What is a rotary piston engine. Rotary piston engine (Wankel engine)

Steam engines, like traditional internal combustion engines, have a common disadvantage - the reciprocating movements of the piston must be converted into rotational movements of the wheels. This is the reason for low efficiency and high wear of main elements.

Many engineers tried to solve this problem by inventing an internal combustion engine, all the parts of which would only rotate. However, a self-taught mechanic who did not graduate from a higher or even a secondary specialized educational institution was able to invent such a unit.

A little history

In 1957, little-known mechanic-inventor Felix Wankel and leading NSU engineer Walter Frede became the first to install a rotary piston engine in a car. The “test subject” was NSU Prinz. The original design was far from perfect. For example, spark plugs had to be changed almost after complete disassembly of the unit. In addition, the reliability of the engine remained in doubt, and efficiency could not be mentioned.

After many tests, the concern began producing cars with a traditional internal combustion engine. However, the first rotary piston DKM-54 could demonstrate great potential.

This is how the original version of the internal combustion engine got its chance to be introduced into car production. Subsequently, it was constantly refined, but the prospects of a rotary piston engine were already obvious then. RPD is included in the classification of rotary motors as one of 5 representatives of the line.

By the 80s of the 20th century, Wankel rotary engines were studied only by the Japanese company Mazda. VAZ also paid attention to this engine. In the USSR, gasoline was quite cheap, and such a unit had quite a lot of power. However, by 2004, production of cars with this engine ceased. Japan has become the only country where development of the rotary engine continues.

There are many types of rotary units. Their only difference is the surface of the housing and the number of edges made on the rotor. Various configurations of such motors are used in automotive and shipbuilding.

Advantages

Since its inception, the Wankel engine has had many beneficial advantages over piston engines. The unit was constantly improved, which made it possible to increase its efficiency and productivity.

Among the advantages of Wankel are:

1. Small dimensions and weight. “Wankel” is almost 2 times smaller than a piston internal combustion engine, which has a positive effect on the car’s handling, promotes optimal installation of the gearbox, and makes the interior much more spacious.
2. Compared to a two-stroke engine, a Wankel engine has much fewer parts. This is more profitable from a repair point of view.
3. Twice the power of standard internal combustion engines.
4. Greater smoothness of operation - the absence of forward-return movements has a beneficial effect on ride comfort.
5. Possibility of refueling with low-octane gasoline.

All motor elements rotate in one direction. This improves the internal balance of the unit and reduces vibrations. The Wankel delivers power evenly and smoothly. During the time the rotor rotates 1 time, the output shaft makes 3 revolutions. Each combustion is carried out in 90 phases of rotor rotation.

This suggests that a 1-rotor rotary engine is capable of delivering power for ¾ of each rotation of the output shaft. A 1 cylinder engine can only produce power for ¼ of each revolution of the output shaft.

Flaws

The disadvantages of the engine include its unfamiliarity to owners and mechanics. Such a unit requires changing many habits. For example, it will not be possible to slow down the RPD, and the assault on the “pull” climbs is doomed to failure. The compact engine has low inertia, which cannot be said about massive piston internal combustion engines. With frequent starts and shutdowns, the spark plugs are “thrown in.” Some car enthusiasts also consider the sound of the engine to be a disadvantage.

More serious are the organic defects of the rotary piston unit. Firstly, it has increased fuel consumption. This can easily be explained by the non-optimal shape of the chamber, which loses heat through the walls. In addition, the engine “eats” quite a lot of oil. The service life of a Wankel is lower than that of a standard internal combustion engine - the rotor seals wear out regularly.

A significant role is assigned to the rigidity of the external characteristics of the rotary piston motor. To drive a car with such an engine, you need to manipulate the gear lever quite often. This is explained by the fact that a short gear range and an increased number of gears are required.

The ideal option is to install a variator. However, automatic transmissions do not take root on sports cars, and family cars require more efficiency.

The disadvantages of RPDs are similar to those of two-stroke piston units. Interestingly, this can be cured using the same methods. Increased fuel consumption is reduced by direct injection, and lack of elasticity is reduced by the installation of variable phases. This improves efficiency and controllability. Also, to increase elasticity, the configuration of pipelines changes. Such changes were made to the Mazda RX-8 engine.

How does it work

The Wankel engine operates on a principle that is quite simple to explain even to a person ignorant of mechanics. The unit has a minimum of parts, which allows you to quickly understand which systems are activated at certain periods of time.

