» in most people causes associations with cylinders and pistons, a gas distribution system and crank mechanism. This is because the vast majority of cars are equipped with the classic and most popular type of engine - piston.
Today we will talk about the Wankel rotary piston engine, which has a whole set of outstanding technical characteristics, and at one time was supposed to open up new prospects in the automotive industry, but could not take its rightful place and did not become massive.
History of creation
The very first heat engine of the rotary type is considered to be eolipil. In the first century AD, it was created and described by the Greek mechanical engineer Heron of Alexandria.
The design of the eolipil is quite simple: on the axis passing through the center of symmetry, there is a rotating bronze sphere. Water vapor used as working body, expires from two nozzles installed in the center of the ball opposite each other and perpendicular to the attachment axis. 
The mechanisms of water and windmills, using the power of the elements as energy, can also be attributed to the rotary engines of antiquity.
Classification of rotary engines
The working chamber of a rotary internal combustion engine can be hermetically closed or have a constant connection with the atmosphere, when from environment it is separated by the blades of the rotor impeller. Gas turbines are built on this principle.
Among rotary piston engines with closed combustion chambers, experts distinguish several groups. Separation can occur by: the presence or absence of sealing elements, by the mode of operation of the combustion chamber (intermittently pulsating or continuous), by the type of rotation of the working body.
It is worth noting that most of the structures described do not have working samples and they exist on paper.
They were classified by Russian engineer I.Yu. Isaev, who himself is busy creating a perfect rotary engine. He analyzed the patents of Russia, America and other countries, more than 600 in total.
Rotary internal combustion engine with reciprocating rotational motion
The rotor in such engines does not rotate, but performs reciprocating arc swings. The blades on the rotor and stator are stationary, and between them there are expansion and contraction strokes. 
With pulsating-rotational, unidirectional movement
Two rotating rotors are located in the engine housing, compression occurs between their blades at the moments of approach, and expansion at the moment of removal. Due to the fact that the rotation of the blades is uneven, the development of a complex alignment mechanism is required. 
With sealing flaps and reciprocating movements
The scheme is successfully used in pneumatic motors, where rotation is carried out due to compressed air, did not take root in engines internal combustion due to high pressure and temperature. 
With seals and reciprocating body movements
The scheme is similar to the previous one, only the sealing flaps are located not on the rotor, but on the motor housing. The disadvantages are the same: the inability to ensure sufficient tightness of the body blades with the rotor while maintaining their mobility. 
Engines with uniform movement of the working and other elements
The most promising and advanced types of rotary engines. Theoretically, they can develop the highest speeds and gain power, but so far it has not been possible to create a single working scheme for internal combustion engines. 
With planetary, rotational movement of the working element
The latter include the most well-known to the general public scheme of the rotary piston engine engineer Felix Wankel.
Although there are a huge number of other planetary-type designs:
- Umpleby
- Gray and Drummond (Gray & Dremmond)
- Marshall (Marshall)
- Spand (Spand)
- Renault
- Thomas (Tomas)
- Wellinder and Skoog (Wallinder & Skoog)
- Senso (Sensand)
- Mylar (Maillard)
- Ferro
History of Wankel
The life of Felix Heinrich Wankel was not easy, being left an orphan early (the father of the future inventor died in the First World War), Felix could not raise funds for studying at the university, and his working specialty did not allow him to get strong myopia.
This prompted Wankel to independent study technical disciplines, thanks to which in 1924 he came up with the idea to create a rotary engine with a rotating internal combustion chamber. 
In 1929, he received a patent for an invention, which was the first step towards the creation of the famous RPD Wankel. In 1933, the inventor, finding himself in the ranks of Hitler's opponents, spends six months in prison. After liberation, BMW became interested in the development of a rotary engine and began to finance further research, having allocated a workshop in Landau for work.
After the war, it goes to the French as a reparation, and the inventor himself goes to prison as an accomplice of the Nazi regime. Only in 1951, Felix Heinrich Wankel gets a job at the NSU motorcycle company and continues his research. 
In the same year, he begins to work together with the chief designer of NSU, Walter Freude, who himself has long been engaged in research in the field of creating a rotary piston engine for racing motorcycles. In 1958, the first sample of the engine takes its place on the test bench. 
How a rotary engine works
The power unit designed by Freude and Wankel is a rotor made in the form of a Reuleaux triangle. The rotor planetarily rotates around a gear fixed in the center of the stator - a stationary combustion chamber. The chamber itself is made in the form of an epitrochoid, which vaguely resembles a figure eight with a center extended outward, it acts as a cylinder.
While moving inside the combustion chamber, the rotor forms cavities of variable volume in which engine cycles take place: intake, compression, ignition and exhaust. The chambers are hermetically separated from each other by seals - apexes, the wear of which is a weak point of rotary piston engines.
The ignition of the fuel-air mixture is carried out immediately by two spark plugs, since the combustion chamber has an elongated shape and a large volume, which slows down the burning rate working mixture.
