PDA

View Full Version : New Rotary Engine design.



Sev
04-05-2011, 03:21 PM
It has a theoretical efficiency of 74% If achievable that would be an excellent improvement.

http://www.technologyreview.com/video/?vid=683

wolfdancer
04-05-2011, 05:58 PM
Interesting!!
I took a course once on the efficiency of combustion engines. The benchmark for comparison is the theoretical "Otto" engine, which operates at 100% efficiency.
AS I remember, and it's been decades, the Wankel engine, a German design?, scored high initially, but had a major problem in that the chamber seals wore down.
Too bad that Deeman has given up on the site, as he is a mechanical Engineer, and might have had a more technical comment to add to the thread.

Sev
04-05-2011, 06:04 PM
I believe the seals are still a major problem for the Wenkel. The engines themselves have a very long lifespan if maintained properly.

sack316
04-05-2011, 11:52 PM
My folks still have an '85 (I believe) RX-7... whatever the last year of the old body style was. Loved the rotary in that thing! And in the 25+ years they have had it, I bet it still doesn't have 50K miles on it!

Sack

pooltchr
04-06-2011, 06:33 AM
I am not a mechanical engineer, but I always thought that a rotary motion would almost have to be more efficient than the reciprocating motion of pistons. I'm somewhat surprised that it has taken so long for someone to take the wankel and explore the possibilities.

Steve

LWW
04-06-2011, 07:15 AM
That depends on how you define efficiency.

Having owned an RX3 in the mid 1970's in the commonwealth of Kentucky I learned the ins and out of the rotary well.

What we would call a crankshaft is replaced by what's called an eccentric shaft,

The eccentric shaft turns at three times the speed of the rotor, so 5,000 RPM on the tach is actually 15,000 RPM ... Mazda uses a reduction gear and a standard tach rather than develop one specifically for the rotary. Or at least they did so in the past.

To make a short story long, for a 1,300 CC or so engine they are very efficient at making power for X displacement as well as for X engine weight of X external engine size.

They are even fairly efficient at fuel use for X horsepower output.

Where they are inefficient, that many buyers are aware of until it's too late, is at fuel consumption for X engine displacement.

They also burn oil as part of the combustion cycle, and most Americans simply won't check the oil at every fill up. If you don't, rotor seals will wear out prematurely.

A great sports car engine ... not so much so as an everyday passenger car engine.

Sev
04-06-2011, 12:30 PM
I could have sworn at one point the guy said they were using gasoline as well as diesel. Of course he could have said gas by accident.

cushioncrawler
04-06-2011, 05:40 PM
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: pooltchr</div><div class="ubbcode-body">I am not a mechanical engineer, but I always thought that a rotary motion would almost have to be more efficient than the reciprocating motion of pistons. I'm somewhat surprised that it has taken so long for someone to take the wankel and explore the possibilities.Steve</div></div>I aint sure, but i think that if u connect wts (pistons) with a rotary style crank then the whole moovment iz az efficient az a 100% rotary moovment. But it mightnt be quite 100%.
When i woz researching my paddlewheel boat one source explained that if u make a pedalling motion with your 2 feet/legs u will soon get tired. But if u pedal proper bike pedals u kan pedal for a long time without getting tired, and u kan apply more power and torq if u want. Koz the pedals link your 2 legs to make a rotary motion, more efficient, less wasted energy.

Wanking iz the same -- so i figure a wankel makes sense.
mac.

wolfdancer
04-06-2011, 11:27 PM
Mac, they did try the Wanker engine over here, in the original Mazda, as I remember:
"Piston engine goes boing, boing, boing, boing. Mazda engine goes Hmmmmmmmmmmmmmmm...."
As I remember....(I have to add that in to most of my posts) the engine was high maintenance, and Mazda changed to the boing, boing engine.
The only rotary piston engine I know of was on airplanes?
The Sub that I was one and there were 5 in it's class, all had "pancake" engines ...rotary diesel engines that never could run at 100% for the required time to be approved. They should have known better...they stole the design from the Germans. The engine room crew spent half of their time rebuilding them.

