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What does it take to be a Transport Correspondent?
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What does it take to be a Transport Correspondent?
On Thu, 21 Apr 2011 08:44:33 +0100, Graeme Wall
wrote: On 21/04/2011 08:35, Roland Perry wrote: In message , at 08:24:16 on Thu, 21 Apr 2011, Graeme Wall remarked: Have a look here http://districtdave.proboards.com/in...?board=jubilee for what really happened, though there is a bit of jargon, I hadn't looked at that site for a while. the first item reads: It is with great sadness that we have to announce that Dave Maloney, known to us all as "District Dave" and the first founder of this site, passed away peacefully at his home this morning following several months illness. Dated a little over a month ago. I'm sure it was reported here, or was it utl? The latter probably, I'm not subscribed to utl. I don't recall seeing anything in uk.railway. |
What does it take to be a Transport Correspondent?
On 21/04/2011 09:20, pippa.moran wrote:
Arthur Figgis wrote: On 20/04/2011 22:40, Jack Taylor wrote: "Instead of using traffic lights trains are linked by radio waves which 'talk' to trackside responders. These in turn send a signal to a computer in the train engine to speed up or stop." Other than being electric multiple units (which normals wouldn't understand) and so not having an "engine", isn't that more or less how it works? What do mean, no engine? Unless the trains are pulled by horses, or the passengers have to get out and push, there must be something - some sort of mechanism or machinery - inside the train to make it move. In other words, an "engine." How could it move without one? Gravity has been used, or cables operated by an engine not inside the train. "Engine" is also used in the sense of "locomotive". -- Arthur Figgis Surrey, UK |
What does it take to be a Transport Correspondent?
wrote in message
In article , () wrote: As a tube driver, and knowing what was what and background information to many things (as any tube staff would), I soon came to realise that most stuff reported about the tube / strikes / whatever was at best misleading or inadequate or at worse, downright lies. As a consequence, I normally treat any newspaper as a comic on the basis that most of what is printed is irrelevant or rubbish! I'm afraid my experience is much the same about anything I know directly about, sadly. To be fair to journos, this is more because they don't have time to find out what they need to know than because they can't be arsed to do so. Yes, I've often been interviewed by journalists from the trade press about my specialist subject (not railways). The UK journos tend to be worse than their, say, French, German or US equivalents, but better than the South Africans. More often than not, these days they're new to the subject and often freelance with just a few hours to research and write a story with no relevant background to draw on. Even if they do a reasonably competent job, the sub-editors dumb it down further, if only by using mixed-case for acronyms. It was better 10 or 20 years ago, but the press now operates on much thinner margins, with less advertisinng to fund it, and having to compete with free Web sources (and news groups, of course). Most UK trade magazines have a skeleton full-time staff, with the gaps filled by freelancers and correspondents (plus advertorial). The press in non-English speaking countries suffers less from on-line competition, and consequently has declined more slowly. |
What does it take to be a Transport Correspondent?
On Apr 21, 7:18*pm, Tom Anderson wrote:
On Thu, 21 Apr 2011, Capt. Deltic wrote: On 21 Apr, 09:58, wrote: On Thu, 21 Apr 2011 09:33:41 +0100 Graeme Wall wrote: Pedantically they have motors, not engines. �The latter being those nasty infernal combustion thingies. �Motors run on nice clean electrickery. Tell that to Arthur Daley! To be even more pedantic, an engine generates power, while a motor consumes power. What? *What*? 'Generates' power? 'Consumes' power? Has that small matter called the first law of thermodynamics passed you by? I assume Uncle Roger means "shaft power" as used in the context of the second law applied to a control volume (ie work rather than heat). All any of these devices do is convert energy from one form to another. They might be coupled to devices capable of storing energy. But whenever they are in operation, the flows of energy in and out are equal; not all of the energy coming out will be useful, but it's there. A flow of energy is power, and so all these devices do is convert power from one form to another. An electric motor converts electrical power to mechanical power. An internal combustion engine converts chemical power - a flow of constant mass in which the output has a lower chemical potential than the input - into mechanical power. An external combustion engine - if you were inclined to exclude the boiler - converts pressure power (which can't be the right name - aerostatic power?) into mechanical power. They're all just power converters. Calling one an engine and one a motor is a matter of convention. It's preposterous to ascribe a fundamental meaning to the distinction. The distinction is related to the second law. A motor converts "work" to other "work" while an engine converts heat to work (and some left over heat). Robin |
What does it take to be a Transport Correspondent?