On a rotary engine, a retard angle is used and not an advance angle, as on a piston. This is necessary so that ignition occurs a little later, and the force of the explosion pushes the rotor in the right direction. 
The Wankel design made it possible to significantly simplify the engine, to abandon many parts. There was no need for a separate gas distribution mechanism, the weight and dimensions of the motor were significantly reduced.
Advantages
As mentioned earlier, the Wankel rotary engine does not require such a large number parts as a piston, therefore it has smaller dimensions, weight and power density (the number of "horses" per kilogram of weight).
There is no crank mechanism (in the classic version), which made it possible to reduce weight and vibration load. Due to the lack of reciprocating movements of the pistons and the low mass of moving parts, the engine can develop and maintain very high speeds, almost instantly responding to pressing the gas pedal.
A rotary ICE produces power in three quarters of each revolution of the output shaft, while a piston engine produces only one quarter.
Flaws
It is precisely because the Wankel engine, with all its advantages, has a large number of disadvantages, that today only Mazda continues to develop and improve it. Although hundreds of companies have bought the patent for it, including Toyota, Alfa Romeo, General Motors, Daimler-Benz, Nissan and others.
Small resource
Chief and most significant disadvantage- small motor resource of the engine. On average, it is equal to 100 thousand kilometers for Russia. In Europe, the US and Japan, this figure is twice as high, thanks to the quality of fuel and competent maintenance. 
Metal plates experience the highest load, apexes are radial end seals between the chambers. They have to withstand high temperature, pressure and radial loads. On the RX-7, the apex height is 8.1 millimeters, replacement is recommended when worn to 6.5, on the RX-8 it was reduced to 5.3 factory, and allowable wear no more than 4.5 millimeters.
It is important to control the compression, the condition of the oil and the oil nozzles that supply lubricant to the engine chamber. The main signs of engine wear and an upcoming overhaul are low compression, oil consumption and difficult hot starting.
Low environmental friendliness
Since the lubrication system of a rotary piston engine implies direct oil injection into the combustion chamber, and also due to incomplete combustion of the fuel, exhaust gases have increased toxicity. This made it difficult to pass the environmental test, which had to be met in order to sell cars in the American market.
To solve the problem, Mazda engineers created a thermal reactor that burned hydrocarbons before being released into the atmosphere. It was first installed on Mazda car R100. 
Instead of curtailing production like others, Mazda began selling cars with a reduction system in 1972. harmful emissions for rotary engines REAPS (Rotary Engine Anti-Pollution System).
high consumption
All cars with rotary engines are distinguished by high fuel consumption.
In addition to Mazda, there were also Mercedes C-111, Corvette XP-882 Four Rotor (four-section, volume 4 liters), Citroen M35, but these are mostly experimental models, and because of the oil crisis that broke out in the 80s, their production was suspended .
The small length of the rotor stroke and the crescent shape of the combustion chamber do not allow the working mixture to burn out completely. The exhaust port opens even before the moment of complete combustion, the gases do not have time to transfer all the pressure force to the rotor. Therefore, the temperature exhaust gases of these engines is so high.
History of the domestic RPD
In the early 80s, technology became interested in the USSR. True, the patent was not bought, and they decided to reach everything with their own mind, in other words, to copy the principle of operation and the design of the Mazda rotary engine.
For these purposes, a design bureau was created, and in Togliatti a workshop for mass production. In 1976, the first prototype of a single-section VAZ-311 engine with a power of 70 hp was produced. With. installed on 50 vehicles. In a very short time, they developed a resource. The poor balance of the REM (rotor-eccentric mechanism) and rapid wear apexes. 
However, special services became interested in the development, for which dynamic characteristics motors were much more important than the resource. In 1982, the VAZ-411 two-section rotary engine saw the light, with a rotor width of 70 cm and a power of 120 hp. with., and VAZ-413 with a rotor of 80 cm and 140 liters. With. Later, VAZ-414 engines are equipped with KGB, traffic police and the Ministry of Internal Affairs vehicles.
Since 1997 on a car common use they put the power unit VAZ-415, the Volga appears with a three-section RPD VAZ-425. Today in Russia, cars are not equipped with such motors.
