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Jet A1 in a Rotary

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HeliDev

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Jul 7, 2003
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108
Just doing some thinking out loud.
Does anyone think it would be possible to modify a rotary to run on heavy fuels.
Asuming you could get the compression high enough, change the spark plugs to glow plugs, what other considerations would be nesseccary?
 

orion

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Mar 2, 2003
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There has been some work on this in the past. The high end development was a four rotor diesel powered rotary, developed I think by Teledyne. The specifics of the engine were very promising however I never heard what happenend to the program after the prototype engine.

As far as converting a Mazda based engine to burn kerosene, I know it has been experimented with but I don't know the details. The last I heard, the work was being done by the engine lab at Western Washington University up in Bellingham, and partially supported by Hayes Rotary Engineering of Bellevue, WA.

The concept of converting the engine to diesel operation is not so far out however there are issues of stress of the case and of the seals, as well as some of the effects of the localized heating and pressures.

Might be worth examining a bit closer though - all it takes is a bit of money.
 

Midniteoyl

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Sep 3, 2003
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Indiana
Diesel Rotary

Rotary Power International was suppose to have been working on a marine version at the end of 2002 - no clue how far they are - if any.

Then there's always SmartPlugs and thier way of 'converting' ;)

Jim
 

wassbiplane

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Apr 1, 2003
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Location
Oklahoma
Just discussing rotary engines w/ my boy when he heard my old Lincoln Knock on acceleration---
His comment was that detonation was Death Knell
for rotary seals--in a hurry---
so---
Sounds like the weak link is the seals, which,
if they can't stand a little knockin', sure as
heck won't burn kerosene, JetA or the likes.

and injecting diesel into a RAPIDLY retreating
combustion chamber, sounds like you might not keep the flame goin'--They have to use 2 spark plugs-
not in parallel, but spaced further around the combustion chamber, just to keep the gasoline burnin good!!
 

HeliDev

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Jul 7, 2003
Messages
108
Glad to hear Im not completely off the wall.
A couple of points Id like to add.
By nature the heavier fuels are higher in viscosity, and for want of a better term, more oily. Wouldnt this help with the life of the seals?
As far as the uneaven burnning of petrol in a rotoary, at first glance, to me, by combusting the fuel through compression, instead of ignition throught a spark, should benefit the rotary. If you think about the curved surface of the rotor and the engine block, it seems that this environment would be better suited to compression ignition.

Thanx for the replies so far guys, keep them coming.
 

Stu

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Oct 4, 2004
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Central California
There are supposedly aircraft in Europe flying with a fully certified Wankel Rotary using Jet A or Diesel. This is still a spark ignition engine, though, folks. It does not attempt to use compression for ignition. Sounds as though compression remains about the same as for a gas engine. With a little fuel system tweak they could be multi-fuel.

Seems like a great idea to me.
 
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StRaNgEdAyS

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Oct 20, 2003
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Northern NSW Australia
This is still a spark ignition engine, though, folks. It does not attempt to use compression for ignition.
I remember many years ago when I used to sell agricultural equipment we had some old Fordson tractors that ran on either gasolene or kerosene, they even had seperate tanks for each!
I also used to run one of my cars on jetA1 back in the '80's when I was in high school cos I could get it for free and it worked just fine. This was also a spark ignition vehicle.
Using a spark ignition engine with kerosene is not a new idea, I have been investigating using it as an aviation fuel instead of mogas, but I have yet to come up with any reliable data regarding performance and reliability comparisons.
 

HeliDev

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Jul 7, 2003
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SD, what did you do to the motor to make it run on Jet A1?
I have seen diesel go through a pertol motor and while it runs the smoke is pretty impressive.
 

Stu

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Be very careful when using fuels with low octane/high cetane ratings in a spark ignition recip engine! When under enough load the fuel will detonate, causing spectacular damage. The higher the compression and more advanced the spark the worse this should be.

A major oil company accidentally delivered a large batch of Jet A mislabeled as 100 octane avgas. They bought a lot of VERY expensive engines, and probably a few airframes as a result.

The Wankel and turbine are the only ones I know which could handle it, aside from very old, slow, very low compression tractor motors which were dual fuel.

My A&P buddy used to frequently get free Jet A to run in his diesel. Now that worked just fine.
 
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727200er

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Fraser Valley BC Canada

Having some (limited) experience in diesel conversion projects I can tell you that a rotary is a very bad candidate for conversion. The worst part being horrible inefficiency and what would turn out to be a VERY low TBO.
 