The engine piston in the RPD is replaced by a rotor with 3 faces, which transmits the pressure force of the combusted gases to the eccentric shaft.

The stator has an epitrochoidal configuration of internal surfaces. It is highly wear-resistant because it has a special coating. There are seals at the tops of the rotor, and on the surface of the stator there are recesses - they are a kind of chambers in which combustion occurs. The shaft rotates on special bearings. They are placed on the body. The shaft is also equipped with an eccentric - the rotor rotates on it.

The gear is mounted in the housing. It is engaged with the rotor gear. The mutual action of these gears creates the movement of the rotor. This allows you to form 3 chambers that constantly change their volume.

The gear ratio is 2:3, which provides one shaft revolution per 120-degree rotor rotation. When the rotor makes a full rotation, all chambers perform a four-stroke cycle. The combusted gases act on the eccentric shaft through the rotor - this is how torque is generated.

There are 3 chambers between the rotor and stator. Intake occurs when one of the rotor tips begins to cross the fuel injection port. The volume of the chamber increases, which forces the mixture to fill it. The next vertex closes the window. Like a traditional engine piston, the rotor compresses the working mixture before ignition.

It contracts, and at the greatest compression a spark appears in the chamber. As a result, a working stroke is carried out. Afterwards, the exhaust window opens under the pressure of the exhaust gases, and they leave the chamber.

With one rotation of the rotor, the engine completes 3 cycles - this makes the use of balancing devices unnecessary.

There are weak links in the work process. The first is an increased load on the seals, and the second is an excess of dynamic phase overlap. The configuration of the combustion chamber is also not optimal. However, there is also a positive point - if you increase the speed, the speed of spread of the flame increases faster than the fuel mixture flows.

This allows the use of gasoline with a reduced octane number for RPD. The operating principle of Wankel is quite simple, which at one time attracted the attention of many car manufacturers to the invention.

Not every car enthusiast knows that Wankel is one of 5 subtypes in the classification of rotary engines.

Compactness, speed, high performance - isn't this what almost all motorcycle manufacturers strive for? This is definitely true. However, the rotary engine did not take root in the motorcycle world. All bets are on classic piston engines.

However, there have been a few exceptions in the history of motorcycle manufacturing. For example, in 1974, Hercules released a mass series of Wankels, which are equipped with a KC-27 engine. These were rotary units that were equipped with air cooling. The engine had a volume of 294 cc. cm. The power of the units was 25 hp. To lubricate the unit, oil had to be poured into the fuel tank yourself.

In the early 1980s, the rotary engine was used to equip Norton motorcycles. Despite the fact that experimental prototypes of such engines appeared back in the 1970s, Norton engineers successfully introduced RPD into sports. By the end of the 80s they had no equal.

Today the company produces a 588 cc model with two NRV588 rotors. Norton engineers are also developing a 700cc version called the NRV700. It is a powerful sports bike equipped with a fuel-injected 170-horsepower Wankel engine.

As you can see, the era of rotary engines has not yet arrived. Piston systems have remained leading in the field of automobile and motorcycle construction. Owners of bikes with rotary engines can form only a small circle of Wankel fans. The renewed interest in Norton's Wankel indicates a rapid rise in developments and advances in this area.

One of the reasons why the engine is not produced to power cars and motorcycles is the need for precision equipment in its production. The slightest defect causes the motor to fail. This does not yet allow a rotary unit to replace a piston engine even in narrow industries.

Unlike more common piston designs, the Wankel engine offers the advantages of simplicity, smoothness, compactness, high rpm and a high power-to-weight ratio. This is primarily due to the fact that three power pulses are produced per revolution of the Wankel rotor, compared to one revolution in a two-stroke piston engine and one per two revolutions in a four-stroke engine.

A RPM is commonly referred to as a rotary motor. Although this name also applies to other designs, most notably aircraft engines with their cylinders located around the crankshaft.

The four-stage cycle of intake, compression, ignition and exhaust occurs at each revolution on each of the three rotor tips, which move inside an oval-matched cross-drilled housing, allowing for three times as many pulses per rotor revolution. The rotor is similar in shape to the Reule triangle, and its sides are flatter.

Design features of the Wankel engine

The theoretical shape of the Wankel RPD rotor between fixed angles is the result of reducing the volume of the geometric combustion chamber and increasing the compression ratio. The symmetrical curve connecting two arbitrary vertices of the rotor is maximum in the direction of the internal shape of the housing.