List of rotary piston engine vehicles
| Brand | Model |
|---|---|
| NSU | Spider |
| Ro80 | |
| Mazda | Cosmo Sport (110S) |
| Familia Rotary Coupe | |
| Parkway Rotary 26 | |
| Capella (RX-2) | |
| Savanna (RX-3) | |
| RX-4 | |
| RX-7 | |
| RX-8 | |
| Eunos Cosmo | |
| Rotary Pickup | |
| Luce R-130 | |
| Mercedes | C-111 |
| XP-882 Four Rotor | |
| Citroen | M35 |
| GS Birotor (GZ) | |
| VAZ | 21019 (Arkan) |
| 2105-09 | |
| GAS | 21 |
| 24 | |
| 3102 |
List of Mazda rotary engines
| Type | Description |
|---|---|
| 40A | First bench copy, rotor radius 90 mm |
| L8A | Dry sump lubrication system, 98 mm rotor radius, 792 cc cm |
| 10A (0810) | Two-section, 982 cu. cm, power 110 hp. s., mixing oil with fuel for lubrication, weight 102 kg |
| 10A (0813) | 100 l. s., weight gain up to 122 kg |
| 10A (0866) | 105 l. s., REAPS emission reduction technology |
| 13A | For front-wheel drive R-130, volume 1310 cc. cm, 126 l. s., rotor radius 120 mm |
| 12A | Volume 1146 cu. cm, rotor material has been strengthened, stator life has been increased, cast iron seals |
| 12A Turbo | Semi-direct injection, 160 hp With. |
| 12B | Single ignition distributor |
| 13B | The most massive engine, volume 1308 cubic meters. cm, low level emissions |
| 13B-RESI | 135 l. with., RESI (Rotary Engine Super Injection) and Bosch L-Jetronic injection |
| 13B-DEI | 146 l. p., variable intake, 6PI and DEI systems, injection with 4 injectors |
| 13B-RE | 235 l. with., large HT-15 and small HT-10 turbines |
| 13B-REW | 280 l. s., 2 sequential turbines Hitachi HT-12 |
| 13B-MSP Renesis | Eco-friendly and economical, can run on hydrogen |
| 13G/20B | Three-rotor racing engines, 1962 cc cm, power 300 l. With. |
| 13J/R26B | Four-rotor, for auto racing, volume 2622 cubic meters. cm, power 700 l. With. |
| 16X (Renesis 2) | 300 l. p., concept car Taiki |
Rules for the operation of a rotary engine
- change the oil every 3-5 thousand kilometers. Normal consumption is 1.5 liters per 1000 km.
- monitor the condition of oil nozzles, their average life is 50 thousand.
- change air filter every 20 thousand.
- use only special candles, a resource of 30-40 thousand kilometers.
- fill the tank with gasoline not lower than AI-95, and preferably AI-98.
- check compression when changing oil. For this, a special device is used, the compression should be within 6.5-8 atmospheres.
When operating with compression below these indicators, a standard repair kit may not be enough - you will have to change the whole section, and possibly the entire engine.
today
To date, the Mazda RX-8 model equipped with the Renesis engine (abbreviation Rotary Engine + Genesis) is being mass-produced. 
The designers managed to halve oil consumption and 40% fuel consumption, and environmental class bring to the Euro-4 level. The engine with a displacement of 1.3 liters produces a power of 250 hp. With.
Despite all the achievements, the Japanese do not stop there. Contrary to the assertions of most experts that the RPD has no future, they do not stop improving the technology, and not so long ago introduced the concept of the RX-Vision sports coupe, with the SkyActive-R rotary engine. 
Design
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.
Wankel engine cycle: intake (blue), compression (green), power stroke (red), exhaust (yellow)
This design allows any 4-stroke Diesel, Stirling or Otto cycle to be carried out without the use of a special gas distribution mechanism. Sealing of the chambers is provided by radial and end sealing plates pressed against the cylinder 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 (the saving is about a thousand parts), and the absence of interface (crankcase space, crankshaft and connecting rods) between individual working chambers ensures extraordinary compactness and high power density. In one revolution, the vankel performs three complete work cycles, which is equivalent to the work of a six-cylinder piston engine.
With all the advantages (high power density, simplicity of the device, easy repairs with proper operation), an important problem is lower efficiency at low speeds compared to conventional internal combustion engines.
Another feature of Wankel engines is their tendency to overheat. The combustion chamber has a lenticular shape, that is, with a small volume, it has a relatively large area. At the combustion temperature of the working mixture, the main energy losses are through radiation. The radiation intensity is proportional to the fourth power of the temperature, so perfect shape combustion chambers - spherical. Radiant energy not only leaves the combustion chamber uselessly, but also leads to overheating of the working cylinder. These losses not only reduce the efficiency of converting chemical energy into mechanical energy, but also cause problems with the ignition of the working mixture, therefore, 2 candles are often provided in the engine design.
High demands on the accuracy of the execution of parts make it difficult to manufacture. It requires high-tech and high-precision equipment - machines capable of moving the tool along a complex trajectory of the epitrochoidal surface of the volumetric displacement chamber.
Application
The engine was originally developed specifically for use in vehicles. First stock car with a rotary engine - the German sports car NSU Wankelspider.
First mass (37,204 copies) - german sedan business class NSU Ro80. The car had enough innovations in addition to the engine - in particular, a body with a record-low aerodynamic drag, semi-automatic box transmission with torque converter, block headlights, and so on. The Ro80 featured not only a unique design, but also an advanced design that proved incomprehensible to the public of the mid-sixties; ten years later, it was he who was the basis for the style of the Audi 100 and 200 generation C2 models.
Unfortunately, the engine resource turned out to be very small (repairs were required after a run of about 50 thousand km), so the car earned a bad reputation and is relatively little known. On many preserved cars original engine replaced by a piston V4 "Essex" from Ford.
Citroën has also experimented with RPDs, the Citroën M35 project.
