If this is your first visit, be sure to check out the FAQ by clicking the link above. You may have to register before you can post: click the register link above to proceed. To start viewing messages, select the forum that you want to visit from the selection below. |
|
|
Thread Tools | Display Modes |
#21
|
|||
|
|||
"John R Weiss" wrote:
:In the US navy, the nuclear powered carriers only carry JP4 or JP8 (and all n-board diesel-powered equipment use the JP), so any smaller ships that refuel :from the carrier (a relatively common practice) get the jet fuel. The US Navy uses neither of these fuels at sea, even to fill aircraft, much less to fill large ship's tanks. The Navy switched from JP4 (which is a hideously dangerous fuel) to JP5 about half a century ago. The Air Force later switched from JP4 to JP8 (essentially Jet-A). The Navy currently uses JP8 ashore (because it's cheaper and easier to get) and JP5 at sea (because it's safer). -- "Insisting on perfect safety is for people who don't have the balls to live in the real world." -- Mary Shafer, NASA Dryden |
#22
|
|||
|
|||
Fred J. McCall wrote in
: "John R Weiss" wrote: :In the US navy, the nuclear powered carriers only carry JP4 or JP8 and all on-board diesel-powered equipment use the JP), so any smaller :ships that refuel from the carrier (a relatively common practice) get :the jet fuel. The US Navy uses neither of these fuels at sea, even to fill aircraft, much less to fill large ship's tanks. The Navy switched from JP4 (which is a hideously dangerous fuel) to JP5 about half a century ago. The Air Force later switched from JP4 to JP8 (essentially Jet-A). IIRC the minimum allowed flash point is 140F. I uderstand that even a little JP4, if mixed with JP5, can dangerously lower flash point. scott s. .. |
#23
|
|||
|
|||
Hi Mr. Tarver,
Diesel engines cannot "detonate". The term "detonation" applies to preignition of part of the charge before ignition or before the flamefront has reached that portion of the charge. Detonation refers to more energy being imparted to the fuel air mixture by compression heating than can be absorbed without igniting the fuel. On a diesel, the fuel is not there until the very moment when it is supposed to ignite. You cannot ignite pure air, no matter how much energy you impart on it. In a turbine engine what you write is true, but you are going to have to educate me as to the process further to make me believe. What exactly is it you don't understand? You surely are aware, that a diesel engine will intake pure air, compress it (much further than a gasoline engine compresses the mixture - temperatures get really hot just from the adiabatic compression), and then injects the fuel into the compressed (and hot!) air, where it immediately ignites due to the high temperature of the compressed air. Thus my comment, that the fuel cannot preignite, as it is not there prior to the time it is supposed to ignite. No preignition - no detonation. Note that not all diesels are the same and I believe I have heard detonation in diesel engines on starting fluid. Now that's a different question, of course. As starting fluid is mixed with the intake air, it will (on a diesel) ignite at a time of it's choosing, when the compressed air is just hot enough. But this has nothing to do with the question of detonation during regular operation of a diesel engine on jetfuel. Detonation damages rod bearings and is a serious problem over the long term in reciprocating engines. Detonation can do much more than that, serious detonation can kill an engine within seconds. I have personally seen melted pistons after such an event. But still detonation is only possible in spark ignition engines, or to be more precise, in engines with external mixture building. I don't buy it. You do now? regards, Friedrich -- bitte für persönliche Antworten die offensichtliche Änderung an meiner Adresse vornehmen |
#24
|
|||
|
|||
Hi John,
Detonation refers to more energy being imparted to the fuel air mixture by compression heating than can be absorbed without igniting the fuel. Detonation damages rod bearings and is a serious problem over the long term in reciprocating engines. John, every power stroke of a diesel engine fits that definition. Diesels, by definition, compress the fuel & air to the point the fuel ignites. only air is compressed, but well beyond the point where fuel will ignite! But the fuel is only added at the moment when it is supposed to ignite. regards, Friedrich -- for personal email please remove "entfernen" from my adress |
#25
|
|||
|
|||
Friedrich Ostertag wrote: Hi Mr. Tarver, Diesel engines cannot "detonate". The term "detonation" applies to preignition of part of the charge before ignition or before the flamefront has reached that portion of the charge. Detonation refers to more energy being imparted to the fuel air mixture by compression heating than can be absorbed without igniting the fuel. On a diesel, the fuel is not there until the very moment when it is supposed to ignite. You cannot ignite pure air, no matter how much energy you impart on it. In a turbine engine what you write is true, but you are going to have to educate me as to the process further to make me believe. What exactly is it you don't understand? You surely are aware, that a diesel engine will intake pure air, compress it (much further than a gasoline engine compresses the mixture - temperatures get really hot just from the adiabatic compression), and then injects the fuel into the compressed (and hot!) air, where it immediately ignites due to the high temperature of the compressed air. Thus my comment, that the fuel cannot preignite, as it is not there prior to the time it is supposed to ignite. No preignition - no detonation. actually you were fine down to this point. what you mean is that when ther is no "premixing" there is no detonation. Detonation involves a supersonic combustion wave moving through the mixture. good discussion at http://www.safetynet.de/Seiten/articles/CMRNov99.pdf |
#26
|
|||
|
|||
In article ,
