As you know, the principle of operation of a rotary engine is based on high revs and the absence of movements that distinguish ICE. 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. RPD does not have 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 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 behind the design of the internal combustion engine, known to us. 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 vehicle.
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 complete cycle RPD work. 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. 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
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 motor 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 corps.
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. Compared to: piston motor 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, toothed 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 rotate continuously in the same direction, as opposed to constantly changing direction pistons in 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 for which the output shaft rotates. 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 as the thermodynamic piston efficiency the engine is reduced in a long combustion chamber, also due to 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 models cars. 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 to boxer engines, which are Subaru's "chip" today. At the same time, the use similar engines almost considered 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, new Mazda is already reaching another 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, 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
The automotive industry is constantly evolving. It is not surprising that alternative technologies appear, which, to me, appear less often in mass production. These are rotary engines.
Important! A stormy impetus to the development of the automotive industry was given by the invention of the internal combustion engine. As a result, cars began to run on liquid fuel, and the gasoline era began.
Machines with a rotary engine
The rotary piston engine was invented by NSU. The creator of the apparatus was Walter Freude. Nevertheless, this device in scientific circles bears the name of another scientist, namely Wankel.
The fact is that a duet of engineers worked on this project. But the main role in the creation of the device belonged to Freud. While he was working on rotary technology, Wankel was working on another project that came to nothing.
However, as a result of undercover games, we now all know this apparatus as a Wankel rotary engine. The first working model was assembled in 1957. The pioneer car was the NSU Spider. At that time, he was able to develop a speed of one hundred and fifty kilometers. The engine power of the "Spider" was 57 hp. With.
"Spider" with a rotary engine was produced from 1964 to 1967. But it did not become massive. Nevertheless, automakers have not put an end to this technology. Moreover, they released another model - NSU Ro-80, and it became a real breakthrough. Proper marketing played a big role.
Pay attention to the title. It already contains an indication that the machine is equipped with a rotary engine. Perhaps the result of this success was the installation of these motors, on such famous cars, How:
- Citroen GS Birotor,
- Mercedes-Benz С111,
- Chevrolet Corvette,
- VAZ 21018.
Rotary engines received the most popularity in the land of the Rising Sun. Japanese company Mazda took a risky step for those times and began to produce cars using this technology.
The first sign from the Mazda company was the Cosmo Sport car. It cannot be said that she gained immense popularity, but she found her audience. Nevertheless, this was only the first step in the output of rotary engines on Japanese market, and soon, on the world.
Japanese engineers not only did not despair, but, on the contrary, began to work with tripled strength. The result of their labors was a series that all street racers in any country of the world remember with reverence - Rotor-eXperiment or RX for short.
As part of this series, several legendary models were released, including the Mazda RX-7. To say that this rotary-powered car was popular is like saying nothing. Millions of street racing fans started with her. At a relatively low price, it had simply incredible specifications:
- acceleration to hundreds - 5.3 seconds;
- maximum speed - 250 kilometers per hour;
- power - 250-280 horsepower, depending on the modification.
The car is a real work of art, it is light and maneuverable, and its engine is admirable. With the characteristics described above, it has a volume of only 1.3 liters. It has two sections, and the operating voltage is 13V.
Attention! Mazda RX-7 was produced from 1978 to 2002. During this time, about a million cars with rotary engines were produced.
Unfortunately, the last model of this series was released in 2008. Mazda RX8 completed the legendary line. Actually, on this, the history of the rotary engine in mass production can be considered complete.
Principle of operation
Many automotive experts believe that the design of a conventional piston apparatus should be left in the distant past. Nevertheless, millions of cars need a worthy replacement, whether a rotary engine can become one, let's figure it out.
The principle of operation of a rotary engine is based on the pressure that is created when fuel is burned. The main part of the design is the rotor, which is responsible for creating movements of the desired frequency. As a result, energy is transferred to the clutch. The rotor pushes it out, transferring it to the wheels.
The rotor has the shape of a triangle. The construction material is alloy steel. The part is located in an oval case, in which, in fact, rotation takes place, as well as a number of processes important for energy generation:
- mixture compression,
- fuel injection,
- spark creation,
- oxygen supply,
- discharge of waste raw materials.
The main feature of the rotary engine device is that the rotor has an extremely unusual movement pattern. The result of such a design decision are three cells completely isolated from each other.
Attention! In each cell, a certain process takes place.
The first cell receives air-fuel mixture. Mixing takes place in the cavity. Then the rotor moves the resulting substance to the next compartment. This is where compression and ignition take place.