A central drive shaft, called the "eccentric" or "E-shaft", runs through the center of the rotor and is supported by fixed bearings. The rollers move on eccentrics (similar to connecting rods) built into an eccentric shaft (similar to a crankshaft). The rotors rotate around eccentrics and make orbital revolutions around the eccentric shaft.

The rotational motion of each rotor on its own axis is caused and controlled by a pair of synchronizing gears. A fixed gear mounted on one side of the rotor housing fits into a ring gear attached to the rotor and ensures that the rotor moves exactly 1/3 of a turn for each revolution of the eccentric shaft. The engine power output is not transmitted through synchronizers. The gas pressure force on the rotor (to a first approximation) goes directly to the center of the eccentric part of the output shaft.

The Wankel RPD is actually a system of progressive cavities of variable volume. Thus, there are three cavities on the body, all repeating the same cycle. As the rotor rotates orbitally, each side approaches and then moves away from the housing wall, compressing and expanding the combustion chamber, similar to the stroke of a piston in an engine. The power vector of the combustion stage passes through the center of the displaced blade.

Wankel engines are generally capable of reaching much higher RPMs than those with similar power output. This is due to the inherent smoothness of the circular motion and the absence of highly stressed parts such as crankshafts, camshafts or connecting rods. Eccentric shafts do not have stress-oriented crank contours.

Device problems and their resolution

Felix Wankel managed to overcome most of the problems that caused previous rotary devices to fail:

1. Rotary RPMs have a problem not found in four-stroke piston units, in which the block housing has intake, compression, combustion and exhaust gases flowing at fixed locations around the housing. The use of heat pipes in air-cooled Wankel rotary engines was proposed by the University of Florida to overcome uneven heating of the housing block. Preheating some body sections with exhaust gases improved performance and fuel economy, while also reducing wear and emissions.
2. Problems also arose during research in the 50s and 60s. For some time, engineers had been confronted with what they called a “devil's scratch” on the inner surface of the epitrochoid. They discovered that the cause was pinpoint compactions reaching resonant vibration. This problem was solved by reducing the thickness and weight of the mechanical seals. The scratches disappeared after the introduction of more compatible sealing and coating materials.
3. Another early problem was the growth of cracks on the stator surface near the plug hole, which was eliminated by installing the spark plugs in a separate metal insert, a copper bushing in the housing instead of a plug screwed directly into the block housing.
4. Four-stroke piston devices are not very suitable for use with hydrogen fuel. Another problem is related to hydration on the lubricant film in piston designs. In Wankel internal combustion engines, this problem can be circumvented by using a ceramic mechanical seal on the same surface, so that there is no oil film to suffer from hydration. The piston shell must be lubricated and cooled with oil. This significantly increases the consumption of lubricating oil in a four-stroke hydrogen internal combustion engine.

Materials for the manufacture of internal combustion engines

Unlike a piston unit, in which the cylinder is heated by the combustion process and then cooled by the incoming charge, Wankel rotor housings are constantly heated on one side and cooled on the other, resulting in high local temperatures and unequal thermal expansion. Although this places great demands on the materials used, the Wankel's simplicity makes it easier to use substances such as exotic alloys and ceramics.

Alloys intended for use in Wankel include A-132, Inconel 625 and 356 with a hardness of T6. Several high-strength materials are used to cover the working surface of the housing. For the shaft, steel alloys with low deformation under load are preferred; for this purpose, the use of massive steel has been proposed.

Engine advantages

The main advantages of the Wankel RPD are:

1. Higher power to weight ratio than piston engine.
2. Easier to fit into small machine spaces than equivalent propulsion mechanism.
3. No piston parts.
4. Ability to reach higher RPMs than a conventional engine.
5. Virtually vibration-free operation.
6. Not subject to motor shock.
7. Cheaper to manufacture because the engine contains fewer parts
8. Wide speed range for greater adaptability.
9. It can use higher octane fuel.

Wankel internal combustion engines are significantly lighter and simpler, with far fewer moving parts than piston engines of equivalent power output. Because the rotor rides directly on a large bearing on the output shaft, there are no connecting rods or crankshaft. Elimination of reciprocating forces and the most heavily loaded and damaged parts ensures high reliability of Wankel.

In addition to removing the internal reciprocating stresses while completely removing the reciprocating internal parts included in the piston engine, the Wankel engine is designed with an iron rotor in an aluminum housing, which has a higher coefficient of thermal expansion. This ensures that even a highly overheated Wankel unit cannot “seize”, as can happen in a similar piston device. This is a significant safety advantage for use in aircraft. In addition, the absence of valves increases safety.