On 21 Apr, 17:36, Graeme Wall wrote:
On 21/04/2011 15:58, Capt. Deltic wrote: While we're OT let's have a test of other interests. The diesel engines include two Oliver Tigers. *Does that mean anything to anyone in this NG? *No remarks about sad gits going in circles, please. Dredging my memory, isn't that a very old model aircraft engine? *From another sad git. -- Graeme Wall This account not read, substitute trains for rail. Railway Miscellany at www.greywall.demon.co.uk/rail Thanks for confirming my general exoperience that however recherche the topic, someone on UKR will iknow about it. Indeed, diesel engines hand made by Mr John Oliver. Which somehow combined easy starting, good 'throttleability' with lots of power. not to be confused with the Italian Super Tigre (got one of those too?. Death to glow-plugs. roger |
What does it take to be a Transport Correspondent?
On Fri, 22 Apr 2011 03:30:17 -0700 (PDT)
bob wrote: The distinction is related to the second law. A motor converts "work" to other "work" while an engine converts heat to work (and some left over heat). Internal combustion engines don't convert heat to work. The work is done by the pressure of the gas from the chemical reaction. Heat is a useless byproduct of this reaction that has to be got rid of. B2003 |
What does it take to be a Transport Correspondent?
On Apr 22, 3:53*pm, wrote:
Internal combustion engines don't convert heat to work. The work is done by the pressure of the gas from the chemical reaction. Heat is a useless byproduct of this reaction that has to be got rid of. I suggest you study thermodynamics andn especially the Otto Cycle and the Diesel Cycle. -- Nick |
What does it take to be a Transport Correspondent?
On Fri, 22 Apr 2011 08:09:23 -0700 (PDT)
D7666 wrote: On Apr 22, 3:53=A0pm, wrote: Internal combustion engines don't convert heat to work. The work is done by the pressure of the gas from the chemical reaction. Heat is a useless byproduct of this reaction that has to be got rid of. I suggest you study thermodynamics andn especially the Otto Cycle and the Diesel Cycle. I would suggest you basic physics. A small volume of liquid is converted into a large volume of gas in a confined space. The fact that heat is also generated is irrelevant other than the chemical reaction requires it to be self sustaining. There are plenty of other chemicals you could react in liquid form that produce heat but no gas - try squirting them in your cylinders and see how well the engine works. B2003 |
What does it take to be a Transport Correspondent?
On Fri, 22 Apr 2011 08:09:23 -0700, D7666 wrote:
On Apr 22, 3:53Â*pm, wrote: Internal combustion engines don't convert heat to work. The work is done by the pressure of the gas from the chemical reaction. Heat is a useless byproduct of this reaction that has to be got rid of. I suggest you study thermodynamics andn especially the Otto Cycle and the Diesel Cycle. There's a reason they're all collectively known as "heat engines". And to state that "the work is done by the pressure of the gas" and then go on to say that "Heat is a useless byproduct" suggests that the very concept of equations of state (starting with PV = NkT) has passed someone by. -- From the Model M of Andy Breen, speaking only for himself. |
What does it take to be a Transport Correspondent?
On Apr 22, 4:27*pm, wrote:
I suggest you study thermodynamics andn especially the Otto Cycle and the Diesel Cycle. I would suggest you basic physics. I have. I am an engineer. Thermodynamics is fundamental. I suggest you study it before you bury yourself deeper. There is waste heat yes, but it is heat that does the work. Heat does all the useful work, the waste heat is that which can't be used. -- Nick |
What does it take to be a Transport Correspondent?
On Fri, 22 Apr 2011 09:21:57 -0700, D7666 wrote:
On Apr 22, 4:27Â*pm, wrote: I suggest you study thermodynamics andn especially the Otto Cycle and the Diesel Cycle. I would suggest you basic physics. I have. I am an engineer. Thermodynamics is fundamental. I suggest you study it before you bury yourself deeper. There is waste heat yes, but it is heat that does the work. Heat does all the useful work, the waste heat is that which can't be used. http://www.iankitching.me.uk/humour/hippo/entropy.html Refers. -- From the Model M of Andy Breen, speaking only for himself. |
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On Apr 22, 5:28*pm, Andy Breen wrote:
http://www.iankitching.me.uk/humour/hippo/entropy.html Refers. :o) Alas that will be lost on the very object who could do with it the most. -- Nick |
What does it take to be a Transport Correspondent?
On Fri, 22 Apr 2011 09:34:30 -0700, D7666 wrote:
On Apr 22, 5:28Â*pm, Andy Breen wrote: http://www.iankitching.me.uk/humour/hippo/entropy.html Refers. :o) Alas that will be lost on the very object who could do with it the most. I fear that entropy enjoyed an early triumph in his cognitive processes. -- From the Model M of Andy Breen, speaking only for himself |
What does it take to be a Transport Correspondent?
