay- Stay out of it.
 Jetfixer From United States of America, joined Oct 2000, 94 posts, RR: 0 Reply 13, posted Fri Jan 11 2002 02:05:45 UTC (13 years 10 months 3 weeks 19 hours ago) and read 4504 times:

 VC-10 From United Kingdom, joined Oct 1999, 3720 posts, RR: 32 Reply 14, posted Sat Jan 12 2002 16:49:09 UTC (13 years 10 months 2 weeks 6 days 4 hours ago) and read 4471 times:

 EP, VC10- 1. You started this entire thread, and have the audacity to call me obsessive? Either you have a problem in understanding how to read who is the author of a post (again) or you are using the above statement to bait me. I will credit you with some intelligence and assume it is the latter. In which case I'm not going to play your game.
 EssentialPowr From United States of America, joined Sep 2000, 1820 posts, RR: 1 Reply 15, posted Sun Jan 13 2002 04:26:38 UTC (13 years 10 months 2 weeks 5 days 16 hours ago) and read 4450 times:

 Airplay From , joined Dec 1969, posts, RR: Reply 16, posted Sun Jan 13 2002 17:39:46 UTC (13 years 10 months 2 weeks 5 days 3 hours ago) and read 4432 times:

 EP, You need to reread the original thread. You are the one who introduced advanced scientific principles to a somewhat simple question. The original question was not about the existance of a bypass valve. I offered a general description of the ACM system and later further offered that I didn't know of any system that used a compressor by-pass valve. Does that mean that none do? No. Does that mean that there are systems that don't use them? Yes. Does that mean that a compressor is "required" to "start" an ACM. I think there is enough information presented to say "No". Clarification over. Defining Enthalpy or Einstein's Special Theory of Relativity for that matter and defining all of the associated equations will help very few in this forum to understand the basic operation of an ACM as was requested in the original post. I certainly can spout off all kinds of techical jargon including discussions regarding enthalpy, but the original question can easily be dicussed without requiring a degree in physics. Stop hiding behind your perceived intellectual superiority in an attempt to reclaim the credibility you've lost already.
 EssentialPowr From United States of America, joined Sep 2000, 1820 posts, RR: 1 Reply 17, posted Mon Jan 14 2002 01:33:25 UTC (13 years 10 months 2 weeks 4 days 19 hours ago) and read 4422 times:

 Airplay, What you perceive as pertinent content of the original thread is your business. Obviously VC10 felt some scientific content was warranted by starting this thread, which I answered, thus reproving MY point. Yes, the def of a cycle was a component of the orig thread. You won't admit that, simply b/c you are ignorant of it, so don't define for me what the "correct" interpretation of the entire thread was. So No, I'm not too impressed w/ your "technical" ability to interpret a schematic correctly or comprehend the concept of enthalpy. Remember, you demanded that I define the ACM cycle...b/c you couldn't.
 EssentialPowr From United States of America, joined Sep 2000, 1820 posts, RR: 1 Reply 18, posted Mon Jan 14 2002 04:14:36 UTC (13 years 10 months 2 weeks 4 days 17 hours ago) and read 4423 times:

 Airplay's completed post on the "orig" ACM thread, 11-17 06:04:03: "And what "cycle" is the most appropriate model for the ACM, in your opinion?" So, Airplay, you didn't even know the ACM utilized a cycle, let alone how to define it. Or another from Airplay 11-17 02:13:49: "The ACM converts heat to rotational energy." Heat convects, conducts, or radiates. Period. Yeah, you can sure spout technical jargon. The problem is, you just don't have a clue about what you're saying. The topic did get technical, and as proven by the comments above, you were in over your head. This isn't germane to the topic? Only from a Fool's viewpoint...
 Airplay From , joined Dec 1969, posts, RR: Reply 19, posted Mon Jan 14 2002 19:05:12 UTC (13 years 10 months 2 weeks 4 days 2 hours ago) and read 4402 times:

 EP, I admit that out of the thousands of words I typed on that thread there are a few inaccuracies. I began assembling a list of incorrect statements offered by you in the subject thread. Unfortunately there is far too much material for the purposes of this thread. If I in fact was in over my head, you had drowned after your first post.
 EssentialPowr From United States of America, joined Sep 2000, 1820 posts, RR: 1 Reply 20, posted Mon Jan 14 2002 23:24:54 UTC (13 years 10 months 2 weeks 3 days 21 hours ago) and read 4401 times:

 So your inaccuracies are less eggregious than mine? From someone who was totally and completely ignorant of the concept of a bypass around the compressor in the first place? The existence and therefore function of the bypass was, by and large, the primary focus of the thread!!! You stated in may have only been present in "large or older a/c"... From someone who claimed to know all about enthalpy, and then couldn't define the ACM cycle as a difference in enthalpy? From someone who joined in this thread and was not astute enough to note that Temperature appears no where in the definition of enthalpy? From someone who has insulted me repeatedly on this and other threads? No I think not. This is your first statement to date that you were wrong about anything. Do you want the final insult? Is that your desire? Fine. How pathetic. Take your final shot, I've proven my point.
 FDXmech From United States of America, joined Mar 2000, 3251 posts, RR: 31 Reply 21, posted Tue Jan 15 2002 00:07:03 UTC (13 years 10 months 2 weeks 3 days 21 hours ago) and read 4397 times:

 No offense EP, but the bypass around the ACM compressor has nothing to do with ACM startup.
 You're only as good as your last departure.
 EssentialPowr From United States of America, joined Sep 2000, 1820 posts, RR: 1 Reply 22, posted Tue Jan 15 2002 06:26:20 UTC (13 years 10 months 2 weeks 3 days 14 hours ago) and read 4393 times:

 FDXMech: So is the check valve always open? No. Always closed? No. Obviously, it's open some time, and closed some time. So as a general statement, what you've said is incorrect, b/c the check valve closes whenever the downstream pressure is greater than the upstream pressure. This pressure difference is certainly a function of whether the ACM is static or not, b/c the downstream pressure is simply compressor discharge pressure. At higher operating speeds, the check valve will seat, and as the compressor spins down, the check will reach a point where it opens, which is to say as the ACM reaches a static condition. As I've said many times, check valves make poor throttles, so their operation is largely binary (ie open or closed). VC10 ref'd this in the orig thread with the statement and schematic on the DC10: "note that the bypass is used anytime the ACM is static". The 727 works in the exact same fashion.
 Airplay From , joined Dec 1969, posts, RR: Reply 23, posted Tue Jan 15 2002 06:36:42 UTC (13 years 10 months 2 weeks 3 days 14 hours ago) and read 4393 times:

 EP I do not NEED the last word, but I will continue to answer to your attacks. True. The definition of Enthalpy does not typically make reference to "temperature". Funny though that enthalpy is sometimes refered to as "total heat" and sometimes even "heat content". Why? Because when considering enthalpy in practical solutions (someday you might even do that) temperature (discharge or otherwise) is typically one of the properties of a system that is being investigated. Doing a study of the enthalpy of an air conditioning system without discussing the resultant temperatures is almost as useless as discussion enthalpy with unexperienced know-it-alls. By the way, you really need to start presenting statements within the context they were presented. You continuously say that I was completely ignorant of the compressor by-pass valve in some systems when I clearly stated that I was merely not aware of them in the systems I am familiar with. Wouldn't it be fair then to say you were completely ignorant of systems WITHOUT by-pass valves? And that because of your statements with respect to the tight clearances of the ACM compressor you were cleary ignorant of the construction of an ACM? And that because you dismissed and discredited anyone or any authoritve data that conflicted with your erroneous statements that you were cleary ignorant of the general accepted operational descriptions of aircraft ACMs? No....that would be jumping to conclusions. You even called my statements idiotic and ridiculous. I never made any statement categorily dismissing the possibility of an ACM compressor bypass valve. In fact in response to VC-10's statement: "One point you omitted was that the airflow doesn't have to go through the compressor on system start up. There is a by-pass valve that by-passes the air around to comp, then, as the turbine spins up and turns the compressor, the comp. delivery air back pressure closes the by-pass valve." I stated: "I'm assuming you're describing one specific type of ACM. I've never seen one that operates the way you describe. Of course that doesn't mean it doesn't exist. This is an example of the difficulty in discussing every aspect of some complex systems. There are countless specific designs! I guess that's what makes it interesting." You never present that quote. Why? Because it doesn't fit your discussion style. You would much rather present statements out of context and then try to intimidate people into seeing things your way. The internet needs fewer people like you on these forums Mr. Powr.
 EssentialPowr From United States of America, joined Sep 2000, 1820 posts, RR: 1 Reply 24, posted Tue Jan 15 2002 06:40:20 UTC (13 years 10 months 2 weeks 3 days 14 hours ago) and read 4391 times:

 FDXmech: VC10's quote 11-18 14:20:36: "In addition I quote from my DC10 training notes: ""The compressor bypass check valve allows air to bypass the compressor and act on the turbine to spin up the ACM. As the unit spins up, compressor output pressure seats the comp by-pass vlv...etc"" So yes, the compressor bypass on the DC10, 727 and I'm sure many designs enables the ACM to spinup. The above is not earthshattering, though; that's just the way a check valve works...
 25 EssentialPowr : Airplay, Nice mouth vomit, but temperature and heat are different things. Your correlations b/t the enthalpy and temp further show your knowledge of p
 26 FDXmech : DC10 If this bypass valve didn't exist, the path of the bleed flow would always interface with the ACM compressor, even if the ACM was idling, due to
 27 EssentialPowr : FDXmech, I am going to limit my comments to the DC10 due to the fact a schematic is readily available on the "orig" thread" that can be ref'd by all,
 28 FDXmech : 1. yes 2.yes 3.yes 3a. ? When you say compressor choking, I can only agree on the premise you mean air flow choking trying to pass the compressor on i
 29 310_engineer : WOW I have been out for three months and thought this discussion would be burried a long time ago, well the first topic is, but part deux started. I h
 30 EssentialPowr : 310 engineer - Uhhh, yeah... Hate to say I knew the diff b/t a centrif and an axial, but I mistyped. Did I get blasted for that or what!!! I was simpl
 31 EssentialPowr : Pls omit above para 3a, sentence 3, as it is directly from the Department of Redundancy Department, and mistyped to boot.
 32 EssentialPowr : FDXmech 3a. I agree completely w/ your statement. Sorry, should have said that first.
 33 Airplay : Hahahahahaha.... EP In a few more posts you'll have flip-flopped completely. Let me ask you this: When the ACM in your world has started and the compr
 34 EssentialPowr : Airplay, Hhhmmm Frankly, I'm fairly pleased with the results of this thread. The only things that stunk it up were a malicious conceptional error abou
 35 Airplay : EP Simply answer the questions at the beginning of my last post.
 36 EssentialPowr : Read 01-16 02:00:24, para 3a. That's half of your problem, Airplay. The answer is posted; you can't decipher it. What's new?
 37 EssentialPowr : Actually, it's your Entire Problem.
 38 EssentialPowr : I'll spell it out for you, since I know you're confused. 01-16 02:00:24 describes how the DC10 ACM goes from idle w/ the comp bypass chk open, cold ai
 39 EssentialPowr : Forget it. I don't want a copied sentence from "Contemporary Physics for Housewives", Large Print Ed.
 40 Airplay : If as you say the "compressor bypass enables the ACM to be bypassed when not needed" then why is air still introduced to the turbine???? Doesn't the a
 41 Airplay : The last post was intended as a response for EssentialPwer....in case you hadn't guessed already!
 42 Jetfixer : Airplay, Essentialpowr, sorry to butt in on your discussion but I beleive 310 Engineer needs to learn to read. Where did I refence the A320 having a C
 43 EssentialPowr : Airplay, Exactly what part of my description of the compressor bypass valve on the DC10, do you not understand? I have described the function of the c
 44 EssentialPowr : REf the DC10 schematic as posted by VC10 in the "original" thread. Of the people who have participated in this thread, is there anyone that diagrees w
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