An additional advantage of Wankel RPMs for aircraft use is that they typically have a smaller frontal area than equivalent power piston units, allowing for a more aerodynamic cone around the engine. The cascading advantage is that the smaller size and weight of the Wankel internal combustion engine allows for savings in aircraft construction costs compared to piston engines of comparable power.

Wankel rotary piston internal combustion engines, operating in accordance with their original design parameters, are almost not subject to catastrophic failures. A Wankel RPM that loses compression, or cooling, or oil pressure will lose a large amount, but will still continue to produce some power, allowing for safer landings when used in aircraft. Piston devices under the same circumstances are susceptible to seized or destroyed parts, which will almost certainly result in catastrophic engine failure and instantaneous loss of all power.

For this reason, Wankel rotary piston engines are very well suited for snowmobiles, which are often used in remote locations where engine failure could result in frostbite or death, and for aircraft, where a sudden failure could result in a crash or forced landing in remote locations.

Design flaws

Although many of the shortcomings are the subject of ongoing research, the current shortcomings of the Wankel device in production are as follows:

1. Rotor seal. This is still a minor issue since the motor housing has very different temperatures in each individual section of the chamber. Different coefficients of expansion of materials lead to imperfect sealing. In addition, both sides of the seals are exposed to fuel, and the design does not allow precise control of rotor lubrication. Rotary units are typically lubricated at all engine speeds and loads and have relatively high oil consumption and other problems resulting from excess lubrication in the engine's combustion zones, such as carbon formation and excessive emissions from oil combustion.
2. To overcome the problem of temperature differences between different areas of the housing and the side and intermediate plates, as well as the associated nonequilibrium temperature dilatations, a heat pipe is used to transport heated gas from the hot to the cold part of the engine. Heat pipes effectively direct hot exhaust gas to cooler parts of the engine, resulting in reduced efficiency and performance.
3. Slow burning. Fuel combustion occurs slowly because the combustion chamber is long, thin and moving. Flame movement occurs almost exclusively in the direction of rotor movement, and ends in extinguishing, which is the main source of unburned hydrocarbons at high speeds. The rear side of the combustion chamber naturally creates a "pressure flow" that prevents the flame from reaching the rear edge of the chamber. Injecting fuel at the leading edge of the combustion chamber can minimize the amount of unburned fuel in the exhaust.
4. Poor fuel economy. This is due to seal leaks and the shape of the combustion chamber. This results in poor combustion and average effective pressure at part load, low speed. Emissions regulations sometimes require a fuel-to-air ratio that is not conducive to good fuel economy. Acceleration and deceleration under average driving conditions also affect fuel economy. However, running the engine at a constant speed and load eliminates excess fuel consumption.

Thus, this type of engine has its disadvantages and advantages.

The only rotary-type motor model currently produced on an industrial scale is the Wankel engine. It is classified as a rotary type of engine that has a planetary circular motion of the main working element. Thanks to this structural arrangement, the solution boasts an extremely simple technical device, but is not characterized by optimality in the way the workflow is organized and therefore has its own inherent and serious disadvantages.

The Wankel rotary engine is presented in many variations, but, in essence, they differ from each other except in the number of rotor faces and the corresponding shape of the internal surfaces of the housing.

In general terms, let's look at the design features of this solution and delve a little into the history of its creation and area of ​​​​use.

The history of solutions of this type starts in 1943. It was then that the inventor Mylar proposed the first similar scheme. After some time, a number of patents were filed for engines of such a design. Also by the developer of the German company NSU. But the main drawback from which the Wankel rotary piston engine suffered was a system of seals located between the ribs at the joints of adjacent faces of a triangular element and the surfaces of the fixed body parts. To solve this difficult task, Felix Wankel, who specializes in seals, got involved. Afterwards, due to his determination and engineering mindset, he headed the development group. And already by 1957, in the bowels of a German laboratory, the first version was assembled, equipped with a main triangular-type rotating element and a working capsule chamber, where the rotational element was tightly fixed, while the rotation was carried out by the body.

A much more practical variation was characterized by a fixed working chamber in which the triangle rotated. This option debuted a year later. By November 1959, the company announced work on creating a functional rotor-type solution. In the shortest possible time, many companies around the world acquired a license for this development, and out of hundreds of companies, about a third were from Japan.

The solution turned out to be quite compact, powerful, with a small number of parts. European showrooms were replenished with cars with rotary engine variations, but, alas, they had a short rotational resource, rapid fuel consumption and toxic exhaust.

