The principle of operation of a rotary internal combustion engine. Disadvantages of rotary motors

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 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 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

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

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

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

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

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

Of course, if the rotary 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, 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 quite difficult (but not impossible) to adjust to the regulation of CO2 emissions in environment, especially in the USA.
• 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 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 with 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 it 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 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, designed as 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

When automobiles with reciprocating internal combustion engines were already widespread throughout the world, some engineers tried to develop rotary engines that were just as efficient and powerful. Significant success was achieved by specialists from Germany, which is not surprising, because it was in this country that the car was invented.

A bit of history

In 1957, the world saw the first rotary piston engine. Subsequently, it was named after one of the developers - Felix Wankel. The second person, Walter Freude, involved in the process of invention, undeservedly fell into the shadow of the co-author. Both engineers were representatives of the German company NSU, which produced cars and motorcycles.

A year later, the first car with RPD was released. Unfortunately, even the main designers of the model new car did not satisfy. The engine was finalized, and in the late 60s a sedan was born, which received the title of "Car of the Year". It was a Ro-80 from the same NSU company. Up to 100 km, it accelerated in just 12.8 s, reached speeds of up to 180 km / h, and weighed a little more than a ton. At that time, these were grandiose indicators. The production license was immediately acquired by one automobile company after another.

It is not known how the fate of Wankel's invention would have developed if the energy crisis had not begun in 1973, and oil prices had risen sharply. internal combustion ate too much fuel, so they began to abandon its use.

In the late 90s, only Russia and Japan produced cars with Wankel engines. Russian cars VAZs equipped with RPDs are little known, but Japanese models achieved worldwide popularity.

At present, cars with rotary engines are produced only by Mazda. Japanese experts have improved car motor to such an extent that he began to consume 2 times less oil and 40% less fuel. Emissions have also been reduced and the engine is now compliant with European environmental standards. A new round in the development of RPD was the use of hydrogen as a fuel.

Basics of a rotary engine

To understand how a rotary engine works, you need to understand its device. Two important details RPD - rotor and stator. The rotor mounted on the shaft rotates around a fixed gear - the stator. The connection with the gear occurs through a gear wheel. The rotor is made of alloy steel and placed in a cylindrical housing.

The motor rotor in cross section has a triangular shape, its edges are convex, and three peaks are constantly in contact with the inner surface of the housing. Thus, the space of the cylinder is divided into three chambers. As a result of rotation, the volume of the chambers changes. At some point, due to the shape of the body profile, there are four cameras.

• At the first stage, fuel is launched into one of the chambers through an opening (inlet window).
• Further, the volume of the chamber with fuel decreases, the inlet window closes completely, and fuel compression begins.
• At the next stage, four chambers are formed, candles (there are two of them) fire, the fuel ignites, and the useful work motor.
• With further rotation of the rotor, an outlet window opens, into which combustion products (exhaust gases) exit.

As soon as the outlet port closes, the inlet port opens and the cycle repeats.

One working cycle is completed in one full revolution of the shaft. For a piston engine to do the same work, it must be a two-cylinder engine.

To ensure tightness, sealing plates are installed on the tops of the rotor. They are pressed against the cylinder by springs and centrifugal force, and gas pressure is also added.

To better understand how a rotary engine works, and what it is in general, you need to study the diagram. It shows the cross section of the unit and the processes that occur during the movement of the rotor. The diagram of a rotary motor shows what stages the rotor goes through, playing the role of a piston.

Types of rotary engines

The oldest rotary engines are water mills, in which the wheel rotates from the action of water and transfers energy to the shaft. The device of a modern rotary engine running on fuel is much more complicated. In it, the camera can be:

• hermetically sealed;
• constant contact with the external environment.

The first type of devices is used on vehicles, and the second in gas turbines. Engines with a closed chamber, in turn, are divided into several types. The classification is as follows.

1. The rotor rotates alternately in one direction, then in the other direction, its movement is uneven.
2. Rotation occurs in one direction, but the speed changes, the movement is pulsating.
3. Engines with sealing flaps made in the form of blades.
4. Uniformly rotating rotor with flaps that move with the rotor and act as a seal.
5. Motors with a rotor making planetary motion.

