Wankel engine: device, principle of operation

2024 Author: Erin Ralphs | [email protected]. Last modified: 2024-02-19 11:41

The internal combustion engine is a brilliant invention of mankind. Thanks to the internal combustion engine, technical progress began to develop significantly. 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 W alter 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? We will consider all this 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. It rotated inside a specially shaped cavity.

After a number of experimental models of motorcycles and cars that occurred in the 70s of the last century, the demand for the Wankel engine has decreased significantly. Although today a number of companies are still working onimprovement of this 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:

• Cases (stators).
• Combustion chambers.
• Inlet and outlet ports.
• Stationary gear.
• Gearwheel.
• Rotor.
• Vala.
• Spark plugs.

What is the working principle of the Wankel engine? We will look at this below.

Working principle

This ICE operates as follows. 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 (large) 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 compression of the mixture, its combustion, expansion of gases (which subsequently put pressure on the working surface of the rotor) and their removal takes place. As a resultignition of the fuel, the rotor is driven, transferring the 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, a four-stroke cycle of operation of the internal combustion engine is performed in each of the three chambers formed by the faces.

Benefits

What are the advantages of this internal combustion engine? The Wankel rotary piston engine has a simpler design than the piston rod engine. 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 have tried to make a homemade Wankel engine with their own hands have suffered numerous failures.

But let's get on with the benefits. In the design of the rotary unit, there is no crankshaft, gas distribution mechanism. Also there are no connecting rods andpistons. 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, there is no camshaft in the design (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 the two-stroke.

Separately, it is worth mentioning the 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 itself. The design lacks the oil pump familiar to everyone, 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 make it possible to use the space of the engine compartment more rationally, as well as provide a more uniform load on the front and rear axles (after all, in cars with conventional engines, more than 70 percent of the load falls on the front part). And due to the low weight, high stability is achieved. Yes, the engine hasminimum vibration level, which has a positive effect on the comfort of the machine.

The next plus of this unit is the high specific power, which is achieved at high shaft speeds. 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 motor 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 directions.

But it is worth noting that in recent years the quality of seals has increased. The designers have improved the Wankel engine, using new materials for seals. But still, gas breakthrough is considered the weakest point in a rotary internal combustion 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 loss of lubricant is excluded or is no more than 100 grams per 1 thousand kilometers, then on rotary engines this parameter ranges 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. The exhaust gases of cars with a Wankel engine contain many substances hazardous to the body and the environment.

Besides, the rotary engine 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.
• The tendency of friction pairs to overheat.

Other problems

Irregular oil changes threatened to reduce the life of the internal combustion engine, as 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 may have been excessive.

The RPD itself has a higher operating temperature than any piston engine. 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 the 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 at high rotor speeds - from 6 to 10 or 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 a 1.3-liter Mazda RX-8 rotary piston engine, according to passport data, it consumes from 14 to 18 liters of fuel. Moreover, only high-octane gasoline is recommended for use.

About the application of RPD in the automotive industry

This engine was most popular 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 backdrop of othersNSU 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 concern, the Mazda company and the VAZ plant experimented with rotary engines (we will talk about this case separately below). The Japanese achieved the greatest success by releasing a passenger car with a rotary engine in the 63rd year. At the moment, the Japanese are still equipping RPDs on their RX series sports cars. To this day, they are free from many of the "childhood diseases" that were inherent in the RAP of that time.

Wankel RPD and 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 an electronic fuel injection system and a variable intake tract.

Interesting facts

These power units are 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 thisaircraft model unit is that it is easy to install in a flying scale model. The ICE is light and compact.

One more 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 tire inflation pumps are designed exactly according to this principle.

RPD and VAZ cars

In Soviet times, they were also engaged in the creation of a rotary piston engine and its installation on domestic VAZ cars. 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 thousandkilometers. 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 figured 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 is characterized by high oil consumption. Also, the new 1.3-liter Mazdas do not differ in fuel efficiency. All these shortcomings of the rotary motor make it impractical and underused in the automotive industry.