Due to the oil crisis of the seventies, attempts to improve development to the required level were curtailed. Only Japanese Mazda continued to work in this area. VAZ also worked, since fuel in the country was very cheap, and powerful, although with a low resource, engines were needed by the power ministries.

But thirty years later, VAZ closed production and only Mazda still mass-produces vehicles with rotary-type engines. At the moment, only one model with this solution is produced - the Mazda RX-8.

After a short excursion into history, it is worthwhile to dwell in detail on the advantages and disadvantages.

High power, almost twice that of four-stroke piston variations. The masses of unevenly moving elements in it are comparatively lower than in the case of piston variations, and the amplitude of movement is much lower. This is possible due to the fact that in piston solutions reciprocating movements occur, while in the type under consideration a planetary design is used.

The greater power is also influenced by the fact that it is produced within three quarters of each shaft revolution. By comparison, a single-cylinder piston engine produces power for only a quarter of each revolution. Therefore, much more power is taken per unit volume of the combustion chamber.

With a chamber volume of one thousand three hundred centimeters, the RX-8 in terms of power reaches two hundred and fifty horsepower. The predecessor, namely the RX-7, with a similar displacement but with a turbine, had three hundred and fifty horsepower. Therefore, excellent dynamics become a special feature of the car: in low gears, you can accelerate the vehicle to hundreds at high engine speeds without unnecessary load on the engine.

The type of engine under consideration is much easier to balance mechanically and gets rid of vibration, which helps to increase the comfort of a light vehicle;

In terms of size, the type of engine under consideration is one and a half to two times smaller compared to piston engines of equal power. The number of parts is less by about forty percent.

Engine disadvantages

Short duration of the working stroke of the rotor faces. Although this indicator cannot be directly compared with other options due to different types of stroke of the pistons and rotating element, for the variety under consideration this indicator is approximately 20% less. There is one significant nuance here - with piston solutions there is a linear increase in volume, which is similar to the direction of the distance from TDC to BDC. But in the case of the type of units under consideration, this action is more complicated and only a segment of the movement trajectory turns out to be directly the line of movement.

Therefore, the solution is characterized by lower fuel efficiency than piston variations. Therefore, a short duration contributes to a very high temperature of the exhaust gases - the working gases do not manage to transfer most of the pressure to the triangle in time, since the exhaust window is opened and the hot masses with the combustion of volumetric fragments that have not yet stopped exit through the exhaust pipe. That's why their temperature is extremely high.

The complexity of the combustion chamber shape. This chamber has a crescent shape and a solid area where gases come into contact with the walls and rotor. Therefore, a large thermal fraction is accounted for by heating the engine elements, and this reduces the heat efficiency, but at the same time the heating of the engine increases. Also, such chamber shapes lead to poor mixture formation and slower combustion of working mixtures. That’s why on the RX-8 engine they put two spark plugs on one rotor section. Such properties also negatively affect the thermodynamic efficiency.

Low torque. In order to remove rotation from a working rotor, the rotational center of which continuously performs planetary-type rotation, this motor uses cylindrical disks on the main shaft. Simply put, these are all elements of the converter. That is, the solution of the type under consideration was not able to fully get rid of the main disadvantage of piston variations, namely the CV joint.

Although it is a lightweight version, the main disadvantages of this mechanism: pulsation of torque, small dimensions of the arm of the main element are also present in the type under consideration.

That is why the variation with one section is not effective, and they need to be increased to two or three sections, in order to obtain acceptable performance characteristics, it is also recommended to install a flywheel on the shaft.

In addition to the presence in the engine of the type of converter mechanism under consideration, the insufficient torque for such a motor can also be affected by the nuance that the kinematic schemes in such solutions are arranged too little rationally in terms of the perception by the surface of the rotating element of the pressure of the working expansion masses. Therefore, only a certain part of the pressure, and this is about one third, is recompiled into the working rotation of the element, thereby creating a torque.

The presence of vibrations inside the housing. The problem is that the type of systems considered in the article implies uneven movement by mass. That is, during rotation, the mass center of the unit performs a continuous rotational type movement around the mass center, and the radius of this movement corresponds to the cylinder arm of the main motor shaft. Therefore, the engine body inside is influenced by a constantly rotating force vector, corresponding to a centrifugal force appearing on the element in rotation. That is, in the process of rotation on a cylindrical shaft also in motion, it is characterized by inevitable and pronounced elements of motion of the oscillatory type.

Which is the cause of inevitable vibrations.