There are also two more types of rotary engines in which the main element rotates uniformly. They differ in the organization of the working chamber and the design of the seals. refers to the fifth item from the above list.

Benefits of RPD

Having considered the device of a rotary engine and the principle of operation, it can be understood that it is completely different from a piston engine. The rotary internal combustion engine is more compact, consists of fewer parts, and its power density is greater than that of a piston engine.

RPDs are easier to balance to keep vibrations to a minimum. This allows you to install it on light vehicles, such as microcars.

The number of parts is less than that of a piston engine by almost 2 times. The dimensions are also much smaller, and this advantage simplifies the weight distribution along the axes, allows you to achieve greater stability on the road.

A traditional piston engine does useful work in only two revolutions of the shaft, while in a rotary engine, useful work is done in one revolution of the rotor. This is the reason for the rapid acceleration of cars with RPD.

High fuel consumption RPD

The device is surprisingly simple, understandable and witty. Why hasn't it gained distribution like a piston internal combustion engine? Last but not least is the economy.

The rotary internal combustion engine consumes too much fuel. With a volume of only 1.3 liters, almost 20 liters of gasoline are used for every 100 km. For this reason, run mass production cars with RPD decided not many companies.

In light of recent developments in the Middle East, with a fierce war over resources and oil and gas prices still quite high, the limited use of RAPs is understandable.

Other important disadvantages

The next disadvantage of a rotary piston engine is the rapid wear of the seals located along the ribs of the rotor. This wear occurs due to rapid rotation, and as a result, friction of the ribs against the walls of the chamber.

In addition, the rib lubrication system becomes more complicated. Mazda has made injectors that inject oil into the combustion chamber. In this regard, the requirements for the quality of the oil have increased. Constant abundant lubrication is also required by the main shaft around which the movement takes place.

The technical solution to lubrication issues required a special approach, and only Japanese engineers were able to cope with the task after many years of experimentation.

Temperature exhaust gases RPD is higher than that of a piston engine. This is due to the relatively short stroke length of the rotor edge. The combustion process barely has time to end, as the edge has already moved so much that the outlet window opens. As a result, in exhaust pipe gases come out that have not completely transferred pressure to the rotor, and their temperature is high. A small part of the unburned fuel mixture also enters the atmosphere, which negatively affects the environment.

In a rotary engine, it is difficult to ensure the tightness of the combustion chamber. During operation, the stator walls heat up unevenly and expand. As a result, gas leaks are possible. Particularly heated is the part in which combustion occurs. To deal with this problem, different parts are made from different alloys. This, in turn, complicates and increases the cost of the engine production process.

The cost of manufacturing Wankel rotary piston engines is not in the best way affected by the complex shape of the chamber. In fact, the cylinder does not have an oval section, as is sometimes said. The cross section has the shape of an epitrochoid and requires high-precision execution.

So, it becomes clear that the rotary engine has pros and cons. They can be summarized in the following table.

Because of rapid wear parts, the resource of a rotary engine is about 65 thousand km. For comparison, the resource of a traditional internal combustion engine is 2 or even 3 times longer. Maintenance of rotary piston engines requires more responsibility, so they attract the attention of mainly professionals. In part, the engineers managed to eliminate the shortcomings of cars with RPD, but some of them still remained.

Mazda rotary piston engines

While other global manufacturers abandoned the production of rotary engines, Mazda continued to work on them. Its specialists have improved the design and received powerful motor, able to compete with the best European units.

The Japanese began working with a rotary piston engine back in 1963. They released several models of buses, trucks and cars.

From 1978 to 2003, the company produced the famous sports car RX-7. Its successor was the RX-8 model, which received more than 30 awards at international motor shows.

The RX-8 was powered by the Renesis (Rotary Engine Genesis) engine. In different configurations, the car was sold all over the world. Most powerful models(250 hp, 8.5 thousand rpm) were sold in North America and Japan. In 2007, a concept car with a Renesis II engine with a power of 300 hp was presented at the Tokyo Motor Show in 2007. With.