On Fri, 22 Apr 2011 16:06:12 +0000 (UTC)
Andy Breen wrote: I suggest you study thermodynamics andn especially the Otto Cycle and the Diesel Cycle. There's a reason they're all collectively known as "heat engines". And to state that "the work is done by the pressure of the gas" and then go on to say that "Heat is a useless byproduct" suggests that the very concept of equations of state (starting with PV = NkT) has passed someone by. It IS done by the gas pressure. The energy is the bond energy in the fuel - its not stored in the fuel as heat FFS. The heat will increase the pressure somewhat but its effect is minimal. If you could somehow reduce the temperature to ambient after the reaction had finished the gas would still be under pressure and would still push the piston down. If you two seriously think the heating of the gas is solely responsible for the work done on a piston then you might want to explain why we're not using hot air balloons to lauch the space shuttle. B2003 |
What does it take to be a Transport Correspondent?
On Apr 22, 5:42*pm, wrote:
If you two seriously think the heating of the gas is solely responsible for the work done on a piston You have already been told - PV=NKT And we never said what you just said we said. -- Nick |
What does it take to be a Transport Correspondent?
On Fri, 22 Apr 2011 16:35:59 +0000 (UTC)
Andy Breen wrote: http://www.iankitching.me.uk/humour/hippo/entropy.html Refers. :o) Alas that will be lost on the very object who could do with it the most. I fear that entropy enjoyed an early triumph in his cognitive processes. Water turning to ice can crack stone or raise objects increasing their potential energy. It requires heat to be removed for this to happen, not added. So where does that leave your simplistic 19th century argument now? B2003 |
What does it take to be a Transport Correspondent?
On Apr 22, 5:50*pm, wrote:
I fear that entropy enjoyed an early triumph in his cognitive processes. Water turning to ice can crack stone or raise objects increasing their potential energy. It requires heat to be removed for this to happen, not added. So where does that leave your simplistic 19th century argument now? You really REALLY R-E-A-L-L-Y do need to study thermodynamics. When you do, you will realise where entropy comes into all that and what we are talking about. You are just burying yourself deeper and deeper by continuing to argue about a subject you clearly know little about. I'll leave you to either study what we have recommended or go on on your false belief. Your choice. Either way this is the last comment from me as clearly you don't want to take advice form professionals who do this sort of thing for a living. -- Nick |
What does it take to be a Transport Correspondent?
D7666 wrote:
On Apr 22, 5:50*pm, wrote: I fear that entropy enjoyed an early triumph in his cognitive processes. Water turning to ice can crack stone or raise objects increasing their potential energy. It requires heat to be removed for this to happen, not added. So where does that leave your simplistic 19th century argument now? You really REALLY R-E-A-L-L-Y do need to study thermodynamics. When you do, you will realise where entropy comes into all that and what we are talking about. You are just burying yourself deeper and deeper by continuing to argue about a subject you clearly know little about. I'll leave you to either study what we have recommended or go on on your false belief. Your choice. Either way this is the last comment from me as clearly you don't want to take advice form professionals who do this sort of thing for a living. Pearls before swine, Nick ... pearls before swine. ;-) |
What does it take to be a Transport Correspondent?
On Fri, 22 Apr 2011 09:55:48 -0700 (PDT)
D7666 wrote: On Apr 22, 5:50=A0pm, wrote: I fear that entropy enjoyed an early triumph in his cognitive processes. Water turning to ice can crack stone or raise objects increasing their potential energy. It requires heat to be removed for this to happen, not = added. So where does that leave your simplistic 19th century argument now? You really REALLY R-E-A-L-L-Y do need to study thermodynamics. When you do, you will realise where entropy comes into all that and what we are talking about. So fill me in then. If heat is required to do work why does removing heat from water to form ice also do work. A simple 1 line explanation will do. I'm sure you're up to the task since apparently you're an expert. B2003 |
What does it take to be a Transport Correspondent?
On Sat, 23 Apr 2011 11:12:36 +0100
Jeremy Double wrote: Heat will spontaneously flow from a high temperature to a low temperature, but not in the other direction (this is the "Zeroth law of thermodynamics"). If you want to create ice when the ambient temperature is above 0 deg C, then work is needed to pump the heat "uphill" from the water you are freezing to the surroundings. That's what the motor does in a refrigerator. The work used to pump the heat need not come from a heat source itself, it could come from hydro power, for instance. But the work done by water expanding as it freezes will be considerably less than the work needed to freeze the water in the first place. I'm not talking about in a fridge - I'm talking about water sitting outside on a cold night with the heat disappearing off into space. No energy is being used to remove the heat yet the water freezes and the ice can do work on anything nearby as it expands. If what is being claimed is true - ie that heat is always required to do work then this should be impossible. Clearly it isn't so that rule is wrong in this instance just as it doesn't apply inside a car cylinder which was my initial statement. B2003 |
What does it take to be a Transport Correspondent?