In the third cell, the used fuel is removed. Well-coordinated work of three bays just gives that amazing performance, which was demonstrated on the example of cars from the RX series.
But the main secret of the device lies elsewhere. The fact is that these processes do not occur one after another, they occur instantly. As a result, three cycles pass in just one revolution.
Above was a diagram of the operation of a basic rotary motor. Many manufacturers are trying to upgrade the technology to achieve more performance. Some succeed, others fail.
Japanese engineers managed to succeed. The Mazda engines already mentioned above have up to three rotors. How much productivity will increase in this case, you can imagine.
Let's bring good example. Let's take a conventional RPD motor with two rotors and find the closest analogue - six-cylinder engine internal combustion. If you add another rotor to the design, then the gap will be completely colossal - 12 cylinders.
Types of rotary engines
Many auto companies took up the production of rotary engines. It is not surprising that many modifications have been created, each of which has its own characteristics:
- Rotary motor with multidirectional movement. The rotor does not rotate here, but, as it were, swings around its axis. The compression process takes place between the motor blades.
- Pulsating-rotary rotary engine. There are two rotors inside the case. Compression passes between the vanes of these two elements as they approach and recede.
- Sealed flap rotary motor - This design is still widely used in air motors. For rotary internal combustion engines, the chamber in which the ignition takes place is significantly altered.
- Rotary engine that works due to rotational movements. It is believed that this design is the most technically advanced. There are no parts that make reciprocating movements. Therefore rotary engines of this type easily reach 10,000 rpm.
- The planetary rotary engine is the very first modification invented by two engineers.
As you can see, science does not stand still, a considerable number of types of rotary motors will allow us to hope for further development technology in the distant future.
Advantages and disadvantages of a rotary engine
As you can see, rotary motors were quite popular at the time. Moreover, indeed legendary cars were equipped with motors of this class. To understand why this unit was installed on advanced models Japanese cars, you need to know all its advantages and disadvantages.
Advantages
From the background presented earlier, you already know that the rotary engine attracted great attention motor manufacturers, there were several reasons for this:
- Increased compact design.
- Light weight.
- RPD is well balanced and creates a minimum of vibrations during operation.
- The number of spare parts in the motor is an order of magnitude less than in the piston counterpart.
- RPD has high dynamic qualities
The most important advantage of the RPD is its high power density. A car with a rotary engine can accelerate to 100 kilometers without switching to high gears while maintaining a large number of revolutions.
Important! The use of a rotary engine allows you to achieve increased vehicle stability on the road due to the ideal weight distribution.
Flaws
So it's time to learn more why, despite all the advantages, most manufacturers have stopped installing rotary engines in their cars. The disadvantages of RPD include:
- Increased consumption fuel when working on low revs. In the most resource-demanding cars, it can reach 20-25 liters per 100 kilometers.
- Difficulty in manufacturing. At first glance, the design of a rotary engine is much simpler than that of a piston engine. But the devil is in the details. They are extremely difficult to make. The geometric accuracy of each part must be at an ideal level, otherwise the rotor will not be able to pass the epitrochoidal curve with the proper result. RPD requires high-precision equipment in its manufacture, which costs a lot of money.
- The rotary engine often overheats. This is due to the unusual structure of the combustion chamber. Unfortunately, even after many years, engineers failed to correct this defect. The excess energy generated by the combustion of the fuel heats up the cylinder. This greatly wears out the motor and shortens its life.
- Also, a rotary engine suffers from pressure drops. The result of this effect is rapid wear of seals. The service life of one well-assembled RPD lies in the range from 100 to 150 thousand kilometers. After passing this milestone, it is no longer possible to do without a major overhaul.
- Complicated procedure oil change. The consumption of rotary engine oil per 1000 kilometers is 600 milliliters. In order for the parts to receive proper lubrication, the oil must be changed once every 5000 km. If this is not done, then it becomes extremely likely serious damage key components of the unit.
As you can see, despite the outstanding advantages of RPD, it has a number of significant shortcomings. However, design departments in leading automobile firms are still trying to modernize this technology, and who knows, maybe one day they will succeed.
Results
Rotary engines have many significant advantages, they are well balanced, allow you to quickly increase speed and provide a set speed of up to 100 km in 4-7 seconds. But rotary motors also have disadvantages, the main of which is a short service life.
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. 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.
The firm soon announced that it had succeeded in creating 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 our own rotary engine began with the fact that they were 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.