Low wear resistance at the end of radial seals at the corners of the rotating triangle. Since they receive a significant radial load, which is inherent due to the fact that this is the operating principle of the Wankel engine.

There is a high probability of breakthrough of gas masses with high pressure from the zone of one operation cycle to another cycle. The reason lies in the fact that the rotor edge contact of the seal and the walls of the combustion chamber is made along a single line of small thickness. There is also a possibility of a breakthrough in the sockets in which the spark plugs are installed at the moment the rib of the main rotating element passes.

The complexity of the lubrication system of the rotating element. As an example, in the previously mentioned model of the Japanese manufacturer, oil is injected into the combustion chambers with special nozzles so that the fins rubbing against the walls of the chamber during rotation are lubricated. Due to this, exhaust toxicity increases and, at the same time, increases the engine’s need for high-quality oil.

Also, at high speeds, demands for lubrication of the surface of the cylindrical type of the cylindrical element of the main shaft, around which rotation occurs, and which is engaged in removing the main force from the rotating element, also translating into rotational movement of the shaft, increase. Because of these two technical difficulties, which are quite problematic to resolve, insufficient lubrication appeared at high speeds of the engine elements that were most loaded with friction, which means that the driving resource of the engine sharply decreased. Because of this insufficient solution, the life of the engines of the type in question, which were produced by the domestic AvtoVAZ, is very short.

Great demands on the precision of execution of elements with complex shapes make such an engine difficult to produce. Its production requires high-precision and expensive equipment - machines capable of making a working chamber with a curved surface.

If we talk about the rotating element, then it also has the shape of a triangle with convex surfaces.

Having drawn conclusions from all of the above, it can be noted that the type in question has not only pronounced advantages, but also a large number of virtually insurmountable disadvantages that do not allow it to defeat piston variations. However, such a prospect was seriously discussed forty or fifty years ago, and analytical reviews were full of opinions that by the early nineties of the last century, rotary solutions of various types would dominate the automotive market.

However, even taking into account the negative aspects and technical problems, this solution was able to prove itself well in technical terms and even snatch its market share, since the disadvantages of the competitive solution - a piston motor with a crankshaft - have an even more serious impact on the work. And this takes into account the fact that they have been trying to improve the piston engine for a long time.

One of the most problematic aspects when implementing any rotary engine is the reconstruction of an effective sealing system necessary to create a closed volume in the working chambers of the type of solution under consideration. So far, this is considered one of the main obstacles in the schemes. Here we have to make a complex sealing system.

In order to improve your skills and gain positive experience in this activity, you can try to implement a compact working version of the solution of the type in question directly from scratch.

The approximate power indicator of one of the rotor sections will be in the region of forty horsepower. This means that the engine of the type in question, say, with two sections, will reach eighty horsepower. And so on according to a similar principle.

In general, the production of this type of solution always proceeds with an optimal rhythm, despite the fact that it is possible to completely abandon third-party elements. As a rule, the body part of such solutions is made of alloyed structural steel, subjected to thermochemical hardening and resistant to high temperatures.

Alternatively, the optimal hardness of the surface layer can be selected around seventy HRC. In terms of depth, the thermally strengthened layer is in the region of one and a half millimeters. Radial and mechanical seals are processed in a similar manner to the same level of hardness and wear resistance.

This solution is air-cooled, and lubricating oil will be supplied to the compression chamber through two special nozzles. That is, in this case there is no need to mix oil and gasoline, as is the case in two-stroke variations.

The engine of the type in question is placed on a lathe, where it is run-in for several hours without exposure to temperature. Thus, the effectiveness of the seals and the tightness of the sections being performed can be assessed as quite acceptable.

Subsequently, the level of pressure that is observed in the compression zone can be measured.

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

The video describes the design and operating principle of the Zheltyshev rotary engine:

Surprisingly, they tried to introduce RPD in our country. Such an engine was developed for installation 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 siphoned out of the treasury.

But the Japanese managed to do it. And they don’t want to stop there. According to the latest data, the manufacturer Mazda will improve the engine and will soon release it with a completely different unit.

Let's take a look inside the RPD

The operating pattern of a rotary engine is something completely different from a conventional internal combustion engine. First, we must leave behind the design of the internal combustion engine as we know it. And secondly, try to absorb new knowledge and concepts.

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

The video shows the operating principle of the Zuev rotary piston engine:

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 body that what happens:

• mixture compression;
• fuel injection;
• oxygen supply;
• ignition of the mixture;
• release 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 seems to run. 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 like this. In the first cavity formed, suction occurs, that is, the chamber is filled with air, which is mixed here.

