Rotary engine: heads and tails. Mazda rotary engine is back: Here's what you need to know about it What is a rotor in a car

steam engines and internal combustion engines have one common drawback - the reciprocating movement of the piston must be converted into rotational movement of the wheels. Hence the obviously low efficiency and high wear of the mechanism elements. Many wanted to build an internal combustion engine so that all moving parts in it only rotated - as happens in electric motors.

However, the task turned out to be not easy, only a self-taught mechanic, who in his entire life never received a higher education, or even a working specialty, managed to successfully solve it.

Felix Heinrich Wankel (1902–1988) was born on August 13, 1902 in the small German town of Lahr. During the First World War, Felix's father died, because of which the future inventor had to leave the gymnasium and go to work as an apprentice seller in a bookstore at a publishing house. Through this work, Wankel became addicted to reading books, from which he independently studied technical disciplines, mechanics and automotive engineering.
There is a legend that the solution to the problem came to the seventeen-year-old Felix in a dream. Whether this is true or not is unknown. But it is obvious that Felix had a very outstanding ability to mechanics and a "non-soapy" look at things. He understood how all four cycles of a conventional internal combustion engine (injection, compression, combustion, exhaust) can be carried out while rotating.
Quite quickly, Wankel came up with the first engine design, and in 1924 he organized a small workshop, which also served as an impromptu "laboratory". Here Felix began to conduct the first serious research in the field of rotary piston internal combustion engines.
From 1921, Wankel was an active member of the NSDAP. He advocated party ideals, was the founder of the All-German Military Youth Association and the Jungführer of various organizations. In 1932, he left the party after accusing one of his former colleagues of political corruption. However, on a counter-charge, he himself had to spend six months in prison. Released from prison thanks to the intercession of Wilhelm Keppler, he continued to work on the engine. In 1934 he created the first prototype and received a patent for it. He designed new valves and combustion chambers for his motor, created several different versions of it, developed a classification of kinematic schemes for various rotary piston machines.

In 1936, BMW became interested in the Wankel engine prototype - Felix received money and his own laboratory in Lindau to develop experimental aircraft engines.
However, until the very defeat of Nazi Germany, not a single Wankel engine went into production. Perhaps it took too much time to bring the design to mind and create mass production.
After the war, the laboratory was closed, the equipment was taken to France, and Felix was left without a job (his former membership in the National Socialist Party affected him). However, Wankel soon got a position as a design engineer at NSU Motorenwerke AG, one of the oldest manufacturers of motorcycles and cars.
In 1957, by the joint efforts of Felix Wankel and NSU lead engineer Walter Froede, a rotary piston engine was first installed on the NSU Prinz car. The initial design turned out to be far from perfect: even to replace the candles, it was necessary to disassemble almost the entire “engine”, reliability left much to be desired, and it was a sin to talk about efficiency at this stage of development. As a result of the tests, a car with a traditional internal combustion engine went into the series. Nevertheless, the first rotary-piston engine DKM-54 proved its fundamental performance, opened up directions for further refinement and demonstrated the colossal potential of the “rotors”.
Thus the new ICE type I finally got my start in life. In the future, it will have many more improvements and improvements. But the prospects for a rotary piston engine are so attractive that nothing could stop engineers from bringing the design to operational excellence.

Before analyzing the advantages and disadvantages of rotary piston internal combustion engines, it is still worth considering their design in more detail.
A round hole was made in the center of the rotor, covered from the inside with teeth like a gear. A rotating shaft of smaller diameter, also with teeth, is inserted into this hole, which ensures that there is no slippage between it and the rotor. The ratios of the diameters of the hole and the shaft are chosen so that the vertices of the triangle move along the same closed curve, which is called the "epitrochoid" - Wankel's art as an engineer was to first understand that this is possible, and then calculate everything exactly. As a result, the piston, which has the shape of a Reuleaux triangle, cuts off three chambers of variable volume and position in the chamber, repeating the shape of the curve found by Wankel.
The design of a rotary piston internal combustion engine allows you to implement any four-stroke cycle without the use of a special gas distribution mechanism. Thanks to this fact, the "rotor" turns out to be much simpler than a conventional four-stroke piston engine, in which, on average, there are almost a thousand more parts.
The sealing of the working chambers in a rotary-piston internal combustion engine is provided by radial and end sealing plates pressed against the "cylinder" by tape springs, as well as centrifugal forces and gas pressure.
Another of its technical features is its high “labor productivity”. For one complete revolution of the rotor (that is, for the cycle "injection, compression, ignition, exhaust"), the output shaft makes three complete revolutions. In a conventional piston engine, such results can only be achieved using a six-cylinder internal combustion engine.

After the first successful demonstration of a rotary internal combustion engine in 1957, the largest auto giants began to show increased interest in the development. At first, the license for the engine, which received the informal name "Wankel", was bought by Curtiss-Wright Corporation, a year later, Daimler-Benz, MAN, Friedrich Krupp and Mazda. In just a very short period of time, licenses for new technology acquired about a hundred companies around the world, including such monsters as Rolls-Royce, Porsche, BMW and Ford. Such an interest in the "wankel" of such large players in the automotive market is due to its great potential and significant advantages - in a rotary piston engine, 40% less parts, it is easier to repair and manufacture.

In addition, the Wankel is almost twice as compact and lighter as a traditional piston ICE, which in turn improves the car's handling, facilitates the optimal location of the transmission and allows for a more spacious and comfortable interior.

The picture is clickable:

The rotary piston engine develops high power with fairly modest fuel consumption. For example, a modern “wankel” with a volume of only 1300 cm3 develops a power of 220 hp, and with a turbocharger - all 350. Another example is the miniature OSMG 1400 engine weighing 335 g (5 cm3 working volume) develops a power of 1.27 liters .With. In fact, this little one is 27% stronger than a horse.
Another important advantage is low level noise and vibration. The rotary piston engine is perfectly balanced mechanically, in addition, the mass of moving parts (and their number) in it is much less, so that the “Wankel” runs much quieter and does not vibrate.
And finally, the rotary piston engine has excellent dynamic characteristics. In low gear, you can accelerate the car to 100 km / h at high engine speeds without much load on the engine. In addition, the Wankel design itself, due to the lack of a mechanism for converting reciprocating motion into rotational motion, is able to withstand higher speeds than a traditional internal combustion engine.

After the NSU Spyder released in 1964, the legendary NSU Ro 80 model followed (there are still many clubs of owners of these cars in the world), Citroen M35 (1970), Mercedes C-111 (1969), Corvette XP (1973). But the only mass manufacturer was the Japanese Mazda, which has been producing since 1967, sometimes 2-3 new models with RPD. Rotary engines were put on boats, snowmobiles and light aircraft. The end of euphoria came in 1973, at the height of the oil crisis. It was then that the main drawback of rotary engines appeared - inefficiency. With the exception of Mazda, all automakers have phased out rotary programs, and Japanese company American sales dropped from 104,960 cars sold in 1973 to 61,192 in 1974. Along with undeniable advantages, the Wankel also had a number of very serious drawbacks. First, durability. One of the first prototypes of rotary-piston engines ran out of service in just two hours. The next, more successful DKM-54 has already withstood a hundred hours, but for this normal operation the car was still not enough. The main problem lay in the uneven wear of the inner surface of the working chamber. During operation, transverse furrows appeared on it, which received the speaking name "devil's marks".