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 taken into service law enforcement agencies THE USSR. They were not particularly worried about fuel consumption and a small engine resource, 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 - 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.
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 Vehicle 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 design. 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.
We tell how a rotary engine is arranged and works.
With the invention of the internal combustion engine, progress in the development of the automotive industry has stepped far ahead. Despite the fact that the general internal combustion engine device remained the same, these units were constantly improved. Along with these motors, more progressive rotary-type units appeared. Why haven't they been widely adopted? automotive world? We will consider the answer to this question in the article.
The history of the unit
The rotary engine was designed and tested by developers Felix Wankel and Walter Freude in 1957. The first car on which this unit was installed was the NSU Spyder sports car. Studies have shown that with an engine power of 57 horsepower this machine had the ability to accelerate to a whopping 150 kilometers per hour. The production of the Spider car equipped with a 57-horsepower rotary engine lasted about 3 years.
After that, this type of engine began to equip the NSU Ro-80 car. Subsequently, rotary engines were installed on Citroens, Mercedes, VAZs and Chevrolets.
One of the most common rotary engine cars is the Japanese sports car Mazda Cosmo Sport. Also, the Japanese began to equip the RX model with this motor. The principle of operation of a rotary engine ("Mazda" RX) was to constantly rotate the rotor with a change in cycles of work. But more on that later.
At the present time, the Japanese automaker is not engaged in serial production of cars with rotary engines. latest model, on which such a motor was installed, became the Mazda RX8 of the Spirit R modification. However, in 2012, the production of this version of the car was discontinued.
Device and principle of operation
What is the principle of operation of a rotary engine? This type of motor is distinguished by a 4-stroke cycle of action, as in a classic internal combustion engine. However, the principle of operation of a rotary piston engine is slightly different from that of conventional piston engines.
What main feature this motor? The Stirling rotary engine has in its design not 2, not 4 and not 8 pistons, but only one. It's called a rotor. revolves given element in a cylinder special form. The rotor is mounted on the shaft and connected to the gear wheel. The latter has a gear clutch with a starter. The element rotates along an epitrochoidal curve. That is, the rotor blades alternately cover the cylinder chamber. In the latter, fuel combustion occurs. The principle of operation of a rotary engine (including Mazda Cosmo Sport) is that in one revolution the mechanism pushes three petals of hard circles. As the part rotates in the body, the three compartments inside change their size. Due to the change in dimensions, a certain pressure is created in the chambers.
Phases of work
How does a rotary engine work? The principle of operation (gif-images and the RPD diagram you can see below) of this motor is as follows. The operation of the engine consists of four repeating cycles, namely:
- Fuel supply. This is the first phase of the engine. It occurs at the moment when the top of the rotor is at the level of the feed hole. When the chamber is open to the main compartment, its volume approaches a minimum. As soon as the rotor rotates past it, the compartment gets fuel-air mixture. After that, the chamber becomes closed again.
- Compressions. As the rotor continues its movement, the space in the compartment decreases. Thus, a mixture of air and fuel is compressed. As soon as the mechanism passes the spark plug compartment, the volume of the chamber decreases again. At this point, the mixture ignites.
- Inflammations. Often, a rotary engine (including the VAZ-21018) has several spark plugs. This is due to the large length of the combustion chamber. As soon as the candle ignites combustible mixture, the level of pressure inside increases tenfold. Thus, the rotor is driven again. Further, the pressure in the chamber and the amount of gases continue to grow. At this moment, the rotor moves and torque is created. This continues until the mechanism passes the exhaust compartment.
- Release of gases. When the rotor passes this compartment, the high-pressure gas begins to move freely into the exhaust pipe. In this case, the movement of the mechanism does not stop. The rotor rotates stably until the volume of the combustion chamber again drops to a minimum. By this time, the remaining amount of exhaust gases will be squeezed out of the engine.
This is exactly the principle of operation of a rotary engine. VAZ-2108, on which the RPD was also mounted, like the Japanese Mazda, was distinguished by quiet engine operation and high dynamic characteristics. But in mass production this modification was never launched. So, we found out what the principle of operation of a rotary engine is.
Disadvantages and advantages
Not in vain this motor attracted the attention of so many automakers. Its special working principle and design have whole line advantages over other types of internal combustion engines.
