Rotary engine: principle of operation. Pros and cons of a rotary engine

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Rotary engine: principle of operation. Pros and cons of a rotary engine
Rotary engine: principle of operation. Pros and cons of a rotary engine
Anonim

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 structure of the internal combustion engine remained the same, these units were constantly improved. Along with these motors, more progressive rotary-type units appeared. But why haven't they become widespread in the automotive world? We will consider the answer to this question in the article.

History of the emergence of the aggregate

The rotary engine was designed and tested by developers Felix Wankel and W alter Freude in 1957. The first car on which this unit was installed was the NSU Spyder sports car. Studies have shown that with an engine power of 57 horsepower, this 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.

rotary engine working principle
rotary engine working principle

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

One of the most common rotary engined cars is the Japanese sports car Mazda Cosmo Sport. Also, the Japanese began to equip the RX model with this motor. The principle of operation of a rotary engine (Mazda RX) was to constantly rotate the rotor with a change in cycles of work. But more on that later.

At the present time, the Japanese automaker is not engaged in serial production of cars with rotary engines. The last model on which such a motor was installed was the Mazda RX8 of the Spirit R modification. However, in 2012, the 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 is distinguished by a 4-stroke cycle of action, as in a classic internal combustion engine. However, the principle of operation of a rotary piston engine is slightly different from that of conventional piston engines.

What is the main feature of this motor? The Stirling rotary engine has in its design not 2, not 4 and not 8 pistons, but only one. It's called a rotor. This element rotates in a cylinder of a special shape. The rotor is mounted on the shaft and connected to the gear wheel. The latter has a gear clutch with a starter. The element rotates along an epitrochoidal curve. That is, the rotor blades alternately cover the cylinder chamber. In the latter, fuel combustion occurs. The principle of operation of a rotary engine (including Mazda Cosmo Sport) is that in one revolution the mechanism pushes three petals of hard circles. As the part rotates in the body, the three compartments inside change their size. By changing the dimensions, a certain pressure is created in the chambers.

Work phases

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

  1. Fuel supply. This is the first phase of the engine. It occurs at the moment when the top of the rotor is at the level of the feed hole. When the chamber is open to the main compartment, its volume approaches a minimum. As soon as the rotor rotates past it, the fuel-air mixture enters the compartment. After that, the chamber becomes closed again.
  2. Compression. As the rotor continues its movement, the space in the compartment decreases. Thus, a mixture of air and fuel is compressed. As soon as the mechanism passes the spark plug compartment, the volume of the chamber decreases again. At this point, the mixture ignites.
  3. Ignitions. Often, a rotary engine (including the VAZ-21018) has several spark plugs. This is due to the large length of the combustion chamber. As soon as the candle ignites the combustible mixture, the level of pressure inside increases tenfold. Thus, the rotor is driven again. Further, the pressure in the chamber and the amount of gases continue to grow. At this moment, the rotor moves and torque is created. This continues until the mechanism passes the exhaust chamber.
  4. Emission of gases. When the rotor passes this compartment, the high pressure gas begins to move freely into the exhaust pipe. In this case, the movement of the mechanism does not stop. The rotor rotates stably until the volume of the combustion chamber again drops to a minimum. By this time, the remaining amount of exhaust gases will be squeezed out of the engine.
VAZ rotary engine
VAZ rotary engine

This is exactly the principle of operation of a rotary engine. The VAZ-2108, on which the RPD was also mounted, like the Japanese Mazda, was distinguished by the quiet operation of the engine and high dynamic performance. But this modification was never launched into mass production. So, we found out what the principle of operation of a rotary engine is.

Disadvantages and advantages

No wonder this engine has attracted the attention of so many automakers. Its special working principle and design has a number of advantages over other types of internal combustion engines.

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

how a mazda rotary engine works
how a mazda rotary engine works

And, of course, the design space. Despite the same number of cycles of operation, the device of this engine is much simpler than that of a piston counterpart. To create a rotary motor, a minimum number of components and mechanisms was required.