At Mazda, after acquiring a license for the Wankel, a whole department was formed to improve the rotary piston engine. Pretty soon it turned out that when the triangular rotor rotates, the plugs on its tops begin to vibrate, as a result of which “devil marks” are formed.
At present, the problem of reliability and durability has been finally solved by using high-quality wear-resistant coatings, including ceramic ones.
Another serious problem is the increased toxicity of the Wankel exhaust. Compared to a conventional reciprocating internal combustion engine, a “rotornik” emits less nitrogen oxides into the atmosphere, but much more hydrocarbons, due to incomplete combustion of fuel. Quite quickly, Mazda engineers, who believed in the bright future of the Wankel, found a simple and effective solution and this problem. They created the so-called thermal reactor, in which the remains of hydrocarbons in exhaust gases just "burned out". The first car to implement this scheme was the Mazda R100, also called the Familia Presto Rotary, released in 1968. This car, one of the few, immediately went through very tough environmental requirements, put forward by the US in 1970 for imported cars.
The next problem of rotary piston engines partially follows from the previous one. This is economy. The fuel consumption of a standard "wankel" due to incomplete combustion of the mixture is significantly higher than that of a standard internal combustion engine. Once again, Mazda engineers set to work. Through a series of measures, including redesigning the thermoreactor and carburetor, adding a heat exchanger to the exhaust system, developing a catalytic converter, and introducing a new ignition system, the company has achieved a 40% reduction in fuel consumption. As a result of this undoubted success, in 1978 a sports Mazda car RX-7.

It is worth noting that at that time only Mazda and ... AvtoVAZ produced cars with rotary piston engines all over the world.
It was in the disastrous year of 1974 that the Soviet government created a special design bureau RPD (SKB RPD) at the Volga Automobile Plant - the socialist economy is unpredictable. In Togliatti, work began on the construction of workshops for the mass production of "wankels". Since VAZ was originally planned as a simple copier of Western technologies (in particular, Fiat ones), the factory specialists decided to reproduce Mazda engine, completely discarding all the ten-year developments of domestic engine-building institutes.
Soviet officials negotiated with Felix Wankel for quite some time regarding the purchase of licenses, some of which took place right in Moscow. True, no money was found, and therefore it was not possible to use some proprietary technologies. In 1976, the first Volga single-section VAZ-311 engine with a power of 65 hp was put into operation, it took another five years to fine-tune the design, after which an experimental batch of 50 pieces of rotary "ones" VAZ-21018 was produced, which instantly dispersed among VAZ workers. It immediately became clear that the engine only outwardly resembled a Japanese one - it began to crumble in a very Soviet way. The management of the plant was forced to replace all engines with serial piston engines in six months, cut the staff of SKB RPD by half and suspend the construction of workshops. The salvation of the domestic rotary engine building came from the special services: they were not very interested in fuel consumption and engine life, but strongly - dynamic characteristics. Immediately, a two-section RPD with a power of 120 hp was made from two VAZ-311 engines, which began to be installed on a “special unit” - VAZ-21019. It is this model, which received the unofficial name "Arkan", that we owe countless tales about police "Cossacks" catching up with fancy "Mercedes", and many law enforcement officers - orders and medals. Until the 90s, the outwardly unpretentious Arkan really easily overtook all the cars. In addition to VAZ-21019, AvtoVAZ also produces small batches of VAZ-2105, -2107, -2108, -2109, -21099 cars. The maximum speed of the rotary "eight" is about 210 km / h, and it accelerates to hundreds in just 8 seconds.
Revived on special orders, SKB RPD began to make engines for water sports and motorsport, where cars with rotary engines began to win prizes so often that sports officials were forced to ban the use of RPD.
In 1987, the head of the SKB RPD, Boris Pospelov, died, and Vladimir Shnyakin, a man who came to the automotive industry from aviation and dislikes ground transport, was elected at a general meeting. The main direction of SKB RPD is the creation of engines for aviation. This was the first strategic mistake: we produce disproportionately fewer cars, and the plant lives from the sold engines.
The second mistake was the orientation in the preserved production of automotive RPDs to low-power VAZ-1185 engines of 42 hp. for the Oka, although more voracious, but more dynamic rotary engines are asking for the fastest domestic cars - for example, for the G8. The same Japanese install "wankels" only on sports models. As a result, there were only a few rotary minicars "Oka" on Russian roads. In 1998, a civilian version of the two-cylinder rotary 1.3-liter VAZ-415 engine was finally prepared, which was installed on the VAZ-2105, 2107, 2108 and 2109.

In May 1998, the ring VAZ-110 "RPD-sport" (190 hp, 8500 rpm, 960 kg, 240 km/h) was homologated. Alas, things did not go further than a single sample, more often shown at exhibitions than starting in races. The 110 was the most powerful in the peloton, but the frankly crude design each time did not allow it to demonstrate its full potential. However, the most offensive thing is that at VAZ they quickly cooled off towards the rotary direction, and the unique Lada was converted into a rally car with a conventional internal combustion engine.

So why haven't all the leading car manufacturers switched to Wankel yet? The fact is that the production of rotary piston engines requires, firstly, a well-honed technology with a wide variety of nuances, and not every company is ready to follow the path of the same Mazda, stepping on numerous "rakes" along the way. And secondly, we need special high-precision machines capable of turning surfaces described by such a cunning curve as an epitrochoid.

The Mazda RX-7 is one of the first cars to feature a Wankel rotary piston engine. There have been four generations in the history of the Mazda RX-7. First generation from 1978 to 1985. Second generation - from 1985 to 1991. Third generation - from 1992 to 1999. Last, fourth generation - from 1999 to 2002. The first generation RX-7 appeared in 1978. It had a mid-engine layout and was equipped with a rotary engine with a capacity of only 130 hp. With.