So, what are the pros and cons of a rotary engine? Let's start with clear benefits. Firstly, the rotary engine has the most balanced design, and therefore practically does not cause high vibrations during operation. Secondly, this motor has a lighter weight and greater compactness, and therefore its installation is especially relevant for sports car manufacturers. In addition, the low weight of the unit made it possible for designers to achieve ideal weight distribution axle loads. Thus, a car with this engine became more stable and maneuverable on the road.
And, of course, the design space. Despite the same number of cycles of operation, the device of this engine is much simpler than that of a piston counterpart. To create a rotary motor, a minimum number of components and mechanisms was required.
However, the main trump card of this engine is not in the mass and low vibrations, but in high efficiency. Due to the special working principle rotary motor had more power and efficiency factor.
Now for the disadvantages. They turned out to be much more than advantages. The main reason why manufacturers refused to buy such engines was their high fuel consumption. On average, for a hundred kilometers, such a unit spent up to 20 liters of fuel, and this, you see, is a considerable expense by today's standards.
Difficulty in manufacturing parts
In addition, it is worth noting the high cost of manufacturing parts for this engine, which was explained by the complexity of manufacturing the rotor. In order to this mechanism correctly passed the epitrochoidal curve, high geometric accuracy is needed (including for the cylinder). Therefore, in the manufacture of rotary engines, it is impossible to do without specialized expensive equipment and special knowledge in technical area. Accordingly, all these costs are pre-packaged in the price of the car.
Overheating and high loads
Also, due to the special design, this unit was often subject to overheating. The whole problem was the lenticular shape of the combustion chamber.
In contrast, classic internal combustion engines have a spherical chamber design. The fuel that burns in the lenticular mechanism is converted into thermal energy, which is consumed not only for the working stroke, but also for heating the cylinder itself. Ultimately, the frequent "boiling" of the unit leads to rapid wear and disable it.
Resource
Not only the cylinder endures heavy loads. Studies have shown that during the operation of the rotor, a significant part of the loads falls on the seals located between the nozzles of the mechanisms. They are exposed constant drop pressure, because the maximum engine life is no more than 100-150 thousand kilometers.
After that, the motor needs overhaul, the cost of which is sometimes equivalent to buying a new unit.
Oil consumption
Also, a rotary engine is very demanding on maintenance.
Its oil consumption is more than 500 milliliters per 1 thousand kilometers, which makes it necessary to fill in liquid every 4-5 thousand kilometers. If you do not replace it in time, the motor will simply fail. That is, the issue of servicing a rotary engine must be approached more responsibly, otherwise slightest mistake fraught with costly repairs to the unit.
Varieties
On this moment There are five varieties of these types of aggregates:
Rotary engine (VAZ-21018-2108)
The history of the creation of VAZ rotary internal combustion engines dates back to 1974. It was then that the first RPD design bureau was created. However, the first engine developed by our engineers had a similar design to the Wankel engine, which was equipped with imported NSU Ro80 sedans. The Soviet counterpart was named VAZ-311. This is the very first Soviet rotary engine. Working principle on VAZ cars of this motor has the same Wankel RPD action algorithm.
The first car on which these engines began to be installed was the VAZ modification 21018. The car practically did not differ from its "ancestor" - model 2101 - with the exception of the internal combustion engine used. Under the hood of the novelty was a single-section RPD with a capacity of 70 horsepower. However, as a result of research on all 50 model samples, numerous engine breakdowns were found, which forced the Volzhsky plant to refuse to use this type of internal combustion engine on its cars for the next few years.
Main cause of failure domestic RPD consisted of unreliable seals. However, Soviet designers decided to save this project by presenting the world with a new 2-section rotary engine VAZ-411. Subsequently, an internal combustion engine of the VAZ-413 brand was developed. Their main differences were in power. The first copy developed up to 120 horsepower, the second - about 140. However, these units were not included in the series again. The plant decided to put them only on official cars used in the traffic police and the KGB.
Motors for aviation, "eights" and "nines"
In subsequent years, the developers tried to create a rotary engine for domestic small aircraft, but all attempts were unsuccessful. As a result, the designers again took up the development of engines for passenger cars (now front-wheel drive) VAZ series 8 and 9. Unlike their predecessors, the newly developed VAZ-414 and 415 engines were universal and could be used on rear-wheel drive models of Volga and Moskvich cars. and so on.
Characteristics of the RPD VAZ-414
For the first time, this engine appeared on the "nines" only in 1992. Compared with its "ancestors", this motor had the following advantages:
- High specific power, which made it possible for the car to reach “hundred” in just 8-9 seconds.
