Just wondering why there haven\'t been any major developments into diesel rotary engines (or have there? :Hammer ). To me it would seem the rotational motion of the rotor is a very efficient way of achieving the high compression ratios required for diesel in air ignition. Surely by reducing the volume of the rotor recesses, compression ratios well inexcess of 20:1 could be achieved providing the necessary air temperatures (~900 deg) within the moving rotor chambers to achieve combustion upon injection of the diesel fuel (which would be injected in roughly the position of where the spark plug would be for a conventional gas rotary motor). I\'m guessing the problem lies with the rotor tips not putting up with the increased pressures during the compression cycle.
Any thoughts? :3Confused
^ pretty much wrote exactly what I thought.
High compression, flakey tips :nono :(
That said, I\'d be interested to know what the RX-8 tips can copy with...
I remember reading a technical paper by a guy who was involved in early rotary development, which I\'ll try and rake out. If memory serves correct, there is some problem with attaining the high compression ratio that diesels need. I also have a feeling it was something to do with the shape and geometry of the combustion chamber that prevents higher compresion ratios, but I could be wrong there.
I thought they were good, I guy commented to my brother about my RX7\'s and he said that his cement mixer had a rotor engined pump that has never let him down. I assumed they would be good as imersed in oil.
Ian, I can see the epitrochoid geometry being the biggest problem as you suggest. With a piston engine, the piston rings are forced against the cylinder walls which are perpendicular (90 degrees) to the force of the piston rings providing the optimum sealing configuration for a high compression chamber. In a rotary engine, the "cylinder" (rotor housing) is at a constantly changing angle to the "piston rings" (apex seals), and during the point of maximum compression the apex seals are at their least optimum angle with the rotor housing to withstand high chamber pressures (see dodgy diagrams). I guess this is the geometry issue you described. I imagine it would require an alternative apex seal design to provide a greater contact pressure between the seal and the rotor housing.
What is the compression ratio of the 13brew after you have put 0.8bar of boost through it? I know the Standard engine has a compression ratio of 9.0bar new.
There have been deisel engines developed - Rolls Royce had apparantely done one.
Deisel rotary engines are larger because to increase compression you need larger rotors & therefore housings to increase what they call "the \'k\' factor" but I cant remember off the top of my head what this is.
There are mentions of it in the History of the Rotary Engine book.
Quote from: Ricco_04What is the compression ratio of the 13brew after you have put 0.8bar of boost through it? I know the Standard engine has a compression ratio of 9.0bar new.
I thought turbo motors were lower compression than N/A?
Would be interesting to see a big Rolls Royce rotary engine. Think i\'ll do a search.
Some pics of a Rolls Royce R6 Rotary Diesel Engine on
http://www.der-wankelmotor.de/Motoren/Rolls-Royce/rolls-royce.html
and a rather large rotor:2eek
http://www.der-wankelmotor.de/Motoren/Curtiss_Wright/curtiss_wright.html
Will a moderator please close this thread, this kind of discussion is \'dirty\' and wrong. Diesel should be kept to busses, trucks, trains and boats. ;)
Quote from: A7NTYWill a moderator please close this thread, this kind of discussion is \'dirty\' and wrong. Diesel should be kept to busses, trucks, trains and boats. ;)
True LOL
But something tells me a diesel rotary wouldn\'t be quite so dull as a diesel piston engine :cool
Gotta wonder what it would sound like.
Quote from: A7NTYWill a moderator please close this thread, this kind of discussion is \'dirty\' and wrong. Diesel should be kept to busses, trucks, trains and boats. ;)
And leman 24hr winning cars :spank :spank :spank :spank :spank
Shaun
Quote from: shaunwilAnd leman 24hr winning cars :spank :spank :spank :spank :spank
Shaun
That just proves if you chuck enough money at something it will win ;) that car was a monstrosity - keep it pure - keep it petrol :D
Quote from: A7NTYThat just proves if you chuck enough money at something it will win ;) that car was a monstrosity - keep it pure - keep it petrol :D
Apparently, you only need luck to win Le Mans
As for keeping it pure, that means ROTARY, and anything ROTARY is good. We should be removing the references to thos funny up and down engines !
:-)
Quote from: A7NTYWill a moderator please close this thread, this kind of discussion is \'dirty\' and wrong. Diesel should be kept to busses, trucks, trains and boats. ;)
:Giggle Yeah, damm soot blowers - imagine our de-cat emissions! :o :D (only joking, would be interesting to see & hear etc)
I would like to see a lot more done with gas fuels - sure that\'s where the future for our engine lie\'s (sp?)
