Just was wondering if a diesel rotary engine would be feasible, since diesels usually have better gas mileage and produce more torque, which would solve a few of the usual rotary downsides. Would you be able to make the compression work? What would the issues be?

 

i think i read somewhere, that at the current level of technological refinement of the rotary engine, that diesel operation is not possible


ask wak, hell know for sure
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Here a Diesel Rotary:

http://www.boatingnews.com/rotarymarine.htm

There was a thread on this a while back ago.

 

actually rolls royce developed diesel rotaries for a while, but eventually ditched the program (though the engines did work just fine). See John B. Hege's book on rotaries for more info

 

Rotary engines has successfully been test run on diesel and other fuels for many years. According to some it's not a real diesel engine because it doesen't use the compression to ignite the diesel, but often a technicue called stratified charge is being used.

Unfortunately a diesel fuelled rotary does not have all the benefit's usually connected to a diesel engine of much lower fuel consumption and higher torque, but it does have more of the benefits of a petrol fuelled rotary, like high rew's (not fully as high as petrol RE), easy starting in extreme temparatures and not to forget (compared to a "normal" diesel engine) size and weight.


Kind regards,
Rothor

 

" According to some it's not a real diesel engine because it doesen't use the compression to ignite the diesel, but often a technicue called stratified charge is being used." - Roth

that is what i read about
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The stratified charge for diesel has quite successfully been developed by RPI (Curtis Wright/John Deere/Rotary Power Inc) and used in the large 5,8 ltr displasement per rotor, 0.7 ltr per displ. (appr. same size as Mazda) and also other sizes.

It would only have taken a lot of money and a production line of rotary engines would have been happening in New Jersey! It was "this" close! and still happen.

Principally the startified charge all happens in the "combustion" area of the rotary engine, it starts with a pilot injection being sprayed toward a normal spark plug whitch ignites this mist and then the main injector sprayes the main area of the combustion camber being set fire to by the already burning pilot flame.

-Rothor

 

Well, it would still have the advantage of the diesel fuel being cheaper than gasoline - with the mpg numbers the rotary delivers, that would mean a significant saving by itself :p
On the other hand, I'm not sure if I understand you correctly when you are saying "easy starting in extreme termperatures". As far as I know, starting a diesel engine in extreme cold is usually a problem... maybe you meant only extreme heat?

 

As long as you keep the diesel lines insulated from the extreme cold it would probably start with ease down to 40 C below 0 without problems if your battery and oil was in good shape. A common thing to do by the way on diesel when that cold is to mix up to 5% gasoline into the diesel to avoid waxing. Usually in this kind of areas they sell winter diesel witch is less sensitive to the low temperature anyway.

And by using the statified charge method and if your fuel pump/injectors would handle it you could run it on Jet A1 (JP5).

-Rothor

 

Check these guys out.

http://rotarypowermarine.com

 

That company is gone very quiet and have sold most of their stuff to a Florida based company called Rotary Power Inc. Originally they where connected with the marine part of Rotary Power International (RPI) in NJ witch again was the managment buyout from John Deere back in 1990. John Deere had in its time bougth out Curtis Wright witch had the first licens ever from NSU/Felix Wankel in Germany in 1958. RPI have the "famous" diesel powered 5,8 ltrs diplacement rotary engines. 2-rotor = 1000hp.

-Rothor

 

I have thought about that concept. I wonder what a TRUE diesel(no spark plugs) RE's performance figures would be. i wonder if it is possible to get the 21:1(i cant remember) comp ratio necessary for reliable self-ignition with the rotary without having to vary the tub size. You gave some links to a diesel FUELED RE but they have spark plugs do they not? it is too late to read fully the articles.

 

I could be enough with 17:1 in compression, so it could be done. One of the downsides could be the increased friction/resistance to hold on such compression, thereof less power, higher wear, etc.

And yes, all todays RE engine running on diesels I know of run with a kind of spark plug.

I fully agree on Hydrogen being the future for RE's. I'm not too sure if the 1/3 ownership from Ford will accelerate or slow down Mazda's RE Hydrogen programme, since they obvious are in competition with each other.

-Rothor

 

Diesel rotaries that used compression for ignition were studied by Rolls Royce. According to John Hege's book, they found that to make a "normal" rotary engine with enough compression to ignite the diesel fuel the engine would end up very big (a result of something called the "k-factor") so they used a different method. They "stacked" two rotary engines, one larger than the other. The large rotary "engine" was used as an air compressor so that high-compression would occur in a "normal" sized wankel. If you all really want to know how it works I can scan a picture ...

 

As a side note to compression ignition diesel, the rotary is not so well suited for it. The geometry being what it is, to obtain a higher compression ratio (i.e. 17:1+) would almost eliminate the rotor tub. This makes the squeeze near the "hips" of the housing VERY small. So much air/fuel in the cycle has to pass that small opening which requires a large amount of pressure (actually pushes back on the upper half of the rotor during expansion i.e. takes away power. More importantly the high velocity of the mix forced through this small opening tends to snuff out the flame front. This is why most (all?) fuctioning diesel rotarys use some external compressor and spark. (Note:this info is a warped version of a discussion of compression ratios in the Racing Beat tech manual based on gasoline)

WN

 

I think this is also why the only successful diesel RE is run og "normal" compression and by sparkplugs (i.e. SCORE technology).

Maybe using the "last rotor" (in like a 20B) as a supercharger instead of on top like the Rolls Royce would be someting for tuning a gasoline engine as well?

If I don't remember incorrectly there was a 5 cylinder Volvo piston engine once that used the fifth cylinder as a supercharger.

Anyway I'm attaching a picture of the R.R engine R6 that produced 350hp@4500rpm and therby beating vipeRX7 to that part.

-Rothor