At present, only Mazda is engaged in serious research in the field of rotary piston engines, gradually improving their design, and most of the pitfalls in this area have already been overcome. "Wankels" are quite consistent with world standards in terms of exhaust toxicity, fuel consumption and reliability. For modern machine tools, the surfaces described by the epitrochoid are not a problem (just as much more complex curves are not a problem), new structural materials make it possible to increase the service life of a rotary piston engine, and its cost is already lower than that of a standard internal combustion engine due to fewer used details.
Like NSU, Mazda in the 60s. was a small company with limited technical and financial resources. The basis of its lineup was delivery trucks and family runabouts. Therefore, it is not surprising that the Mazda 110S Cosmo sports coupe (982 cm3, 110 hp, 185 km/h) was created for more than 6 years and turned out to be very capricious and expensive. And the damaged reputation of the NSU Ro80 did not contribute to the excitement (in 1967-1972 only 1175 "spaces" found their owners), but the world interest in the 110S contributed to an increase in sales of all the rest of the company's products!
To prove that the RPD is just as reliable (its superiority in power has already become obvious to everyone), Mazda took part in the competition for almost the first time in its life, and chose the most difficult and longest race - the 84-hour Marathon De La Route, held on Nurburgring. How the crew from Belgium managed to take 4th place (the second car retired three hours before the finish line due to jammed brakes), losing only to the Porsche 911 “grown up” on the Nordschleife, seems to remain a mystery.

Wankel workshop in Lindau

Although since then Japanese "rotorniks" have become regulars on the racetracks, major success in Europe they had to wait 16 years. In 1984, the British won the prestigious Spa-Francochamps daily race with an RX-7. But in the USA, in the main market of the "seven", her racing career developed much more successfully: from the moment she made her debut in the IMSA GT championship in 1978 and until 1992, she won more than a hundred stages in her class, and from 1982 to 1992 she won more than a hundred stages. excelled in the main race of the series - 24 hours of Daytona.
In the rally, the Mazda did not go so smoothly. As was often the case with Japanese teams (Toyota, Datsun, Mitsubishi), they performed only at certain stages of the World Rally Championship (New Zealand, Great Britain, Greece, Sweden), which were primarily of interest to the marketing departments of concerns. There were enough national titles: for example, in 1975-1980. Rod Millen won as many as five in New Zealand and the USA. But in the WRC, the successes were exclusively local: the best that the RX-7 showed was 3rd and 6th places in the Greek Acropolis in 1985.
Well, the loudest success of Mazda in general and RPD in particular was the victory of its sports prototype 787B (2612 cm3, 700 hp, 607 Nm, 377 km/h) at Le Mans in 1991. Moreover, it was not only fast pilots and competitive equipment that helped to overcome the factory Porsches, Peugeot and Jaguars: the perseverance of Japanese managers also played a role, regularly “knocking out” all sorts of relaxations in the regulations for rotors. So, on the eve of the victory of the 787th, the organizers of the race agreed to compensate for the voracity of the “rotors” with a 170-kilogram (830 versus 1000) weight reduction. The paradox was that, unlike gasoline engines, the "appetite" of the RPD with further forcing grew at a much more modest pace than that of conventional piston engines, and the 787th turned out to be more economical than its main competitors!

It was a shock. Mercedes, which Stern magazine for its conservatism called nothing more than “a car manufacturer for 50-year-old gentlemen in hats,” presented a supercar in 1969 that even struck the imagination in color. The defiant bright orange color, emphatically wedge-shaped shape, mid-engine layout, gull-wing doors and a heavy-duty three-section RPD (3600 cm3, 280 hp, 260 km / h) - for a conservative Mercedes it was something!

And since the company did not build concepts, everyone believed that the C111 had only one way: a small-scale (homologation) assembly and a great racing future, because since 1966 the FIA allowed the RPD to official competitions. And checks rained down at Mercedes headquarters asking them to enter the required amount for the right to own the C111. The Stuttgarters, on the other hand, further fueled interest in the Eske, in 1970 introducing the second generation of the coupe with an even more fantastic design, a 4-section rotor and mind-blowing performance (4800 cm3, 350 hp, 300 km/h). To fine-tune, Mercedes built five mock-ups that spent days and nights at the Hockenheimring and Nurburgring, preparing to set a series of speed records. The press relished the upcoming "clash of the titans" between the rotary Mercedes, the naturally aspirated Ferrari and the supercharged Porsche in the World Endurance Championship. Alas, the return to big sport did not take place. Firstly, the C111 was very expensive even for Mercedes, and secondly, the Germans could not sell such a crude design. And after the Caribbean oil crisis, they generally covered the project, focusing on diesel engines. They equipped the latest versions of the C111, which set several world records.

Not having completed technical education, at the end of his life, Felix Wankel achieved world recognition in the field of engine building and sealing technology, having won a lot of awards and titles. The streets and squares of German cities (Felix-Wankel-Strasse, Felix-Wankel-Ring) are named after him. In addition to engines, Wankel developed a new concept for high-speed craft and built several boats himself.

The most interesting thing is that the rotary engine, which made him a millionaire and brought him worldwide fame, Wankel did not like, considering him an "ugly duckling." Real working RPDs were made according to the so-called "KKM concept", which provides for planetary rotation of the rotor and requires the introduction of external counterweights. A significant role was played by the fact that this scheme was proposed not by Wankel, but by NSU engineer Walter Freude. Until recently, Wankel himself considered the ideal engine layout “with rotating pistons without unevenly rotating parts” (Drehkolbenmasine - DKM), conceptually much more beautiful, but technically complex, requiring, in particular, the installation of spark plugs on a rotating rotor. Nevertheless, rotary engines all over the world are associated precisely with the name of Wankel, since everyone who knew the inventor closely unanimously claims that without the irrepressible energy of the German engineer, the world would not have seen this amazing device. Felik Wankel passed away in 1988.
The history of the Mercedes 350 SL is curious. Wankel really wanted to have a rotary Mercedes C-111. But the company Mercedes did not go to meet him. Then the inventor took the serial 350 SL, threw out the “native” engine from there and installed a rotor from the C-111, which was 60 kg lighter than the previous 8-cylinder, but developed significantly more power(320 hp at 6500 rpm). In 1972, when the engineering genius finished work on his next miracle, he could have been behind the wheel of the fastest Mercedes SL-class at that time. The irony was that Wankel never got a driver's license for the rest of his life.

We owe the revival of interest in RPD to the new Mazda Renesis engine (from RE - Rotary Engine - and Genesis). Over the past decade, Japanese engineers have managed to solve all the main problems of RPD - exhaust toxicity and inefficiency. Compared to its predecessor, it was possible to reduce oil consumption by 50%, gasoline by 40% and bring the emission of harmful oxides to Euro IV standards. A two-cylinder engine with a volume of only 1.3 liters produces 250 hp. and takes up much less space in the engine compartment.
Specially for new engine the Mazda RX-8 was developed, which, according to the brand manager of Mazda Motor Europe Martin Brink, was created according to a new concept - the car was "built" around the engine. As a result, the weight distribution along the axes of the RX-8 is ideal - 50 to 50. The use of a unique shape and small dimensions of the engine made it possible to place the center of gravity very low. "The RX-8 isn't a racing monster, but it's the best handling car I've ever driven," Martin Brink enthused Popular Mechanics.
Barrel of honey...
Without a doubt, at first glance, a rotary piston engine has a lot of advantages over traditional internal combustion engines:
- 30-40% fewer parts;
- Smaller in 2-3 times dimensions and weight, in comparison with the standard internal combustion engine corresponding in power;
- Smooth response torque throughout the entire rev range;
- Absence of a crank mechanism, and, consequently, a much lower level of vibration and noise;
- High level of revolutions (up to 15000 rpm!).
A spoon of tar…
It would seem that if the Wankel has such advantages over the piston engine, then who needs these bulky, heavy, rattling and vibrating piston engines? But, as is often the case, in practice, everything is far from so chocolate. Not a single ingenious invention, having left the threshold of the laboratory, was sent to the basket marked "for waste." Serial production was found not on one stone, but on a whole placer of granite:
- Development of the combustion process in a chamber of unfavorable shape;
- Ensuring tightness of seals;
- Ensuring work without warpage of the body in conditions of uneven heating;
- Low thermal efficiency due to the fact that the RPD combustion chamber is much larger than that of a traditional internal combustion engine;
- High fuel consumption;
- High toxicity of gaseous products of combustion;
- A narrow temperature zone for RPD operation: at low temperatures, engine power drops sharply, at high temperatures, rapid wear of the rotor seals.