On Fri, 22 Apr 2011, bob wrote:
On Apr 21, 7:18*pm, Tom Anderson wrote: On Thu, 21 Apr 2011, Capt. Deltic wrote: On 21 Apr, 09:58, wrote: On Thu, 21 Apr 2011 09:33:41 +0100 Graeme Wall wrote: Pedantically they have motors, not engines. �The latter being those nasty infernal combustion thingies. �Motors run on nice clean electrickery. Tell that to Arthur Daley! To be even more pedantic, an engine generates power, while a motor consumes power. What? *What*? 'Generates' power? 'Consumes' power? Has that small matter called the first law of thermodynamics passed you by? I assume Uncle Roger means "shaft power" as used in the context of the second law applied to a control volume (ie work rather than heat). I'm afraid i'm not familiar with the term "shaft power"; a quick google suggests it means the mechanical power at the drive shaft, but i don't see how that's relevant here. Is that what you meant? In what way does an electric motor consume it? Calling one an engine and one a motor is a matter of convention. It's preposterous to ascribe a fundamental meaning to the distinction. The distinction is related to the second law. A motor converts "work" to other "work" while an engine converts heat to work (and some left over heat). There's no difference between what a combustion and an electric engine do he matter flows from a place where it has a high potential to where it has a low potential, increasing entropy as a result, and that flow is harnessed to turn a shaft. In a combusion engine, the matter is steam or combustion gases, and the potential is of the heat-and-pressure kind. In an electric engine, the matter is electrons, and the potential is of the electrical kind. To get another angle on it, do you think a watermill is a motor or an engine? What about a piston engine driven by pressurised water? IMHO, the whole heat/work dichotomy has been really unhelpful since it did its part in getting thermodynamics started. There are states with different potentials, and various amounts of stuff in those states. Stuff wants to flow from high-potential states to low-potential states, and you can harness such flows. There's no value in drawing a distinction between potentials where the states are is in the same place in space (eg chemical potential, electron potential in an atom) and those where they aren't (primarily heat gradients). tom -- If I want consciousness expansion, i go to my local tabernacle and i SING! |
What does it take to be a Transport Correspondent?
On 22/04/2011 11:57, Capt. Deltic wrote:
On 21 Apr, 17:36, Graeme wrote: On 21/04/2011 15:58, Capt. Deltic wrote: While we're OT let's have a test of other interests. The diesel engines include two Oliver Tigers. Does that mean anything to anyone in this NG? No remarks about sad gits going in circles, please. Dredging my memory, isn't that a very old model aircraft engine? From another sad git. -- Graeme Wall This account not read, substitute trains for rail. Railway Miscellany atwww.greywall.demon.co.uk/rail Thanks for confirming my general exoperience that however recherche the topic, someone on UKR will iknow about it. Indeed, diesel engines hand made by Mr John Oliver. Which somehow combined easy starting, good 'throttleability' with lots of power. Never had one myself but friends used to swear by them not to be confused with the Italian Super Tigre (got one of those too?. Death to glow-plugs. Aforesaid friends used to swear at them! Me I never really moved on from rubber bands, preferred gliders myself. -- Graeme Wall This account not read, substitute trains for rail. Railway Miscellany at www.greywall.demon.co.uk/rail |
What does it take to be a Transport Correspondent?
On Sat, 23 Apr 2011 10:20:22 +0000 (UTC), d put
finger to keyboard and typed: On Sat, 23 Apr 2011 11:12:36 +0100 Jeremy Double wrote: Heat will spontaneously flow from a high temperature to a low temperature, but not in the other direction (this is the "Zeroth law of thermodynamics"). If you want to create ice when the ambient temperature is above 0 deg C, then work is needed to pump the heat "uphill" from the water you are freezing to the surroundings. That's what the motor does in a refrigerator. The work used to pump the heat need not come from a heat source itself, it could come from hydro power, for instance. But the work done by water expanding as it freezes will be considerably less than the work needed to freeze the water in the first place. I'm not talking about in a fridge - I'm talking about water sitting outside on a cold night with the heat disappearing off into space. No energy is being used to remove the heat yet the water freezes and the ice can do work on anything nearby as it expands. The energy being used is the heat from the sun which liquifies the water to begin with. That energy is stored in the water in liquid form, and used up when the water reverts to ice. If it were not for the heat applied in the first instance, water would never be liquid at all. The natural (ie, non-energetic) form of water is ice. The only reason we assume that the normal form is a liquid is because we live in an environment where heat is being continuously applied to it in order to keep it that way. Mark -- Blog: http://mark.goodge.co.uk Stuff: http://www.good-stuff.co.uk |
What does it take to be a Transport Correspondent?
