This is for the engineers out there:
alfadriver wrote:
No, it *still* would not be a contest. The rotary has some serious flaws WRT emissions that makes it a lot harder than piston engines. #1 being the massive surface area which quenches the flame front- which is both a waste of fuel and a huge source of HC emissions. If you could re-design the wankel so that the surface area was a lot smaller, then you'd be onto something.
Here's a question, then:
It's my understanding that the typical rotary chamber is squared off in its swept area, so that its volume resembles a stretched tuna can.
- Could the rotary chamber instead be reshaped to look like a stretched filled doughnut instead (or stretched flattened sphere), so that rather than apex seals and face seals on the rotor, it has a single curving seal?
- Would that have a higher volume to surface area ratio than the standard rotary chamber?
- Is that even workable?
- Would it improve anything?
Just some thoughts.
Being not too strong on wankel geometry- since it's odd...
Short of getting a metal car and start messing with it, seems like you need to find or make a model so you can mess around with it.
I've seen some good info about that layout, and how to "change" it (I can't recall if it were just CR or whatever), so there are some documents out there to look at.
For sure, no harm in wondering. or wandering with the design.
If you can plit it in paper, then theoretically you can make it in wood, which is a lot easier/cheaper than metal.... Or find a local 3D printer...
Emissions were drastically improved by changing to exhaust side ports on the Renesis engine in the Rx8. http://www.mazda.com/mazdaspirit/rotary/about/
The new redesign, 16X engine further improves emissions and torque.
http://www.mazda.com/mazdaspirit/rotary/16x/
I forget which year it was, it was one of the 12A engines, but they worked the shape of the rotor face a bit and improved gas mileage, too. I have no idea why they didn't continue that into the 13B.
I could probably draw what I'm thinking of, but it's sorta hard to explain. The void that the rotor spins in is the "stretched tuna can" shape right now.
In reply to scardeal:
The picture I posted above doesn't show it, but the inside also has the eccentric shaft passing through it. Any changes in geometry would have to account for power delivery through the eccentric shaft as well.
http://www.rotaryengineillustrated.com/how-a-wankel-rotary-engine-works/anatomy-eccentric-shaft.html
Your idea would not be an improvement because:
Also, this would be much more difficult to manufacture, and it would be a challenge to make the round apex seal, seal.
I agree with JamesMcD. I can see all kinds of sealing and machining problems, sort of like Honda's oval pistons a few years back.
That had to be enough of a machining nightmare. I can see trying to make epitrochoidial torodial housings now; the machinists would run screaming. 
I personally think the rotary's power and emission characteristics could be drastically improved with direct gasoline injection. Much better control of atomization and thus mixture, better placement of the mixture (it wouldn't have time to go far past the 'bathtub'), all kinds of things. Best of all, it wouldn't require a radical rework of the engine. It could probably even be retrofitted to existing rotor housings.
In reply to Curmudgeon:
IIRC, the 16X will include direct injection. Mazda has met its fuel efficiency goals but not its emissions goals, so the engine is delayed until they can get the emissions right.
http://www.autoblog.com/2010/10/21/report-mazda-rotary-reportedly-at-least-a-year-behind-schedule/
Cool. Didn't know that. The guys at Mazda are definitely smart enough to get the emissions strightened out.
I'm just glad that Mazda hasn't and probably won't give up on the Rotary. They have dumped millions if not billions in the development if the Rotary engine. I can only hope for a better engine soon. Realize that it's still young compared to the piston engine in development.
As of late however, I am coming across people who think Mazda should dump the Rotary all together, they feel it's a waste of time. But these people seem to also be the ones that think Porsche shouldn't be running horizontally-opposed engines out back and that it was great when Jeep dumped the ancient 4.0L six.
In reply to SyntheticBlinkerFluid:
In other words, these people hate cars and want them to all be the same.
In reply to Brett_Murphy:
I'm pretty sure these "car enthusiasts" just want everything to be V12 supercars.
SyntheticBlinkerFluid wrote:
I'm just glad that Mazda hasn't and probably won't give up on the Rotary. They have dumped millions if not billions in the development if the Rotary engine. I can only hope for a better engine soon. Realize that it's still young compared to the piston engine in development.
As of late however, I am coming across people who think Mazda should dump the Rotary all together, they feel it's a waste of time. But these people seem to also be the ones that think Porsche shouldn't be running horizontally-opposed engines out back and that it was great when Jeep dumped the ancient 4.0L six.
The reality is that the rotary is inherently flawed from a thermodynamics standpoint, period. It's BSFC performance would not equal the piston engine, even if an equal amount of development had been poured into it. You just can't cheat physics.
Now, I'm not knocking the rotary or saying that it should not exist. But it finds itself increasingly out of place in todays automotive marketplace due to various government standards and consumer expectations and proclivities.
The rotary mythology that seems obligatorily to begin EVERY-SINGLE RX-related magazine article, that the rotary makes ____-HP with only so many liters and makes more HP/weight than a piston engine, is just hyperbole, to put it kindly. A 13B is not 1.3 liters and the rotary is heavier than you'd think.
The only real objective advantages I see in the rotary are related to packaging. And subjectively, you have the zingy "rotary character" and the "oddball factor." Now obviously, only a very small subset of consumers find that those "advantages" justify dealing with the poor mpg and "special needs" that come with the rotary. So, there really is no good business case for the rotary. They would probably be better positioned as a company if all the resources they have poured into the rotary since the FD ceased production had been instead invested in other things. Mazda sticks with it because they love it.
RexSeven wrote:
In reply to Curmudgeon:
IIRC, the 16X will include direct injection. Mazda has met its fuel efficiency goals but not its emissions goals, so the engine is delayed until they can get the emissions right.
http://www.autoblog.com/2010/10/21/report-mazda-rotary-reportedly-at-least-a-year-behind-schedule/
Good luck to them, for sure, but some of the major advantages to DI are lost on the roatary geometry. There are some great tricks that can be played via injection timing, but for the rotary- timing is more based on where the injector is placed (if you were able to inject on the intake stroke, you could not do it on the compression stroke, and vise versa- or it needs to be part way inbetween.... Very hard to find the correct compromise).
How about a five lobed rotor?
(I don't know where that came from. Just popped into my head...)
Scott
I don't have anyhting to add, except the thread title should be THINKING OUT LOUD - ROTARY CONTENT