In 2009, Mazda's rotary-powered cars were banned in Europe because carbon dioxide emissions exceeded then-existing regulations. In 2102 mass production Japanese cars with rotary engines was discontinued. On this moment RPD from Mazda installed only on sports racing cars.

The main types of internal combustion engines and steam engines have one common drawback. It consists in the fact that reciprocating movement requires transformation into rotational movement. This, in turn, causes low productivity, as well as a rather high wear of mechanism parts included in various types of engines.

Quite a lot of people thought about how to create such a motor in which moving parts only rotated. However, only one person managed to solve this problem. Felix Wankel, a self-taught mechanic, became the inventor of the rotary piston engine. During his life, this man did not receive any specialty or higher education. Let us consider further the Wankel rotary piston engine.

Brief biography of the inventor

Felix G. Wankel was born in 1902, on August 13, in the small town of Lahr (Germany). In World War I, the father of the future inventor died. Because of this, Wankel had to quit his studies at the gymnasium and get a job as a sales assistant in a bookstore at a publishing house. As a result, he developed a passion for reading. Felix studied the technical characteristics of engines, automotive, mechanics on his own. He drew knowledge from books that were sold in the shop. It is believed that the Wankel engine scheme implemented later (more precisely, the idea of ​​its creation) was visited in a dream. It is not known whether this is true or not, but it can be said for sure that the inventor had extraordinary abilities, a craving for mechanics and a peculiar

Advantages and disadvantages

Convertible reciprocating motion is completely absent in a rotary engine. The formation of pressure occurs in those chambers that are created using the convex surfaces of the triangular rotor and various parts of the body. The rotational movement of the rotor is carried out by combustion. This can reduce vibration and increase rotation speed. Due to the increase in efficiency thus brought about, the rotary engine is much smaller than a conventional piston engine of equivalent power.

The rotary engine has one main of all its components. This important component is called a triangular rotor, which rotates inside the stator. All three vertices of the rotor, thanks to this rotation, have a permanent connection with the inner wall of the housing. With the help of this contact, combustion chambers, or three volumes of a closed type with gas, are formed. When the rotational movements of the rotor inside the housing occur, the volume of all three formed combustion chambers changes all the time, resembling the actions of a conventional pump. All three side surfaces of the rotor work like a piston.

Inside the rotor is a small gear with external teeth, which is attached to the body. The gear, which is larger in diameter, is connected to this fixed gear, which sets the very trajectory of the rotational movements of the rotor inside the housing. The teeth in the larger gear are internal.

Due to the fact that together with the output shaft the rotor is connected eccentrically, the rotation of the shaft occurs in the same way as the handle will rotate the crankshaft. The output shaft will rotate three times for each rotation of the rotor.

The rotary engine has the advantage of being light in weight. The most basic of the blocks of the rotary engine has a small size and weight. At the same time, the handling and characteristics of such an engine will be better. He gets less mass due to the fact that there is simply no need for a crankshaft, connecting rods and pistons.

The rotary engine has dimensions that are much smaller than a conventional engine of corresponding power. Thanks to the smaller engine size, handling will be much better, and the car itself will become more spacious, both for passengers and for the driver.

All of the parts of a rotary engine carry out continuous rotational movements in the same direction. The change in their movement occurs in the same way as in the pistons of a traditional engine. Rotary motors are internally balanced. This leads to a decrease in the vibration level itself. The power of the rotary engine seems to be much smoother and more uniform.

The Wankel engine has a convex special rotor with three faces, which can be called its heart. This rotor makes rotational movements inside the cylindrical surface of the stator. The Mazda rotary engine is the world's first rotary engine designed specifically for series production. This development began in 1963.

What is RPD?

