Rotary engine: principle of operation, features

2024 Author: Erin Ralphs | [email protected]. Last modified: 2024-02-19 11:42

The engine is the foundation of any vehicle. Without it, the movement of the car is impossible. At the moment, the most common are piston internal combustion engines. If we talk about most cross-country cars, these are in-line four-cylinder internal combustion engines. However, there are cars with such engines, where the classic piston is absent in principle. These motors have a completely different device and principle of operation. They are called rotary internal combustion engines. What are these units, what are their features, pros and cons? Consider in our today's article.

Characteristic

A rotary engine is one of the types of thermal internal combustion engines. For the first time such a motor was developed back in the distant 19th century. Today, a rotary engine is used on the Mazda RX-8 and on some other sports cars. Such a motor has a key feature - it does not have reciprocating movements, as in a conventional internal combustion engine.

Here rotation is carried outspecial triangular rotor. He is in a special building. A similar scheme was practiced back in the 50s of the last century by the German company NSU. The author of such an internal combustion engine was Felix Wankel. It is according to his scheme that all modern rotary engines are produced (the Mazda RX is no exception).

Device

The design of the power unit includes:

• Case.
• Output shaft.
• Rotor.

The case itself is the main working chamber. On a rotary engine, it has an oval shape. Such an unusual design of the combustion chamber is due to the use of a trihedral rotor. So, when it comes into contact with the walls, isolated closed contours are formed. It is in them that the working cycles of the internal combustion engine are carried out. This is:

• Inlet.
• Compression.
• Ignition and working stroke.
• Release.

Among the features of a rotary internal combustion engine, it is worth noting the absence of classic intake and exhaust valves. Instead, special holes are used. They are located on the sides of the combustion chamber. These holes are directly connected to the exhaust system and the power system.

Rotor

The basis of the design of the power plant of this type is the rotor. It performs the function of pistons in this engine. However, the rotor is in a single copy, while the pistons can be from three to twelve or more. The shape of this element resembles a triangle with rounded edges.

Such edges are neededfor more airtight and high-quality sealing of the combustion chamber. This ensures proper combustion of the fuel mixture. Special plates are located in the upper part of the face and on its sides. They act as compression rings. The rotor also contains teeth. They serve to rotate the drive, which also drives the output shaft. We will talk about the appointment of the latter below.

Val

As such, there is no crankshaft in a rotary piston engine. Instead, an output element is used. Relative to its center there are special protrusions (cams). They are located asymmetrically. The torque from the rotor, which is transmitted to the cam, causes the shaft to rotate around its axis. This creates the energy needed to move the drives and wheels in the car.

Beats

What is the working principle of a rotary engine? The algorithm of action, despite similar cycles with a piston engine, is different. So, the beginning of the cycle occurs when one of the ends of the rotor passes through the inlet channel of the internal combustion engine housing. At the moment, under the action of vacuum, a combustible mixture is sucked into the chamber. With further rotation of the rotor, the compression stroke of the mixture occurs. This happens when the other end passes the inlet. The pressure of the mixture gradually increases. It eventually ignites. But it does not ignite from the force of compression, but from the spark of a spark plug. After that, the working cycle of the rotor stroke begins.

Since the combustion chamber in such an engine has an oval shape, it is advisable to use two candles in the design. This allows you to quickly ignite the mixture. Thus, the flame front spreads more evenly. By the way, two candles per combustion chamber can also be used in a conventional piston internal combustion engine (this design is extremely rare). However, for a rotary engine, this is a must.

After ignition, a high pressure of gases is formed in the chamber. The force is so great that it allows the rotor to spin on the eccentric. This contributes to the generation of torque on the output shaft. As the top of the rotor approaches the outlet, the force and pressure of the energy of the gases is reduced. They spontaneously rush into the outlet channel. After the camera is completely free of them, a new process begins. The rotary engine starts again with the intake stroke, compression, ignition, and then the power stroke.

About the lubrication system and nutrition

This unit has no differences in the fuel supply system. It also uses a submersible pump that delivers gasoline under pressure from the tank. But the lubrication system has its own characteristics. So, the oil for the rubbing parts of the engine is fed directly into the combustion chamber. A special hole is provided for lubrication. But the question arises: where does the oil then go if it enters the combustion chamber? Here the principle of operation is similar to a two-stroke engine. Grease enters the chamber and burns with gasoline. This scheme of operation is used on every rotary vane engine, including piston engines. Due to the special design of the lubrication system, such motors cannot meet modernenvironmental regulations. This is one of several reasons why rotary engines are not commercially used on VAZ and other car models. However, first we note the advantages of RPD.

Pros

There are many advantages to this type of engine. Firstly, this motor has a small weight and size. This allows you to save space in the engine compartment and place the internal combustion engine in any car. Also, low weight contributes to a more correct weight distribution of the car. After all, most of the mass on cars with classic internal combustion engines is concentrated in the front of the body.

Secondly, the rotary piston engine has a high power density. Compared to classic motors, this figure is one and a half to two times higher. Also, the rotary engine has a wider torque shelf. It is available almost from idle, while conventional internal combustion engines need to be spun up to four to five thousand. By the way, a rotary motor is much easier to gain high speed. This is another plus.

Thirdly, such an engine has a simpler design. There are no valves, no springs, no crank mechanism as a whole. At the same time, there is no usual gas distribution system with a belt and a camshaft. It is the absence of KShM that contributes to an easier set of revolutions by a rotary internal combustion engine. Such a motor spins up to eight to ten thousand in a fraction of a second. Well, another plus is less propensity to detonate.