- Great efficiency. From one liter of burnt fuel, it was possible to get up to 110 horsepower (and this without any forcing and additional boring of the cylinder block).
- High potential for forcing. At correct setting it was possible to increase the engine power by several tens of horsepower.
- High speed motor. Such an engine was able to work even at 10,000 rpm. Under such loads, only a rotary engine could function. The principle of operation of classic internal combustion engines does not allow them to be operated for a long time at high speeds.
- Relatively low fuel consumption. If the previous copies "ate" about 18-20 liters of fuel per "hundred", then this unit consumed only 14-15 in average operation.
The current situation with the RPD at the Volga Automobile Plant
All of the above engines did not gain much popularity, and soon their production was curtailed. In the future, the Volga Automobile Plant has no plans to revive the development of rotary engines. So the RPD VAZ-414 will remain a crumpled piece of paper in the history of domestic engineering.
So, we found out which rotary engine has the principle of operation and device.
A rotary engine is an internal combustion engine, the device of which is fundamentally different from a conventional piston engine.
In a piston engine, four cycles are performed in the same volume of space (cylinder): intake, compression, power stroke and exhaust. The rotary engine performs the same cycles, but they all take place in different parts of the chamber. This can be compared to having a separate cylinder for each stroke, with the piston gradually moving from one cylinder to the next.
The rotary engine was invented and developed by Dr. Felix Wankel and is sometimes referred to as the Wankel engine or Wankel rotary engine.
In this article, we will talk about how a rotary engine works. First, let's look at how it works.
The principle of operation of a rotary engine
Rotor and housing of a Mazda RX-7 rotary engine. These parts replace the pistons, cylinders, valves and camshaft of a piston engine.
Like a piston engine, a rotary engine uses the pressure that is created during combustion air-fuel mixture. In piston engines, this pressure builds up in the cylinders and drives the pistons. The connecting rods and crankshaft convert the piston's reciprocating motion into rotational motion that can be used to turn the car's wheels.
In a rotary engine, the combustion pressure is generated in a chamber formed by the part of the casing that is closed by the side of the triangular rotor that is used in place of the pistons.
The rotor rotates along a path resembling a line drawn by a spirograph. Thanks to this trajectory, all three vertices of the rotor are in contact with the housing, forming three separated volumes of gas. The rotor rotates, and each of these volumes alternately expands and contracts. This ensures that the air-fuel mixture enters the engine, compression, useful work expansion of gases and release of exhaust.
Mazda RX-8
Mazda pioneered the mass production of rotary-powered vehicles. The RX-7, which went on sale in 1978, was perhaps the most successful car with rotary engine. But it was preceded by a range of rotary-powered cars, trucks and even buses, starting with the 1967 Cosmo Sport. However, the RX-7 hasn't been produced since 1995, but the rotary engine idea hasn't died. The Mazda RX-8 is powered by a rotary engine called RENESIS. This engine was named the best engine 2003 It is naturally aspirated twin rotor and produces 250 hp.
The structure of the rotary engine
The rotary engine has an ignition system and a fuel injection system similar to those used in piston engines. The structure of a rotary engine is fundamentally different from a piston engine. Rotor
The rotor has three convex sides, each of which acts as a piston. Each side of the rotor is recessed, which increases the speed of the rotor, allowing more space for the air-fuel mixture.At the top of each face is a metal plate that divides the space into chambers. Two metal rings on each side of the rotor form the walls of these chambers.
In the center of the rotor is a gear wheel with an internal arrangement of teeth. It mates with a gear mounted on the body. This pairing sets the trajectory and direction of rotation of the rotor in the housing.
Housing (stator)
The body is oval in shape (an epitrochoid shape to be exact). 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 isolated gas volumes. In each part of the body, one of the internal combustion processes takes place. The body space is divided into four bars:
- Inlet
- Compression
- Working cycle
- Release
output shaft
Output shaft (note the eccentric cams)
The output shaft has rounded lobes located eccentrically, i.e. offset from the central axis. Each rotor is paired with one of these protrusions. The output shaft is analogous to the crankshaft in piston engines. When rotating, the rotor pushes the cams. 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.
Rotary engine assembly
The rotary engine is assembled in layers. The twin rotor engine consists of five layers held together by long bolts arranged in a circle. Coolant flows through all parts of the structure.The two outermost layers have seals and bearings for the output shaft. They also insulate the two parts of the housing where the rotors are located. The inner surfaces of these parts are smooth to ensure proper sealing of the rotors. An inlet supply port is located in each of the outermost parts.