Stu

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No question that a high compression direct injected engine without an air inlet restriction will be more efficient in converting those BTU's into motion, at the cost of engine weight. But I am curious about the low TBO. Why? Seal problems, coking? How was the diesel introduced into the combustion chamber? Was this based on a Mazda 13b? Would side porting have made it less prone to wear/damage? Care to mention whose project this was, if it was a publicized project?

While not conversions, it has been done commercially in a new certified european engine and in maring engines. What the final outcome will be I have no idea. If it proves to be a bad idea then at least it was tried. If it proves to be not marketable simply because folks are not interested in new ideas then it is a shame. For those who cannot easily obtain mogas it could still be a great alternative to the cost of a turbine.
 

Jman

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727200er,

I don't pretend to have any 1st hand experience but I've been following the Rotary Mail list for quite awhile now and it seems that some amazing strides are being made with the 13b Rotary. Also, with the advent of the Renesis (next gen Mazda rotary), the outlook for the Rotary aircraft conversion seems very bright. Anyone care to comment?

One of the downsides of the Rotary that has bothered me is the inability to burn readily available aircraft fuels. If It could burn Jet A, it would definitely step up a notch on my mind.


Jake
 

orion

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The rotary has been in development by several organizations for a variety of technologies, including those that address the use of diesel or kerosene. I don't know if these tasks are still under way, but Western Washington University has an internal combustion lab that is known to have done quite a bit with the rotary, including investigations into uses of diesel fuel (using spark ignition, not compression). The work was very promising and the rotary seems to be ideal for such a conversion due to its inherent durability and toughness.

Another site that looks promising for this type of work is at http://www.smartplugs.com/indexi.html.

I just wish I had the time to dig into all this stuff deeper. It seems like a lot of these organizations do a bit here or a bit there, but no-one has really gone far enough to produce a dependable (and affordable) product line that we could use in our aircraft.
 

727200er

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OK most of the work we did was a group of experimenters. The engines used were the 12a and 13b variants. We started the program building a drag racing engine, that would run on AvGas so that we could up the compression. We were quite successful with spark tech engines and with compression levels that required AvGas and/or alcohol. The only issue we had is the one that computer tech has effectively solved, fuel mileage. This isn't that big of a concern though in a drag racing environment.

I would like to point out however, that I really like the great power to weight ratio of the rotary engine, and as such I am a big fan.

Now to the diesel conversion. We used strictly the 13b for this project. The idea here was to come up with a really light and powerful diesel engine for automotive use. We redsigned the rotor barrels for greater strength, and the rotors themselves to achieve the compression required for compression ignition. We used 14 different alloys for rotor seals, none of which were very successful. Our actual engineer was killed in a racing incident and the project stagnated after that. Unfortunately the rest of us were "backyard engineers" and basically unable to continue. My original post may have been a bit harsh but I truly believe that the rotary compression ignition engine is doomed to failure. Now a spark fired jetA project is interesting.

I like the idea of a rotary engine for GA, because I DO love the power to weight ratio of the engine. I would dearly love for someone to prove me wrong on the compression ignition version of the engine. The group that I was involved with were basically an amateur group attempting to create a "better mousetrap" so to speak. If we had been successful, there were a few corporate entities that were VERY interested at the time. Also bear in mind that this was in the mid 1980s.
 

StRaNgEdAyS

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As I have stated before, I have successfully run a carburettor spark ignition auto engine (mini cooper S) on jetA with very favourable results, it just smelt a little wierd:whistle: Direct injection will certainly improve the results dramatically.
Diesel can also be ignited by a spark, a phenomenon which can be seen in almost every hot water pressure cleaner out there. Has anyone seen what happens to a pressure cleaner that has been filled with mogas instead of diesel? :eek: It's not pretty. Some will run on kero, but the amount of airflow needs to be increased to clear the chamber of gases before the next burn cycle.
If I had to choose between the two fuels for a spark ignition engine, I'd be looking at kero (jetA) bcause it is the easier to ignite.
 

GaryBuster

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Jun 3, 2011
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Location
Frankston, Texas
Sorry to bring up yet another old thread... one of our gyroplane friends is using gas in his mazda 12a to start, and then get the engine hot, then switches to Jet A after just a few minutes... it's already a proven entity for flying guys!!
 
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