In classic four-stroke engine the same cylinder is used for different operations - injection, compression, combustion and exhaust. In a rotary engine, each process is performed in a separate compartment of the chamber. The effect is not much different from dividing the cylinder into four compartments for each of the operations.
In a piston engine, the pressure generated by combustion of the mixture causes the pistons to move back and forth in their cylinders. The connecting rods and crankshaft convert this pushing motion into the rotational motion required to propel the vehicle.
In a rotary engine, there is no rectilinear motion that would have to be translated into rotational. Pressure builds up in one of the chamber compartments causing the rotor to rotate, which reduces vibration and increases the potential engine speed. The result is greater efficiency and smaller dimensions for the same power as a conventional piston engine.

How does RPD work?

The function of the piston in the RPD is performed by a three-vertex rotor, which converts the force of gas pressure into the rotational movement of the eccentric shaft. The movement of the rotor relative to the stator (outer housing) is provided by a pair of gears, one of which is rigidly fixed on the rotor, and the second on the side cover of the stator. The gear itself is fixedly fixed to the motor housing. With it in engagement is the gear of the rotor from the gear wheel, as it were, rolls around it.
The shaft rotates in bearings placed on the body and has a cylindrical eccentric on which the rotor rotates. The interaction of these gears ensures the expedient movement of the rotor relative to the housing, as a result of which three separated chambers of variable volume are formed. The gear ratio of the gears is 2:3, so for one revolution of the eccentric shaft, the rotor returns 120 degrees, and for a full revolution of the rotor, a full four-stroke cycle occurs in each of the chambers.

Gas exchange is controlled by the top of the rotor as it passes through the inlet and outlet ports. This design allows for a 4-stroke cycle without the use of a special gas distribution mechanism.

The sealing of the chambers is provided by radial and end sealing plates, which are pressed against the cylinder by centrifugal forces, gas pressure and band springs. The torque is obtained as a result of the action of gas forces through the rotor on the shaft eccentric

mixture formation

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

From liquid fuel, the mixture is prepared as follows:

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

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

Specifications of rotary piston engine

options	VAZ-4132	VAZ-415
number of sections	2	2
The working volume of the engine chamber, cc	1,308	1,308
compression ratio	9,4	9,4
Rated power, kW (hp) / min-1	103 (140) / 6000	103 (140) / 6000
Maximum torque, N * m (kgf * m) / min-1	186 (19) / 4500	186 (19) / 4500
Minimum speed of the eccentric shaft per Idling, min-1	1000	900
Engine weight, kg
Overall dimensions, mm
Oil consumption as % of fuel consumption
Engine resource before the first overhaul, thousand km
appointment	VAZ-21059/21079	VAZ-2108/2109/21099/2115/2110

models are produced

	RPD engine	Acceleration time 0-100, sec	Maximum speed, km \ h

Efficiency of rotary piston design

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

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

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

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

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

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

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

Wankel rotary piston engine

The principle of operation of the RPD is based on the expansion pressure of gases, which is created during the combustion of fuel. The main difference and positive moment of RPD is the absence of masses with reciprocating movements. All movement of parts occurs in a circle without sudden stops. In a conventional piston internal combustion engine, the piston and connecting rod come to a complete stop at the top and bottom. dead spots, which creates significant inertial forces and requires the use of high-strength materials.

The main part of the design is a rotor that converts pressure into Roundabout Circulation. The rotor in the simplest case has the shape of a triangle with convex edges (the so-called Reuleaux triangle) and is / rotates in an oval housing of a special profile, the surface of which is made according to the epitrochoid (options with a different shape of the rotor and housing are possible). In the cavities between the rotor and the housing, completely isolated from each other and changing their volume as the rotor rotates, a number of processes (cycles) take place - air supply, fuel injection, mixture compression, creation of a spark, exhaust gases removal:

• enters the first cavity through the inlet window and mixes air-fuel mixture(opening and closing of the window is performed by the edge of the rotor, similar to a two-stroke piston engine);
• the rotor moves the resulting substance into the second cavity, where compression and ignition take place;
• in the third cavity, the mixture expands and the exhaust gases are removed through the outlet window (it also opens and closes with the edge of the rotor).

The key point is that these processes do not occur sequentially, but simultaneously and in parallel, i.e. for one revolution of the rotor, all three cycles occur.