On 23/04/2011 11:20, d wrote:
On Sat, 23 Apr 2011 11:12:36 +0100 Jeremy wrote: Heat will spontaneously flow from a high temperature to a low temperature, but not in the other direction (this is the "Zeroth law of thermodynamics"). If you want to create ice when the ambient temperature is above 0 deg C, then work is needed to pump the heat "uphill" from the water you are freezing to the surroundings. That's what the motor does in a refrigerator. The work used to pump the heat need not come from a heat source itself, it could come from hydro power, for instance. But the work done by water expanding as it freezes will be considerably less than the work needed to freeze the water in the first place. I'm not talking about in a fridge - I'm talking about water sitting outside on a cold night with the heat disappearing off into space. No energy is being used to remove the heat yet the water freezes and the ice can do work on anything nearby as it expands. If what is being claimed is true - ie that heat is always required to do work then this should be impossible. Heat isn't always required to do work _directly_: hydro-power uses the potential energy of water flowing downhill to perform work, for instance. But in that case the energy that moved the water from the seas to the hills to allow it to perform work came from the heat of the sun. If work is performed using heat as the energy source, then the laws of thermodynamics apply, and there is a limit to the amount of work that can be got out of a certain quantity of heat, which can be calculated from the ratio of the absolute temperature of the heat source to the absolute temperature of the heat sink. Clearly it isn't so that rule is wrong in this instance just as it doesn't apply inside a car cylinder which was my initial statement. You originally wrote: Internal combustion engines don't convert heat to work. The work is done by the pressure of the gas from the chemical reaction. Heat is a useless byproduct of this reaction that has to be got rid of. Internal combustion engines _are_ a type of heat engine, they do convert heat to work. The laws of thermodynamics apply to them just as they do to a steam engine or steam turbine. The only difference is that the heat is created inside the cylinder, not outside. The fuel burns in the air charge, converting chemical energy to (mostly) heat and a small amount of work. The heat causes the gases to expand, allowing them to do work and move the piston. Almost all of the expansion of the combustion gases is due to the heat liberated by combustion, not due to the increased number of moles of gas (for instance, 1 mole of carbon burning uses 1 mole of oxygen to give 1 mole of carbon dioxide). Remember that most of the gas in the cylinder of an engine is nitrogen from the charge air (air is about 79% nitrogen). You are right that there is some useless heat created in combustion, which has to be got rid of. That is a consequence of the second law of thermodynamics, which says that there is a limit to the amount of heat that can be converted to work. The useful work depends on the ratio of the temperatures of the heat source (i.e. the combustion temperature of the fuel) to the heat sink (i.e. the temperature of the exhaust gas). If you need to understand this better, I suggest you read the book I quoted. -- Jeremy Double {real address, include nospam} Rail and transport photos at http://www.flickr.com/photos/jmdoubl...7603834894248/ |
What does it take to be a Transport Correspondent?
On 23/04/2011 11:12, Jeremy Double wrote:
Thermodynamics is a very important subject for understanding how the technological world works. If you don't understand thermodynamics, then a relatively simple book which explains it (without all the differential equations that are usually found in thermodynamics textbooks) is "The refrigerator and the universe: understanding the laws of energy" by Martin Goldstein and Inge F Goldstein, published by the Harvard University Press in 1993. Or there is Flanders & Swann, definitely no calculus. -- Graeme Wall This account not read, substitute trains for rail. Railway Miscellany at www.greywall.demon.co.uk/rail |
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On Apr 23, 11:25*am, Tom Anderson wrote:
On Fri, 22 Apr 2011, bob wrote: On Apr 21, 7:18�pm, Tom Anderson wrote: On Thu, 21 Apr 2011, Capt. Deltic wrote: On 21 Apr, 09:58, wrote: On Thu, 21 Apr 2011 09:33:41 +0100 Graeme Wall wrote: Pedantically they have motors, not engines. �The latter being those nasty infernal combustion thingies. �Motors run on nice clean electrickery. Tell that to Arthur Daley! To be even more pedantic, an engine generates power, while a motor consumes power. What? *What*? 'Generates' power? 'Consumes' power? Has that small matter called the first law of thermodynamics passed you by? I assume Uncle Roger means "shaft power" as used in the context of the second law applied to a control volume (ie work rather than heat). I'm afraid i'm not familiar with the term "shaft power"; a quick google suggests it means the mechanical power at the drive shaft, but i don't see how that's relevant here. Is that what you meant? In what way does an electric motor consume it? That is the derivation of the term, but thermodynamically things like electricity and magnetic forces Behave in the same way. It is a general term for energy entering a system that does not have an associated entropy change with it. Calling one an engine and one a motor is a matter of convention. It's preposterous to ascribe a fundamental meaning to the distinction. The distinction is related to the second law. *A motor converts "work" to other "work" while an engine converts heat to work (and some left over heat). There's no difference between what a combustion and an electric engine do he matter flows from a place where it has a high potential to where it has a low potential, increasing entropy as a result, and that flow is harnessed to turn a shaft. In a combusion engine, the matter is steam or combustion gases, and the potential is of the heat-and-pressure kind. In an electric engine, the matter is electrons, and the potential is of the electrical kind. The difference is entropy. In a control volume type analysis, shaft work (electrical power) adds no entropy to the system, heat transfer does. If you have a motor, you put some work in and get some work out (in the case of hydraulics the difference in work is the pressure x volume pumping work to get it in or out). In a heat engine (including all combustion engines) the second law places constraints on the engine behaviour requirig a heat rejection as well as heat input and work input in order to do work. It all comes down to entropy. To get another angle on it, do you think a watermill is a motor or an engine? What about a piston engine driven by pressurised water? Water mill: work done by a falling weight is converted to work in a shaft. No heat. Hydraulic motor: work done pumping water in is converted to work in the shaft. No heat. IMHO, the whole heat/work dichotomy has been really unhelpful since it did its part in getting thermodynamics started. There are states with different potentials, and various amounts of stuff in those states. Stuff wants to flow from high-potential states to low-potential states, and you can harness such flows. There's no value in drawing a distinction between potentials where the states are is in the same place in space (eg chemical potential, electron potential in an atom) and those where they aren't (primarily heat gradients). But to ignore the difference between these is to ignore entropy and to therefore ignore the second law of thermodynamics. The entire basis of the second law is the difference between heat and work, the relation between heat and temperature, and the limitations on things like the maximum efficiency of heat engines (motors can be100% efficient, heat engines can not). Robin |
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"bob" wrote in message
... [...] It's not just the "Standard". Christian Wolmar, writing in Friday's "Times" states that an HST "has a locomotive at one end". Last time I checked, it was one at each end. A pity, since his basic premise that it is nuts to transport dead diesel engines round under the wires (in bi-mode IEP) was sound. Regards Jonathan |
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On Sat, 23 Apr 2011 13:11:36 +0100, Jonathan Morton wrote:
"bob" wrote in message news:7087ab16-d6c1-45c5-b5b6- ... [...] It's not just the "Standard". Christian Wolmar, writing in Friday's "Times" states that an HST "has a locomotive at one end". Last time I checked, it was one at each end. Maybe he was thinking back to the period when the HSTs were being re- numbered, and some sets would have had something in the 43xxx range at one end and something in the 254xxx at the other - a locomotive at one end and a DEMU driving motor brake at the other? ;-) -- From the Model M of Andy Breen, speaking only for himself |
What does it take to be a Transport Correspondent?
In message , at 13:11:36 on
Sat, 23 Apr 2011, Jonathan Morton remarked: It's not just the "Standard". Christian Wolmar, writing in Friday's "Times" states that an HST "has a locomotive at one end". Yerse - but it does have a locomotive at one end... and another at the other end :) -- Roland Perry |
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What does it take to be a Transport Correspondent?
