Why are Mazda persisting with the Rotary Wankel engine?
Discussion
RayTay said:
Mave said:
Really?
Yes. They don't like being revved up and down. Rotaries have by their architecture a poor surface area to volume ratio for their combustion chamber(s) so cannot match the BSFC of a reciprocating engine. They do indeed provide give you high power density package, but in 2016, efficiency has become extremely important.
Look up SPARCS and CREEV. CREEV is a ‘exhaust reactor’ consuming unburnt exhaust products, which dogged the rotary, delivering lower emissions and improved fuel efficiency. Also HCCI ignition is making great strides.
Yes, a rotary can exceed piston engine efficiencies at a constant speed/load.
Yes, a rotary can exceed piston engine efficiencies at a constant speed/load.
RayTay said:
Look up SPARCS and CREEV. CREEV is a ‘exhaust reactor’ consuming unburnt exhaust products, which dogged the rotary, delivering lower emissions and improved fuel efficiency. Also HCCI ignition is making great strides.
Yes, a rotary can exceed piston engine efficiencies at a constant speed/load.
No, no it can't. And of course you can also add all that exhaust after-treatement to a normal reciprocating engine and have EVEN higher efficiency and lower emissions..........Yes, a rotary can exceed piston engine efficiencies at a constant speed/load.
RayTay said:
Look up SPARCS and CREEV. CREEV is a ‘exhaust reactor’ consuming unburnt exhaust products,
This website shows that CREEV is simply a secondary expansion scheme. The marketing phrase "exhaust reactor" is used because the basic wankel is so horribly inefficient that plenty of unburnt mixture is pushed out on the exhaust cycle, so secondary expansion gives it a chance to complete combustion. There's nothing particularly clever going on here, and secondary expansion can also be applied to a conventional four stroke engine.
Mr2Mike said:
This website shows that CREEV is simply a secondary expansion scheme. The marketing phrase "exhaust reactor" is used because the basic wankel is so horribly inefficient that plenty of unburnt mixture is pushed out on the exhaust cycle, so secondary expansion gives it a chance to complete combustion.
There's nothing particularly clever going on here, and secondary expansion can also be applied to a conventional four stroke engine.
Mr2Mike, the poor fuel efficiencies and poor emissions were because of poor combustion - unburnt fuel ended up in the exhaust. The exhaust reactor burns the unburnt fuel increasing HP and efficiency. Also HCCI ign is being R&D's by Mazda, with one Mazda engineer stating that a new Mazda rotary will most probably have HCCI ign. CREEV takes the exhaust pressure down to atmospheric meaning a very quite exhaust. If perfected that is a major step in the evolution of the rotary. This takes the rotary right up with the best of piston engines in fuel and emissions. And then you have its exceptional and clear advantages over piston engines. There's nothing particularly clever going on here, and secondary expansion can also be applied to a conventional four stroke engine.
Recall, the rotary fires three times in one rev of the rotor. The gearing from rotor to the mainshaft makes that one firing per rev of the mainshaft. This can be geared to 3 firings per rev of the mainshaft if the application need is there.
Rotaries suffered from tip seal lift off when being revved up and down, as in normal direct drive driving, because pressures from adjacent chambers would be higher as some points and escape to the next chamber lifting off the seals. When run at an optimum constant speed this is not an issue.
Exhaust reactors and HCCI apply equally to piston engines, however they improve the rotary dramatically while only improving piston engines marginally.
BTW, the Mazda RX-Vision sports car has been dropped after being announced. Mazda want a high production rate on any rotary they make to pay for tooling costs, so low volume sports cars are not the answer. Mazda say they are looking a range-extender use for the rotary in hybrids. Toyota have teamed up with Mazda to R&D/produce a range-extender engine. Toyota have being doing R&D on free-piston linear generators and Mazda on rotaries.
I personally can only see rotaries being used as generators on road vehicles. They can be direct drive on small planes as they rev at pretty constant speeds and at high revs as well.
Look at the comments. AIE UK say:
"No the exhaust reactor does not have a separate ignition source, the hot exhaust gasses (around 950◦C) from the engine will transfer to the CREEV unit in a turbulent manner with unconsumed oxygen present and continue to "react" as expansion takes place."
https://www.youtube.com/watch?v=AQJsmbzlMM0&t=...
