The Atkinson cycle in practice. The engine on the Atkinson cycle


2018-09-24 12:00:38




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The engine used in cars for a century. In General, the principle of operation of them has not changed significantly since the early release. But since this engine has a number of drawbacks, engineers continuously reinvent innovations to improve the motor. Refer to one of them, which is called the Atkinson cycle. Today you can hear that in some machines it is applied. But what it represents and how the engine is getting better with them?

Atkinson Cycle

Atkinson cycle

Nikolaus Otto, an engineer from Germany, suggested in 1876, the cycle consisting of:

  • Intake;
  • Compression;
  • Stroke;
  • Release.

A decade later the English inventor James Atkinson developed his. However, to understand in detail, can be called completely original view of the Atkinson cycle.

Internal combustion Engines are qualitatively different. After all, the crankshaft has an offset mounting point, so the loss of energy by friction is reduced, and the compression ratio is increased.

running on the Atkinson cycle

Also, it there are other gas distribution phase. On a normal engine the piston is closed immediately after passing the dead point. A different scheme has the Atkinson cycle. Here the beat is significantly longer, since the valve closes only half way through the piston to top dead center (where Otto already is compressed).

Theoretically, the Atkinson cycle is more efficient Otto is approximately ten percent. However long it is not used in practice due to the fact that he is able to function in the working mode only at high rpm. Additionally required mechanical supercharger, which is sometimes called all that “the Atkinson cycle, Miller”. However, it turned out that with him the advantages of the considered development was lost.

the engine on the Atkinson cycle

So in cars like this the Atkinson cycle in practice almost never used. But in hybrid models like the Toyota Prius, manufacturers began to use it, even commercially. This was made possible thanks to the specific work of these types of engines: at low speed the vehicle moves by electric traction only when accelerating goes to the petrol unit.


The First engine on the Atkinson cycle was cumbersome gas-distributing mechanism, which emits a lot of noise. But when, with the opening of the American Charles knight instead of the usual valves with actuator began to use special valve cores in the shape of a pair of sleeves which are arranged between the cylinder and the piston, the motor has almost ceased to make noise. However, the complexity of used construction cost is not cheap, but in the prestigious brands of cars motorists were willing to pay for such convenience.

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

The Development of engines in this direction is known today — maybe engineers will be able to get rid of the model shortcomings of Charles knight and reap the benefits.

Universal model of the future

Currently, many manufacturers are developing a universal engine where are combined power and petrol units, and a great thrust and efficiency of the diesels.

In this regard, the very fact that petrol units with direct injection, reached the highest level of compression of the order of thirteen or fourteen units (diesel engines this level is slightly more than seventeen or nineteen), proves successful steps in this direction. They even work the same as the engines with compression ignition. Only the working mixture must artificially ignited candle.

In experimental models of compression comes even higher - up to fifteen or sixteen units. But before ignition until the level reaches. But the candle is disabled when uniform motion, whereby the engine switches to a mode similar to diesel, and consumes little fuel.

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

The Developers claim that this engine is very economical. However, for batch production studies were not carried out.

Variable compression ratio

The Figure is very important. Because the capacity, efficiency and cost effectiveness are directly dependent on high compression. Naturally increase infinitely. So since then, development has stopped. Otherwisethere is a risk of detonation, which could damage the engine.

Particularly this figure is reflected in the motors with boost. Because they heat up stronger, and therefore the percentage probability of the triggering of detonation is much higher. Therefore, the degree of compression, sometimes have to reduce, which, of course, decreases the efficiency of the motor.

Ideally, the compression should vary smoothly depending on the operating mode and load. Developments were very many, but they are too complicated and expensive.

Legendary Saab

Atkinson cycle Miller

Best results were achieved Saab when she in 2000 released five-cylinder engine with 1.6 liters of volume were given about two hundred and twenty-five horses. This achievement and now seems incredible.

The Engine is divided into two parts, where the parts are connected to each other hinge means. The bottom is the crankshaft, rods and pistons, and above the cylinder heads. A hydraulic actuator capable of tilting mono-block cylinders and heads, changing the compression ratio when you enable the drive of the compressor. Despite the efficiency, the development also had to be postponed due to the high cost of construction.

Atkinson cycle in practice


Thus, we can conclude that an engine running on the Atkinson cycle, played a significant role in the way of improving the mechanism of the motor in the future. It appears that improvement, based one on the other, the engine will lead finally to the optimal mode.

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