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What is the maximum compression ratio of the wankel?

 
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RickW



Joined: 13 Sep 2005
Posts: 8

PostPosted: Tue Sep 13, 2005 9:52 am    Post subject: What is the maximum compression ratio of the wankel? Reply with quote

I know there is a limit of how wide the epitrochoid can be before it impedes the triangular rotor's ability to rotate along the curve. But what is that limit?

What is the compression ratio of the standard wankel engine?

If you could increase the ratio, what is the limit?
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Blake
Been there, done that


Joined: 12 Jul 2005
Posts: 135
Location: Portland, OR

PostPosted: Tue Sep 13, 2005 2:06 pm    Post subject: Re: What is the maximum compression ratio of the wankel? Reply with quote

RickW wrote:
I know there is a limit of how wide the epitrochoid can be before it impedes the triangular rotor's ability to rotate along the curve. But what is that limit?

What is the compression ratio of the standard wankel engine?

If you could increase the ratio, what is the limit?


Typical compression ratios are 8.5:1 (turbo RX-7) 9.0:1 (turbo RX-7), 9.4 (NA RX-7), 9.7 (NA RX-7) and 10.0:1 (RX-Cool. The "limit" depends on a great many things, including the fuel type and combustions timing. Usually, if you keep increasing compression ratio, then the requisite retardation of ignition timing to avoid detonation eventually nets you less power...so that is the practical limit for a given fuel. It's all in the tradeoff. One set of compromises could make you more power while a different set of compromises is more efficient. If you can do both, you are really going somewhere.
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RickW



Joined: 13 Sep 2005
Posts: 8

PostPosted: Tue Sep 13, 2005 2:39 pm    Post subject: Re: What is the maximum compression ratio of the wankel? Reply with quote

Blake wrote:

Typical compression ratios are 8.5:1 (turbo RX-7) 9.0:1 (turbo RX-7), 9.4 (NA RX-7), 9.7 (NA RX-7) and 10.0:1 (RX-Cool. The "limit" depends on a great many things, including the fuel type and combustions timing. Usually, if you keep increasing compression ratio, then the requisite retardation of ignition timing to avoid detonation eventually nets you less power...so that is the practical limit for a given fuel. It's all in the tradeoff. One set of compromises could make you more power while a different set of compromises is more efficient. If you can do both, you are really going somewhere.


Okay assume for now that fuel is not involved. I'm talking theoretical now - what is the geometrical limitation.
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Arawn



Joined: 06 Nov 2005
Posts: 11
Location: Bridgeport, Conn

PostPosted: Sun Nov 06, 2005 11:48 am    Post subject: Epicycloid? Reply with quote

I'm still endevouring to grok the Trigonometry of the Rotary Engine, but you're probably limited by the internal gearing.

I don't even know if I've the Java Compiler, to model the motions on.

Where do we find a text on Cycloid and Roleaux(sp?) Trigonometry?

Arawn
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Blake
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Joined: 12 Jul 2005
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Location: Portland, OR

PostPosted: Mon Nov 07, 2005 8:29 pm    Post subject: Re: Epicycloid? Reply with quote

Arawn wrote:
I'm still endevouring to grok the Trigonometry of the Rotary Engine, but you're probably limited by the internal gearing.

I don't even know if I've the Java Compiler, to model the motions on.

Where do we find a text on Cycloid and Roleaux(sp?) Trigonometry?

Arawn


Do you mean the geometry of the peritrochoid?





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Arawn



Joined: 06 Nov 2005
Posts: 11
Location: Bridgeport, Conn

PostPosted: Tue Nov 08, 2005 8:57 pm    Post subject: Crank on a Gear Reply with quote

Quote:
Theoretically, the peritrochoid is defined as a locus...

I'd describe it as the path of a crank on a gear, and that crank radius might correlate to the Eccentricity. I'm not sure how to describe the gears the crank is theoretically on, or how to relate them to the Roleau Triangle, or whatever that curve is.

When the original question was asking about the theoretical limit of Epitrochoid Width, before the shape gets in the way of the Rotor, is that as the Epitrochoid goes to Circular? The opposing limit would be defined by the circle of the Internal Gear.

The motion of the system still boggles this imagination, and I'm far enough out to question the need for a Compression Stroke.

Arawn
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jptg



Joined: 25 Jul 2005
Posts: 66
Location: CA

PostPosted: Thu Nov 10, 2005 3:18 pm    Post subject: Reply with quote

Blake, is it ok if you can tell me were you got those petrichoid references? Thanks JP
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Blake
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PostPosted: Thu Nov 10, 2005 7:19 pm    Post subject: Reply with quote

jptg wrote:
Blake, is it ok if you can tell me were you got those petrichoid references? Thanks JP


"Rotary Engine" by Kenichi Yamamoto, copyright 1969. Long out of print and hard to find.
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Arawn



Joined: 06 Nov 2005
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Location: Bridgeport, Conn

PostPosted: Fri Nov 11, 2005 10:04 pm    Post subject: Diesel Reply with quote

Blake wrote:
Typical compression ratios are 8.5:1 (turbo RX-7) 9.0:1 (turbo RX-7), 9.4 (NA RX-7), 9.7 (NA RX-7) and 10.0:1 (RX-. The "limit" depends on a great many things, including the fuel type and combustions timing. Usually, if you keep increasing compression ratio, then the requisite retardation of ignition timing to avoid detonation eventually nets you less power...so that is the practical limit for a given fuel. It's all in the tradeoff. One set of compromises could make you more power while a different set of compromises is more efficient. If you can do both, you are really going somewhere.

With a bit of Charging, these ratios would make Dieselling an option. You'd simply inject the fuel as the Trough went by, as much fuel as appropriate.

I've been thinking that a Diesel would be useful for the office power of a Police Car, while Police Officers think the accelleration of a Wankel would make more sense.

I find my town's library has something on Rotaries, but not the Yamamoto.

Arawn
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