On the mass Soviet cars there were no special technical innovations - no diesel, no automatic transmission, no hydropneumatic suspension, no turbocharging. In a vast country, any cars were in demand - and, for various reasons, quite simple and maintainable designs were mass-produced.
It is all the more surprising that “the Soviets had their own pride”, and even what kind of rotary engine designed for passenger cars. piston engine! Moreover, the “rotary theme” was overgrown with rumors, speculations and legends back in the early eighties, and even the appearance of VAZ cars with RPD on free sale in the crazy nineties did not dot the i.
Forerunners: Felix Heinrich Wankel
Felix Wankel, a self-taught German engineer, began developing the rotary piston engine back in the twenties, but in the pre-war period he did not manage to bring prototype aircraft engines to perfection, despite the support of BMW and the Ministry of Aviation.
After World War II, Wankel's equipment was dismantled and taken to France. Despite this, the design engineer did not stop working on his own RPD - now with the support of NSU. By the mid-fifties, Wankel completed the theoretical part and in 1957 produced a prototype, based on the results of testing of which the necessary changes were made to the design.
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Rotor's father - Felix Wankel
Wankel's work was by no means "academic" in nature: in 1963, the production of the first production model NSU - Prince Spyder, and later the NSU Ro 80 business class sedan was also equipped with an innovative engine.
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When Audi"by inheritance" got the NSU brand and its developments, she even released a prototype of the Audi KKM based on the "weave" of the second generation. In the future, the topic of Wankel engines was not continued at Audi.
However, rather quickly, the features of the RPD prevented him from winning a market victory over traditional piston ICEs with a crank mechanism. However, during the years of serial production of Wankel engines, many major automakers, some of which took up the development of the "rotary theme" seriously and for a long time. Perhaps the most famous RPD manufacturer is the Japanese Mazda company who created the Renesis engine.
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Mazda immediately began to equip its engines with an unusual design. sport coupe
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Mazda immediately began to equip its sports coupes with an unusual engine design.
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Mazda immediately began to equip its sports coupes with an unusual engine design.
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Mazda immediately began to equip its sports coupes with an unusual engine design.
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Mazda immediately began to equip its sports coupes with an unusual engine design.
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Mazda immediately began to equip its sports coupes with an unusual engine design.
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Mazda immediately began to equip its sports coupes with an unusual engine design.
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Mazda Roadpacer - under this name, the Japanese sold the Australian Holden sedan with its RPD in the USA!
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Over decades of production, it was the Japanese company Mazda that “brought to mind” the rotor - of course, as far as it was possible.
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Over decades of production, it was the Japanese company Mazda that “brought to mind” the rotor - of course, as far as it was possible.
Made in USSR
How could the idea to start producing rotary piston engines come up at VAZ?
Various alternative designs of piston engines were worked in the USSR in the middle of the 20th century - of course, not for the automotive industry, but for aviation. Potentially, such motors could provide a higher return, which was especially valuable in aircraft construction. Directly to the topic of RPD in the Soviet Union began in the "pre-VAZ" period - at the direction of the Ministry of Automotive Industry and the Ministry of Agriculture, three research institutes (NAMI, NATI and VNIImotoprom) took up research work for the creation of the RPD.
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Therefore, the development of Wankel and its practical implementation on production cars in the Soviet Union did not go unnoticed. Moreover, a light and powerful engine could become in demand for some cars. special purpose- for example, the so-called "catchers" or sports cars.
Traditionally, for the automotive industry of the USSR, a strong-willed decision could only be made "at the very top" - that is, at the level of the ministry.
However, the rotor at the VAZ was taken up by order Director General Volga Automobile Plant in 1973 - it would seem, at its own discretion. But not everything is so simple: before switching to new project- the construction of the Volga auto giant, back in 1965, Viktor Nikolayevich Polyakov served as Deputy Minister of the Automobile Industry of the USSR, and in 1975 he completely returned to the ministerial chair, heading the USSR Ministry of Automotive Industry. Thus, it can be argued that the work on the rotor was approved "without two minutes" by the Minister of the Automotive Industry and his former deputy in one person.
So, after the release of the corresponding order of the General Director, a special design bureau was created, whose task was not only to develop motors of its own design, but also to eliminate the “generic flaws” of the Wankel motor, which Soviet designers were already aware of.
