Difference between JP8 and diesel

[mxhdroom]

OK, all you fuel experts:

We've been doing some research on the possibility of using Jet Propulsion 8 (JP8) fuel in some of our diesel equipment to reduce the types of fuels we need at some of our remote projects. From what I've seen, the main difference is that JP8's viscosity creates a pressure problem for diesel injectors and there is not as much lubricative properties in the JP8 either. So, while it may work, some mechanical modifications may have to be made for it to run reliably over the long term (in HD electrical generators, for instance).

Any comments from the rest of you? You guys and gals have helped me out a ton on the motor oil side, so I thought I'd turn to the BITOG experts for this one as well.

G.

 

[dwendt44]

Do you need that grade of jet fuel?
Early jet engines ran on plain kerosene.
In the 60's, they were up to JP-4.
The SR-71 needed JP-7, IIRC.

 

[mxhdroom]

JP8 (or its NATO equivalent) is the standard used now by many deployed air forces (although I think the navy may still use JP5), and it is what is readily available to us in bulk. So, if we can modify/standardize our equipment to run on JP8, we save storage, shipment, and supplier costs.

G.

 

[Big Jim]

As you may already know, the US armed forces have moved to single fuel for logistical reasons. Almost everything in the US military is now running JP8. One of the rare exceptions is the U2 which still uses JP7.

Those I have talked to in military maintenance groups say that they have had little or no trouble running JP8 instead of diesel. The one thing I did learn is that an "unofficial" cure for lack of lubricity on the rare occasions it seemed to be a problem was to dump some ATF or motor oil into the fuel.

 

[mxhdroom]

Thanks Big Jim!
I wonder how much they meant by dumping "some" ATF or motor oil into the JP8(what the mix ratio would be)? I wouldn't think it would take much.

G.

 

[JHZR2]

Originally Posted By: dwendt44
Do you need that grade of jet fuel?
Early jet engines ran on plain kerosene.
In the 60's, they were up to JP-4.
The SR-71 needed JP-7, IIRC.


The Navy still uses JP-5. It is not "inferior" to JP-8, on the contrary, it is actually a more finished product. JP-8 is like an additized kerosine or cross between kero and diesel. JP-5 is a high flashpoint fuel with a far narrower distrobution of hydrocarbons.

 

[Rat407]

I would think running a 2 cycle oil for lube would be better than ATF or motor oil, at least a cleaner burn, wouldn't it? I know that some of our equipment runs on JP-8 like the load jammers that load the bombs onto the jets. No issues there. We also run what is called JP-8 plus 100, it has an additive in it to help reduce the coking we are getting in our fuel tubes inside the jet engines. It is amazing how full of coke they get to the point that the tubes are just about completely blocked.

 

[mojo]

Actually, the only difference between JP8 and JP5 is their minimum flash point requirement. JP8 has a minimum limit of 100 C whereas JP5 has a minimum limit of 140 C. This higher limit is a requirement that the Navy has for all onboard fuels due to the potential for fuel vapors under deck creating an explosive situation. They both have the same additive requirements.

 

[tom slick]

I thought JP-5 was gone over 15 years ago, maybe that was only in the Air Force.

OT
I believe plus 100 was developed for a coking issue in P&W f-100 series engines' augmentor sprayrings. a non-issue on GE's equivelant F-110 series.

 

[XS650]

Check with the engine manufacturer for effects of JP8 on injection systems. With the US military requiring that all new systems with diesel engines run on JP8 for many years, any big manufacturer should be able to give you a good answer. Talk to someone familiar with their military programs, not just some regular customer rep or dealer.

Unless you recalibrate your fuel injections system, JP8 will cost you about a 5% power loss compared to DF2. It's not as dense.

Perhaps more importantly, you will also consume about 5% more JP8 to do the same amount of work you would have done with DF2.

I dug this up with the help of Mr Google. It pretty much agrees with what I remember for a development program I was running about 12 years ago that used JP8 in a diesel.

JP8 article

 

[tom slick]

I just realized I was thinking of JP-4. the USAF no longer uses JP-4.

the U-2 runs on JPTS, not JP-7.

some JP-8 info from wikipedia

Quote:
Commercial aviation uses a similar mixture under the name Jet-A. JP-8 in PIE contains icing inhibitor, corrosion inhibitors, lubricants, and antistatic agents.

JP-5 has even higher flash point than JP-8, but it also has prohibitively higher cost, limiting its use to aircraft carriers.

 

[Ken2]

JP-8

#2-D

 

[Steve S]

Sounds like the difference between Gasoline and LPG around 10% loss in power and mpgs but I would say the fuel will work as the diesel engine is flexible with the fuel it can run .If there is any major problem to be concerned about would be the amount lubricity [which may not matter]with the JP fuel as compared to D2 and possibly ease of starting .I know that it can and is done as a matter of convience .

 

[mxhdroom]

Thanks to everyone for your input. My colleague has written a position paper on the issue and hopefully our next step will be to test JP8 in one of our non-critical pieces of equipment at one of our projects. From what I've read, I don't think there will be any major issues.

I'll let you all know how it works out. Thanks again!

G.

 

[XS650]

Do you use DF1 or DFA in some of your equipment in remote sites in the winter? IIRC, JP8 has similar characteristics.