On Sat, 23 Apr 2011 11:56:21 +0100
Jeremy Double wrote: If what is being claimed is true - ie that heat is always required to do work then this should be impossible. Heat isn't always required to do work _directly_: hydro-power uses the Exactly. Which was my point. allowing them to do work and move the piston. Almost all of the expansion of the combustion gases is due to the heat liberated by combustion, not due to the increased number of moles of gas (for instance, 1 mole of carbon burning uses 1 mole of oxygen to give 1 mole of carbon dioxide). Remember that most of the gas in the cylinder of an engine is nitrogen from the charge air (air is about 79% nitrogen). That doesn't matter - 1 mole of CO2 at room temperature takes up vastly more volume than 1 mole of liquid a hydrocarbon. If all the reaction did was to heat the air in the cylinder up by 500 hundred degrees and didn't produce any extra gas then very little would happen. The same applies to a steam engine - you don't heat air up and shove hot air into the cylinders, you need to convert a liquid (water) into a gas (steam) to get work out. B2003 |
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On Apr 21, 1:07*pm, Paul Corfield wrote:
On Wed, 20 Apr 2011 22:40:29 +0100, "Jack Taylor" wrote: The standard of railway-related writing has, for some while, been plummeting steadily lower and we often lambast the BBC for their reporting but today's efforts in the London "Evening Standard" by their Transport Correspondent, Dick Murray, are spectacularly dismal. It is interesting to note that a fair proportion of the comments under today's "6 lines closed over Easter" article are strongly critical of the article and the quality of the journalism. No longer the case - perhaps a moderator's been along? The article in question* did annoy me on Thursday, particularly for its opening sentence: "Huge sections of London's transport system will shut down over the four-day Easter break, it emerged today." Er, no, it didn't emerge on Thursday. It probably emerged weeks, if not months before on http://www.tfl.gov.uk/livetravelnews...r/default.aspx - and also the day previously in TfL's weekly closures email. * http://goo.gl/DXO66 or http://www.thisislondon.co.uk/standa...er-meltdown.do |
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On Mon, 25 Apr 2011 03:51:02 -0700 (PDT)
martin wrote: "Huge sections of London's transport system will shut down over the four-day Easter break, it emerged today." Er, no, it didn't emerge on Thursday. It probably emerged weeks, if When journos say "it emerged today" what they actually mean is "I just heard about it today when my sub editor told me to look into it". That said, it doesn't make LU's **** poor planned works schedule look any better. B2003 |
What does it take to be a Transport Correspondent?
On 25/04/2011 09:25, d wrote:
On Sat, 23 Apr 2011 11:56:21 +0100 Jeremy wrote: allowing them to do work and move the piston. Almost all of the expansion of the combustion gases is due to the heat liberated by combustion, not due to the increased number of moles of gas (for instance, 1 mole of carbon burning uses 1 mole of oxygen to give 1 mole of carbon dioxide). Remember that most of the gas in the cylinder of an engine is nitrogen from the charge air (air is about 79% nitrogen). That doesn't matter - 1 mole of CO2 at room temperature takes up vastly more volume than 1 mole of liquid a hydrocarbon. If all the reaction did was to heat the air in the cylinder up by 500 hundred degrees and didn't produce any extra gas then very little would happen. The same applies to a steam engine - you don't heat air up and shove hot air into the cylinders, you need to convert a liquid (water) into a gas (steam) to get work out. You're talking complete b*******. 1. The volume of one mole CO2 gas is no greater than the volume of the one mole carbon (from either solid or liquid fuel) plus the one mole of oxygen from the air needed to burn it (at the same temperature). 2. If you keep the volume the same, a quantity of air at 500 deg C has nearly three times the pressure of the same quantity of air at ambient temperatures. (This is easily estimated using the Ideal Gas Law or a more sophisticated equation of state such as Van der Waals). And the adiabatic combustion temperature of hydrocarbon fuel is _a lot_ higher than 500 deg C. 3. There is a well-known external-combustion hot-air engine, called the Stirling engine. This was invented by a clergyman, Robert Stirling, father of the 19th century steam locomotive engineers Patrick and James Stirling. It's not as commonly used as the steam engine, but that doesn't mean it's impossible. I suggest you learn some thermodynamics before making further pronouncements. -- Jeremy Double {real address, include nospam} Rail and transport photos at http://www.flickr.com/photos/jmdoubl...7603834894248/ |
What does it take to be a Transport Correspondent?
On Tue, 26 Apr 2011 07:36:39 +0100
Jeremy Double wrote: That doesn't matter - 1 mole of CO2 at room temperature takes up vastly more volume than 1 mole of liquid a hydrocarbon. If all the reaction did was to heat the air in the cylinder up by 500 hundred degrees and didn't produce any extra gas then very little would happen. The same applies to a steam engine - you don't heat air up and shove hot air into the cylinders, you need to convert a liquid (water) into a gas (steam) to get work out. You're talking complete b*******. 1. The volume of one mole CO2 gas is no greater than the volume of the one mole carbon (from either solid or liquid fuel) plus the one mole of oxygen from the air needed to burn it (at the same temperature). Ok, you've got me there. However , it doesn't just produce CO2, it produces steam which is also a gas at those temperatures so you do end up with more gas that you had before since 1 molecule of O2 gives rise to 2 molecules of water. Mind you , it requires heat to convert the water into steam which rather undermines my original argument. Ah well, can't win them all! 3. There is a well-known external-combustion hot-air engine, called the Stirling engine. This was invented by a clergyman, Robert Stirling, father of the 19th century steam locomotive engineers Patrick and James Stirling. It's not as commonly used as the steam engine, but that doesn't mean it's impossible. Since the wikipedia entry on it is huge and I don't have time to read it I'm not going to comment other than to say it can't be that efficient or powerful or we'd all be using them today. I suggest you learn some thermodynamics before making further pronouncements. Actually I think its more my chemistry I need to brush up on. B2003 |
What does it take to be a Transport Correspondent?