After that serial and finely mass production Wankel rotary piston engines were produced only by VAZ, which ultimately took the design of the engine as a basis
Modern engines
Euro IV engineers. The two-cylinder Renesis engine with a volume of only 1.3 liters produces a power of 250 hp. With. and takes up much less space in the engine compartment. The next model of the Renesis 2 16X engine has a smaller volume, but more power, and heats up less.
Footnotes
Literature
- Rotary piston engine// Great Soviet Encyclopedia
Links
- Mazda's latest RPD: Renesis 16X, www.mazda.com
- Wankel-ag.de (German) (English)
- English-language forum on RPD (eng.)
RPD USSR/Russia
- VAZ: Description of models with RPD, Ladaonline.ru
| Reciprocating engines and engine configurations | |
|---|---|
| Single cylinder · · · · · · · · · | |
The automotive industry is constantly evolving. It is not surprising that alternative technologies appear, which, to me, are less likely to appear in mass production. These are rotary engines.
Important! A stormy impetus to the development of the automotive industry was given by the invention of the internal combustion engine. As a result, cars began to run on liquid fuel, and the gasoline era began.
Machines with a rotary engine
The rotary piston engine was invented by NSU. The creator of the apparatus was Walter Freude. Nevertheless, this device in scientific circles bears the name of another scientist, namely Wankel.
The fact is that a duet of engineers worked on this project. But the main role in the creation of the device belonged to Freud. While he was working on rotary technology, Wankel was working on another project that came to nothing.
However, as a result of undercover games, we now all know this apparatus as a Wankel rotary engine. The first working model was assembled in 1957. The pioneer car was the NSU Spider. At that time, he was able to develop a speed of one hundred and fifty kilometers. The engine power of the "Spider" was 57 hp. With.
"Spider" with a rotary engine was produced from 1964 to 1967. But it did not become massive. Nevertheless, automakers have not put an end to this technology. Moreover, they released another model - NSU Ro-80, and it became a real breakthrough. Proper marketing played a big role.
Pay attention to the title. It already contains an indication that the machine is equipped with a rotary engine. Perhaps the result of this success was the installation of these motors on such well-known cars as:
- Citroen GS Birotor,
- Mercedes-Benz С111,
- Chevrolet Corvette,
- VAZ 21018.
Rotary engines received the most popularity in the land of the Rising Sun. Japanese company Mazda took a risky step for those times and began to produce cars using this technology.
The first sign from the Mazda company was the Cosmo Sport car. It cannot be said that she gained immense popularity, but she found her audience. Nevertheless, this was only the first step in the output of rotary engines on Japanese market, and soon, on the world.
Japanese engineers not only did not despair, but, on the contrary, began to work with tripled strength. The result of their labors was a series that all street racers in any country of the world remember with reverence - Rotor-eXperiment or RX for short.
Within this series, several legendary models, including the Mazda RX-7. To say that this rotary-powered car was popular is like saying nothing. Millions of street racing fans started with her. At a relatively low price, it had simply incredible specifications:
- acceleration to hundreds - 5.3 seconds;
- maximum speed- 250 kilometers per hour;
- power - 250-280 horsepower, depending on the modification.
The car is a real work of art, it is light and maneuverable, and its engine is admirable. With the characteristics described above, it has a volume of only 1.3 liters. It has two sections and operating voltage 13V.
Attention! Mazda RX-7 was produced from 1978 to 2002. During this time, about a million cars with rotary engines were produced.
Unfortunately, latest model this series was released in 2008. Mazda RX8 completed the legendary line. Actually, on this, the history of the rotary engine in mass production can be considered complete.
Principle of operation
Many automotive experts believe that the design of a conventional piston apparatus should be left in the distant past. Nevertheless, millions of cars need worthy replacement, whether a rotary engine can become one, let's figure it out.
The principle of operation of a rotary engine is based on the pressure that is created when fuel is burned. The main part of the design is the rotor, which is responsible for creating movements of the desired frequency. As a result, energy is transferred to the clutch. The rotor pushes it out, transferring it to the wheels.
The rotor has the shape of a triangle. The construction material is alloy steel. The part is located in an oval case, in which, in fact, rotation takes place, as well as a number of processes important for energy generation:
- mixture compression,
- fuel injection,
- spark creation,
- oxygen supply,
- discharge of waste raw materials.
The main feature of the rotary engine device is that the rotor has an extremely unusual movement pattern. The result of such a design decision are three cells completely isolated from each other.
Attention! In each cell, a certain process takes place.
The first cell receives air-fuel mixture. Mixing takes place in the cavity. Then the rotor moves the resulting substance to the next compartment. This is where compression and ignition take place.
In the third cell, the used fuel is removed. The well-coordinated work of the three compartments just gives that amazing performance, which was demonstrated on the example of cars from the RX series.
But the main secret of the device lies elsewhere. The fact is that these processes do not occur one after another, they occur instantly. As a result, three cycles pass in just one revolution.
Above was a diagram of the operation of a basic rotary motor. Many manufacturers are trying to upgrade the technology to achieve more performance. Some succeed, others fail.
