I've heard of rotary engines with no apex seals. anyone have any pictures of these internals or know anything about them, any advantages or dis-advantages? just curious

 

apex seal r like piston rings, without them, there's no compression.

 

some of the first engines made by mr. wankel i believe
had no apex seals, these were the engines that rotated
while the e shaft was fixed, they started at 5000+ rpm
and started to make power at over 15,000 rpm.
a rotary starts much easier with apex seals

matt

 

wow thats crazy thanks

 

The E-shaft wasn't fixed, but the rotor was fixed to the shaft. The shaft rotated and was mounted off-center in a big cylindrical housing, and the rotor housing rotated on-center in the cylindrical housing.

 

The DKM (drehkolbenmotor), or what could be seen as the first engine, did have apex seals. Right from the first visions (in 1923) Dr Felix Wankel understood the importance of the sealing. He developed seals for 30 years, and build the first engine only then when he had achieved a good sealing quality.
The engine idea can be seen here:
http://www.der-wankelmotor.de/Felix_...ix_wankel.html
The pic does show apex seals, doesn't it?
This is how it worked:
http://www.der-wankelmotor.de/Techni...km_vs_kkm.html
The DKM is the upper one, the KKM (kreiskolbenmotor, or the basic engine we are all using) is in the middle, the 3rd drawing shows the KKM's working order.
The DKM is different in a few ways, one of them being that the rotor does not tansfer energy, it's there only for sealing purposes. The housing (moving part) transfers the energy, while being mounted in another housing.
Positive points: no bitemarks from the apex' in the housing, perfect sealing, very high revs without shaking, much better running.
Negative: impossible to use: to change spark plugs the engine has to be taken apart!

 

Spark plugs these days are quite good. I'm sure the DKM could find a niche out there.

 

Maybe this one will make the rotary / Wankel much more efficient and do away with the apex seal issues. Combined with hydrogen enriched fuels you may reduce emissions, increase power and decrease heat.

https://www.hotcars.com/how-tiny-wan...d-not-to-fail/

 

Wankel's DKM engine does not need to be dissasembled to change the spark plugs in the rotor faces.

There was an engine cover that was removed, outer rotor (rotor housing) rotated and a spark plug removal tool inserted through the exhaust port in the outer rotor.

Because there was no eccentricity apex seals did not have a varying leaning angle like in our KKM Wankel rotary engines.

They would wear straight down from the tip (matching the rotor housing profile like a piston ring to cylinder bore).

 

DKM should be revisited with ceramics, cerametallics and carbon materials technology.

The inner three faced rotor could have a centrifugal supercharger machined inside it since the airflow is from rotor center out to ports at the rotor corners.

A radial flow turbine/flywheel could be housed on the back geared down to the outer rotor for exhaust energy recouperation (like an over road diesel with mechanical turbo compounding).

Could be a good, cheap quasiturbine capable of quick start/stops for a hybrid car's generator.

 

This isn't true, the eccentricity has nothing to do with the apex seal angle, just the rotor housing shape. Specifically, the fact that there IS a shape to the rotor housing.

DKM and KKM engines have exactly the same rotor to rotor housing interface, the only difference is that the rotor housing is stationary in the KKM, so the rotor has to orbit the shaft.

 

Norbye
"The Wankel Engine"
1971

Pg 36
"The maximum 'leaning' angle in a parricular engine is dependent on the radius/eccentricity ratio. The angle gets higher with lower R/e ratios. Extreme angles (from perpendicular) are detrimental to proper sealing, and therefore are to be avoided. It is generally held that 30 degrees is a practical limit."

The preceeding illustration shows two KKMs Wankels.

-One with a bigger rotor having a K factor (Radius/eccentricity) of 7.68 and an eccentricity of 8.5 generating a max apex seal lean angle of 23°

-The second with a smaller rotor having a K factor (Radius/eccentricity) of 5.66 and the same eccentricity of 8.5 generating a max apex seal lean angle of 32°.

The converse is of course also true. The more eccentricity per a given rotor radius provides more max apex seal lean angle.


When Mazda stroked the 16X rotary (and whatever they call the new production rotary) giving it more eccentricity they also made the rotor a larger diameter to keep the K factor high avoiding apex seal lean angle over 30°.

 

However, I was wrong that the DKM has no eccentricity.

Though the triangular inner rotor and peanut shaped outer rotor rotate concentrically (share a center) and each rotates along its own center of gravity (hence the perfect mechanical balance) the outer rotor does not rotate along its geometrical centerline as the inner rotor does.

Its like Peejay says, this eccentricity is what gives the DKM the same familiar peanut rotor housing shape as the Mazda KKM rotary. The eccentricity just isnt in the shaft, its in the outer rotor housing in the DKM.