After this, the rotor rotates and pushes this mixed mixture into another chamber. Here the mixture is compressed and ignited with the help of two candles.

The mixture then goes into the third cavity, where parts of the used fuel are displaced.

This is the full cycle of RPD operation. But it's not that simple. We examined the RPD scheme only from one side. And these actions take place constantly. To put it differently, processes occur on three sides of the rotor at once. As a result, in just one revolution of the unit, three cycles are repeated.

In addition, it was possible to improve the rotary engine. Today, Mazda rotary engines have not one, but two or even three rotors, which significantly increases 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 one is comparable to a twelve-cylinder one. So it turns out that the Japanese turned out to be so far-sighted and immediately recognized the advantages of the rotary engine.

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

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

With the invention of the internal combustion engine, progress in the development of the automotive industry has stepped far forward. Despite the fact that the general design of the internal combustion engine remained the same, these units were constantly improved. Along with these engines, more progressive rotary-type units appeared. But why have they never become widespread in the automotive world? We will look at the answer to this question in the article.

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 Spider sports car. Research has shown that with an engine power of 57 horsepower, this car was able to accelerate to a whopping 150 kilometers per hour. The production of Spider cars equipped with a 57-horsepower rotary engine lasted about 3 years.

After this, the NSU Ro-80 car began to be equipped with this type of engine. Subsequently, rotary engines were installed on Citroens, Mercedes, VAZs and Chevrolets.

One of the most common cars with a rotary engine is the Japanese sports car Mazda Cosmo Sport model. The Japanese also began to equip the RX model with this engine. The operating principle of the rotary engine (Mazda RX) consisted of constant rotation of the rotor with alternating cycles of operation. But more on that a little later.

At present, the Japanese automaker is not engaged in serial production of cars with rotary engines. The last model to which such an engine was installed was the Mazda RX8 modification of the Spirit R. However, in 2012, production of this version of the car was discontinued.

Design and principle of operation

What is the operating principle of a rotary engine? This type of motor has a 4-stroke cycle, just like a classic internal combustion engine. However, the operating principle of a rotary piston engine is slightly different from that of a conventional piston engine.

What is the main feature of this motor? The rotary Stirling engine has in its design not 2, not 4 or 8 pistons, but only one. It's called a rotor. This element rotates in a specially shaped cylinder. The rotor is mounted on a shaft and connected to a gear. The latter has a gear clutch with the starter. The element rotates along an epitrochoidal curve. That is, the rotor blades alternately overlap 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 rigid circles. As the part rotates in the body, the three compartments inside change size. Due to the change in size, a certain pressure is created in the chambers.

Work phases

How does a rotary engine work? The operating principle (gif images and RPD diagram you can see below) of this motor is as follows. The operation of the engine consists of four repeating cycles, namely:

1. Fuel supply. This is the first phase of engine operation. It occurs at the moment when the top of the rotor is at the level of the feed hole. When the camera is open to the main compartment, its volume approaches its minimum. As soon as the rotor rotates past it, the fuel-air mixture enters the compartment. After this, the camera becomes closed again.
2. Compression. As the rotor continues to move, the space in the compartment decreases. Thus, the mixture of air and fuel is compressed. As soon as the mechanism passes the compartment with the spark plugs, the volume of the chamber decreases again. At this moment, the mixture ignites.
3. Ignition. Often a rotary engine (including VAZ-21018) has several spark plugs. This is due to the large length of the combustion chamber. As soon as the candle ignites the combustible mixture, the pressure level inside increases tens of times. Thus, the rotor is driven again. Further, the pressure in the chamber and the amount of gases continue to increase. At this moment, the rotor moves and torque is created. This continues until the mechanism passes the exhaust compartment.
4. Release of gases. When the rotor passes this compartment, 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 steadily 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 operating principle of a rotary engine. The VAZ-2108, on which the RPD was also mounted, like the Japanese Mazda, was distinguished by quiet engine operation and high dynamic characteristics. But this modification was never put into mass production. So, we found out what the operating principle of a rotary engine is.

Disadvantages and advantages

It’s not for nothing that this engine has attracted the attention of so many automakers. Its special operating principle and design have a number of advantages compared to other types of internal combustion engines.