Japanese engineers managed to succeed. The Mazda engines already mentioned above have up to three rotors. How much productivity will increase in this case, you can imagine.
Let's take an illustrative example. Let's take a conventional RPD motor with two rotors and find the closest analogue - six-cylinder engine internal combustion. If you add another rotor to the design, then the gap will be completely colossal - 12 cylinders.
Types of rotary engines
Many auto companies took up the production of rotary engines. It is not surprising that many modifications have been created, each of which has its own characteristics:
- Rotary motor with multidirectional movement. The rotor does not rotate here, but, as it were, swings around its axis. The compression process takes place between the motor blades.
- Pulsating-rotary rotary engine. There are two rotors inside the case. Compression passes between the vanes of these two elements as they approach and recede.
- Sealed flap rotary motor - This design is still widely used in air motors. For rotary internal combustion engines, the chamber in which the ignition takes place is significantly altered.
- Rotary engine that works due to rotational movements. It is believed that this design is the most technically advanced. There are no parts that make reciprocating movements. Therefore rotary engines of this type easily reach 10,000 rpm.
- The planetary rotary engine is the very first modification invented by two engineers.
As you can see, science does not stand still, a considerable number of species rotary motors will hope for further development of technology in the distant future.
Advantages and disadvantages of a rotary engine
As you can see, rotary motors were quite popular at the time. Moreover, indeed, the legendary cars were equipped with engines of this class. To understand why this unit was installed on advanced models Japanese cars, you need to know all its advantages and disadvantages.
Advantages
From the background presented earlier, you already know that the rotary engine at one time attracted a lot of attention from motor manufacturers, for several reasons:
- Increased compact design.
- Light weight.
- RPD is well balanced and creates a minimum of vibrations during operation.
- The number of spare parts in the motor is an order of magnitude less than in the piston counterpart.
- RPD has high dynamic qualities
The most important advantage of the RPD is its high power density. A car with a rotary engine can accelerate to 100 kilometers without switching to high gears while maintaining a large number of revolutions.
Important! The use of a rotary engine makes it possible to achieve increased stability car on the road thanks to the ideal weight distribution.
Flaws
So it's time to learn more why, despite all the advantages, most manufacturers have stopped installing rotary engines in their cars. The disadvantages of RPD include:
- Increased fuel consumption when running at low speeds. In the most resource-demanding cars, it can reach 20-25 liters per 100 kilometers.
- Difficulty in manufacturing. At first glance, the design of a rotary engine is much simpler than that of a piston engine. But the devil is in the details. They are extremely difficult to make. The geometric accuracy of each part must be at an ideal level, otherwise the rotor will not be able to pass the epitrochoidal curve with the proper result. RPD requires high-precision equipment in its manufacture, which costs a lot of money.
- The rotary engine often overheats. This is due to the unusual structure of the combustion chamber. Unfortunately, even after many years, engineers failed to correct this defect. The excess energy generated by the combustion of the fuel heats up the cylinder. This greatly wears out the motor and shortens its life.
- Also, a rotary engine suffers from pressure drops. Result similar effect rapid wear of seals. The service life of one well-assembled RPD lies in the range from 100 to 150 thousand kilometers. After passing this milestone, it is no longer possible to do without a major overhaul.
- Complicated oil change procedure. The consumption of rotary engine oil per 1000 kilometers is 600 milliliters. In order for the parts to receive proper lubrication, the oil must be changed once every 5000 km. If this is not done, then serious damage to the key components of the unit becomes extremely likely.
As you can see, despite the outstanding advantages of RPD, it has a number of significant drawbacks. However, design departments at leading automotive firms are still trying to modernize this technology, and who knows, maybe one day they will succeed.
Results
Rotary engines have many significant advantages, they are well balanced, allow you to quickly increase speed and provide a set speed of up to 100 km in 4-7 seconds. But rotary motors also have disadvantages, the main of which is a short service life.
The internal combustion engine is a brilliant invention of mankind. Thanks to the internal combustion engine, it began to develop significantly technical progress. There are several types of these settings. But the most famous are connecting rod and piston and rotary piston. The latter was invented by the German engineer Wankel in collaboration with Walter Freude. This power unit has a different device and principle of operation, when compared with the classic connecting rod-piston internal combustion engine. What is the principle of operation of the Wankel engine and why has this internal combustion engine not become so popular? All this we will consider in our today's article.
Characteristic
So what is this motor? This is an internal combustion engine that was developed by Felix Wankel in 1957. The function of the piston in this unit was performed by a three-vertex rotor. He made rotational movements inside a cavity of a special shape.
After a number of experimental models of motorcycles and cars, which occurred in the 70s of the last century, the demand for the Wankel engine decreased significantly. Although today a number of companies are still working on improving this internal combustion engine. So, you can meet the Wankel engine on the Mazda PX series. Also, this unit has found its application in modeling.
Wankel engine device
This power unit consists of several components:
- Housings (stator).
- combustion chambers.