Unlike Western colleagues, the “own design” in the USSR really meant the development of its own version, and not the purchase of a patent or a ready-made license. As in the case of an automatic transmission for, for lack of options, Soviet engineers were forced to make their own version of the single-section Wankel engine, having disassembled one Japanese RPD for this. However, beforehand for “field tests”, the engine, taken from a Mazda RX-2 specially purchased to work on the rotor, was installed on the Zhiguli of the third model.
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Mazda RX-2 became a donor for VAZ of both the design and the very first RPD installed on the Zhiguli
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Mazda RX-2 became a donor for VAZ of both the design and the very first RPD installed on the Zhiguli
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Mazda RX-2 became a donor for VAZ of both the design and the very first RPD installed on the Zhiguli
Already in the early stages at VAZ, they were faced with the fact that, despite their compactness and high power-to-weight ratio, the light and powerful RPD was not very economical and environmentally friendly, and was also distinguished by frequent failure of seals. In fact, this problem has been fought for decades by everyone who took on Wankel engines, starting with the German engineer himself - the bearer of this surname. And, by the way, it was the low reliability of the seals that was the reason for the rapid failure of the engines on the NSU Ro-80, which forced the manufacturer to soon stop producing this car and “close the rotor theme”.
The first prototype of the SKB RPD under the designation VAZ-301 was ready already in 1976, but it was still too early to talk about any launch of the rotor in Togliatti - the design turned out to be clearly “raw”.
The VAZ version of the rotary piston engine was even appreciated by ... Felix Wankel himself, who specially visited the Volga Automobile Plant for this. The "father of the rotor" approved the overall layout of the Togliatti RPD.
Already in 1982, the VAZ-21018 was demonstrated - the usual VAZ-21011 with a VAZ-311 engine with a power of 70 hp.
In order to identify design flaws in real-life conditions, a batch of 50 engines was produced, which were installed on five dozen Zhiguli, but just six months later, all engines, except for one (!), Had to be replaced with traditional ones. Seals and bearings quickly failed, and in addition, the motor turned out to be poorly balanced and quite voracious.
On earth and in heaven
After the first serious failure and the ensuing disciplinary punishments, VAZ did not stop working on rotors, but decided to finally switch from a single-section design to a two-section one. Such a motor was potentially not only more powerful, but also more reliable.
By that time, the Soviet rotor potentially already had a quite tangible scope - for example, for installation on official cars of special forces of the traffic police, the Ministry of Internal Affairs and the KGB. On departmental vehicles, shortcomings like not the best fuel economy faded into the background, and high dynamic performance was of decisive importance. It is very important that when operating on official vehicles, VAZ specialists could receive in the form of standardized reports detailed information about the shortcomings and defects identified in practice, but in more or less the same conditions, which ensured a certain objectivity of the assessment.
From time to time, the Soviet press reported sparsely about the motor of an unusual design.
By 1983, two new two-section RPDs were developed - the VAZ-411 with a capacity of 110-120 horsepower and the 140-horsepower VAZ-413. It was assumed that the rotors will be installed not only on the "native" for the Zhiguli plant various models, but also to other vehicles of law enforcement agencies - in particular, the Volga. Of course, installing such a power unit on a sedan Gorky Automobile Plant required a corresponding revision of the mount and some transmission units.
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VAZ-21059 - rotary "five". Still no difference from the usual outside.
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VAZ-21059 - rotary "five". Still no difference from the usual outside.
At the same time, aviators also drew attention to the almost ready-to-use RPDs, who ordered the Togliatti Bureau to develop a variant for use on helicopters and light aircraft.
However, many other enterprises became interested in the rotary-piston type of engine, which ordered the development of units for boats, amphibians and even motorcycles from Togliatti! The plant provided these services under contracts on the terms of self-support, which was widely used at that time, so the activities of the Special Design Bureau were not unprofitable for VAZ. Also, prototypes of aircraft engines VAZ-416 and VAZ-426 were developed already in the era of the functioning of the STC VAZ in the mid-nineties.
