A lost technology.
The Wankel engine is a type of internal combustion engine using an eccentric rotary design to convert pressure into rotating motion. In contrast to the more common reciprocating piston designs, the Wankel engine delivers advantages of simplicity, smoothness, compactness, high revolutions per minute, and a high power-to-weight ratio primarily because three power pulses per rotor revolution are produced compared to one per revolution in a two-stroke piston engine and one per two revolutions in a four-stroke piston engine, although at the actual output shaft, there is only one power pulse per revolution. Since the output shaft spins three times as fast as the actual rotor, as can be seen in the animation below, it makes it roughly equivalent to a 2-stroke piston engine of the same displacement.
Mazda 12A wankel
engine. Rotor 1
This is also why the displacement only measures one face of the rotor, since only one face is working for each output shaft revolution.
The engine is commonly referred to as a rotary engine,although this name also applies to other completely different designs, primarily aircraft engines with their cylinders arranged in a circular fashion around the crankshaft. All parts rotate consistently in one direction, as opposed to the common reciprocating piston engine, which has pistons violently changing direction.
The four-stage cycle of intake, compression, ignition, and exhaust occur each revolution at each of the three rotor tips moving inside the oval-like epitrochoid shaped housing, enabling the three power pulses per rotor revolution. The rotor is similar in shape to a Reuleaux triangle with sides that are somewhat flatter. The design was conceived by German engineer Felix Wankel. Wankel
received his first patent for the engine in 1929. He began development in the early 1950s at NSU, and completed a working prototype in 1957. NSU subsequently licensed the design to companies around the world, who have continually added
improvements. The engines produced are of spark ignition, with compression ignition engines only in research projects.
The Basic Components of a Wankel engine
The Wankel is probably the best racing engine ever created. - Paul Newman.
The Wankel engine has the advantages of compact design and low weight over the most commonly used internal combustion engine employing reciprocating pistons. These advantages have given rotary engine applications in a variety of vehicles and devices, including: automobiles, motorcycles, racing cars, aircraft, go-karts, jet skis, snowmobiles, chainsaws, and auxiliary power units.The point of power to weight has been reached of under one pound weight per horsepower output.
ADVANTAGES
A far higher power to weight ratio than a piston engine
Approximately one third of the size of a piston engine of equivalent power output
Able to reach higher revolutions per minute than a piston engine by operating with almost no vibration
Cheaper to mass-produce, because the engine contains fewer parts
Superior breathing, filling the combustion charge in 270 degrees of mainshaft rotation rather than 180 degrees in a piston engine
It can use fuels of wider octane ratings
LIMITATIONS
Rotor sealing. This is still a minor problem as the engine housing has vastly different temperatures in each separate chamber section. The different expansion coefficients of the materials leads to imperfect sealing.
Apex seal lifting. Centrifugal force pushes the apex seal onto the housing surface forming a firm seal. Gaps can develop between the apex seal and troichoid housing in light-load operation when imbalances in centrifugal force and gas pressure occur.
Bad fuel economy. This is due to seal leakages, and the shape of the combustion chamber, which results in poor combustion behavior and mean effective pressure at part load, low rpm. Meeting the emissions regulations requirements sometimes mandates a fuel-air ratio that is not conducive to good fuel economy.
High emissions. As unburnt fuel is in the exhaust stream, emissions requirements are difficult to meet. This problem may be overcome by implementing direct fuel injection into the combustion chamber.
In Conclusion,
I believe that the Wankel Rotary engine could have been developed into a mainstream engine design. But due to various manufacturers pulling out, only Mazda carried the torch for the rotary engine till 2013.
I think we will see a resurgence of the rotary soon but in a different application like powering a generator or a small range extender engine in an electric car etc.
I will remin hopeful for the future.
