As you may realize a rotary engine works different than the recipricating conventional piston engine you would find in most cars. The rotary engine is still a combustion engine in the sence that it burns fuel in order to run, but instead of using pistons the engine uses rotars, Triangular shaped discs. The rotars are justifiably the equivilence of the piston in a recipricating engine.
In a piston engine the cylinder that the piston is in provides the space for four different actions--The intake, compression, combustion, and exhaust-- to take place. The rotary does the same four actions but basically has an individual housing for each. This allows the rotor to keep moving. Instead of being like a piston and going up the cylinder, stopping, asking for dirrections, and then going back down, the rotor keeps moving around in a cockeyed circular motion.
Basic layout of a Wenkel Engine
The rotor for the engine sits in a housing, called a chamber. The chamber, as seen in the picture above is like a figure 8 pattern that isnt connected in the center allowing the rotor to move around in it. The rotor has metal plates on each of the tips, called apex seals. These seals seal the rotar to the camber, acting like piston rings from a conventional engine, allowing for no compression or gases to escape. Also instead of having valves the engine has ports, which are small holes that allow gases to enter and escape when needed. The rotor has a hole in the middle with a small gear sitting to one edge, this is what the rotar rotates around and keeps going the right direction. Instead of being like most piston engines and having a sparkplug per piston, a rotary engine has two spark plugs per camber, at which there are normally two chambers, four spark plugs all together. there is a wall seperating the two chambers and there is a wall on the ends of each of the chambers encasing the whole engine. The two rotars move around on a shared shaft, normally reffered to as the eccentric shaft because of the eccentric lobes. There is also a counterbalance weight that keeps the engine balanced
How it produces power
The Wenkel engine uses the same for strokes as the conventional engine does, but it acts in a completely different manner. Instead of using one cylinder to complete each of the four steps, intake, compression, combustion, and exhaust, it uses 3 chambers in one housing sealed off by the rotors apex seals. In one section of the housing the Intake is taking place, In another the combustion is taking place, and in another the exhaust is taking place. The compresion cycle happens as the rotor rotates between the Intake "stroke" and the Combustion "stroke". So the rotor keeps moving constantly through each cycle. While one phase is happening another is beginning, and another is ending.
So a break down of each of the steps would be, as the rotor moves pass the Intake port it causes a vacuum and sucks in the air/fuel mixture. It then moves onward forcing the air/fuel mixture to condence into the tightened space provided by the cast, or housing. From there it move towards the first spark plug growing into the combustion stage of the cycle. The combustion chamber of the rotary engine is long so if there was only one spark plug the "flame" would move too slowly, so there is two spark plugs to assist with this problem. The spark plugs then ignite causing the gases to combust forming the exhaust. The exhaust then expands due to its hot temperatures keeping the rotor moving toward the exhaust port allowing the gases to escape out of the engine. Every time one of the sides of the rotor moves to the next step there is also two other steps begining and happening. So for every revolution there is three steps that happened per side, which adds up to nine steps per rotor revolution, and eightteen steps per revolution of both rotors. Also there is two intake, compression, power, and exhaust "strokes" that happen at the same time. When one rotor has a step happening the other rotor follows closley behind but not exactly at the same time. So this in turn provides more power output than a regular conventional engine seems thought there all the steps are happening all the time and its a continuos flow of "energy" so to speak.
Comparisons of Wenkel and Conventional
Some main differences between the two engines is that the rotary engine has far fewer moving parts, and parts in general, than a regular recipricating engine. An rotary engine only has three major moving parts, the two rotors and the output shaft. An Recipricating engine has at least fourty, on the smaller engines and almost double on the larger V8/V10 designs. This in part allows for a simpilar sequence to take place making it more eficient in that sence.
Also with there not being as many moving parts as in a conventional engine the rotary engine runs much smoother. Theres the fact of the rotor constantly moving at all times allowing it to aid in the smoother running, compared to the piston engine having the piston go up the cylinder, stop, and then come back down, stop, then go back up, ect. You can see how it would be smoother and also more reliable at that.
Though the wenkel engines have come along way, back in the day they werent exactally emmisions friendly. Being a totaly different kind of engine it was hard for the rotary producing companies to keep up with the times. As the emmisions laws started to stricten as the time went on the deadline for the updates on the rotary engines were growing short, not allowing for very good compatibility. Though now days with the RX-8's new emmissions friendly Renesis two rotor natuarly aspirated engine it looks like Mazda has made a turn for the best concerning the rotary engines.
Something thats easily overlooked, is the power comparison between the two engines. Each combustion stage lasts about 90 degrees of the rotors revolution, and the output shafts travels three revolutions per revolution of the rotor, the combustion event lasts about 270 degrees of the output shafts revolution,meaning that a single rotary engine delivers power for three quarters of each revolution of the output shaft. When a conventional single cylinder engines combustion only occurs during a 180 degree turn every two rotations, or in other words a qaurter of a revolution of the crankshaft. Thats an extra 90 degree difference that the rotary engine puts out of combustion, which allows for more power.
Weight is also a big difference, because there is not as many parts or parts in motion as a conventional engine it is by far lighter than the piston engine, almost to the point to where an average person could lift the engine with a little help, taking in note it is just the engine not the intake or exhaust manifold and all its components.
Some of the difficulties with the wenkel engines would probably be... The emissions problems, though they are advancing rapidly, are still effecting the production of more rotary engines by Mazda and other companies. Another difficulty is the fact that, though they are somewhat easier to work on, they are different engines and required specialized technicians to service them, which in turn can get a little costly. Another big one is the fact that they do tend to consume a little bit more fuel than a piston engine, due to the reduced dynamic efficency due to the low compression ratio and the combustion chamber long shape. And the last big deal about rotary engines is the apex seals arent really the best for longevity, even under normal driving conditions. They need to be serviced rather often to keep up with the engine and to help it last and run at its best.
But these problems are normally set aside by the consumers due to the fun driving conditions of the engines and cars.