Edited by RayTay on Friday 9th December 10:57
Max_Torque said:
It can, but lets say you put in a huge amount of development effort to "double" something. If you start with a better solution, doubling that is still better than doubling a less-good-in-the-first-place thing!
I agree with you, but, that assumes all things are equal. They must have a good reason "in their minds" at leastRayTay said:
This takes the rotary right up with the best of piston engines in fuel and emissions.
What is the basis of this claim? You keep saying this technology makes a rotary engine as good as or better than the best piston engines in terms of fuel consumption / efficiency and emissions, but I can't see the basis of that statement in any of the links or discussion you've presented.RayTay said:
Exhaust reactors and HCCI apply equally to piston engines, however they improve the rotary dramatically while only improving piston engines marginally.
That's like saying slim fast works best on fat people. That doesn't mean slim fast will turn you into an athlete.The basis of this claim are the press releases on R&D and quality mag' articles. In the past year quite a few patents have been filed on the rotary engine. I have given some of the recent advances. If Lith-air battery technology comes about in 5 years or so on the market, IC advancements will be for little. It is best to be open mined on these matters, not cynical.
Edited by RayTay on Saturday 10th December 13:55
RayTay said:
The basis of this claim are the press releases on R&D and quality mag' articles. In the past year quite few patents have been filed on the rotary engine. I have given some of the recent advances.
And I haven't found your claim in any if them. Improving efficiency and emissions yes. Improving them to the level of piston engines no. Have I missed it?Yes you did.
At constant speeds the rotary meets piston engines in fuel & emissions.
The rotary engine is not dead or dying as there is ongoing R&D - UAVs use it. New patents were filed only weeks ago on the engine. As I wrote and moreso articles point to, the ideal application of the rotary looks like range-extending (a genny). Its small size, low weight and exceptional smoothness are great advantages in a part time engine-genny tucked away out of sight in a car. Have a piston range-extender and rotary range-extender of exactly the same physical dimensions - the rotary will strip the piston engine in output, which is a great advantage. Electric motors in wheel hubs and very small in physical size range-extender gives car designers so much scope.
With range-extenders, it is a case of watch this space - either free-piston linear generators or rotary generators look like the leaders. All exciting stuff. Only at the beginning of the automobile has so much R&D and change been seen. Exciting times ahead.
At constant speeds the rotary meets piston engines in fuel & emissions.
The rotary engine is not dead or dying as there is ongoing R&D - UAVs use it. New patents were filed only weeks ago on the engine. As I wrote and moreso articles point to, the ideal application of the rotary looks like range-extending (a genny). Its small size, low weight and exceptional smoothness are great advantages in a part time engine-genny tucked away out of sight in a car. Have a piston range-extender and rotary range-extender of exactly the same physical dimensions - the rotary will strip the piston engine in output, which is a great advantage. Electric motors in wheel hubs and very small in physical size range-extender gives car designers so much scope.
With range-extenders, it is a case of watch this space - either free-piston linear generators or rotary generators look like the leaders. All exciting stuff. Only at the beginning of the automobile has so much R&D and change been seen. Exciting times ahead.
Edited by RayTay on Saturday 10th December 13:53
RayTay said:
The basis of this claim are the press releases on R&D and quality mag' articles. In the past year quite a few patents have been filed on the rotary engine. I have given some of the recent advances. If Lith-air battery technology comes about in 5 years or so on the market, IC advancements will be for little. It is best to be open mined on these matters, not cynical.
Press releases and magazine articles derived from press releases, so nothing that you can hang a hat on; I'll wait this one out and be pleasantly surprised if any of it graduates from vapourware.Edited by RayTay on Saturday 10th December 12:28
hidetheelephants said:
Press releases and magazine articles derived from press releases, so nothing that you can hang a hat on; I'll wait this one out and be pleasantly surprised if any of it graduates from vapourware.
Many articles quote directly from R&D engineers, see back on my posts and I did as well, saving many the hassle of Googling. We will all have to ride it out and wait as in any advancements. Electric battery advancements may render all internal combustion engine advances superfluous. Top R&D institutions like Cambridge and MIT are working on battery advances with some breakthrough results.As for vapourware, the rotary is made by a number of companies around the world. If you read my posts you will see that new patents from a number of sources, inc' Mazda, were filed on the engine only a few months ago.
One thing is clear is that the outdated and highly inefficient "piston engine/g-box/direct-drive" arrangement is on its way out. We are on the way to the tipping point.
Edited by RayTay on Saturday 10th December 13:52
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