The rotation of the rotor occurs on an eccentric - a pair of gears, the largest of which is located on the inner surface of the rotor, and the smaller, supporting one, is rigidly attached to the inner surface of the engine side cover. The rotational motion of the rotor is transmitted to an eccentric shaft mounted on bearings and transmitting torque to the transmission mechanisms. Thus, two mechanical pairs work simultaneously in the RPD: the first one regulates the movement of the rotor and consists of a pair of gears; and the second - converting the circular motion of the rotor into rotation of the eccentric shaft. The gear ratio of the rotor and stator gears is 2:3, so for one complete revolution of the eccentric shaft, the rotor has time to turn 120 degrees. In turn, for one complete revolution of the rotor in each of the three chambers formed by its faces, a complete four-stroke cycle of the internal combustion engine is performed.

To ensure balance (especially on idling) requires a minimum of two rotors, although a single rotor design is also used. Mazda engines have up to three rotors (sections).

General Rotary efficiency Wankel engine (thermal and mechanical efficiency) is about 40-45%. For comparison, conventional piston internal combustion engines have 25% efficiency (according to other sources - 34%), and modern turbodiesels up to 40% (according to other sources - 50%).

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Classification of rotary internal combustion engines

To uncover...

The classification of rotary engines occurs according to the type of operation of the combustion chamber - it is hermetically sealed for a while, or has a constant connection with the atmosphere. The latter type includes gas turbines, the combustion chambers of which are separated from the exhaust nozzle (from the atmosphere) only by a thick "palisade" of the rotor impeller blades.

Rotary internal combustion engines with hermetically sealed combustion chambers are divided into 7 different structural layouts:

1. Rotary engines with non-uniform multidirectional (reciprocating-rotational) movement of the main working element. The rotor does not rotate here, but, as it were, swings around its axis. The compression process takes place between the motor blades.
2. Rotary engines with uneven unidirectional (pulsating-rotational) movement of the main working element. There are two rotors inside the case. Compression passes between the vanes of these two elements as they approach and recede.
3. Rotary motors with a simple and uniform rotational movement of the main working element and with sealing flaps-blades moving in the rotor. This design is still widely used in pneumatic motors. For rotary internal combustion engines, the chamber in which the ignition takes place is significantly altered.
4. A special case - with dampers-blades deviating on hinges on the rotor.
5. Rotary motors with a simple and uniform rotational movement of the main working element and with sealing flaps moving in the housing.
6. Rotary motors with a simple and uniform rotational movement of the main working element and using the same simple rotational movement of the sealing elements.
7. Rotary motors with a simple rotational movement of the main working element, without the use of separate sealing elements and a spiral organization of the shape of the working chambers. They are considered the most technically advanced due to the absence of parts that perform reciprocating movements. They are the RPD (“Wankel engine”) in the classical modern sense. RPDs of this type easily reach 10,000 rpm.
8. Rotary motors with planetary rotational movement of the main working element and without the use of separate sealing elements. The very first modification invented by Freude and Wankel.

Advantages of RPD

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• The design of the RPD is relatively small (1.5-2 times less than a classic internal combustion engine of the same power) and has a low weight, which improves the controllability of the machine, facilitates the optimal location of the transmission (weight distribution) and frees up more internal layout space.
• Due to the lack of conversion of reciprocating motion into rotational and the associated inertia forces, the RPD can withstand much high speed compared with traditional engines. As a result - excellent dynamic qualities (high power density - a 1.3-liter engine produces 220 hp, and with a turbocharger - 350 hp!), high maximum speed (up to 10,000 rpm), excellent throttle response and a flat torque curve.
• Power output from each section during 3/4 revolution of the output shaft (single-piston internal combustion engine produces power only 1/4 revolution).
• Minimum vibration, excellent balance (especially in twin-rotor engines).
• 35-40% fewer parts in the design in general and moving masses in particular (there are no pistons, connecting rods, crankshaft, in the "classic version" - a gas distribution mechanism), a much smaller mass of moving parts.
• In the simplest version of the RPD, there is no separate lubrication system - oil is added to the fuel, as in the operation of two-stroke motorcycle engines. Lubrication of friction pairs (primarily of the rotor and working surface combustion chamber) in this embodiment is produced by the fuel-air mixture itself.