Various types of RPD applications have made it possible for designers to understand that Constructive decisions automobile and aircraft engines cannot be completely identical due to a significant difference in the operating modes of engines in air and road transport.
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Therefore, the simultaneous development of a “single” rotor is devoid of practical meaning - rather, the work can be combined according to technological and production base rather than specific solutions.
RPD and front wheel drive
The question arises: what about front-wheel drive cars? Really VAZ did not pay attention to its own "eight"?
Of course, he drew attention: work on the RPD for a fundamentally new family began when the VAZ-2108 was just being prepared for production - in 1979, but they returned to the topic of the “front-wheel drive rotor” more specifically at the beginning of perestroika, having concluded an agreement with the Zaporozhye Automobile Plant. And by 1987, prototypes of the VAZ-414 were developed for front wheel drive vehicles VAZ and ZAZ, and also in Tolyatti, created a version of their 40-horsepower RPD under the index 1185 even for ... Oka! But in the future, the leadership gave preference to the aviation direction, and work on automobile RPDs was suspended.
Small-scale production of an unusual modification of the Zhiguli based on the "five" continued until the collapse of the USSR, although government purchases of such vehicles by law enforcement agencies were quite small, and cars with rotors under the hood were not sold "to the side".
But soon the plant was not at all up to its own new developments - in the late eighties governmental support automobile plants was curtailed, and the factory workers had nothing to do without, for example, the creation of a promising or.
Latest car RPD VAZ
To the topic of rotary automotive engines they returned to VAZ only during the Russian period of the plant’s activity, finding an opportunity even in the difficult nineties to “get out of the cloth” an interesting development. Indeed, in the world at that time there had long been “warmed up” modifications of ordinary urban hatchbacks, with which the VAZ RPD was quite comparable in terms of developed power.
The presence of such a motor on cars of the 2108 family could “cheer up” consumer interest - at least in Togliatti they counted on it.
Even in difficult conditions, the new RPD for Samara was mastered quite quickly - fortunately, the VAZ-415 engine did not need to be developed from scratch. Some sources claim that the finishing work during its transformation into a serial product was carried out quite hastily or not very successfully, as a result of which the motor still retained a number of shortcomings inherent in the rest of the VAZ RPDs. However, there is another opinion that this motor, on the contrary, has absorbed all the advantages of past developments - both a sufficient resource, known from the 413th motor, and a “dense” layout inherited from the VAZ-414.
Almost simultaneously, the classics were also updated: in 1992, on the basis of the "seven", the production of a modification of the Zhiguli VAZ-21079 with a 140-horsepower VAZ-4132 engine began.
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The seventh model was the last Zhiguli with RPD
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The seventh model was the last Zhiguli with RPD
However, in 1997, the VAZ-415 finally received a certificate that allowed it to be installed on ordinary commodity cars, which soon appeared in car dealerships.
“In civilian life”: having become accessible to mere mortals, RPD immediately appeared on the pages of Russian auto publications
Of course, the price of the car increased by quite tangible at that time 2.2-2.5 thousand dollars, but the dynamics of the G8 improved by an order of magnitude. After all, 120-140 "rotary" horsepower made it possible to gain a hundred from a standstill in 8-9 seconds, and the real maximum speed came close to the cherished 200 km / h. Fuel consumption, of course, at the same time ranged from 8 to 14 liters. But the compact rotary motor spun up to a mind-blowing 8 thousand revolutions, providing the “pilot” with sensations incomparable with the acceleration of a conventional “chisel”.
RPD-415 under the hood of the VAZ-2108 looks quite organic. But at the same time, the motor is noticeably more compact than the native one. Photo: Alexander Podzolkov
RPD has always been famous for its "hot temper", so oil radiator he needed it like air. Or water. In general, for cooling. Photo: Alexander Podzolkov
The bottom view hints that this is some kind of very difficult "eight". Photo: Alexander Podzolkov
Microprocessor ignition could also be found on the VAZ-2108 with a conventional internal combustion engine. But very rarely. Photo: Alexander Podzolkov
Alas, at the same time, the rotor, obscure to most, remained a “thing in itself” - ordinary minders did not know the technology for its repair, and spare parts were not sold in any store around the corner.
In addition, by that time it was already gaining momentum on ordinary VAZ engines, and on the RPD, the archaic Solex carburetor was still in charge of power.