The part of the housing that houses the rotor (note the location of the exhaust port)
The next layer includes an oval shaped rotor housing and an exhaust port. The rotor is installed in this part of the body.
The central part includes two inlet ports - one for each rotor. It also separates the rotors so its inner surface is smooth.
At the center of each rotor is an internally toothed gear that rotates around a smaller gear mounted on the motor housing. It determines the trajectory of rotation of the rotor.
Rotary motor power
In the central part there is an inlet port for each rotor
Like piston engines, the rotary internal combustion engine uses a four-stroke cycle. But in a rotary engine, such a cycle is carried out differently.
For one complete revolution of the rotor, the eccentric shaft performs three revolutions.
The main element of a rotary engine is the rotor. It acts as pistons in a conventional piston engine. The rotor is mounted on a large round cam on the output shaft. The cam is offset from the central axis of the shaft and acts as a crank, allowing the rotor to rotate the shaft. Rotating inside the housing, the rotor pushes the cam around the circumference, turning it three times in one complete revolution of the rotor.
The size of the chambers formed by the rotor changes as it rotates. This change in size provides a pumping action. Next, we will look at each of the four strokes of a rotary engine.
Inlet
The intake stroke begins when the top of the rotor passes through the intake port. At the time of the passage of the top through the inlet port, the volume of the chamber is close to the minimum. Further, the volume of the chamber increases, and the air-fuel mixture is sucked in.As the rotor turns further, the chamber is isolated and the compression stroke begins.
Compression
With further rotation of the rotor, the volume of the chamber decreases, and the air-fuel mixture is compressed. When the rotor passes through the spark plugs, the volume of the chamber is close to the minimum. At this point, ignition occurs.Working cycle
Many rotary engines have two spark plugs. The combustion chamber has a large enough volume, so with one candle, ignition would occur more slowly. When the air-fuel mixture is ignited, pressure is generated that sets the rotor in motion.Combustion pressure rotates the rotor in the direction of increasing the volume of the chamber. The combustion gases continue to expand, turning the rotor and generating power until the top of the rotor passes through the exhaust port.
Release
When the rotor passes through the exhaust port, the combustion gases under high pressure come out in exhaust system. With further rotation of the rotor, the volume of the chamber decreases, pushing the remaining exhaust gases into the exhaust port. By the time the chamber volume approaches the minimum, the top of the rotor passes through the inlet port and the cycle repeats.It should be noted that each of the three sides of the rotor is always involved in one of the cycle cycles, i.e. for one complete revolution of the rotor, three working cycles are performed. For one complete revolution of the rotor, the output shaft makes three revolutions, because There is one cycle per revolution of the shaft.
Differences and problems
Compared to a piston engine, a rotary engine has certain differences.Fewer moving parts
Unlike a piston engine, a rotary engine uses fewer moving parts. A two-rotor engine has three moving parts: two rotors and an output shaft. Even in the simplest four-cylinder engine at least 40 moving parts are used, including pistons, connecting rods, camshaft, valves, valve springs, rocker arms, timing belt and crankshaft.By reducing the number of moving parts, the reliability of the rotary engine is increased. For this reason, some manufacturers use rotary engines instead of piston engines in their aircraft.
Smooth operation
All parts of a rotary engine rotate continuously in the same direction, rather than constantly changing direction like pistons in a conventional engine. Rotary engines use balanced rotating counterweights designed to dampen vibrations.The power delivery is also smoother. Due to the fact that each stroke of the cycle proceeds for a rotation of the rotor by 90 degrees, and the output shaft makes three revolutions for each revolution of the rotor, each stroke of the cycle proceeds for a rotation of the output shaft by 270 degrees. This means that a single rotor motor delivers power at 3/4 revolution of the output shaft. In a single cylinder piston engine, the combustion process occurs at 180 degrees every second revolution, i.e. 1/4 of each revolution of the crankshaft (piston engine output shaft).
Slow work
Because the rotor rotates at 1/3 the speed of the output shaft, the main moving parts of a rotary engine move slower than the parts in a piston engine. This also ensures reliability.Problems
Rotary engines have a number of problems:- Sophisticated production in accordance with emission regulations.
- The production costs of rotary engines are higher compared to piston engines, since the number of rotary engines produced is less.
- Fuel consumption of vehicles with rotary engines is higher compared to piston engines, due to the fact that the thermodynamic efficiency is reduced due to the large volume of the combustion chamber and low compression ratio.