However, the main trump card of this engine is not its weight and low vibrations, but its high efficiency. Due to the special principle of operation, the rotary motor had greater power and efficiency.

Now for the downsides. They turned out to be much more than advantages. The main reason why manufacturers refused to buy such engines was their high fuel consumption. On average, for a hundred kilometers, such a unit spent up to 20 liters of fuel, and this, you see, is a considerable expense by today's standards.

Difficulty in producing parts

In addition, it is worth noting the high cost of manufacturing parts for this engine, which was explained by the complexity of manufacturing the rotor. In order 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 lenticular shape of the combustion chamber.

rotary stirling engine
rotary stirling engine

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

Resource

Not only the cylinder endures heavy loads. Studies have shown that during the operation of the rotor, a significant part of the loads falls on the seals located between the nozzles of the mechanisms. They are subject to a constant pressure drop, so the maximum engine life is no more than 100-150 thousand kilometers.

rotary engine principle of operation on a vaz
rotary engine principle of operation on a vaz

After that, the motor needs a major overhaul, the cost of which is sometimes equivalent to buying a new unit.

Oil consumption

Also, the rotary engine is very demanding on maintenance.

principle of operation of a rotary piston engine
principle of operation of a rotary piston engine

It has an oil consumption of more than 500 milliliters per 1 thousand kilometers, which makes it necessary to fill in liquid every 4-5 thousand kilometers.kilometers of run. 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 is fraught with costly repairs to the unit.

Varieties

Currently, there are five varieties of these types of aggregates:

  1. Rotor motors with reciprocating shaft movements.
  2. With uniform shaft rotation. At the same time, no sealing mechanisms are used in its design. The location of the combustion chambers they have a spiral type.
  3. rotary engine principle of operation disadvantages and advantages
    rotary engine principle of operation disadvantages and advantages
  4. Units with pulsating-rotary movement directed in 1 direction.
  5. With planetary shaft rotation, without sealing elements. A striking example of this is the Wankel engine.
  6. RPD with uniform operation of working elements and a spiral type of arrangement of combustion chambers.

Rotary engine (VAZ-21018-2108)

The history of the creation of VAZ rotary internal combustion engines dates back to 1974. It was then that the first RPD design bureau was created. However, the first engine developed by our engineers had a similar design to the Wankel engine, which was equipped with imported NSU Ro80 sedans. The Soviet counterpart was named VAZ-311. This is the very first Soviet rotary engine. The principle of operation on VAZ cars of this motor has the same Wankel RPD operation algorithm.

The first car that these engines were installed on was the VAZ 21018 modification. The car practically did not differ from its "ancestor" - model 2101 - with the exception of the internal combustion engine used. Under the hood of the novelty was a single-section RPD with a capacity of 70 horsepower. However, as a result of research on all 50 model samples, numerous engine breakdowns were found, which forced the Volzhsky plant to refuse to use this type of internal combustion engine on its cars for the next few years.

rotary engine working principle
rotary engine working principle

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

Motors for aviation, "eights" and "nines"

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

Characteristics of RPD VAZ-414

rotary engine principle of operation disadvantages and advantages
rotary engine principle of operation disadvantages and advantages

For the first time this engine 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 dial "hundred" in just 8-9 seconds.
  • Great efficiency. It was possible to get up to 110 horsepower from one liter of burnt fuel (and this is without any forcing and additional boring of the cylinder block).
  • High potential for forcing. With the right settings, it was possible to increase engine power by several tens of horsepower.
  • High speed motor. Such an engine was able to work even at 10,000 rpm. Under such loads, only a rotary engine could function. The principle of operation of classic internal combustion engines does not allow them to operate 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.

Today's situation with the RPD at the Volga Automobile Plant

All the engines described above did not gain much popularity, and soon their production was curtailed. In the future, the Volga Automobile Plant has no plans to revive the development of rotary engines. So the RPD VAZ-414 will remain a crumpled piece of paper in the history of domestic engineering.

So, we found out which rotary engine has the principle of operation and device.

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