The RPD mixture was prepared by the familiar Solex, but with its own adjustments. "Gas sector" had an additional lever to drive the dosing oil pump- lubricator. Photo: Alexander Podzolkov
Top view of the VAZ-415 with a dismantled carburetor. Photo: Alexander Podzolkov
And, despite the presence of a microprocessor ignition system (MPSZ), the rotor could not boast of the complaisance and (most importantly!) Durability of a conventional piston ICE. Indeed, with a declared resource of 125,000 km, many engines began to quickly “die” after 50,000 km, which was facilitated by the use of the “wrong” oil. As with Japanese cars Mazda with RPD, while starting the engine deteriorated sharply and oil consumption for waste increased, and in the future the engine could completely fail.
The tightness of the seals is a sore point of any RPD, not only the VAZ-415. Photo: Alexander Podzolkov
Numerous tuning companies that appeared in Tolyatti and around it like mushrooms after the rain at that time offered tuning programs for conventional motors of various budgets and degrees of intervention, which made it possible to remove almost the same power as the rotor without a noticeable loss of resource. But RPD with a traditional power system was impossible to squeeze into the future environmental regulations Euro 2, to which the newly mastered VAZ injection corresponded without any problems.
Due to the non-mass production in the future, neither the work nor the production of the RPD itself was very interesting for VAZ, since, as in the history of Mazda, they could only be dictated by image considerations. Which in the case of the Togliatti Automobile Plant was not a strong enough argument ...
For a number of reasons listed, already at the beginning of the 2000s, the VAZ rotor began to sharply lose momentum. Yes, the VAZ-415 managed to try on even the “ten” and “tag” in modifications 2110-91 and 2115-91, respectively, but soon the production of rotary engines at VAZ was discontinued, and the SKB RPD itself, which developed its latest product in 2001, was re-registered.
Almost four dozen developments over 26 years - the designers of SKB RPD have worked a lot on the rotary theme
After 2004, the activities of the design bureau as part of work on RPD engines were finally terminated, and around 2007, the equipment was partially removed and disposed of. It seems that the final point was put on this in the history of the Soviet-Russian rotor.
Do you regret that rotary VAZs did not work out?
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 engine internal combustion not in RPD.
The work of the classic RPD is based on the simple movement of the rotor inside the 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 it has an ingeniously 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. Connecting rods and crankshaft convert the reciprocating motion of the piston into a rotational motion that can be used to rotate the wheels of the car.
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 will.
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: in the first cavity formed, suction occurs, that is, the chamber is filled 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 face is a 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. Exhaust port connected directly to exhaust pipe, and the inlet 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 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. In particular, this is not explained enough good contact the rotor itself with the walls of the cylinder. 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 endowed with a completely different combustion chamber and produces power for three quarters of the working time of the internal combustion engine, and the efficiency is as much as 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, along with the main design flaw in the form of high fuel consumption.
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 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 fuel consumption.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, there was not enough state budget money, which is 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
As you know, the vast majority of modern cars are equipped with internal combustion engines or internal combustion engines. The essence of their work is to convert the energy generated during combustion fuel mixture, into the rotation of the shaft, from which, with the help of mechanical drive the movement is transferred to the wheels of the vehicle. The vast majority of cars now use internal combustion engines arranged according to a piston scheme. But, there is another type of internal combustion engines, namely rotary engines. We will talk about this type of engine in this article.
The history of rotary engines began in 1957, when German engineers Felix Wankel and Walter Freude demonstrated the first workable sample of such a power unit. At first, many of the world's leading car manufacturers (in particular, Mercedes-Benz, General Motors, Citroen), but in the end, only the Japanese Mazda decided to master the production of rotary engines in large series and not abandon them for a very long time.
By the way, even the domestic VAZ for a number of years produced limited series Zhiguli with rotary power units. They were not supplied to “ordinary” buyers, but these cars were sent to the KGB fleets and, in very small quantities, the USSR Ministry of Internal Affairs.
The principle of operation of a rotary engine, as well as a conventional piston engine, is based on the conversion of combustion energy into rotational energy, but this conversion is carried out in a slightly different way. In a rotary engine, the rotational movement is performed directly by its main working element - the rotor. This is the most important difference between a rotary internal combustion engine and a piston internal combustion engine, in which the main moving working elements are pistons that perform not rotational, but reciprocating motion.