"Friedrich Ostertag" writes: Hi John, Detonation refers to more energy being imparted to the fuel air mixture by compression heating than can be absorbed without igniting the fuel. Detonation damages rod bearings and is a serious problem over the long term in reciprocating engines. John, every power stroke of a diesel engine fits that definition. Diesels, by definition, compress the fuel & air to the point the fuel ignites. only air is compressed, but well beyond the point where fuel will ignite! But the fuel is only added at the moment when it is supposed to ignite. Just so, Friedfrich. To get to teh original point, In the U.S.,(Or NATO, for that matter, Kerosene, #1 Diesel, and Jet-A type (JP-5 and JP-8) are considered interchangable. The U.S. Army, and, IIRC, all of NATO, by now, is using JP-8 as its sole aviation adn diesel fuel. in order to ease logistical demands. Jet-B type fuels, (Jet-B, JP-4), aren't considered suitable for use in Diesels. (THey've got gasoline in them) #2 Diesel fuel, used in warmer climates in the U.S., had a higher sulphur content (It doesn't anymore, pollution, you know) and some engines used the greater viscosity that they brought about to lubricate parts of teh fuel system (Injector pumps, usually). Of course, without the sulphur, it doesn't do that anymore, so there are additives available for the engines which need it. (Sort of like the aftermarket Lead Substitutes for older gasoline engines). # Heating Oil is similar, but doesn't have the Dyes placed in U.S. #2 Diesel fuel to show that the necessary fuel taxes have been paid. (Note for homeowners between Heating Oil deliveries - These dyes tend to leave residues in the cumbustor of the furnace that can shorten its life. If you need a small dollop of additional fuel, use Kerosene instead) I note the Tarver has popped in. Just to translate from Tarver to English, "Cut and Paste" means Performed Research - in this case, sources are Chevron's Technical Notes on Fuels, and the NATO logistics manuals. Mine are hard copies, buy they are probably available on the Web. As for hands-on experience, current Diesels in the family Truck Park include a 1945 Cable-Lift Catepillar D-6, and a 1959 Mack B61. -- Pete Stickney A strong conviction that something must be done is the parent of many bad measures. -- Daniel Webster |
#27
|
|||
|
|||
"John Keeney" wrote in message ... "Tarver Engineering" wrote in message ... "Friedrich Ostertag" wrote in message ... Hi NG, The high compression ratios for diesel piston engines cause detonation using wide cut jet fuel. Diesel engines cannot "detonate". The term "detonation" applies to preignition of part of the charge before ignition or before the flamefront has reached that portion of the charge. Detonation refers to more energy being imparted to the fuel air mixture by compression heating than can be absorbed without igniting the fuel. Detonation damages rod bearings and is a serious problem over the long term in reciprocating engines. John, every power stroke of a diesel engine fits that definition. Diesels, by definition, compress the fuel & air to the point the fuel ignites. Then I am correct that the diesel reciprocating engine can experiance detonation from too short a carbon molecule. Thanks, Mr. Keeney, the thread was starting to confuse me. |
#28
|
|||
|
|||
"Friedrich Ostertag" wrote in message ... Hi Mr. Tarver, Diesel engines cannot "detonate". The term "detonation" applies to preignition of part of the charge before ignition or before the flamefront has reached that portion of the charge. Detonation refers to more energy being imparted to the fuel air mixture by compression heating than can be absorbed without igniting the fuel. On a diesel, the fuel is not there until the very moment when it is supposed to ignite. You cannot ignite pure air, no matter how much energy you impart on it. In a turbine engine what you write is true, but you are going to have to educate me as to the process further to make me believe. What exactly is it you don't understand? You surely are aware, that a diesel engine will intake pure air, compress it (much further than a gasoline engine compresses the mixture - temperatures get really hot just from the adiabatic compression), and then injects the fuel into the compressed (and hot!) air, where it immediately ignites due to the high temperature of the compressed air. Thus my comment, that the fuel cannot preignite, as it is not there prior to the time it is supposed to ignite. No preignition - no detonation. So then a diesel engine is like a turbojet? Are the two stroke diesels the same as the 4 stroke version in this? |
#29
|
|||
|
|||
"Peter Stickney" wrote in message ... #2 Diesel fuel, used in warmer climates in the U.S., had a higher sulphur content (It doesn't anymore, pollution, you know) and some engines used the greater viscosity that they brought about to lubricate parts of teh fuel system (Injector pumps, usually). Nice cut and paste Pete, but there is more to #2 diesel than what you write. California made #2 diesel madatory, so that the injector clearances can be tightened. More recently, California has required additives to #2 diesel that cause the engine's seals to disintegrate. This change has managed to run this County's long haul trucking businesses to Oklahoma and other operators to evade California road taxes by filling up before entering the State. |
#30
|
|||
|
|||
"Friedrich Ostertag" writes:
As said before, Diesel engines will burn jetfuel, however the lubrication properties are much lower so the injection system has to be designed to live with that. Indeed. When I worked on a pipeline delivering JetA to CLE, we'd chat with the mechanics that maintained the refueling trucks. They were run on JetA, as was much of the ramp lice. The logistical advantage of doing so must have exceeded the cost difference of trucking in #2. The mechanics told me that neither Detroit or Cummings recommended #1, and it likely reduced the time between overhauls, but it still made sense on the bottom line. -- A host is a host from coast to & no one will talk to a host that's close........[v].(301) 56-LINUX Unless the host (that isn't close).........................pob 1433 is busy, hung or dead....................................20915-1433 |
Thread Tools | |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
AOPA Stall/Spin Study -- Stowell's Review (8,000 words) | Rich Stowell | Aerobatics | 28 | January 2nd 09 02:26 PM |
General Aviation Legal Defense Fund | Dr. Guenther Eichhorn | Aerobatics | 0 | May 11th 04 10:43 PM |
General Aviation Legal Defense Fund | Dr. Guenther Eichhorn | Aviation Marketplace | 0 | May 11th 04 10:43 PM |
Here's the Recompiled List of 82 Aircraft Accessible Aviation Museums! | Jay Honeck | Home Built | 18 | January 20th 04 04:02 PM |
Associate Publisher Wanted - Aviation & Business Journals | Mergatroide | Aviation Marketplace | 1 | January 13th 04 08:26 PM |