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Jet-A vs. diesel

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pictsidhe

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Yup, the additives are added at the time of tanker loading. Many "brand name" fuels are base stock with a certain detergent/optimiser chem pack added before the tank is filled. Tank Wagons use the "slosh" method of mixing. Will have to walk across the street to the Biodiesel guys and ask what they add.

Derswede
Biodiesel is used as a lubricant additive itself. Very slippery stuff. Might need other additives to meet national standards. Lots of home brewers run it neat. It does need careful washing.
 

Twodeaddogs

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The thing about biodiesel is that in Europe, in some countries, it is available from the pump yet some countries won't allow it to be sold in their forecourts and some car manufacturers wont allow it to be run in their cars. My 2014 Citroen Picasso has a 1.6 turbo diesel that is very efficient yet it is placarded that biodiesel is not to be used. I asked someone who knows of these things and he said that some bioddiesels clog up the electronic injectors. The older big bore Bosch injectors could cope with any kind of biodiesel. Making the stuff on an industrial scale has long since been proven and it shouldnt be beyond the wit of man to produce biodiesel for aviation, either for a compression ignition piston engine or a turbine. If you could run a small turboprop on biodiesel, for a few pence per litre, you'd be sorted.
 

donjohnston

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Just so I understand...

In order for a "diesel" engine (say an existing automotive diesel engine design) to be able to burn Jet-A, it would need some modifications? Or would it need to be built pretty much from the ground up to burn Jet-A?

And if it can be done with modifications, could they be post build modifications or would the engine need to be modified during construction?

Just curious.
 

Vigilant1

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Or, how hard would it be to add the needed lubricity modifiers to the Jet-A during fueling of the plane? There might even be a way to automatically check for/verify their presence in the plane's tanks as a backup measure.
 

pictsidhe

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A few injection systems will tolerate Jet-A. Continental and Thielert are therefore being very picky about which systems it uses. At least one of these certified conversions is using a pump from an older model engine for that reason.

Adding a modifier would be like mixing 2 stroke fuel. I would just slosh the tank a bit after fuelling and oiling a bike. In something with a fuel pump, we could add stuff then run the pump for a while to stir the tank up. Two stroke oil is dyed so you can spot premix.
 

Twodeaddogs

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Any diesel will burn Jet A. Any liquid that can be vapourised and ignited by compression will run in a diesel.The first one ran on peanut oil. A basic diesel that does not have an ECU and has large bore injectors will happily run on Jet A as long as you add lubricant so stick in some two-stroke or some engine oil at the two-stroke ratio and the pump will be lubricated, which is the most critical thing. When you work in oil fields and see diesels running on natural gas or crude oil or marine grade diesel that you appreciate how useful they are.
 

pictsidhe

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Run and last are different things...
It would be prudent to test any additive. IIRC, the standard test involves measuring the wear scar created by a rotating cylinder rubbing on a steel test piece. This is something a competent experimenter could get fairly close to in his workshop. Calibrate your rig with pump diesel, then try combinations of Jet-A and additives. I'd be starting with 2 stroke oils.
You don't want to be testing fuels by running them and seeing if it breaks the pump. That gets expensive in a hurry.
 

pictsidhe

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I remembered incorrectly. The standard test is HFRR. It involves a ball bearing and a steel plate.

Test results of additives for untreated ULSD. Results would differ for jet-A, but it is probably a good indication of what to try. PM was using MMO, until shouted at and shown this report. He then switched to running the Raptor on diesel, but because "it has a higher energy content and gives more power".
 

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lelievre12

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Theilert/Continental have a number of Patents concerning the hardening of the Bosch CP1 high pressure pump cams and bearings. As these pumps are lubricated by the fuel, Jet-A is not suitable as it does not have sufficient lubricity. The pump must be hardened to cope under the greater wear. This is what Theilert did with its first engines.

Then when they changed from the 1.7L CD135 to the CD155 based on the later 2.0L OM640 engine, they kept the old CP1 pump, mainly as they already had figured out how to harden it. Plus it is smaller and lighter than later Bosch CP2 and CP3 pumps.

The standard Audi engine in the Raptor also has a Bosch pump, so will not be suitable to run Jet-A without hardening. Alternatively, lubricating oil can be added to the fuel to provide the missing lubricity. I don't have data, but I believe 1 or 2% of motor oil is OK.
 
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Vigilant1

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Just watched a video about the 120mm mortar in USMC service which uses a small prime mover with a 2.8 l diesel engine that "is modified to run on JP-8".
True. JP-8 is burned in a lot of tactical vehicles. JP-8 has lubricity enhancers, anti-corrosion agents, anti-icing agents, and antistatic agents that aren't present in Jet-A
Of course you aren't supposed to touch it, but if you DID, JP-8 would feel noticably oilier/slipperier than Jet-A, but less slippery than diesel fuel.
 

Twodeaddogs

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It's a bit like the Western quest for multi-fuel diesels for tanks. The various companies spent millions and had various levels of success.The Russians just said; this is a large diesel engine; use whatever is specified in the manual,be it diesel, kerosene, chip fat, boiled horsemeat or whatever, as long as you capture it when you invade the West (i'm joking!).On one of their engines, when changing to another grade of fuel, the driver simply moved a lever on the diesel pump to an arrow that indicated the fuel type and continued on. Quite simply,if you need to get somewhere, make use of what you have and use a bit of common sense.
 

Markproa

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I'm building a French Gazaile2 with a diesel engine so this is of interest to me. Many Gazailes are flying in France using both service station diesel and Jet A. Their solution is to add 2 stroke oil to Jet A at a 50:1 ratio. Or you can add up to 40% Jet A to the quantity of diesel already in the tank without adding oil. It works for them.
 
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