Rotary piston engine (RPD), or Wankel engine. Internal combustion engine developed by Felix Wankel in 1957 in collaboration with Walter Freude. In RPD, the function of a piston is performed by a three-vertex (trihedral) rotor, which performs rotational movements inside a complex-shaped cavity. After a wave of experimental models of cars and motorcycles that fell on the 60s and 70s of the twentieth century, interest in RPD has decreased, although a number of companies are still working on improving the design of the Wankel engine. Currently, RPDs are equipped with Mazda cars. The rotary piston engine finds application in modeling.

Principle of operation

The gas pressure force from the burnt fuel-air mixture drives the rotor, which is mounted through bearings on the eccentric shaft. The movement of the rotor relative to the motor housing (stator) is carried out through a pair of gears, one of which, of a larger size, is fixed on the inner surface of the rotor, the second, a support one, of a smaller size, is rigidly attached to the inner surface of the side cover of the motor. The interaction of gears leads to the fact that the rotor makes circular eccentric movements, in contact with the edges of the inner surface of the combustion chamber. As a result, three isolated chambers of variable volume are formed between the rotor and the engine housing, in which the processes of fuel-air mixture compression, its combustion, expansion of gases that put pressure on the working surface of the rotor and purification of the combustion chamber from exhaust gases take place. The rotational motion of the rotor is transmitted to an eccentric shaft mounted on bearings and transmitting torque to the transmission mechanisms. Thus, two mechanical pairs work simultaneously in the RPD: the first one regulates the movement of the rotor and consists of a pair of gears; and the second - converting the circular motion of the rotor into rotation of the eccentric shaft. The gear ratio of the rotor and stator gears is 2:3, so for one complete revolution of the eccentric shaft, the rotor has time to turn 120 degrees. In turn, for one complete revolution of the rotor in each of the three chambers formed by its faces, a complete four-stroke cycle of the internal combustion engine is performed.
RPD scheme
1 - inlet window; 2 outlet window; 3 - body; 4 - combustion chamber; 5 - fixed gear; 6 - rotor; 7- gear; 8 - shaft; 9 - spark plug

Advantages of RPD

The main advantage of a rotary piston engine is its simplicity of design. The RPD has 35-40 percent fewer parts than a four-stroke piston engine. There are no pistons, connecting rods, crankshaft in RPD. In the "classic" version of the RPD there is no gas distribution mechanism. The fuel-air mixture enters the working cavity of the engine through the inlet window, which opens the edge of the rotor. Exhaust gases are ejected through the exhaust port, which crosses, again, the edge of the rotor (this resembles the gas distribution device of a two-stroke piston engine).
The lubrication system deserves special mention, which is practically absent in the simplest version of the RPD. Oil is added to the fuel - as in the operation of two-stroke motorcycle engines. The friction pairs (primarily the rotor and the working surface of the combustion chamber) are lubricated by the fuel-air mixture itself.
Since the mass of the rotor is small and easily balanced by the mass of counterweights of the eccentric shaft, the RPD is characterized by a low level of vibration and good uniformity of operation. In cars with RPD, it is easier to balance the engine, achieving a minimum level of vibration, which has a good effect on the comfort of the car as a whole. Twin-rotor engines are particularly smooth-running, in which the rotors themselves act as vibration-reducing balancers.
Another attractive quality of the RPD is its high specific power at high speeds of the eccentric shaft. This allows you to achieve excellent speed characteristics from a car with RPD with relatively low fuel consumption. The low inertia of the rotor and the increased specific power compared to piston internal combustion engines improve the dynamics of the car.
Finally, an important advantage of the RPD is its small size. rotary engine less than a piston four-stroke engine of the same power by about half. And this allows you to more rationally use the space of the engine compartment, more accurately calculate the location of the transmission units and the load on the front and rear axles.

Disadvantages of RPD

The main disadvantage of a rotary piston engine is the low efficiency of gap seals between the rotor and the combustion chamber. The RPD rotor having a complex shape requires reliable seals not only along the edges (and there are four of them on each surface - two along the top, two along the side faces), but also along the side surface in contact with the engine covers. In this case, the seals are made in the form of spring-loaded strips of high-alloy steel with particularly precise processing of both working surfaces and ends. The allowances for metal expansion from heating included in the design of the seals worsen their characteristics - it is almost impossible to avoid gas breakthrough at the end sections of the sealing plates (in piston engines, the labyrinth effect is used by installing sealing rings with gaps in different directions).
In recent years, the reliability of seals has increased dramatically. Designers have found new materials for seals. However, there is no need to talk about any breakthrough yet. Seals are still the bottleneck of the RPD.
The complex sealing system of the rotor requires efficient lubrication of the friction surfaces. RPD consumes more oil than a four-stroke piston engine (from 400 grams to 1 kilogram per 1000 kilometers). In this case, the oil burns along with the fuel, which adversely affects the environmental friendliness of the engines. There are more substances hazardous to human health in the exhaust gases of RPD than in the exhaust gases of piston engines.
Special requirements are also imposed on the quality of oils used in RPD. This is due, firstly, to the tendency to increased wear (due to the large area of contact parts - the rotor and inner chamber engine), and secondly, to overheating (again due to increased friction and due to the small size of the engine itself). Irregular oil changes are deadly for RPDs - since abrasive particles in old oil dramatically increase engine wear and engine hypothermia. Starting a cold engine and insufficient warming up lead to the fact that there is little lubrication in the contact zone of the rotor seals with the surface of the combustion chamber and side covers. If a piston engine seizes when overheated, then the RPD most often occurs during a cold engine start (or when driving in cold weather, when cooling is excessive).
Generally working temperature RPD is higher than that of piston engines. The most thermally stressed area is the combustion chamber, which has a small volume and, accordingly, an elevated temperature, which makes it difficult to ignite the fuel-air mixture (RPDs are prone to detonation due to the extended shape of the combustion chamber, which can also be attributed to the disadvantages of this type of engine). Hence the exactingness of RPD on the quality of candles. Usually they are installed in these engines in pairs.
Rotary piston engines, with excellent power and speed characteristics, turn out to be less flexible (or less elastic) than piston ones. They give out optimal power only at sufficiently high speeds, which forces designers to use RPDs in tandem with multi-stage gearboxes and complicates the design of automatic transmissions. Ultimately, RPDs are not as economical as they should be in theory.