I\'m suprised this isn\'t on the site, it\'s a really good read, especially for the technically minded.
http://varel.force9.co.uk:1133/RX7/RotaryEngineWhitePaper.pdf
The site may not be live 100% of the time, so I\'ll try to get it moved to a better place, but will have to do for now.
Nice link there buddy - will read that laters! :wave
Quote from: MartinyApparently, you only need luck to win Le Mans
Hehe - nice one Martin.
Given our fuel economy - a rotary I could run on chippy fat would be awesome :driving :Hammer :rollin
Quote from: ianelvarI\'m suprised this isn\'t on the site, it\'s a really good read, especially for the technically minded.
http://varel.force9.co.uk:1133/RX7/RotaryEngineWhitePaper.pdf
The site may not be live 100% of the time, so I\'ll try to get it moved to a better place, but will have to do for now.
Thankyou for that Ian, and yes your right it should be in our FAQ section.
No worries. :Thumbs-up
I\'ve got a bunch of similar stuff I\'ve collected during my research on rotaries. It\'s being uploaded to some more permanent (and faster) hosting at the moment, so I\'ll put a post up when it\'s done, and maybe someone could choose what they want (if any) to put links to in the FAQ section. There\'s a good video I found that explains pull clutch removal.
Sorry for the thread hijack!
Again, this is slightly off topic, but has anyone seen the drawings for a steam powered, external combustion rotary? While we\'re on the subject of alternative rotary power I think it\'s worth a look.
http://ghlin2.greenhills.net/~apatter/wankel.html
I particularly like the compounding idea. I work with steam locos at didcot at the weekends, so I have a bit of a fascination with steam.
Would put an end to det problems... :Laugh
still slightly off topic but anyone who has read this far into the post might actually appreciate this, this is an illustration taken from ianelvar\'s rotary engine whitepaper link:
(http://i15.photobucket.com/albums/a399/dandantrash/Planetaryrotors.jpg)
I can\'t believe that all these variations of a rotor cross section are possible! It seems the wankel shape (top right) is just one of many, and I always thought the number of tips (3) was an unchangeable constant.
Very enlightening thread this. :)
EDIT: now where\'s my spirograph...?
Middle middle one looks just like an oil pump!!
Theres another site Dan, cant find link has illustrations of up to 8 seals
Quote from: dandanI can\'t believe that all these variations of a rotor cross section are possible! It seems the wankel shape (top right) is just one of many, and I always thought the number of tips (3) was an unchangeable constant.
I read that NSU/Felix Wankel expirimented with 4 & IIRC 5 sided rotarys.
The rotary we know today is, as Felix Wankel said, "a bastardised" version of the one he wanted to market - where the rotor spun in a perfect circle and not on an eccentricity (sp?) which was even more smoother and could potentially rev higher. They decided to test this and had it revving at 25,000rpm without blowing up!! :InLove That\'s what I want to see another version of! :D
how would a centrally rotating version work? cos surely the chambers would not change in volume so there would be no compression/expansion? unless the outer housing was an odd shape that created the changes in the chamber volume, but then you would only get one combustion cycle per 360 rotation of the rotor instead of 3 like in a wankel? i\'m sure it can all be explained away with lots of complicated circles....
Anyone got any links to pics of this, or a description to explain it?
Dan - I agree, I\'ve never been able to work out how a rotary without an eccentric produces any torque.
That being said, take a look at this:
http://auto.howstuffworks.com/quasiturbine.htm
It has chambers that change volume by having a variable geometry rotor. It\'s supposed to work, but I can\'t see, and the article doesn\'t explain, how it imparts any torque upon the output shaft. Can see how it could work as a compressor, though.
Ian, thanks for that white paper link, good find and a good read. The bit on the diesel rotary is interesting as it suggests a single cycle system would not work too well. Its nice to hear it from the horse\'s mouth though :Giggle
Surely for the tips to withstand the explosion forces on combustion they could withstand the compression forces? Sealing may be an issue but I would expect the fuel to actually act as a lubricant and thus protecting the engine withough the need for oil injectors...