Thus, in rotary engines, due to their design, crank mechanisms that are quite complex in design and require periodic maintenance, converting reciprocating motion into rotational motion of the crankshaft, are completely excluded.
Just like in a piston engine, the pressure of the gases resulting from combustion is used in a rotary engine. fuel-air mixture. However, it does not occur in the cylinders, but in the chamber, which is formed by that part of the body, which is closed by the side of the triangular rotor inside it. It is he who is used instead of pistons.
The rotation of the rotor under the influence of this pressure occurs along a trajectory that is very reminiscent of a line drawn by a spirograph. Due to this, all three vertices of the triangular rotor, when in contact with the inner walls of the engine housing, form sealed combustion chambers. As the rotor rotates, each of these three volumes alternately expands and contracts. This mode of operation of a rotary internal combustion engine ensures the implementation of such processes as:
- Receipt of the fuel-air mixture;
- Compression;
- useful work;
- Exhaust release.
Thus, the rotary engine, just like the standard piston engine of a modern car, is a four-stroke.
The ignition system and fuel injection system in rotary engines is similar to those used in piston engines, but the structure of these internal combustion engines is completely different. The main structural elements of a rotary engine are:
- Rotor;
- Stator (case);
- output shaft.
As mentioned above, the rotor is located inside the stator (case) and has three convex sides. Each of them, in fact, plays the role of a piston and has a recess necessary in order to increase the speed of rotation. On each side of the rotor there are two metal rings that form the necessary for the operation of this ICE camera combustion.
An important component of the rotor is a gear located in its center and mating with a gear fixed to the body. It is thanks to this pairing that the necessary trajectory and direction are set along which the rotor rotates in the housing.
The housing of a rotary internal combustion engine has an oval shape, which is designed and implemented in such a way that all three rotor vertices always come into contact with its inner walls. This is necessary so that at any time inside this power unit there are three volumes of gas completely isolated from each other. In addition, the intake and exhaust ports are located in the body, and they do not have valves: the intake port connects directly to the throttle, and the exhaust port directly to the exhaust system.
The output shaft of a rotary engine is not at all like the crankshaft of a reciprocating internal combustion engine. It is eccentric, that is, with some offset relative to the central axis, special protrusions are located. A separate rotor is associated with each of them (by the way, there are not one, but several of them in a rotary engine). During rotation, each of the rotors pushes "its" cam, as a result of which a torque appears on the shaft.
It should be noted that all rotary engines are assembled in layers. The most commonly used twin rotors have five of them, and all of them are held with bolts installed in a circle. Cooling of rotary engines is carried out with the help of coolant, which is like through all parts of the structure. Bearings and seals for the output shaft are located in the two outermost layers. They also share the parts of the body, in which the rotors themselves are located. Inlet ports are located in the central part, and outlet ports are located in each of the extreme parts.
Advantages and disadvantages of rotary engines
The main advantages of rotary engines compared to piston engines are:
- Fewer moving parts;
- Smoother operation;
- Higher reliability.
In a two-rotor engine, only the output shaft and both rotors move, while even in the simplest design piston internal combustion engine, there are at least forty moving parts. Accordingly, the reliability of the rotary power unit is significantly higher.
In rotary engines, all moving parts rotate in only one direction, which greatly reduces vibration. To effectively dampen those that do arise, counterweights are used. It should also be noted that the rotation of the rotor in a rotary engine is only a third of the speed of rotation of the shaft. This also has a positive effect on the reliability of the power unit.
Rotary engines also have several significant drawbacks. Perhaps the main one is that compared to piston internal combustion engines, they consume significantly more fuel. At the same time, the cost of their production is much higher, so today they are not produced in large batches.
Related video
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 to bring the design to mind and create mass production it took too long.