Practical application in the automotive industry

RPDs were most widely used in the late 60s and early 70s of the last century, when the patent for the Wankel engine was bought by 11 leading automakers in the world.
In 1967, the German company NSU produced a serial a car business class NSU Ro 80. This model was produced for 10 years and sold around the world in the amount of 37204 copies. The car was popular, but the shortcomings of the RPD installed in it, in the end, ruined the reputation of this wonderful car. Against the background of durable competitors, the NSU Ro 80 model looked “pale” - the mileage was up to overhaul engine with the declared 100 thousand kilometers did not exceed 50 thousand.
Concern Citroen, Mazda, VAZ experimented with RPD. The greatest success was achieved by Mazda, which launched its passenger car with RPD back in 1963, four years before the introduction of the NSU Ro 80. Today, Mazda is equipping RX series sports cars with RPD. Modern Mazda RX-8 cars are free from many of the shortcomings of the Felix Wankel RPD. They are quite environmentally friendly and reliable, although they are considered “capricious” among car owners and repair specialists.

Practical application in the motorcycle industry

In the 70s and 80s, some motorcycle manufacturers experimented with RPD - Hercules, Suzuki and others. Currently, small-scale production of "rotary" motorcycles has been established only at Norton, which produces the NRV588 model and is preparing the NRV700 motorcycle for serial production.
Norton NRV588 is a sport bike equipped with a twin-rotor engine with a total volume of 588 cubic centimeters and developing a power of 170 Horse power. With a dry weight of a motorcycle of 130 kg, the power-to-weight ratio of a sportbike looks literally prohibitive. The engine of this machine is equipped with variable intake tract systems and electronic injection fuel. All that is known about the NRV700 model is that the RPD power of this sportbike will reach 210 hp.

A rotary piston engine or Wankel engine is a motor where planetary circular motions are carried out as the main working element. This is a fundamentally different type of engine, different from piston counterparts in the ICE family.

The design of such a unit uses a rotor (piston) with three faces, externally forming a Reuleaux triangle, carrying out circular movements in a cylinder of a special profile. Most often, the surface of the cylinder is made along an epitrochoid (a flat curve obtained by a point that is rigidly connected to a circle that moves along outside another circle). In practice, you can find a cylinder and a rotor of other shapes.

Components and principle of operation

The device of the RPD type engine is extremely simple and compact. A rotor is installed on the axis of the unit, which is firmly connected to the gear. The latter is coupled to the stator. The rotor, which has three faces, moves along an epitrochoidal cylindrical plane. As a result, the changing volumes of the working chambers of the cylinder are cut off using three valves. Sealing plates (end and radial type) are pressed against the cylinder by the action of gas and due to the action of centripetal forces and band springs. It turns out 3 isolated chambers of different volume sizes. Here, the processes of compressing the incoming mixture of fuel and air, expanding the gases that put pressure on the working surface of the rotor and clean the combustion chamber from gases are carried out. The circular motion of the rotor is transmitted to the eccentric axis. The axle itself is on bearings and transmits the torque to the transmission mechanisms. In these motors, the simultaneous operation of two mechanical pairs is carried out. One, which consists of gears, regulates the movement of the rotor itself. The other converts the rotating motion of the piston into the rotating motion of the eccentric axle.

Rotary Piston Engine Parts

The principle of operation of the Wankel engine

Using the example of engines installed on VAZ vehicles, the following technical characteristics can be mentioned:
- 1.308 cm3 - working volume of the RPD chamber;
- 103 kW / 6000 min-1 - rated power;
- 130 kg engine weight;
- 125,000 km - engine life until its first complete repair.

mixture formation

In theory, RPD uses several types of mixture formation: external and internal, based on liquid, solid, gaseous fuels.
Regarding solid fuels, it is worth noting that they are initially gasified in gas generators, as they lead to increased ash formation in cylinders. Therefore, gaseous and liquid fuels have become more widespread in practice.
The very mechanism of mixture formation in Wankel engines will depend on the type of fuel used.
When using gaseous fuel, its mixing with air occurs in a special compartment at the engine inlet. The combustible mixture enters the cylinders in finished form.

From liquid fuel, the mixture is prepared as follows:

Air is mixed with liquid fuel before entering the cylinders where the combustible mixture enters.
Liquid fuel and air enter the engine cylinders separately, and already inside the cylinder they are mixed. The working mixture is obtained by contact with residual gases.

Accordingly, the fuel-air mixture can be prepared outside the cylinders or inside them. From this comes the separation of engines with internal or external mixture formation.

RPD Features

Advantages

Advantages of rotary piston engines compared to standard gasoline engines:

- Low vibration levels.
In motors of the RPD type, there is no conversion of reciprocating motion into rotational, which allows the unit to withstand high speeds with less vibration.

— Good dynamic characteristics.
Thanks to its design, such a motor installed in the car allows it to be accelerated above 100 km / h at high speeds without excessive load.

- Good power density with low weight.
Due to the absence in the design of the engine crankshaft and connecting rods, a small mass of moving parts in the RPD is achieved.

- In engines of this type, there is practically no lubrication system.
Oil is added directly to the fuel. The fuel-air mixture itself lubricates friction pairs.

- The rotary piston type motor has small overall dimensions.
Installed rotary piston motor allows you to maximize the use of the usable space of the engine compartment of the car, evenly distribute the load on the axles of the car and better calculate the location of the elements of the gearbox and assemblies. For example, a four-stroke engine of the same power will be twice the size of a rotary engine.

Disadvantages of the Wankel engine

— Quality of engine oil.
When operating this type of engine, it is necessary to pay due attention to the quality composition of the oil used in Wankel engines. The rotor and the engine chamber inside have a large contact area, respectively, the engine wears out faster, and such an engine constantly overheats. Irregular oil changes cause great damage to the engine. The wear of the motor increases many times due to the presence of abrasive particles in the used oil.

— The quality of the spark plugs.
The operators of such engines have to be particularly demanding on the quality of the composition of the spark plugs. In the combustion chamber, due to its small volume, elongated shape and high temperature the process of ignition of the mixture is difficult. The consequence is an increased operating temperature and periodic detonation of the combustion chamber.

