Atkinson's cycle: how it works. Presentation on the topic "Piston DVS with a cycle" Atkinson-Miller "" The principle of operation of the Atkinson cycle

Engine internal combustion (DVS) is considered one of the most important nodes in the car, from its characteristics, power, pickup and efficiency depends on how comfortable the driver will feel behind the wheel. Although cars are constantly being improved, "turn" with navigation systems, fashion gadgets, multimedia and so on, the motors remain almost unchanged, at least, the principle of their work does not change.

Cycle Otto Atkinson, which lay down car DVS, It was designed at the end of the 19th century, and since that time almost no global changes. Only in 1947, Ralph Miller managed to improve the development of its predecessors, taking the best from each of the models of engine construction. But in common features to understand the principle of operation of modern power units, you need to look a little in history.

OTO engines Otto

The first engine for a car, which could normally work not only theoretically, was developed by the Frenchman E. Lenoar in the distant 1860, was the first model with a crank-connecting mechanism. The unit worked on gas, was used by boats, its efficiency (efficiency) did not exceed 4.65%. In the future, Lenoire united with Nicholas Otto, in collaboration with the German designer in 1863, 2-stroke 2-CPS from the efficiency of 15% was created.

The principle of the four-stroke engine was first proposed by N. A. Otto in 1876, this designer self-taught is considered the creator of the first motor for the car. The engine had gas system Food, the inventor of the 1st in the world of carburetor engine in gasoline is considered Russian designer O. S. Kostovich.

OTTO cycle operation is applied on many modern engines, there are four tact here:

• inlet (when the inlet valve is discovered, the cylindrical space is filled with fuel mixture);
• compression (valves are sealed (closed), compressing the mixture occurs, at the end of this process - ignition that provides the ignition candle);
• work move (due to high temperatures And a large pressure piston rushes down, makes the connecting rod and crankshaft move);
• release (at the beginning of this tact, the exhaust valve opens, freeing the path of exhaust gases, the crankshaft as a result of the conversion of heat in mechanical energy continues to rotate, lifting the rod with the piston up).

All tacts are docked and go in a circle, and the flywheel that poins energy contributes to the spinning of the crankshaft.

Although compared with a two-stroke option, the four-stroke scheme seems more perfect, the efficiency of the gasoline motor even at the best case does not exceed 25%, and the greatest efficiency - in diesel engines, here it can increase as much as possible to 50%.

Thermodynamic cycle of Atkinson

James Atkinson - a British engineer who decided to modernize the invention Otto offered its own option to improve the third cycle (working stroke) in 1882. The designer was delivered to increase the efficiency of the engine and reduce the compression process, to make the engine more economical, less noisy, and the difference in its construction scheme consisted in changing the drive of the crank-connecting mechanism (CSM) and in the passage of all clocks for one crankshaft turn.

Although Atkinson and managed to increase the efficiency of its motor with respect to the already patented OTTO invention, the scheme was not implemented in practice, the mechanics were too complicated. But Atkinson became the first designer who offered the work of the DVS with a reduced degree of compression, and the principle of this thermodynamic cycle was further taken into account by the inventor Ralph Miller.

The idea of \u200b\u200breducing the compression process and more saturated intake did not go into oblivion, the American R. Miller returned to it in 1947. But this time the engineer proposed to implement the scheme without the help of complication of KSM, but by changing the phases of gas distribution. Two versions were considered:

• working stroke with the laundering of the inlet valve (LICV or short compression);
• stroke with early closure valve (EICV or shortened inlet).

With a late closure of the inlet valve, there is a reduced compression relative to the OTTO engine, which is why fuel mixes It comes back to the intake canal. Such a constructive solution gives:

• more "soft" geometric compression of the fuel mixture;
• additional fuel savings, especially on small revolutions;
• smaller detonation;
• low noise.

By the cons of this scheme, it is possible to take a reduction in power on large revs, since the compression process is reduced. But due to the more complete filling of cylinders, the efficiency increases on low revs and the geometric degree of compression increases (the actual decreases). The graphic image of these processes can be seen in the figures with the conventional charts below.

Miller Scheme engines lose OTTO at high high-speed modes In terms of power, but in urban operating conditions it is not so important. But such motors are more economical, they are smaller, softer and sweeters work.