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, new type ICE finally got its 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 the new technology were acquired by about a hundred companies around the world, including such monsters as Rolls-Royce, Porsche, BMW and Ford. - in a rotary piston engine, there are 40% fewer 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 a 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 had already endured a hundred hours, but this was still not enough for the normal operation of the car. 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 normal piston ICE"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 to 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 whole range of measures, including reworking the thermoreactor and carburetor, adding a heat exchanger to the exhaust system, developing a catalytic converter, and introducing new system ignition, the company 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 the VAZ was originally planned as a simple copyer of Western technologies (in particular, Fiat ones), the factory specialists decided to reproduce the 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 capacity of 65 hp was put into operation, it took another five years to fine-tune the design, after which an experimental batch of 50 units of VAZ-21018 rotary "units" 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 they were very interested in 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. Max speed rotary "eight" is about 210 km / h, and up to a hundred it accelerates 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 was elected at the general meeting - a man who came to the automotive industry from aviation and dislikes ground transport. 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 automotive RPD for 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, on the "eight". The same Japanese install "wankels" only on sports models. As a result, on Russian roads there were only a few rotary minicars "Oka". 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 the Japanese “rotorniks” have become regulars on the race tracks, they had to wait 16 years for a major success in Europe. 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, C111 was very expensive even for Mercedes, Secondly, the Germans could not put such a crude design on sale. 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.
Having no 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. Wankel himself last days 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 Mercedes did not go towards 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 driver license Wankel never received it until the end of his life.
We owe the revival of interest in RPD to a new Mazda engine Renesis (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.
The Mazda RX-8 car was specially developed for the new engine, 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. "RX-8 is not racing monster, but it's the best driving 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 engines internal combustion:
- 30-40% fewer parts;
- Smaller in 2-3 times dimensions and weight, in comparison with the standard internal combustion engine corresponding in power;
- Smooth torque response over the entire rpm range;
- Absence of a crank mechanism, and, consequently, a much lower level of vibration and noise;
- High level 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;
- Narrow temperature zone for RPD operation: at low temperatures engine power drops sharply, at high - rapid wear of the rotor seals.
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, everything was a little different: a talented engineer, Felix Wankel really worked on the development of a new, simple engine internal combustion, but it was a different engine based on the co-rotation of the 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. The basic scheme and engineering concept are due 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
And here Soviet Union I didn't buy a license at all. The development of their own rotary engine began with the fact that the German Ro-80 car, the production of which NSU began in 1967, was brought to the Union and dismantled.
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.
First Soviet stock 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 soared, 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.
Chambers are formed between the edges of the rotor and the walls of the capsule, their shape is variable crescent, which is the cause of some significant design flaws. 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.
Advantages and disadvantages of rotary engines
Advantages
The rotary engine is good because consists of far fewer parts than its competitor - by 35-40 percent.
Two engines of the same power - rotary and piston - will differ greatly in size. Piston twice as big.
rotary motor does not experience a lot of load at high speeds even if you accelerate the car to a speed of more than 100 km / h in low gear.
A car with a rotary engine is easier to balance that gives increased stability cars on road.
Even the lightest of vehicles do not suffer from vibration because RPD vibrates much less than the "piston". This is due to the greater balance of the RPD.
Flaws
The main disadvantage of a rotary engine motorists would call it small resource, which is a direct consequence of its construction. Seals wear extremely quickly, as their working angle is constantly changing.
Motor test temperature fluctuations every cycle, which also contributes to the wear of the material. Add to this the pressure that is exerted on the rubbing surfaces, which is treated only by injecting oil directly into the manifold.
Worn seals causes leakage between the chambers, the pressure differences between which are too great. Because of this Engine efficiency is falling and environmental damage is increasing.
crescent the shape of the chambers does not contribute to the completeness of fuel combustion, and the speed of rotation of the rotor and the short length of the working stroke are the reason for pushing out still too hot, not completely burned gases to the exhaust. In addition to the combustion products of gasoline, oil is also present there, which together makes the exhaust very toxic. Piston - brings less harm to the environment.
exorbitant appetites engine for gasoline have already been mentioned, and it "eats" oil up to 1 liter per 1000 km. And once you forget about the oil and you can get into a major repair, if not an engine replacement.
High price- due to the fact that for the manufacture of the motor you need high-precision equipment and very high quality materials.
As you can see, the rotary engine is full of flaws, but the piston engine is also imperfect, so the competition between them did not stop for so long. Is it over forever? Time will show.