— Materials of sealing elements.
A significant flaw in the RPD-type motor can be called the unreliable organization of seals between the gaps between the chamber where the fuel burns and the rotor. The device of the rotor of such a motor is rather complicated, therefore seals are required both along the edges of the rotor and along the side surface in contact with the engine covers. Surfaces that are subject to friction must be constantly lubricated, which results in increased consumption oils. Practice shows that an RPD-type motor can consume from 400 g to 1 kg of oil for every 1000 km. The environmental performance of the engine is reduced, as the fuel burns together with the oil, resulting in environment a large amount of harmful substances are emitted.

Due to their shortcomings, such motors are not widely used in the automotive industry and in the manufacture of motorcycles. But on the basis of RPD, compressors and pumps are manufactured. Aeromodellers often use these engines to build their models. Due to the low requirements for efficiency and reliability, designers do not use a complex sealing system in such motors, which significantly reduces its cost. The simplicity of its design allows it to be integrated into an aircraft model without any problems.

Efficiency of rotary piston design

Despite a number of shortcomings, studies have shown that the overall Engine efficiency Wankel is quite tall by today's standards. Its value is 40 - 45%. For comparison, in piston internal combustion engines, the efficiency is 25%, in modern turbodiesels - about 40%. The highest efficiency for piston diesel engines is 50%. To date, scientists continue to work to find reserves to improve the efficiency of engines.

The final efficiency of the motor consists of three main parts:

Fuel efficiency (an indicator characterizing the rational use of fuel in the engine).

Research in this area shows that only 75% of the fuel burns out in full. It is believed that this problem is solved by separating the processes of combustion and expansion of gases. It is necessary to provide for the arrangement of special chambers under optimal conditions. Combustion should take place in a closed volume, subject to an increase in temperature and pressure, the expansion process should occur at low temperatures.

Mechanical efficiency (characterizes the work, the result of which was the formation of the torque of the main axis transmitted to the consumer).

About 10% of the engine's work is spent on setting in motion auxiliary units and mechanisms. This defect can be corrected by making changes to the engine device: when the main moving working element does not touch the stationary body. A constant torque arm must be present along the entire path of the main working element.

Thermal efficiency (an indicator reflecting the amount of thermal energy generated from the combustion of fuel, which is converted into useful work).

In practice, 65% of the received thermal energy escapes with the exhaust gases into the external environment. A number of studies have shown that it is possible to achieve an increase in thermal efficiency in the case when the design of the motor would allow the combustion of fuel in a heat-insulated chamber so that maximum temperatures are reached from the very beginning, and at the end this temperature is reduced to minimum values by turning on the vapor phase.

The current state of the rotary piston engine

Significant technical difficulties arose in the way of mass application of the engine:
– development of a high-quality work process in an unfavorable chamber;
- ensuring the tightness of the sealing of working volumes;
– designing and creating a structure of body parts that will reliably serve the entire life cycle of the engine without warping with uneven heating of these parts.
As a result of the huge research and development work done, these firms managed to solve almost all the most difficult technical problems on the way to the creation of RPDs and enter the stage of their industrial production.

The first mass-produced NSU Spider with RPD was produced by NSU Motorenwerke. Due to frequent overhauls of engines due to the above technical problems early in the development of the Wankel engine design, warranties taken by NSU led it to financial ruin and bankruptcy and the subsequent merger with Audi in 1969.
Between 1964 and 1967, 2375 cars were produced. In 1967 the Spider was discontinued and replaced by the NSU Ro80 with a second generation rotary engine; in ten years of Ro80 production, 37,398 cars were produced.

Mazda engineers have dealt with these problems most successfully. It remains the only mass manufacturer of machines with rotary piston engines. The modified engine has been serially installed on the Mazda RX-7 since 1978. Since 2003, succession has taken Mazda model RX-8, it is currently the mass and only version of the car with a Wankel engine.

Russian RPDs

The first mention of a rotary engine in the Soviet Union dates back to the 60s. Research work on rotary piston engines began in 1961, by the relevant decree of the Ministry of Automotive Industry and the Ministry of Agriculture of the USSR. An industrial study with a further conclusion to the production of this design began in 1974 at the VAZ. specifically for this, a Special Design Bureau for Rotary Piston Engines (SKB RPD) was created. Since it was not possible to buy a license, the serial Wankel from NSU Ro80 was disassembled and copied. On this basis, the VAZ-311 engine was developed and assembled, and this significant event took place in 1976. At VAZ, they developed a whole line of RPDs from 40 to 200 strong engines. The finalization of the design dragged on for almost six years. Managed to solve whole line technical problems associated with the performance of gas and oil seals, bearings, to debug an efficient workflow in an unfavorable chamber. VAZ presented its first production car with a rotary engine under the hood to the public in 1982, it was the VAZ-21018. The car was externally and structurally like all models of this line, with one exception, namely, under the hood there was a single-section rotary engine with a capacity of 70 hp. The duration of development did not prevent embarrassment from happening: at all 50 experimental machines during operation, engine breakdowns occurred, forcing the plant to install a conventional piston engine in its place.

VAZ 21018 with rotary piston engine

Having established that the cause of the malfunction was the vibration of the mechanisms and the unreliability of the seals, the designers undertook to save the project. Already in the 83rd, two-section VAZ-411 and VAZ-413 appeared (with a capacity of 120 and 140 hp, respectively). Despite the low efficiency and short resource, the scope of the rotary engine was still found - the traffic police, the KGB and the Ministry of Internal Affairs needed powerful and inconspicuous vehicles. Equipped with rotary engines, Zhiguli and Volga easily overtook foreign cars.

Since the 80s of the 20th century, SKB has been passionate about new topic- the use of rotary engines in a related industry - aviation. The departure from the main industry of using RPDs led to the fact that for front-wheel drive vehicles the VAZ-414 rotary engine was created only by 1992, and it was brought up for another three years. In 1995, the VAZ-415 was submitted for certification. Unlike its predecessors, it is universal, and can be installed under the hood of both rear-wheel drive (classic and GAZ) and front-wheel drive cars (VAZ, Moskvich). The two-section "Wankel" has a working volume of 1308 cm 3 and develops a power of 135 hp. at 6000 rpm. "Ninety-ninth" he accelerates to hundreds in 9 seconds.

Rotary piston engine VAZ-414

At the moment, the project for the development and implementation of the domestic RPD is frozen.

Below is a video of the device and the operation of the Wankel engine.

As you know, the principle of operation of a rotary engine is based on high revolutions and the absence of movements that distinguish an internal combustion engine. This is what distinguishes the unit from a conventional piston engine. RPD is also called the Wankel engine, and today we will consider its operation and obvious advantages.

The rotor of such an engine is located in the cylinder. The case itself is not of a round type, but of an oval type, so that the rotor of triangular geometry fits normally in it. The RPD does not have a crankshaft and connecting rods, and there are no other parts in it, which makes its design much simpler. In other words, about a thousand parts of a conventional internal combustion engine are not in the RPD.

The work of the classical RPD is based on simple movement rotor inside an oval housing. During the movement of the rotor along the circumference of the stator, free cavities are created, in which the processes of starting the unit take place.