Quote from: dandanhow would a centrally rotating version work? cos surely the chambers would not change in volume so there would be no compression/expansion? unless the outer housing was an odd shape that created the changes in the chamber volume, but then you would only get one combustion cycle per 360 rotation of the rotor instead of 3 like in a wankel? i\'m sure it can all be explained away with lots of complicated circles....
Anyone got any links to pics of this, or a description to explain it?
This is the forementioned engine (which is also the front cover of the History of the Wankel Rotary Engine - the book I keep referring to)
(http://www.digitaljournal.com/photo/020823Wankel.jpg)
I may have this wrong but will need to read the book again to make sure. The rotor rotates counter clockwise while the inner housing rotstes the other way at 2x the speed. It then has an outer shell for mounting which made it larger. It was also deemed unfit for everyday use as the engine would need to be torn down to replace the spark plugs whish where in the 2nd housing or the rotor.
Cant quite figure it out now so must have something wrong, book comes out again later then! (maybe I should have read it first! :Giggle )
Whilst that Quasi Motor doesnt have eccentricity, it DOES have parts that are going, stopping, and changing direction all the time. So for me, its not a Rotary.
The original Drehkolbenmotor (DKM) had the "rotor" in the middle, and the housing moving around this. It comes down to this:
http://www.der-wankelmotor.de/Wankelmotor/wankelmotor.html
Both rotor and housing moved, in a casing. Thbig advantage is the perfect round movement, causing NO "chippingmarks" on the housings, and long lasting tipseals. There\'s no vibration at all in such an engine. In many ways, it is the most perfect engine one can build. But it\'s a little useless: to change the spark plugs, it engine has to be rebuild! Also, it\'s not suitable for automotive use as the power is not transfered to a central shaft (E-shaft, ...) but to the "housing". It did do over 20.000rpm in the fifties though!
Later Felix Wankel deloped more ideas. Some of his engines did 50.000rpm, and got more power from 500cc then our turbo\'d 13B\'s do now!
As for diesels: the higher compression needed cannot be achieved since the "K" factor is not unlimited. The tip-seals cannot seal very well anymore if the angle between them and the housing becomes to flat.
RR used a chamber as a compressor to solve this.
And these guys apparantly build a new diesel/multifuel engine:
http://www.wankelsupertec.de/index.htm
Quote from: rotary emotionsBut it\'s a little useless: to change the spark plugs, it engine has to be rebuild! Also, it\'s not suitable for automotive use as the power is not transfered to a central shaft (E-shaft, ...) but to the "housing". It did do over 20.000rpm in the fifties though!
Later Felix Wankel deloped more ideas. Some of his engines did 50.000rpm, and got more power from 500cc then our turbo\'d 13B\'s do now!
As for diesels: the higher compression needed cannot be achieved since the "K" factor is not unlimited. The tip-seals cannot seal very well anymore if the angle between them and the housing becomes to flat.
RR used a chamber as a compressor to solve this.
And these guys apparantly build a new diesel/multifuel engine:
http://www.wankelsupertec.de/index.htm
Cant see why you couldn\'t have an access plate in the outer housing to get at the spark plugs :xconfused I\'m sure they would\'ve thought of that though.
I wonder if any of his early motors have been kept in working order, cant even imagine what a 50000 rpm rotor sounds like.
I guess if it was that simple Felix Wankel would have thought about it? ;)
Several of these early engines are in museums, but I doubt there are any in "working order".
It\'s a shame actually, the early ones were superior to any other engine. Hardly any wear, high rpm, no vibration... Somehow I wonder if it wouldn\'t be possible with modern technology to make these DKM engines useable.
I\'m sure we are getting to the age where people are trying with them again, what with them being better at using gas fuel.
I read on another thread that Honda had been expirementing with the Rotary mmmmmm.
How quickly does diesel burn ? I seem to think rotaries run best on slow burning fuels due to the long combustion chamber so a long push is much better than a sharp explosion. If that thinking works out, rotaries should be quite well suited to methanol as thats a "slow" burn fuel. I seem to think this is the same case with hyrogen.
Can you imagine the apex seals required for a diesel rotary ? surely a compression ignition (basically the same as preigntion in a petrol engine) based cycle is going to make for a hard life for them ?
The multifuel diesel engine I mentioned before was not a self-igniter: it used a sparkplug to start the ignition. Rotaries are actually good with any fuel type, but gas (hydrogen or LPG for example) is what they are superior with, because the lack of valves. These tend to pre-ignite mixtures because they stay hot. Which is why we can run unleaded in our oldies without problems too.