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Using ship fuel as aviation fuel?



 
 
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  #11  
Old April 16th 04, 08:10 AM
Eunometic
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"Tarver Engineering" wrote in message ...
"John R Weiss" wrote in message
news:[email protected]_s51...

snip
I've talked
with several "oil kings" in the past, and they all told me the diesels

much
preferred diesel fuel over JP because of its lubricity and energy content.

The
big turbines didn't much care.


The high compression ratios for diesel piston engines cause detonation using
wide cut jet fuel.


Multi-fuel diesel engines can be built and frequently are for the
military vehicles such as tanks. It involves specialy adjustable
injection systems and other provisions to do with lubriticity.
Running on Jet fuel or Gaoline is not problem in the short term for
such engines.

A critical factor for the diesel engine is the "cetane number" and it
is important to have a high centane number. A high cetane number
means that the fuel will ignite easily but burn slowly.

One problem that the German Fischer Tropsh snthetic fuel plants had in
WW2 was that the fuel had far to high a cetane number and burned a
little to slowly. This lowered efficiency and increased exhaust
temperature althout it had to be used frequently. The solution was to
blend the fuel with the low cetane output of the Bergius Hydrogenation
plants.

At one point prior to WW2 kerosene powered spark ignition were quite
popular and they still have their proponents.

Gas turbines are ofcourse indifferent to both centane number and
octane rating and even viscosity and are uneffected in life or
efficiency (whuch reduce in multifuel diesels)

At the moment there are attempts to develop 'photo detonation'
internal combustion engines that do not rely on deflageration
combustion (ie combustion along a flame front rather than by infra red
light) and thus will be indifferent to octane ratings.
Ads
  #12  
Old April 16th 04, 09:21 AM
scott s.
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"Thomas Schoene" wrote in
hlink.net:


I suggest the same for you, especialy before you dismiss a reasonable
question from a regualr, and usually well-informed, poster.

1) Ship power plants are not "jet engines" -- they are marine gas
turbines. Sometimes these are derived from aircraft jet engines, but
they are not the same. Terminology matters.

2) Marine gas turbines can burn fuels, like F76 diesel, that are not
considered suitable for aircraft engines. They can also burn jet fuel,
but the reverse is not true. A jet aircraft probably cannot burn F76,
at least not for very long. So I'd agree with several earlier posts
that this "swing" tankage would be jet fuel diverted to ship
propulsion if need be, rather than F76 diverted to aircraft use.


In the 963/47 classes, there are cross connects from the JP-5 system
to the FO service system. We did a test, back in the 70s, running
one of the Allison GTGs on JP-5 only. I think NAVSEA was interested in
the impact on the fuel nozzles. I don't think the results showed that
JP-5 was cost effective as a replacement for Nato F-76.

IIRC, the emergency diesel (tandem Detroit Diesel) on the 1052s
were fed JP-5? I'm having a "senior moment" on that.

I suppose it could be fixed, but once JP-5 gets into the ship's service
system, I don't think you're allowed to use it in aircraft.

I don't recall ever getting JP-5 from any CV, but what I did get was
crap. I think CVs just use the opportunity to offload their off-spec
fuel.

I can't remember now what we burned at Great Lakes, either. Probably
commercial diesel.

scott s.
..
  #13  
Old April 16th 04, 09:40 AM
Friedrich Ostertag
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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. Sometimes if the
flamefront goes supersonic this is also called "detonation". Neither
can happen on a diesel engine, as the charge contains only air and the
fuel burnes as it is injected.

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. (As a matter of fact, the same thing
applies to Diesel engines for GA aircraft, which are just hitting the
market now, and all of which run on Jetfuel!) Also energy content is
somewhat lower. If designed for it, this can be compensated by
increasing the amount of injected fuel accordingly.

regards,
Friedrich

--
bitte für persönliche Antworten die offensichtliche Änderung an meiner
Adresse vornehmen

  #14  
Old April 16th 04, 03:44 PM
Tarver Engineering
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"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.


  #15  
Old April 16th 04, 04:51 PM
John R Weiss
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"Tarver Engineering" wrote...

The high compression ratios for diesel piston engines cause detonation using
wide cut jet fuel.


AFAIK, neither JP-5 nor JP-8 nor Jet A -- the 3 jet fuels currently in common
use -- are "wide cut."

  #16  
Old April 16th 04, 05:41 PM
Tarver Engineering
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"John R Weiss" wrote in message
news:[email protected]_s01...
"Tarver Engineering" wrote...

The high compression ratios for diesel piston engines cause detonation

using
wide cut jet fuel.


AFAIK, neither JP-5 nor JP-8 nor Jet A -- the 3 jet fuels currently in

common
use -- are "wide cut."


One of them seems to be number one diesel, from what other posters have
posted here.


  #17  
Old April 16th 04, 09:43 PM
Friedrich Ostertag
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Hi,

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.

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.

regards,
Friedrich

--
for personal email please remove "entferrnen" from my adress

  #18  
Old April 17th 04, 12:37 AM
Tarver Engineering
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"Friedrich Ostertag" wrote in message
...
Hi,

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. Note that not all
diesels are the same and I believe I have heard detonation in diesel engines
on starting fluid.

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.


  #19  
Old April 17th 04, 07:15 AM
Jim E
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"Eunometic" wrote in message
om...


At the moment there are attempts to develop 'photo detonation'
internal combustion engines that do not rely on deflageration
combustion (ie combustion along a flame front rather than by infra red
light) and thus will be indifferent to octane ratings.


Where can I learn more about this?
Curious old school gear head here

Jim E


  #20  
Old April 17th 04, 07:26 AM
John Keeney
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"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.


 




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