Surprisingly, the rotary unit is a kind of paradox. What is it? And the fact that he has a genius simple design, which for some reason did not take root. But a more complex piston version has become popular and is used everywhere.

The structure and principle of operation of a rotary engine

The scheme of operation of a rotary engine is something completely different than a conventional internal combustion engine. First, we should leave the design of the internal combustion engine as we know it in the past. And secondly, try to absorb new knowledge and concepts.

Like a piston engine, a rotary engine uses the pressure that is created when a mixture of air and fuel is burned. In piston engines, this pressure builds up in the cylinders and moves the pistons back and forth. The connecting rods and crankshaft convert the piston's reciprocating motion into rotational motion that can be used to turn the car's wheels.

The RPD is named so because of the rotor, that is, the part of the motor that moves. This movement transfers power to the clutch and gearbox. Essentially, the rotor pushes energy from the fuel, which is then transferred to the wheels through the transmission. The rotor itself is necessarily made of alloy steel and has, as mentioned above, the shape of a triangle.

The capsule where the rotor is located is a kind of matrix, the center of the universe, where all processes take place. In other words, it is in this oval case that:

mixture compression;
fuel injection;
supply of oxygen;
mixture ignition;
return of burnt elements to the outlet.

In a word, six in one, if you like.

The rotor itself is mounted on a special mechanism and does not rotate around one axis, but rather runs. Thus, cavities isolated from each other are created inside the oval body, in each of which one of the processes occurs. Since the rotor is triangular, there are only three cavities.

It all starts as follows: suction occurs in the first cavity formed, that is, the chamber is filled with an air-fuel mixture, which is mixed here. After that, the rotor rotates and pushes this mixed mixture into another chamber. Here the mixture is compressed and ignited with two candles.

The mixture then goes into the third cavity, where parts of the used fuel are forced out into the exhaust system.

This is the full cycle of the RPD. But not everything is so simple. We have considered the RPD scheme only from one side. And these actions happen all the time. In other words, processes occur immediately from three sides of the rotor. As a result, in just one revolution of the unit, three cycles are repeated.

In addition, Japanese engineers managed to improve the rotary engine. Today, Mazda rotary engines have not one, but two or even three rotors, which greatly improves performance, especially when compared with a conventional internal combustion engine. For comparison: a two-rotor RPD is comparable to a six-cylinder internal combustion engine, and a 3-rotor RPD is comparable to a twelve-cylinder. So it turns out that the Japanese turned out to be so far-sighted and immediately recognized the advantages of a rotary engine.

Again, performance is not the only virtue of RPDs. He has many of them. As mentioned above, a rotary engine is very compact and uses as many as a thousand parts less than in the same internal combustion engine. There are only two main parts in the RPD - a rotor and a stator, but you can’t imagine anything simpler than this.

The principle of operation of a rotary engine

The principle of operation of a rotary piston engine made at one time many talented engineers raise their eyebrows in surprise. And today, Mazda's talented engineers deserve all the praise and approval. It's no joke to believe in the performance of a seemingly buried engine and give it a second life, and what a life!

Rotor has three convex sides, each of which acts like a piston. Each side of the rotor has a recess in it, which increases the speed of rotation of the rotor as a whole, providing more space for the fuel-air mixture. At the top of each facet is metal plate, which form the chambers in which the engine cycles occur. Two metal rings on each side of the rotor form the walls of these chambers. In the middle of the rotor is a circle in which there are many teeth. They are connected to a drive that is attached to the output shaft. This connection determines the path and direction in which the rotor moves inside the chamber.

Engine chamber approximately oval in shape (but to be precise, it is an Epitrochoid, which in turn is an elongated or shortened epicycloid, which is a flat curve formed by a fixed point of a circle rolling along another circle). The shape of the chamber is designed so that the three vertices of the rotor are always in contact with the chamber wall, forming three enclosed gas volumes. In each part of the chamber, one of four cycles occurs:

Inlet
Compression
Combustion
Release

The inlet and outlet openings are in the chamber walls and do not have valves. The exhaust port is connected directly to the exhaust pipe, while the intake port is directly connected to the gas.

output shaft has semicircular cams placed asymmetrically relative to the center, which means that they are offset from the shaft centerline. Each rotor is put on one of these protrusions. The output shaft is analogous to the crankshaft in piston engines. Each rotor moves inside the chamber and pushes its own cam.

Since the cams are not symmetrically mounted, the force with which the rotor presses on it creates a torque on the output shaft, causing it to rotate.

The structure of the rotary engine

The rotary engine consists of layers. Twin rotor engines are made up of five main layers that are held together by long bolts arranged in a circle. Coolant flows through all parts of the structure.

The two outer layers are closed and contain bearings for the output shaft. They are also sealed in the main sections of the chamber where the rotors are contained. The inner surface of these parts is very smooth and helps the rotors work. The fuel supply section is located at the end of each of these parts.

The next layer contains directly the rotor itself and the exhaust part.

The center consists of two fuel supply chambers, one for each rotor. It also separates these two rotors so its outer surface is very smooth.

At the center of each rotor are two large gears that rotate around smaller gears and are attached to the motor housing. This is the orbit for the rotation of the rotor.

Of course, if the rotary engine had no drawbacks, then it would certainly be used on modern cars. It is even possible that if the rotary engine were sinless, we would not have known about the piston engine, because the rotary engine was created earlier. Then the human genius, trying to improve the unit, created a modern piston version of the motor.

But unfortunately, the rotary engine has disadvantages. Such obvious blunders of this unit include the sealing of the combustion chamber. And in particular, this is due to insufficiently good contact of the rotor itself with the cylinder walls. During friction with the walls of the cylinder, the metal of the rotor heats up and, as a result, expands. And the oval cylinder itself also heats up, and even worse - the heating is uneven.

If the temperature in the combustion chamber is higher than in the intake / exhaust system, the cylinder must be made of high-tech material installed in different places in the body.

In order for such an engine to start, only two spark plugs are used. No longer recommended due to the characteristics of the combustion chamber. The RPD is sometimes endowed with a completely different combustion chamber and produces power for three quarters of the working time of the internal combustion engine, and the coefficient useful action is forty percent. In comparison: for a piston engine, the same figure is 20%.

Benefits of a rotary engine

Fewer moving parts

A rotary engine has many fewer parts than, say, a 4-cylinder piston engine. A twin rotary engine has three main moving parts: two rotors and an output shaft. Even the simplest 4 cylinder piston engine has at least 40 moving parts including pistons, connecting rods, rod, valves, rockers, valve springs, timing belts and crankshaft. Minimizing moving parts allows rotary engines to be more high reliability. That is why some aircraft manufacturers (Skycar for example) use rotary engines instead of piston engines.