LWW
04-07-2011, 02:35 AM
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: cushioncrawler</div><div class="ubbcode-body">[I aint sure, but i think that if u connect wts (pistons) with a rotary style crank then the whole moovment iz az efficient az a 100% rotary moovment. But it mightnt be quite 100%.

mac. </div></div>

Can't be done.

The inherent inefficiency that is locked in to piston engines is that the piston has to intake - accelerate - decelerate - stop - accelerate - decelerate - stop - exhaust as a full cycle.

All the rotor need do is spin at a consistent speed ... or accelerate, or decelerate ... as the two distinct stops in each of the cycles aren't required.

LWW
04-07-2011, 02:37 AM
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Sev</div><div class="ubbcode-body">I could have sworn at one point the guy said they were using gasoline as well as diesel. Of course he could have said gas by accident. </div></div>

I didn't listen to the whole video, but I've never heard of a diesel rotary.

Making a workable engine which would be both spark ignition and compression ignition would be quite the challenge.

LWW
04-07-2011, 02:39 AM
A rotary piston engine is pistons in a circle around a crankshaft and is nothing remotely close to a Wankel design.

Sev
04-07-2011, 06:46 AM
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: LWW</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Sev</div><div class="ubbcode-body">I could have sworn at one point the guy said they were using gasoline as well as diesel. Of course he could have said gas by accident. </div></div>

I didn't listen to the whole video, but I've never heard of a diesel rotary.

Making a workable engine which would be both spark ignition and compression ignition would be quite the challenge. </div></div>

He def said diesel and gas at one point. Give it a listen and let me know what you think.

cushioncrawler
04-07-2011, 05:29 PM
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: cushioncrawler</div><div class="ubbcode-body">I aint sure, but i think that if u connect wts (pistons) with a rotary style crank then the whole moovment iz az efficient az a 100% rotary moovment. But it mightnt be quite 100%. mac.</div></div><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: LWW</div><div class="ubbcode-body">Can't be done. The inherent inefficiency that is locked in to piston engines is that the piston has to intake - accelerate - decelerate - stop - accelerate - decelerate - stop - exhaust as a full cycle. All the rotor need do is spin at a consistent speed ... or accelerate, or decelerate ... as the two distinct stops in each of the cycles aren't required.</div></div>Yes we can. It might not be az efficient az a proper rotary setup, but the piston duznt havta accelerate and decelerate -- the pistons akt on eech other, they all accel and decel eech other, allmost the same efficiency az having a proper rotary.

The same for a bike. If u lie on your back with feet in the air and air-pedal u will soon tire (they say), but if u sit on a bike and free-pedal with the crank helping to giv a rotary aktion and (allmost) rotary efficiency etc then u sort of never tire (they say).
But its a bit hard to imagine what iz going on.
For instance with a pedal powered paddlewheeler of the type where eech foot pushes a board and the board haz a linkage back to a crank on the axel of the paddlewheel then this too iz a rotary style setup -- but i am thinking that the efficiency here gets a C, kompared to A for a proper rotary, and B for a bike pedal type rotary.
mac.

wolfdancer
04-07-2011, 11:43 PM
Thanks, but as I took a course covering diesel engines, while studying for my 3rd engineer's license (merchant marines); also passed the Coast Guard (which issues the licenses)exam on diesel engines....I suspected as much.
Our Sub had Fairbanks Morse "16 in-line" diesel engines. I did not work on them, but did see them being worked on. They installed these after the "pancake" engines (rotary piston engine) "is pistons in a circle around a crankshaft" were scrapped.
I also read up on the Wankel engine, as I was considering getting a Mazda....

JohnnyD
04-08-2011, 01:23 AM
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: wolfdancer</div><div class="ubbcode-body">Thanks, but as I took a course covering diesel engines, while studying for my 3rd engineer's license (merchant marines); also passed the Coast Guard (which issues the licenses)exam on diesel engines....I suspected as much.
Our Sub had Fairbanks Morse "16 in-line" diesel engines. I did not work on them, but did see them being worked on. They installed these after the "pancake" engines (rotary piston engine) "is pistons in a circle around a crankshaft" were scrapped.
I also read up on the Wankel engine, as I was considering getting a Mazda.... </div></div>
Looks like LWW had to tell you again.

REMEMBER TO STAY AWAY FROM CHILDREN.