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Disadvantages of RPD

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• Low efficiency of gap seals between the rotor and the combustion chamber. The RPD rotor, which has a complex shape, requires reliable seals not only along the edges (and there are four of them on each surface - two along the top, two along the side faces), but also along the side surface in contact with the engine covers. In this case, the seals are made in the form of spring-loaded strips of high-alloy steel with particularly precise processing of both working surfaces and ends. The allowances for expansion of the metal from heating impair their characteristics - it is almost impossible to avoid gas breakthrough at the end sections of the sealing plates (in piston engines, the labyrinth effect is used by installing sealing rings with gaps in different directions).
• The complex sealing system of the rotor requires sophisticated and efficient lubrication of the friction surfaces. RPD consumes more oil than a four-stroke piston engine (from 400-1200 ml per 1000 km, change every 5000 km). RPD owners recommend checking the oil level every morning. In this case, the oil burns along with the fuel, which sharply worsens the ecology of the RPD.
• Special requirements for oil quality - due to the tendency to increased wear(due to the large area of ​​contacting parts - the rotor and the inner chamber of the engine) and overheating (due to increased friction and the small size of the engine itself). For RPDs, irregular oil changes are deadly (abrasive particles in old oil dramatically increase wear) and engine hypothermia. Starting a cold engine and insufficient warming up lead to the fact that there is little lubrication in the contact zone of the rotor seals with the surface of the combustion chamber and side covers. If a piston engine most often seizes when overheating, then the RPD most often during a cold engine start or during operation in cold weather, when cooling is excessive.
• High fuel consumption for low revs(and generally speaking). Theoretically, it can be eliminated by turning off part of the sections at low speeds, which at the same time reduces the temperature load.
• High demands on the geometric accuracy of parts manufacturing and, as a result, high complexity of production. The use of high-tech and high-precision equipment is required: machines capable of moving the tool along a complex trajectory of the epitrochoidal surface of the volumetric displacement chamber.
• The connection of the rotor with the output shaft through an eccentric mechanism ( salient feature RPD Wankel) causes pressure between the rubbing surfaces, which, in combination with high temperature leads to additional wear and heating of the engine.
• High pressure drops between the rotor chambers with a very small contact patch area. As a result, rapid wear of seals and very high requirements for them, in general, a short engine life (the key problem of RPD is high leakage between chambers, a drop in efficiency and an increase in exhaust toxicity). So, for the Mazda RX-8, the engine resource is about 100-150 thousand kilometers with proper and timely maintenance, after which it goes overhaul with replacement seals. Partly the problem of rapid wear of seals on high speed shaft rotation was solved by using high-alloy steel.
• Less elasticity relative to classic piston ICEs - RPD gives out optimal power only at high speeds, which requires the complexity of the transmission.
• Poor geometry of the combustion chamber, which in RPD has a lenticular shape, i.e. relatively large area with a small volume. When burning working mixture the main energy losses go through radiation, therefore perfect shape combustion chambers - spherical. Heat losses not only reduce the efficiency of converting chemical energy into mechanical energy, but also lead to severe engine overheating (i.e., higher thermal conditions), as well as poor combustion of the fuel-air mixture and a tendency to knock. Partially, this problem is solved by installing two candles in different zones on one combustion chamber.
• Small resource of spark plugs, their overheating, the need to replace every 10,000 km.

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RPD device

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The rotor mounted on the shaft is rigidly connected to the gear wheel, which engages with the fixed gear - the stator. The diameter of the rotor is much larger than the diameter of the stator, despite this, the rotor with the gear wheel rolls around the gear. Each of the vertices of the trihedral rotor moves along the epitrochoidal surface of the cylinder and cuts off the variable volumes of the chambers in the cylinder with three valves.