- inlet and outlet windows.
- Fixed gear.
- gear wheel.
- Rotor.
- Vala.
- Spark plug.
What is the working principle of the Wankel engine? We will consider this below.
Principle of operation
This ICE operates in the following way. The rotor, mounted on an eccentric shaft through bearings, is driven by the force of gas pressure, which was formed as a result of the combustion of the air-fuel mixture. The motor rotor relative to the stator through a pair of gears. One of them ( big size) is located on the inner surface of the rotor. The second (support) is smaller and is tightly attached to the side cover of the engine. Through the interaction of the gears, the rotor produces eccentric circular motions. Thus, its edges are in contact with the inner surface of the combustion chamber.
As a result, several isolated chambers of variable volume are formed between the motor housing and the rotor. Their number is always 3. In these chambers, the process of mixture compression, its combustion, expansion of gases (which subsequently put pressure on the working surface of the rotor) and their removal takes place. As a result of the ignition of the fuel, the rotor is driven, transferring torque to the eccentric shaft. The latter is mounted on bearings and then transfers power to the transmission units. And only then the moment of forces of the Wankel engine goes to the wheels according to the classical scheme - through a cardan drive and axle shafts to the hubs. Thus, several mechanical pairs work simultaneously in a rotary motor. The first is responsible for the movement of the rotor and consists of several gears. The second de converts the movement of the rotor into revolutions of the eccentric shaft.
The gear ratio of the stator (housing) and gears is always stable and is 3:2. Thus, the rotor has time to rotate for a full revolution of the shaft by 120 degrees. In turn, for a full revolution of the rotor, internal combustion is produced in each of the three chambers formed by the faces.
Advantages
What are the advantages of this ICE? Wankel has more simple design than a connecting rod and piston. So, the number of parts in it is 40 percent less than in a piston four-stroke internal combustion engine. But still, it is not possible to create a Wankel engine with your own hands without sophisticated equipment. After all, the rotor has a very complex shape. Those who tried to make a Wankel with their own hands suffered numerous failures.
But let's move on to the benefits. The design of the rotary unit is missing crankshaft, gas distribution mechanism. Also, there are no connecting rods and pistons. The combustible mixture enters the chamber through the inlet window, which is opened by the edge of the rotor. And the exhaust gases at the end of the working cycle are released from the body through the exhaust port. Again, the role of the valve here is performed by the edge of the rotor itself. Also missing in the design camshaft(of which several are now used on connecting rod units). The Wankel rotary piston engine, according to the principle of operation of the gas distribution mechanism, is similar to a two-stroke one.
Special mention should be made of lubrication system. In fact, it is absent in the Wankel rotary engine. But how then do friction pairs work? It's simple: oil is added to the combustible mixture itself (as in primitive motorcycle engines). Thus, the lubrication of rubbing parts is carried out by the air-fuel mixture. The design lacks the usual oil pump, which takes the lubricant from the sump and sprays it under special pressure.
Another advantage of the Wankel engine is its light weight and size. Since almost half of the parts that are mandatory in piston engines are missing here, the rotary unit is more compact and can fit in any engine compartment. compact dimensions allow space to be used engine compartment more rationally, as well as provide a more uniform load on the front and rear axle(After all, in a car with conventional motors, more than 70 percent of the load falls on the front part). And due to the low weight, high stability is achieved. So, the engine has a minimum level of vibration, which has a positive effect on the comfort of the car.
The next plus of this unit is the high specific power, which is achieved with high speed shaft. This feature allows you to achieve good technical characteristics. This is why the Wankel engine is used in Mazda sports cars. The motor easily spins up to seven or more thousand revolutions. At the same time, it provides much more torque and power at a small volume. All this has a positive effect on the accelerating dynamics of the car. For example, you can take the car "Mazda RX-8". With a volume of 1.3 liters, the engine produces 210 horsepower.
Design flaws
Considering the device and principle of operation of the Wankel rotary engine, it is worth noting the main design flaw. This is the low efficiency of the gap seals between the combustion chamber and the rotor. The latter has a rather complex shape, which requires reliable sealing not only along the edges (of which there are four in total), but also along the side surface (which are in contact with the engine cover). At the same time, they are made in the form of steel spring-loaded strips with particularly precise processing both from the ends and from the working surfaces. All allowances for expansion during heating, incorporated in the design, degrade these characteristics. Because of this, it is impossible to avoid the breakthrough of gases in the end places of the sealing plates. In piston engines, the labyrinth effect is applied. So, the design uses three sealing rings with gaps in different sides.
But it is worth noting that in last years seal quality has improved. The designers have improved the Wankel engine, using new materials for seals. But still, gas breakthrough is considered the most weak point in a rotary engine.
Oil consumption
As we said earlier, there is no lubrication system as such in this engine. Due to the fact that the oil enters along with the combustible mixture, its consumption increases significantly. And if on connecting rod engines the natural care of the lubricant is excluded or is no more than 100 grams per 1 thousand kilometers, then on rotary this parameter is from 0.4 to 1 liter per thousand kilometers. This is because a complex sealing system requires more effective lubrication of the surfaces. Also, due to the high oil consumption, these motors cannot meet modern environmental standards. IN exhaust gases cars with a Wankel engine contain many substances hazardous to the body and the environment.
