[erd39030]

A few years ago I read something about an engine like the Wankel's kind, but without its typical sealing problems.
They said something about the Brayton cycle wich in turn will make that engine 3 times more efficient that the actual internal combustion engines.

Have you heard about it? It was called Star Rotor.

http://www.starrotor.com/Engine.htm

I think it would be nice to keep an eye on that subject... and perhaps build something fun.

Have a nice day:

Everardo

P.D. For the link to work, you must change the "e" of engine to "E"

[Gumby]

Your link doesn't work.

I've heard of other rotary engine designs but they all suffer from sealing and reliability issues. There have been very few rotary engine designs that have actually made it to production because of those issues and only one to have had any notable success.

[307startup]

Gumby,

Because of the problem of the vanishing capital letters here on the zone, you will need to capitalize the first E in engine to get the link to work.

Erd39030,

It's basically two gerotors on a shaft. Most modern engines uses gerotors for the oil pump design. You could probably find two gerotor gears and their mating outer rotors from the Ford Modular engine and build your own "Star rotor" engine fairly easy if you are able to discern the rest of the components they are using.

[samco]

hmmm
http://www.starrotor.com/ (click on 'engine' on the left)

since when did the laws of thermal dynamics change?

I thought the maximum possible efficency out of converting heat energy into mechanical energy was 50%. (and that was pretty much impossible to reach). But I am sure this is all covered up by big oil... I would like to have 120mpg..

Benefits:
The StarRotor engine is projected to be very efficient (45-60%). By simply replacing conventional engines (15-20% efficiency) with a StarRotor engine, fuel economy will double or triple. For example, a conventional luxury car getting about 25 mpg on the highway would get about 75 mpg. A conventional economy car getting 40 mpg would get about 120 mpg.

[JBV]

"i thought the maximum possible efficency out of converting heat energy into mechanical energy was 50%"

http://people.bath.ac.uk/ccsshb/12cyl/
"At maximum economy the engine exceeds 50% thermal efficiency."

[erd39030]

Wow!

That diesel engine is bigger than my shop.

I don't know about thermodynamics. So why it is that thermal-to-mechanical efficience is topped at 50%? Is it related to the temperature difference inside-outside the combustion chamber?

I will study those gerotors in the mechanical pumps.

[Gumby]

Where did you get 50% from? There are Brayton engines that get better than 60% efficiency. The theoretical limit of efficiency of the Carnot cycle is 90%.

Steam turbines have been known to get 90+% however if you take into account the inefficiencies of the rest of the system (ie boiler) then it tends to put the entire systems efficiency at 10 - 20% lower than the engine's efficiency.

[erd39030]

Now the big question:

Would be more economical to make starotor engines with low precision, than make high precision machined conventional engines? They shold give the same mpg.

[zhagoox]

I'm an inventor and mine is currently the most advanced one:



Here is my patent application:

http://www.wipo.int/pctdb/en/wo.jsp?wo=2007097608

Would love to see someone in the forum build a prototype. With all those CNCs around I bet it would be pretty simple...

[EdgeOfEpsilon]

In response to zhagoox:

Your gate seems to be of less than optimum design. Firstly, it would produce a great deal of wear where the gate strikes the rotor. Additionally, the potential energy stored in the spring would be wasted when the gate strikes the rotor. Wouldn't it be more efficient to shape the gate and piston like a sine curve? That way, the gate would contribute its potential energy back into the rotation of the rotor, and the acceleration of all components (including the gate) would be smooth and continuous, rather than jerky as in the current diagram.

I'm not quite sure I understand the diagram here, but it seems as if your design attempts to ignite an uncompressed fuel-air mixture. Is this the case? Or is this just a diagram of the expander portion?

[zhagoox]

Yeah, it can be refined quite a bit. It's by no means a finished design; in fact, it's no design at all, just a conceptual drawing for a patent. I've done my part on research, it needs a bit of development and I welcome all ideas.

Your idea sounds good, but it has to retain the sharp angles (and thus jerky movement) because the gate must close quickly after the piston passes.

Also, this engine is a mixture of an internal combustion engine and a turbine. It's an engine because it uses a piston with seals, but it's a turbine also because it does not perform the compression cycle inside the assembly. So it's essentially a 3 stroke engine where all of them are performed simultaneously.

So no... the mixture is pre-carburated and compressed before it enters the combustion chamber. That job is done simultaneously by an identical assembly running backwards, as all engines are, when reversed, compressors and vice versa. In fact, this engine started as a compressor and it worked pretty well (we built a prototype).

[erd39030]

Well, Zhagoox. You put the materials, I'll make them for free (and for fun)
I am in Ciudad Juárez.

Everardo Rascon
[email protected]

[samco]

I thought 50% was the limit - I must be wrong. (trying to remember my college physics.) (converting heat into mechanical engergy)

zhagoox: As far as the engine above.. What about changing the taper on the rotor into a 'Gear tooth' - then having a 5 or so tooth gear in place of the gate? Every time around it would advace the 5 tooth gear one tooth and seal at the same time. (perfect matching profile on the teeth)

sam

[delt0r]

So as a physics dude I can comment on efficiency.

The maximum efficiency of *any* heat engine is limited to carnot cycle efficiency. It depends on the temperature difference only.

The formula is: Th/(Th+Tc)

Where Th is the hot temperature in kelvin or rankine and Tc is the cold temperature.

http://en.wikipedia.org/wiki/Heat_engine

Example: A steam turbine with a steam inlet temperature of 1000 deg C (1273 kelvins) and a exit temperature of 100 deg C (373 kelvins) has a max Efficiency of 1273/(1273+373)=0.773 or 77%. Modern power stations get 50% these days. Car engines get about 25% to 30% and bigger gas turbines are somewhere in between.

As for the star rotor design. They look good on paper, but getting the seals to work over the required temperature range is very hard to do. The other problem is that current generation piston engines are just so dam good at what they do.

[greybeard]

I followed the Star Rotor link and thought I had seen it earlier today.
Admittedly this is steam, but there you go.

http://www.dself.dsl.pipex.com/MUSEU...oule/soule.htm

Regards
John