This design allows any 4-stroke Diesel, Stirling or Otto cycle to be carried out without the use of a special gas distribution mechanism. The sealing of the chambers is provided by radial and end sealing plates pressed against the cylinder by centrifugal forces, gas pressure and band springs. The absence of a gas distribution mechanism makes the engine much simpler than a four-stroke piston engine, and the absence of interface (crankcase space, crankshaft and connecting rods) between individual working chambers ensures extraordinary compactness and high power density. For one revolution of the eccentric shaft, the engine performs one work cycle, which is equivalent to the operation of a two-cylinder piston engine. In one revolution of the rotor, the eccentric shaft performs 3 revolutions and 9 working strokes, which leads to erroneous comparisons between a rotary engine and a six-cylinder piston engine.

The mixture formation, ignition, lubrication, cooling, start-up are fundamentally the same as in a conventional piston internal combustion engine.

Practical application was received by engines with trihedral rotors, with the ratio of gear and gear radii: R: r = 2: 3, which are installed on cars, boats, etc.

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Application

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The first production car with a rotary engine was the NSU Spider, which was released in 1964. NSU- German company, founded in 1873, which produced cars and motorcycles. Until 1969, it existed as separate company, then was bought Volkswagen Group group.

The first mass model (37204 copies) was the NSU Ro-80 model, a real breakthrough thanks to the right marketing. However, relying on the "revolutionary technology" of the RPD, which has not yet been debugged in real conditions, has become a serious mistake. The engine resource was no more than 50 thousand kilometers, and often much less. The RPD was often replaced with a Ford L4 "Essex" piston.

RPDs were also installed on cars:

• Citroen GS Birotor (Citroën M35 project)
• Mercedes-Benz С111
• Chevrolet Corvette
• VAZ 21018 (1976), 21079 and 2110 (modifications for special services)
• Mazda (since 1978, Cosmo Sport and Rotor-eXperiment series commonly known as RX)

The RX series ended in 2008 with the RX-8 model. In total, more than a million cars with RPD were produced in the series. In total, at the peak of its popularity, the patent for the Wankel engine was bought by 11 of the world's leading automakers.

Interestingly, Mazda cars with the letters RE in the name (the first letters of the name "Renesis") can use both gasoline and hydrogen as fuel (because it is less sensitive to detonation than a conventional engine using a reciprocating piston).

RPDs are also used on motorcycles (in small series) and in aviation modeling.

Interestingly, having received a patent for RPD in 1936, Felix Wankel became the inventor of not only the internal combustion engine, but also the rotary piston pump and compressor. And these devices can be found much more often than RPDs - in production, in repair shops, in everyday life. For example, portable electric compressors for motorists are very often arranged on the principle of a rotary piston pump.

A rotary engine (RD) is considered an internal combustion engine, which is almost completely different from the usual piston unit. As you know, several cycles are performed in the cylinder of a piston engine: intake, compression, then a power stroke, and finally, exhaust.

As for the RD, it performs all the same cycles, while they are carried out in different parts of the chamber. It would be possible to compare them only if a separate cylinder was present in the piston unit for each of the cycles and the piston would gradually move from cylinder to cylinder.

The rotary engine was invented and designed by Dr. Felix Wankel, which is why it is often called the Wankel engine.

Principle of operation

The rotary engine uses the pressure generated during combustion air-fuel mixture. Such pressure in piston engines is created in the cylinders that drive the pistons.

The crankshaft and connecting rods cause the piston to rotate and due to this, the wheels of the car begin to rotate. IN this engine, pressure during combustion occurs in the chamber, which is formed by part of the housing itself and is closed by one of the sides of the triangular rotor, which acts as pistons.

In this video, you will be shown how the rotary engine for the Mazda RX-8 works. Enjoy watching!

The rotations of the rotor resemble a line drawn by a spirograph. Such a trajectory allows the tops of the rotor to contact the body of the engine, which forms three volumes of gas separated from each other.

When the rotor rotates, these volumes alternately expand and contract. This is what ensures that the air-fuel mixture enters the engine, as well as the compression and exhaust exhaust. It has an ignition and fuel injection system that is similar to the systems used in piston units.