In addition, the rotary motor could only run on high-quality and expensive oils. This is due to several factors:
- Tendency of contacting parts of the motor chamber and rotor to high wear.
- Tendency of friction pairs to overheat.
Other problems
Irregular oil changes threatened to reduce the resource of the internal combustion engine, since the particles of the old lubricant acted as an abrasive, increasing the gaps and the likelihood of exhaust gas breakthrough in the chamber. This unit also wedges when overheated. And when driving in cold weather, cooling could be excessive.
RPD itself has a higher operating temperature than any piston motor. The combustion chamber is considered the most loaded. it has a small volume. And because of the extended shape, the chamber is prone to detonation. In addition to oil, the Wankel engine is demanding on the quality of candles. They are installed in pairs and changed strictly according to technical regulations. Among other points, it is worth noting the insufficient elasticity of the rotary motor. So, these internal combustion engines can produce excellent speed and power characteristics only when high revs rotor - from 6 to 10 and more thousand per minute. This feature forces designers to refine the design of gearboxes, making them multi-stage.
Another disadvantage is high fuel consumption. For example, if you take the 1.3-liter rotary piston engine of the Mazda RX-8, according to passport data, it consumes from 14 to 18 liters of fuel. Moreover, only high-octane gasoline is recommended for use.
On the use of RPD in the automotive industry
Most popular this engine received in the late 60s and early 70s of the last century. The Wankel RPD patent has been acquired by 11 leading automakers. So, in the 67th year, NSU developed the first business-class car with a rotary engine, which was called the NSU RO 80. This model was mass-produced for 10 years. In total, more than 37 thousand copies were released. The car was popular, but the shortcomings of the rotary engine eventually tarnished the reputation of this car. Against the background of other NSU models, the NSU RO 80 sedan was the most unreliable. The mileage before the overhaul was only 50 thousand with the declared 100.
Also, the Peugeot-Citroen concerns, the Mazda company and the VAZ plant experimented with rotary engines (we will talk about this case separately below). The greatest success was achieved by the Japanese, releasing a car with a rotary engine in the 63rd year. On this moment the Japanese still equip RPDs on their RX series sports cars. TO today they are spared many of the "childhood diseases" that were inherent in the RPD of that time.
RPD Wankel and the motorcycle industry
In the 70s and 80s of the last century, some motorcycle manufacturers experimented with rotary engines. These are Hercules and Suzuki. Now mass production of rotary motorcycles has been established only at Norton. This brand produces NRV588 sportbikes equipped with twin-rotor engines with a total volume of 588 cubic centimeters. The power of the Norton bike is 170 horsepower. with a curb weight of 130 kilograms, this motorcycle has excellent dynamic performance. Additionally, these RPDs are equipped with a system electronic injection fuel and intake tract variable.
Data power units widely used among aircraft modellers. Since there are no requirements for efficiency and reliability in the model internal combustion engine, the production of such motors turned out to be inexpensive. In such internal combustion engines, there are no rotor seals at all, or they have the most primitive design. The main advantage of such an aircraft model unit is that it is easy to install it in a flying aircraft. scale model. ICE is light and compact.
Another fact: Felix Wankel, having received a patent for RPD in 1936, became the inventor of not only rotary engines, but also compressors, as well as pumps that operated according to the same scheme. Such units can be found in repair shops and in production. By the way, portable electric pumps for pumping tires, cars are arranged exactly according to this principle.
RPD and VAZ cars
During Soviet times, they were also engaged in the creation of a rotary piston engine and its installation on domestic cars VAZ. So, the first RPD in the USSR was the VAZ-311 engine with a capacity of 70 horsepower. It was created on the basis of the Japanese unit 13V. But since the creation of the motor was carried out according to unrealistic plans, the unit turned out to be unreliable after being put into mass production. The first car with this engine was the VAZ-21018.
But the story of installing the Wankel engine on the VAZ does not end there. The second in a row was the VAZ-415 power unit, which was used in small batches on the G8 in the 80s. This power unit had better technical characteristics. Power with a volume of 1308 cubic centimeters increased to 150 horsepower. Thanks to this, the Soviet VAZ-2108 with a rotary engine accelerated to hundreds in 9 seconds. And the maximum speed was limited to 190 kilometers per hour. But this engine was not without flaws. In particular, it is a small resource. He barely reached 80 thousand kilometers. Also among the minuses it is worth noting the high cost of creating such a car. Oil consumption was 700 grams for every thousand kilometers. Fuel consumption is about 20 liters per hundred. Therefore, the rotary unit was used only on special services vehicles, in small batches.
Conclusion
So, we found out what the Wankel engine is. This rotary unit is now used in series only on Mazda cars, and only on one model. Despite numerous improvements and attempts by Japanese engineers to improve the design of the RPD, it still has a rather small resource and differs high flow oils. Also, the new 1.3-liter Mazdas do not differ in fuel efficiency. All these shortcomings of the rotary motor make it impractical and little used in automotive industry.