On Apr 26, 10:38*am, wrote:
On Tue, 26 Apr 2011 07:36:39 +0100 Jeremy Double wrote: That doesn't matter - 1 mole of CO2 at room temperature takes up vastly more volume than 1 mole of liquid a hydrocarbon. If all the reaction did was to heat the air in the cylinder up by 500 hundred degrees and didn't produce any extra gas then very little would happen. The same applies to a steam engine - you don't heat air up and shove hot air into the cylinders, you need to convert a liquid (water) into a gas (steam) to get work out. You're talking complete b*******. 1. The volume of one mole CO2 gas is no greater than the volume of the one mole carbon (from either solid or liquid fuel) plus the one mole of oxygen from the air needed to burn it (at the same temperature). Ok, you've got me there. However , it doesn't just produce CO2, it produces steam which is also a gas at those temperatures so you do end up with more gas that you had before since 1 molecule of O2 gives rise to 2 molecules of water. Mind you , it requires heat to convert the water into steam which rather undermines my original argument. Right, let's have some numbers here. Consider an Air Standard Otto Cycle. This is a conceptual cycle used for teaching engine thermodynamics, is an approximation to the characteristics of a petrol engine. In this cycle, air is compressed by a certain volume ratio, then heat is added at constant volume (reflecting the fact that combustion is fast compared with the rotating speed of engines), then the resultant mix is expanded by the same volume ratio back to the initial volume, and heat is rejected to restore the initial conditions. There is no change in the chemistry of the working fluid. If we take initial conditions of 288 K (about 15 celsius) and 10^5 Pa (1 bar). Let's let the maximum combustion temperature be 1600 K (to reflect material limitations in our engine), and assume a compression ratio of 10 (ie the ratio of compressed volume to uncompressed volume). Assuming air to have a specific gas constant of 287 kJ/kg K and gamma of 1.4, and idealised compression/expansion, and a cp of 1006 kJ/kg K (reasonable values, you can look them up), then after compression, before combustion, the gas conditions are 24.5x10^5 Pa and 748.5 K. After the heat addition, the conditions are 53.14x10^5 Pa and 1600 K, with the conditions at the end of expansion being 637 K and 2.09x10^5 Pa. The heat addition here is (1600-748.5)*(1006-287)=61.2 kJ/kg (ie per kg of air in the cylinder), producing a pressure increase of 2.14 times. Now, petrol has a lower calorific value of 44.4 MJ/kg (but the values for hydrocarbon fuels are all in the mid 40s, changing between methane and heavy oil makes no big difference), so to get 61.2 kJ we would need to burn 1.3 grammes of petrol for every kg of air. In molar terms, that's 0.011 moles of fuel burning in 34.5 moles of air. If we assume petrol to be octane (C8H18), then the combustion reaction will be C8H18 + 12.5O2 - 8CO2 + 9H2O For 0.011 moles of petrol, we consume 0.011 moles of fuel (the fuel is in the gas phase at this temperature and pressure) and 0.1375 moles of O2 and create 0.187 moles of combustion products. So we have 34.511 moles in the gas phase to start with and 34.5495 moles after combustion. The fact is, the heat release from the fuel is so enormous that the effect of the heat release is several orders of magnitude greater than the effect of changes in mole numbers. 3. There is a well-known external-combustion hot-air engine, called the Stirling engine. *This was invented by a clergyman, Robert Stirling, father of the 19th century steam locomotive engineers Patrick and James Stirling. *It's not as commonly used as the steam engine, but that doesn't mean it's impossible. Since the wikipedia entry on it is huge and I don't have time to read it I'm not going to comment other than to say it can't be that efficient or powerful or we'd all be using them today. Stirling engines can be both efficient and powerful. The problem with them is that they require heat to be transferred from metal to air in the heat addition and rejection stages, and gases generally have poor heat transfer properties, meaning very large heat exchangers. Liquids, on the other hand, have massively better heat transfer characteristics, so heating water in a boiler and cooling it in a condenser gives rise to a much smaller (cheaper) peice of kit, in the form of a steam cycle, for similar performance. Robin |
What does it take to be a Transport Correspondent?
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What does it take to be a Transport Correspondent?
On Tue, 26 Apr 2011 11:22:42 -0700 (PDT)
bob wrote: The fact is, the heat release from the fuel is so enormous that the effect of the heat release is several orders of magnitude greater than the effect of changes in mole numbers. Ok, fine. I'm big enough to admit when I've got it wrong unlike a lot of people on here. B2003 |
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