Softness

All parts in a rotary engine continuously rotate in the same direction, unlike the constantly changing direction of pistons in a conventional engine. The rotary engine uses balanced rotating counterweights to dampen any vibrations. The power delivery in a rotary engine is also softer. Each combustion cycle takes place in one rotation of the rotor of 90 degrees, the output shaft rotates three times for each rotation of the rotor, each combustion cycle takes 270 degrees to rotate the output shaft. This means that a single rotary engine produces three-quarters of the power. Compared to a single-cylinder piston engine, combustion occurs every 180 degrees of each revolution, or only a quarter of a revolution of the crankshaft.

Slowness

Due to the fact that the rotors rotate at one third of the output shaft rotation, the main parts of the engine rotate more slowly than the parts in a conventional piston engine. It also helps with reliability.

Small dimensions + high power

The compactness of the system, together with high efficiency (compared to a conventional internal combustion engine), makes it possible to produce about 200-250 hp from a miniature 1.3-liter engine. True, together with the main drawback of the design in the form high flow fuel.

Disadvantages of rotary motors

The most important problems in the production of rotary engines:

It is difficult (but not impossible) to comply with CO2 regulations, especially in the US.
Production can be much more expensive, in most cases due to low volume production, compared to piston engines.
They consume more fuel because the thermodynamic efficiency of a reciprocating engine is reduced in a long combustion chamber and also because of the low compression ratio.
Rotary engines, due to their design, are limited in resource - on average, this is about 60-80 thousand km

This situation simply forces us to classify rotary engines as sports car models. And not only. Adherents of the rotary engine were found today. This is the famous automaker Mazda, who embarked on the path of the samurai and continued the research of master Wankel. If we recall the same situation with Subaru, then success becomes clear Japanese manufacturers, clinging, it would seem, to everything old and discarded by Westerners as unnecessary. But in fact, the Japanese manage to create something new from the old. The same then happened with boxer engines, which are Subaru's "chip" today. At the same time, the use of such engines was considered almost a crime.

The work of the rotary engine also interested Japanese engineers, who this time took up the improvement of Mazda. They created the 13b-REW rotary engine and gave it a twin-turbo system. Now Mazda could easily argue with German models, as it opened up as many as 350 horses, but again sinned with high fuel consumption.

I had to take extreme measures. Mazda's latest rotary-engined RX-8 model is already out with 200 horsepower to cut fuel consumption. But this is not the main thing. Something else deserves respect. It turned out that before that, no one except the Japanese had guessed to use the incredible compactness of a rotary engine. After all, the power of 200 hp. Mazda RX-8 opened with a 1.3-liter engine. In a word, the new Mazda is already reaching a different level, where it is able to compete with Western models, taking not only engine power, but also other parameters, including low flow fuel.

Surprisingly, they tried to put RPD into operation in our country as well. Such an engine was designed to be installed on the VAZ 21079, intended as a vehicle for special services, but the project, unfortunately, did not take root. As always, not enough budget money states that are miraculously pumped out of the treasury.

But the Japanese managed to do it. And they do not want to stop at the achieved result. According to the latest data, the manufacturer Mazda will improve the engine and a new Mazda will soon be released, already with a completely different unit.

Different designs and developments of rotary engines

Wankel engine

Zheltyshev engine

Zuev engine

The idea of a rotary engine is too tempting: when a competitor is very far from ideal, it seems that we are about to overcome shortcomings and get not a motor, but perfection itself ... Mazda was in captivity of these illusions right up to 2012, when the last model with rotary engine - RX-8.

The history of the creation of a rotary engine

The second name of a rotary engine (RPD) is a wankel (a kind of analogue of a diesel engine). It is Felix Wankel who today is credited with the laurels of the inventor of the rotary piston engine, and even a touching story is told about how Wankel went to his goal at the same time that Hitler was going to his own.

In fact, things were a little different: a talented engineer, Felix Wankel, really worked on the development of a new, simple internal combustion engine, but it was a different engine based on the co-rotation of rotors.

After the war, Wankel was recruited by the German company NSU, which was mainly engaged in the production of motorcycles, to one of the working groups working on the creation of a rotary engine under the leadership of Walter Freude.

Wankel's contribution is extensive research on rotary valve seals. Basic scheme and the engineering concept belong to Freud. Although Wankel had a patent for dual rotation.

The first engine had a rotating chamber and a fixed rotor. The inconvenience of the design led to the idea to change the scheme in some places.

The first rotating rotor engine began operation in mid-1958. It differed little from its descendant of our days - except that the candles had to be moved to the body.

Soon the company announced that it had managed to create a new and very promising engine. Nearly a hundred car manufacturing companies have purchased licenses to produce this engine. A third of the licenses ended up in Japan.

RPD in the USSR

But the Soviet Union did not buy a license at all. The development of our own rotary engine began with the fact that they brought to the Union and dismantled german car Ro-80, which NSU began production in 1967.

Seven years later, a design bureau appeared at the VAZ plant, developing exclusively rotary piston engines. Through his work, in 1976, the VAZ-311 engine arose. But the first pancake turned out to be lumpy, and it was finalized for another six years.

The first Soviet production car with a rotary engine is the VAZ-21018, introduced in 1982. Unfortunately, already in the experimental batch, the motors of all the machines failed. They finalized another year, after which the VAZ-411 and VAZ 413 appeared, which were adopted by the law enforcement agencies of the USSR. They were not particularly worried about fuel consumption and a short engine life, but they needed fast, powerful, but inconspicuous cars that could keep up with a foreign car.

RPD in the West

In the West, the rotary engine did not boom, and its development in the US and Europe ended with the fuel crisis of 1973, when gasoline prices skyrocketed, and car buyers began to ask about fuel-efficient models.

Considering that the rotary engine ate up to 20 liters of gasoline per hundred kilometers, its sales during the crisis fell to the limit.

The only country in the East that has not lost faith is Japan. But even there, manufacturers quickly lost interest in the engine, which did not want to improve. And in the end there was one steadfast tin soldier left - the Mazda company. In the USSR, the fuel crisis was not felt. The production of machines with RPD continued after the collapse of the Union. VAZ stopped doing RPD only in 2004. Mazda reconciled only in 2012.

Rotary motor features

The design is based on a triangular-shaped rotor, each of the faces of which has a bulge (). The rotor rotates in a planetary type around the central axis - the stator. At the same time, the vertices of the triangle describe a complex curve called an epitrochoid. The shape of this curve determines the shape of the capsule inside which the rotor rotates.

The rotary motor has the same four cycle duty cycle as its competitor, the piston motor.

The chambers are formed between the edges of the rotor and the walls of the capsule, their shape is variable crescent, which is the reason for some significant shortcomings designs. To isolate the chambers from each other, seals are used - radial and end plates.

If we compare a rotary internal combustion engine with a piston one, then the first thing that catches your eye is that in one revolution of the rotor the working stroke occurs three times, and the output shaft rotates three times faster than the rotor itself.

At RPD no gas distribution system which greatly simplifies its design. A high power density with a small size and weight of the unit are due to the absence of a crankshaft, connecting rods and other interfaces between cameras.