Not many people know that along with classic piston engines, rotary units are used in the automotive industry, called Wankel motors by the name of the inventor. They are engines with an internal principle of fuel combustion, however, its structure and operating principles are completely different. Today we will talk about rotary motors in more detail.
Structural device of a rotary engine
The main parts of the Wankel engine in their design have nothing to do with classic internal combustion engines.
Its main parts are as follows:
1. Main working chamber
The body of any rotary unit is an oval metal chamber in which the main working processes take place - intake mode, compression stroke, fuel combustion process and exhaust gases. The shape of the camera is not accidental. It is made in such a way that when interacting with the rotor, its walls come into contact with all its vertices, forming several closed contours. The intake and exhaust ports of such motors do not have valves. They are located directly on the sides of the working chamber and are connected directly to the exhaust pipe and power system.
2. Rotor
The shape of the rotor is somewhat reminiscent of a triangle, the edges of which have a convex outward rounding. In addition, each side is made with a small selection, which increases the volume of the resulting closed combustion chamber and increases speed indicators rotor rotation. The purpose of this component is similar to the functions of pistons in a conventional internal combustion engine. The occurrence of work cycles occurs by creating the three child chambers already mentioned above. The central part of the rotor is endowed with a toothed hole connecting the rotor to the drive, fixed in turn to the output shaft. This link determines in which direction and along which trajectory the rotor will move inside the main working chamber.
3. Output shaft
The functions of the output shaft of a rotary engine are similar to those of the crankshaft of classical power units. It is endowed with semicircular protrusions-cams that have an asymmetrical alignment with a clear offset from the central working axis. Several rotors are placed on the shaft, put on their working cam. Their asymmetric arrangement creates the prerequisites for the formation of a torque that occurs as a result of the force pressure of each of the rotors.
We think you have already guessed that rotary engines have a multilayer structure, which implies the creation of several working chambers in which several rotors rotate. The only unifying link in this work is the output shaft rotating as a result of this synchronous interaction. "Layers" are securely fastened together with many bolts located along the edges. The cooling of such engines is flow-through. It implies the presence of antifreeze not only around the common block, but also in each of its parts.
In the Wankel engine, all work is built by the same method of combustion of the fuel mixture as in piston engines. However, they do not provide any static combustion chambers. The pressure arising from the combustion of fuel is created in separately formed chambers, which are separated from the common working chamber by rotary faces.
The rotor itself is constantly in contact with its tops with the walls of the chamber, at each moment of time creating another closed loop. When it rotates, the contours alternately expand, then compress. During these cycles, air and fuel enter the chamber, which, as a result of the force of the rotor, is compressed and ignited, by its expansion giving the rotor another rotational impulse. Exhaust gases are ejected through the holes into the exhaust system, after which the chamber is again filled with fuel-air composition.
Advantages and disadvantages of rotary motors
The use of rotary motors has a number of undeniable advantages.
- Less quantity internal components . Similar to the four-cylinder piston engine, the rotary "brother" is endowed with only four main parts: a common chamber, a pair of rotors and a camshaft. A classic ICE with similar cycles of operation consists of at least forty moving parts, each of which is subject to wear.
- Softness of work. During the operation of rotary units, vibrations practically do not occur, due to the fact that all moving parts rotate in only one direction. We think you know that the work of pistons in a conventional engine is multidirectional. She alternates forward movement with reversible.
- low rhythm. Since each rotor is only responsible for rotating one third of the full circle of the output shaft, the movement required for this is noticeably slower, which greatly increases the reliability of the Wankel motor.
Negative factors in the use of rotary engines, of course, cannot be ruled out.
- No rotary engine can clearly adapt to the regulations of the environmental standards of various countries.. It can in no way be called environmentally friendly due to the serious amount of carbon dioxide emissions, which are unrealistic to reduce.
- The high cost of manufacturing. The production of rotary engines is very expensive, mainly due to small serial batches. Concerns produce very few of them, which does not require special cost optimization in manufacturing.
- Resource limitation. The functional stock of Wankel rotary motors is very limited. It rarely exceeds 100-150 thousand kilometers, upon reaching which they require a complete overhaul (overhaul) or replacement.
- Increased fuel consumption. main reason increased "voracity" is their low compression ratio. The engine, holding the required power, compensates for it due to more supplied inside the closed chambers of fuel.
Outcome
Summing up, let's say that rotary power units, of course, have the right to exist. They have a number of undeniable "advantages" that make them possible, albeit small, application in automotive manufacturing. On the other hand, the severity of the "minuses" is very noticeable. In many countries of the world, they simply cannot be applied due to existing environmental standards, and serious fuel consumption and a limited working life make the purchase of cars with rotary engines completely unprofitable. We predict that they will still be on the market for some time, but soon enough they will be replaced by hybrid power systems, the development of which is carried out at an absolutely grandiose pace.