So, what are the pros and cons of a rotary engine? Let's start with the obvious advantages. Firstly, the rotary engine has the most balanced design, and therefore practically does not cause high vibrations during operation. Secondly, this motor is lighter in weight and more compact, and therefore its installation is especially relevant for sports car manufacturers. In addition, the light weight of the unit made it possible for designers to achieve ideal weight distribution of loads along the axles. Thus, a car with this engine became more stable and maneuverable on the road.

And, of course, the spaciousness of the design. Despite the same number of strokes, the design of this engine is much simpler than that of its piston counterpart. To create a rotary motor, a minimum number of components and mechanisms were required.

However, the main advantage of this engine is not its mass and low vibrations, but its high efficiency. Thanks to the special operating principle, the rotary motor had greater power and efficiency.

Now about the disadvantages. There were many more of them than advantages. The main reason why manufacturers refused to buy such engines was their high fuel consumption. On average, such a unit spent up to 20 liters of fuel per hundred kilometers, and this, you see, is a considerable expense by today’s standards.

Difficulty in producing parts

In addition, it is worth noting the high cost of producing parts for this engine, which was explained by the complexity of manufacturing the rotor. In order for this mechanism to correctly pass 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 the technical field. Accordingly, all these costs are included in the price of the car in advance.

Overheating and high loads

Also, due to the special design, this unit was often subject to overheating. The whole problem was the lens-shaped shape of the combustion chamber.

In contrast, classic internal combustion engines have a spherical chamber design. The fuel that burns in the lens-shaped mechanism is converted into thermal energy, which is spent not only on the working stroke, but also on heating the cylinder itself. Ultimately, frequent “boiling” of the unit leads to rapid wear and failure.

Resource

It's not just the cylinder that bears heavy loads. Studies have shown that during rotor operation, a significant part of the load falls on the seals located between the nozzles of the mechanisms. They are subject to a constant pressure difference, so the maximum engine life is no more than 100-150 thousand kilometers.

After this, the engine requires major repairs, the cost of which is sometimes equivalent to purchasing a new unit.

Oil consumption

Also, the rotary engine is very demanding on maintenance.

Its oil consumption is more than 500 milliliters per 1 thousand kilometers, which forces you to fill in fluid 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 the slightest mistake can lead to costly repairs of the unit.

Varieties

At the moment, there are five varieties of these types of units:

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 on imported NSU Ro80 sedans. The Soviet analogue was called VAZ-311. This is the very first Soviet rotary engine. The principle of operation of this engine on VAZ cars has the same algorithm of operation of the Wankel RPD.

The first car on which these engines began to be installed was the VAZ modification 21018. The car was practically no different from its “ancestor” - model 2101 - with the exception of the internal combustion engine used. Under the hood of the new product was a single-section RPD with a capacity of 70 horsepower. However, as a result of research on all 50 model samples, numerous engine failures were discovered, which forced the Volzhsky Plant to abandon the use of this type of internal combustion engine on its cars for the next few years.

The main reason for malfunctions of the domestic RPD was unreliable seals. However, Soviet designers decided to save this project by presenting to the world a new 2-section rotary engine VAZ-411. Subsequently, the VAZ-413 brand internal combustion engine was developed. Their main differences were in power. The first copy developed up to 120 horsepower, the second - about 140. However, these units were again not included in the series. The plant decided to install them only on official vehicles used by the traffic police and the KGB.

Motors for aviation, "eights" and "nines"

In subsequent years, developers tried to create a rotary engine for domestic small aircraft, but all attempts were unsuccessful. As a result, the designers again began developing engines for passenger (now front-wheel drive) VAZ cars of the 8 and 9 series. Unlike their predecessors, the newly developed VAZ-414 and 415 engines were universal and could be used on rear-wheel drive car models such as Volga and Moskvich. and so on.

Characteristics of RPD VAZ-414

This engine first appeared on the “nines” only in 1992. Compared to 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.
• High efficiency. From one liter of burned fuel it was possible to obtain up to 110 horsepower (and this without any boost or additional boring of the cylinder block).
• High potential for forcing. With proper tuning, it was possible to increase engine power by several tens of horsepower.
• High speed motor. Such an engine was capable of operating even at 10,000 rpm. Only a rotary engine could function under such loads. The operating principle 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.

Current situation with RPD at the Volzhsky Automobile Plant

All of the engines described above did not gain much popularity, and their production was soon discontinued. In the future, the Volzhsky Automobile Plant does not yet plan to revive the development of rotary engines. So the VAZ-414 RPD will remain a crumpled piece of paper in the history of domestic mechanical engineering.

So, we found out what the rotary engine’s operating principle and design are.