Its design is completely different from the piston engine. The rotor has three convex sides that act as pistons. On each side of the device, there is a special recess that increases the speed of rotation of the rotor itself.

This leaves more room for the air-fuel mixture. At the top of all faces are metal plates that separate all free place on cameras. On each side of the rotor there are two metal rings that form the walls of the chambers.

In the central part of the device, there is a gear wheel, the teeth of which look inward. This wheel mates with a gear, which is mounted on the engine housing. This pairing sets the direction and trajectory of rotation in the engine body.

Rotary Engine Features

In this video, you will be told about the history of engines, as well as why they are so remarkable.

The motor housing is oval in shape. The shape of the chamber itself is designed in such a way that all the tops of the rotor are in contact with the chamber wall.

They form three separated volumes of gas. The process of internal combustion takes place in the body. The free space of the body is divided into four parts for intake, compression, power stroke and exhaust.

It is important to note that the inlet and outlet ports are in the housing. There are no valves in the port. The intake port is directly connected to the throttle and the exhaust port is directly connected to the exhaust system.

The output shaft is characterized by rounded lobes, which are eccentrically located. A rotor is associated with each of the protrusions. The output shaft is an analogue of the crankshaft in a piston engine. As the rotor rotates, it pushes the cams.

Since they are not symmetrical, the rotor presses on them with a force that causes the output shaft to rotate.

The rotary engine is assembled in layers. An engine with two rotors is assembled in five layers, which are fastened with long bolts arranged in a circle.

Coolant passes through all structural elements. The two outer layers have seals and bearings for the output shaft.

In addition, they insulate the parts of the motor casing that contain the rotors. The inner surface of each part is smooth and this ensures proper sealing of the rotors.

It should be noted that the inlet port is present in the extreme parts. The oval rotor housing and outlet port is located in the next layer. This is where the rotor is installed.

In the central part there are inlet ports - one such port is allocated for each rotor.

Mazda RX-8 rotary engine

The central part separates the rotors, which is why its surface inside is completely smooth.

Advantages and disadvantages

At one time, many leading car manufacturers drew attention to the rotary engine.

Due to its design and principle of operation, it had significant advantages over piston engines. First of all, the rotary unit is better balanced and subject to minimal vibration.

In addition, this engine has excellent dynamic characteristics(in low gear, a car with such an engine can be easily dispersed by more than 100 km / h at high speeds).

This unit is much lighter and more compact than a piston engine. This engine uses fewer components, and it has a high power compared to a piston unit.

Among the disadvantages of the rotary engine should be highlighted:

• increased fuel consumption at low speeds;
• complexity of production individual parts, which requires the use of expensive high-precision equipment;
• tendency to overheat due to the special shape of the combustion chamber;
• wear of the seals that are located between the nozzles due to frequent pressure drops;
• the need for timely and frequent changes engine oil(replacement should be done every 5000 kilometers).

The operation of rotary units must be approached more responsibly than the maintenance of piston units.

Their overhaul and maintenance is important to carry out on time.

Feature of Mazda car engines

Mazda began production of models with rotary engines back in 1963.

Most successful auto The company equipped with a rotary unit was the RX-7 model, released in 1978. True, many cars, buses and trucks with rotary engines were produced before it. After the RX-7 model, the production of which was stopped in 1995, the rotary engine began to supply the RX-8 model.

This engine was considered the best unit in 2003. This engine with two rotors produced 250 Horse power. However, in 2008 the company stopped sale of Mazda RX-8 in Europe due to emissions from its engine that did not meet European standards.

However, the company's developers decided not to stop there and created a modern Renesis 16X rotary engine that meets international and European standards.

The injection system has been significantly redesigned, thanks to which fuel is consumed much more economically.

In addition, the body of the engine is made of modern aluminum alloy. The company also released a rotary unit that can run on hydrogen. The latest development The current manufacturer with a rotary engine is the Premacy Hydrogen RE Hybrid.