Miller Cycle Engine by car Mazda Xedos (2.3 L)

The special mechanism of gas distribution with the overlapping of the valves provides an increase in the degree of compression (SZ), if in the standard embodiment, it is supposed to be 11, then in a short compression engine, this figure is increased to 14. On 6-cylinder 2) 2.3 L Mazda Xedos (SkyActiv family) Theoretically, it looks like this: the intake valve (VC) opens when the piston is located in the upper dead point (abbreviated - NTT), it is not closed in lower point (NMT), and later, remains open 70º. In this case, part of the fuel and air mixture is pushed back into the intake manifold, the compression begins after the closing of VC. By returning the piston in the NMT:

• the volume in the cylinder decreases;
• pressure increases;
• candle ignition occurs at a certain point, it depends on the load and the number of revolutions (the ignition advance system works).

Then the piston goes down, the extension occurs, while the heat transfer on the walls of the cylinders is not as high as in the OTTO scheme due to short compression. When the piston comes to NMT, there is a gas release, then all actions are repeated again.

Special intake manifold configuration (wider and shorter than usual) and the opening angle of VC 70 degrees at SZ 14: 1 makes it possible to set the ignition advance 8º idling Without any tangible detonation. Also this scheme provides a greater percentage of useful mechanical work, or, in other words, allows you to raise the efficiency. It turns out that the work calculated by the formula A \u003d P DV (P is pressure, DV - the volume change), is directed not to heating the walls of the cylinders, the head of the block, but goes to the operation of the working stroke. Schematically, the whole process can be viewed in the figure, where the beginning of the cycle (NMT) is indicated by the number 1, the compression process is to point 2 (NTT), from 2 to 3 - the heat supply under the fixed piston. When the piston comes from point 3 to 4, there is an extension. The work performed is indicated by the shaded AT area.

Also, the entire scheme can be viewed in the coordinates T S, where T is temperature, and S is entropy, which grows with a heat supply to a substance, and with our analysis, this is conditional. Designations q p and q 0 - the amount of exhaust and removal of heat.

The lack of the SkyActiv series - compared with classic Otto, these engines have less specific (actual) power, on the motor 2.3 l with six cylinders, it is only 211 horsepower, and then when registering turbocharging and 5300 rpm. But the engines have tangible advantages:

• high compression degree;
• the ability to establish early ignition, while not to get detonation;
• ensuring rapid acceleration from the place;
• great efficient efficiency.

And one more important advantage of the Miller Cycle engine from the manufacturer Mazda is an economical fuel consumption, especially at low loads and on idling.

Atkinson engines on Toyota cars

Although the Atkinson cycle did not find his practical application in the 19th century, the idea of \u200b\u200bits engine was implemented in the power units of the 21st century. Such motors are installed on some hybrid models passenger cars Toyota, working simultaneously on gasoline fuel, and on electricity. It is necessary to clarify that in a pure form the theory of Atkinson is not used, rather, the new developments of Toyota engineers can be called an internal combustion engine, designed by the Atkinson / Miller cycle, as they use a standard crank-connecting mechanism. Reducing the compression cycle is achieved due to changes in gas distribution phases, while the cycle of the working stroke is extended. Motors using a similar scheme are found on Toyota car:

• Prius;
• Yaris;
• Auris;
• Highlander;
• Lexus GS 450h;
• Lexus CT 200h;
• Lexus HS 250H;
• Vitz.

The model range of motors with the ATKINSON / MILLER implemented scheme is constantly updated, so at the beginning of 2017, the Japanese concern began to produce a 1.5-liter four-cylinder engine operating on high-octane gasoline, providing 111 horsepower for power, with a compression ratio in cylinders 13.5: one. The engine is equipped with a VVT-IE phasemator that can switch OTTO / ATKINSON modes depending on the speed and load, with this power unit, the car can accelerate to 100 km / h in 11 seconds. The engine is in economy, high efficiency (up to 38.5%), provides excellent overclocking.

Diesel cycle

First diesel engine was designed and built by the German inventor and engineer Rudolph Diesel in 1897, the power unit had large sizes, was even more steam machines Those years. Just like the Otto engine, it was four-stroke, but was distinguished by an excellent efficiency, ease of operation, and the compression ratio in the engine was significantly higher than that of the gasoline power unit. The first diesel engines of the late XIX century worked on light oil products and vegetable oils, was also an attempt as fuel to use coal dust. But the experiment fell almost immediately:

• ensure the supply of dust into the cylinders was problematic;
• having abrasive properties, coal quickly caught a cylinder-piston group.

Interestingly, the English inventor Herbert Eykroyd Stewart patented similar engine Two years earlier than Rudolf Diesel, but diesel was able to construct a model with increased pressure in the cylinders. The Stuart model in the theory provided 12% of thermal efficiency, while according to the Diesel scheme, the efficiency reached up to 50%.

