Noobie Tech Question:Rotary?Rotate what?
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from howstuffworks.com
A rotary engine is an internal combustion engine, like the engine in your car, but it works in a completely different way than the conventional piston engine.
In a piston engine, the same volume of space (the cylinder) alternately does four different jobs -- intake, compression, combustion and exhaust. A rotary engine does these same four jobs, but each one happens in its own part of the housing. It's kind of like having a dedicated cylinder for each of the four jobs, with the piston moving continually from one to the next.
The rotary engine (originally conceived and developed by Dr. Felix Wankel) is sometimes called a Wankel engine, or Wankel rotary engine.
Like a piston engine, the rotary engine uses the pressure created when a combination of air and fuel is burned. In a piston engine, that pressure is contained in the cylinders and forces pistons to move back and forth. The connecting rods and crankshaft convert the reciprocating motion of the pistons into rotational motion that can be used to power a car.
In a rotary engine, the pressure of combustion is contained in a chamber formed by part of the housing and sealed in by one face of the triangular rotor, which is what the engine uses instead of pistons.
The rotor follows a path that looks like something you'd create with a Spirograph. This path keeps each of the three peaks of the rotor in contact with the housing, creating three separate volumes of gas. As the rotor moves around the chamber, each of the three volumes of gas alternately expands and contracts. It is this expansion and contraction that draws air and fuel into the engine, compresses it and makes useful power as the gases expand, and then expels the exhaust. -
The Parts
A rotary engine has an ignition system and a fuel-delivery system that are similar to the ones on piston engines. If you've never seen the inside of a rotary engine, be prepared for a surprise, because you won't recognize much.
Rotor
The rotor has three convex faces, each of which acts like a piston. Each face of the rotor has a pocket in it, which increases the displacement of the engine, allowing more space for air/fuel mixture.
At the apex of each face is a metal blade that forms a seal to the outside of the combustion chamber. There are also metal rings on each side of the rotor that seal to the sides of the combustion chamber.
The rotor has a set of internal gear teeth cut into the center of one side. These teeth mate with a gear that is fixed to the housing. This gear mating determines the path and direction the rotor takes through the housing.
Housing
The housing is roughly oval in shape. The shape of the combustion chamber is designed so that the three tips of the rotor will always stay in contact with the wall of the chamber, forming three sealed volumes of gas.
Each part of the housing is dedicated to one part of the combustion process. The four sections are:
* Intake
* Compression
* Combustion
* Exhaust
The intake and exhaust ports are located in the housing. There are no valves in these ports. The exhaust port connects directly to the exhaust, and the intake port connects directly to the throttle. -
Output Shaft
The output shaft has round lobes mounted eccentrically, meaning that they are offset from the centerline of the shaft. Each rotor fits over one of these lobes. The lobe acts sort of like the crankshaft in a piston engine. As the rotor follows its path around the housing, it pushes on the lobes. Since the lobes are mounted eccentric to the output shaft, the force that the rotor applies to the lobes creates torque in the shaft, causing it to spin.
Producing Power
Rotary engines use the four-stroke combustion cycle, which is the same cycle that four-stroke piston engines use. But in a rotary engine, this is accomplished in a completely different way.
The heart of a rotary engine is the rotor. This is roughly the equivalent of the pistons in a piston engine. The rotor is mounted on a large circular lobe on the output shaft. This lobe is offset from the centerline of the shaft and acts like the crank handle on a winch, giving the rotor the leverage it needs to turn the output shaft. As the rotor orbits inside the housing, it pushes the lobe around in tight circles, turning three times for every one revolution of the rotor.
animation of how rotary engines work[/url] -
hmm Rotary engines..Rx-7 is one example
Advantages: Very small and lightweight, high revs, extreme HP/lt ratio, cool sound
Disadvantages: Expensive, burns too much fuel and oil, slightly unreliable
By the way: there are also inline, V/W, flat/boxer engines -
The shape of the oval-like housing is called an epithrochoid...
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no wonder peak power at 9500rpm...Originally posted by HENG@: -
I just thought of something, the seals look like they can hit the wall of both the intake and the exhaust area...Originally posted by HENG@:
I guess that's why early Wankel engines aren't reliable...
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its called precision engineering... its the same for piston engines... why do you think cars were so expensive back then?Originally posted by bunny2002sg:I just thought of something, the seals look like they can hit the wall of both the intake and the exhaust area...
I guess that's why early Wankel engines aren't reliable... -
no. he is right. they DID hit the walls of the intake and exhaust ports which led to seal failure and unrealiablity in early rotary engines. which is why the ports have been moved to the walls perpendicular to the axis of piston rotation.Originally posted by TwinTurbo_Supra:its called precision engineering... its the same for piston engines... why do you think cars were so expensive back then? -
i didnt say he was wrong...Originally posted by HENG@:no. he is right. they DID hit the walls of the intake and exhaust ports which led to seal failure and unrealiablity in early rotary engines. which is why the ports have been moved to the walls perpendicular to the axis of piston rotation. -
i just found out how fast a rotary engined car could go
after watching the Lemans 24hr video........the one when a mazda won......
weeeeeeeeeeeeeeeeeeeeeeeeeeeee
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siao ah u...
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well in SG i dun see any pt of having a rotary car apart from performance and even so its expensive compared to a normal piston engine....yes its light,compact and so on but i won't wanna spend so much esp on petrol(nowadays so expensive) reliablity wise its ALOT better but still lose out 2 piston and torque-wise too...wnat a high revving engine go get the integra la
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cannot...must be like cyclops.....Originally posted by AE86tofu:well in SG i dun see any pt of having a rotary car apart from performance and even so its expensive compared to a normal piston engine....yes its light,compact and so on but i won't wanna spend so much esp on petrol(nowadays so expensive) reliablity wise its ALOT better but still lose out 2 piston and torque-wise too...wnat a high revving engine go get the integra la
Zaaaaaaaap!!!!!! -
or the Skyline R32 GTR...can ram till 10000rpm as well