Cons

Now let's talk about the disadvantages due to which the use of rotarymotors became limited. The first minus is the high requirements for the quality of the oil. Although the motor works like a two-stroke, you can’t fill in cheap “mineral water” here. The parts and mechanisms of the power unit are subjected to significant loads, therefore, to save the resource, a dense oil film is needed between the rubbing pairs. By the way, the oil change schedule is six thousand kilometers.

The next disadvantage concerns the rapid wear of the sealing elements of the rotor. This is due to the small contact patch. Due to the wear of the sealing elements, a high differential pressure is formed. This has a negative impact on rotary engine performance and oil consumption (and consequently on environmental performance).

Listing the shortcomings, it is worth mentioning the fuel consumption. Compared to a cylinder-piston engine, a rotary engine does not have fuel efficiency, especially at medium and low speeds. A striking example of this is the Mazda RX-8. With a volume of 1.3 liters, this engine consumes at least 15 liters of gasoline per hundred. Remarkably, the highest fuel efficiency is achieved at high rotor speeds.

Also, rotary engines are prone to overheating. This is due to the special lenticular shape of the combustion chamber. It does not remove heat well compared to a spherical one (as on conventional internal combustion engines), therefore, during operation, you must always monitor the temperature sensor. In case of overheating, the rotor is deformed. When working, it will form significant scuffs. As a result, the motor resource will approach the end.

Despite the simple design and the lack of a crank mechanism, this motor is difficult to repair. Such engines are very rare and few of the craftsmen have experience with them. Therefore, many car services refuse to "capitalize" such motors. And those who are engaged in rotors ask fabulous sums of money for this. You have to pay or install a new engine. But this is not a guarantee of a high resource. Such motors take care of a maximum of 100 thousand kilometers (even with moderate operation and timely maintenance). And the Mazda RX-8 engines were no exception.

VAZ rotary engine

Everyone knows that such engines were used by the Japanese manufacturer Mazda in their years. However, few people know the fact that the RPD was also used in the Soviet Union on the VAZ Classic. Such a motor was developed by order of the ministry for special services. VAZ-21079, equipped with such an engine, was an analogue of the famous black "Volga-catch-up" with an eight-cylinder engine.

The development of a rotary piston engine for the VAZ began in the mid-70s. The task was not easy - to create a rotary engine that would surpass the traditional piston internal combustion engine in all respects. The development of a new power unit was carried out by specialists from Samara aviation enterprises. The head of the assembly and design bureau was Boris Sidorovich Pospelov.

The development of power units went simultaneously with the study of rotary motors of foreign models. The first copies did not differ in high performance, and they did not go into the series. A few years later, several variants of the RPD for the classic VAZ were created. The VAZ-311 engine was recognized as the best of them. This engine had the same geometrical parameters as the Japanese 1ZV engine. The maximum power of the unit was 70 horsepower. Despite the imperfection of the design, the management decided to release the first industrial batch of RPDs, which were installed on official VAZ-2101 vehicles. However, a lot of shortcomings were soon discovered: the motor generated a wave of complaints, a scandal broke out and the number of employees in the design bureau was significantly reduced. Due to frequent breakdowns, the first VAZ-311 rotary engine was discontinued.

But the story of the Soviet RPD did not end there. In the 80s, engineers still managed to create a rotary engine that significantly exceeded the characteristics of a piston internal combustion engine. So, it was a VAZ-4132 rotary engine. The unit developed a power of 120 horsepower. This gave the VAZ-2105 excellent dynamic performance. With this engine, the car accelerated to hundreds in 9 seconds. And the maximum speed of the "catch-up" was 180 kilometers per hour. Among the main advantages, it is worth noting the high engine torque available throughout the entire rev range and the high liter power that was achieved without any boost.

In the 90s, AvtoVAZ began to develop a new rotary engine, which was to be installed on the "nine". So, in 1994m year, a new power unit VAZ-415 was born. The engine had a working volume of 1300 cubic centimeters and two combustion chambers. the compression ratio of each was 9.4. This power plant is capable of spinning up to ten thousand revolutions. At the same time, the engine was distinguished by low fuel consumption. On average, the unit consumed 13-14 liters per hundred in the combined cycle (this is a good indicator for an old rotary internal combustion engine by today's standards). At the same time, the engine was distinguished by a low curb weight. Without attachments, he weighed only 113 kilograms.

The oil consumption of the VAZ-415 engine is 0.6 percent of the specific fuel consumption. The resource of the internal combustion engine before overhaul is 125 thousand kilometers. The motor, installed on the "nine", showed good dynamic characteristics. So, acceleration to hundreds took only nine seconds. And the maximum speed is 190 kilometers per hour. There were also experimental samples of the VAZ-2108 with a rotary engine. Thanks to its lighter weight, the rotary "eight" accelerated to hundreds in just eight seconds. And the maximum speed during the tests was 200 kilometers per hour. However, these motors never entered the series. You can’t find them on the secondary market and on disassemblies either.

Summing up

So, we found out what a rotary engine is. As you can see, this is a very interesting development aimed at obtaining maximum efficiency and power. However, due to their design, the rotor mechanisms wore out quickly. This affected the resource of the engine. EvenJapanese RPD, it is no more than one hundred thousand kilometers. Also, these motors have high requirements for lubricants and cannot meet modern environmental standards. Therefore, rotary piston internal combustion engines have not become particularly popular in the automotive industry.