In 1898, Gustav Trinker constructed a high-pressure oil engine equipped with a forkamera, this model is a direct prototype of modern diesel engine.

Modern diesel engines for cars

Both at the gasoline engine along the cycle of Otto and the diesel engine, schematic scheme Building has not changed, but modern diesel engine "Obros" with additional nodes: turbocharger, electronic system Fuel control, intercooler, various sensors and so on. Recently, more and more often developed and run into a series power units With the direct fuel injection "Common Rail", providing an eco-friendly exhaust of gases in accordance with modern requirements, high pressure Injection. Diesels with direct injection possess quite tangible advantages over motors with a conventional fuel system:

• economically consume fuel;
• have a higher power at the same volume;
• working with low noise;
• allows the car faster accelerate.

Disadvantages of engine COMMON RAIL.: sufficiently high complexity, the need for repair and maintenance to use special equipment, demandingness to the quality of diesel fancy, relatively high price. Like gasoline вс, diesel engines are constantly being improved, everything is more technological and more difficult.

In the automotive structure of passenger cars for more than a century is standardly used internal combustion engines. They have some minuses over which scientists and designers are fighting over the years. As a result of these studies, quite interesting and strange "engines" are obtained. About one of them will be discussed in this article.

The history of the creation of the Atkinson cycle

The history of the creation of a motor with Atkinson's cycle roots goes back in a distant story. Start with the fact that first classic four-stroke engine The German Nikaula Otto was invented in 1876. The cycle of such a motor is pretty simple: inlet, compression, work move, release.

In just 10 years after the invention of Otto engine, the Englishman James Atkinson offered to modify german Motor . In fact, the engine remains four-stroke. But Atkinson slightly changed the duration of two of them: the first 2 clocks are shorter, the remaining 2 is longer. Sir James implemented this scheme by changing the length of the piston moves. But in 1887, such a modification of the engine OTTO did not find applications. Despite the fact that the motor performance increased by 10%, the complexity of the mechanism did not allow massively to use the atkinson cycle for cars.

But engineers continued to work on Sir James cycle. American Ralph Miller in 1947 improved the Atkinson cycle, simplifying it. This allowed to apply the engine in the automotive industry. It would seem, it would be more correct to call the atkinson cycle of Miller. But the engineering community left for Atkinson the right to call the motor according to his name on the principle of the discoverer. In addition, with the use of new technologies, it became possible to use a more complex Atkinsonian cycle, therefore, from the Miller cycle, they refused over time. For example, in the new Toyota costs the Atkinson's engine, not Miller.

Nowadays, the engine running on the principle of the Atkinson cycle is put on hybrids. Especially succeeded in this Japanese, who always care about the ecology of their cars. Hybrid Prius from Toyota Actively fill the world market.

Principle of operation of the Atkinson cycle

As mentioned earlier, the Atkinson's cycle repeats the same clocks as the Otto cycle. But when using the same principles, Atkinson created a completely new engine.

Motor designed so that piston makes all four clocks for one crankshaft turn. In addition, the tacts have a different length: the moves of the piston during compression and expansion is shorter than during intake and release. That is, in the cycle of Otto, the intake valve closes almost immediately. In Atkinson's cycle this the valve closes at half the path to the top dead point.. In the usual ICE at this moment there is already a compression.

The engine is modified by a special crankshaft, which displays the attachment points. Due to this, the compression of the motor has increased, and friction losses minimized.

Difference from traditional engines

Recall that the Atkinson cycle is four-stroke (inlet, compression, expansion, emission). An ordinary four-stroke engine works on the OTTO cycle. Briefly, we will remind his work. At the beginning of the working stroke in the cylinder, the piston goes up to the top operating point. A mixture of fuel and air burns, gas expands, pressure at the maximum. Under the influence of this gas, the piston is driving down, comes to the bottom dead point. The working stroke is over, an exhaust valve opens through which the spent gas comes out. In this place there are losses of release, because Exhaust gas still has residual pressure, which is impossible to use.

Atkinson reduced the loss of release. In its engine, the volume of the combustion chamber is less at the same working volume. It means that the degree of compression is higher, and the piston move is more. In addition, the duration of the compression tact compared to the working stroke is reduced, the engine works on a cycle with an increased extension degree (the compression ratio is lower than the extension degree). These conditions allowed to reduce the loss of the release using the energy of exhaust gases.

Let's return to Otto cycle. When sucking the working mixture, the throttle is closed and creates resistance to the inlet. It happens when the gas pedal is incomplete. Due to the closed damper, the engine spends energy invested, creating pumping losses.

Atkinson worked with the intake clock. His extension, