The Atkinson cycle in practice. Atkinson cycle engine

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

ICE have been used in cars for a century. In general, their principle of operation has not undergone major changes since the start of production. But since this engine has a large number of shortcomings, engineers do not stop inventing innovations to improve the motor. Let's turn to one of them, which is called the Atkinson cycle. Today you can hear that it is used in some machines. But what is it and how does the engine get better with it?

Atkinson cycle

Nikolaus Otto, an engineer from Germany, proposed in 1876 a cycle consisting of:

• inlet;
• compression;
• stroke;
• release.

And a decade later, English inventor James Atkinson developed it. However, having understood the details, we can call the Atkinson cycle completely original.

Internal combustion engines are qualitatively different. After all, the crankshaft has offset mounting points, so that frictional energy loss is reduced and the compression ratio is increased.

It also has other gas distribution phases. On a conventional engine, the piston closes immediately after passing dead center. The Atkinson cycle has a different scheme. Here, the stroke is significantly longer, since the valve closes only halfway up the piston to top dead center (where, according to Otto, compression is already taking place).

Theoretically, the Atkinson cycle is about ten percent more efficient than Otto. However, for a long time it was not used in practice due to the fact that it is able to function in the operating mode only at high speeds. Additionally, a mechanical supercharger is needed, with which all this is sometimes called the “Atkinson-Miller cycle”. However, it turned out that with him the advantages of the development in question were lost.

Therefore, in passenger cars, such an Atkinson cycle was almost never used in practice. But in hybrid models, like the Toyota Prius, manufacturers began to use it even in series. This became possible due to the specific operation of these types of engines: at low speed, the car moves due to electric traction and only during acceleration does it switch to a gasoline unit.

Gas distribution

The first Atkinson cycle engine had a bulky gas distribution mechanism that made a lot of noise. But when, thanks to the discovery of the American Charles Knight, instead of the usual actuated valves, they began to use special spools in the form of a pair of sleeves that were arranged between the cylinder and the piston, the motor almost stopped making noise. However, the complexitythe design used was quite expensive, but in prestigious car brands, car owners were willing to pay for such convenience.

However, already in the thirties, such an improvement was abandoned, because the engines were short-lived, and the consumption of gasoline and oil was too high.

Engine developments in this direction are known even today - maybe engineers will be able to get rid of the shortcomings of the Charles Knight model and take advantage of the benefits.

Universal Model of the Future

Currently, many manufacturers are developing universal engines, which will combine the power of gasoline units, and excellent traction and efficiency of diesel engines.

In this regard, the fact that gasoline units with direct fuel injection have reached a high compression ratio of about thirteen to fourteen units (for diesel engines this level is a little more than seventeen to nineteen) proves successful steps in this direction. They even operate in the same way as compression ignition units. Only the working mixture should be artificially set on fire with a candle.

In experimental models, the compression is even higher - up to fifteen or sixteen units. But until self-ignition, the level does not reach. Instead, the spark plug shuts off during steady motion, allowing the engine to switch to a diesel-like mode and consume less fuel.

Combustion is controlled by electronics, making adjustments depending on external circumstances.

The developers claim thatthis engine is very economical. However, not enough research was done for mass production.

Variable compression ratio

The indicator is very important. After all, power, efficiency and economy are directly dependent on a high compression ratio. Naturally, it cannot be increased indefinitely. Therefore, for some time now, development has stopped. Otherwise, there was a risk of detonation, which could lead to engine damage.

This indicator is especially reflected in supercharged engines. After all, they heat up more strongly, and therefore the percentage of the probability of detonation is much higher here. Therefore, the compression ratio sometimes has to be reduced, which, of course, reduces the efficiency of the motor.

Ideally, the compression ratio should change smoothly depending on the operating mode and load. There were a lot of developments, but they are all too complicated and expensive.

Legendary Saab

The best results were achieved by Saab when in 2000 it released a five-cylinder engine, which, with 1.6 liters of volume, produced about two hundred and twenty-five horses. This achievement still seems incredible today.

The engine is divided in two, where the parts are connected to each other in a hinged way. The crankshaft, connecting rods and pistons are located below, and the cylinders with heads are located at the top. The hydraulic drive is able to tilt the monoblock with cylinders and heads, changing the compression ratio when the drive compressor is turned on. Despite all the effectiveness,development also had to be delayed due to the high cost of construction.

Easier and more affordable

Thus, we can conclude that the Atkinson cycle engine has played a significant role in the improvement of the motor mechanism in the future. It seems that improvements, based on one another, will finally lead the internal combustion engine to the optimal mode of operation.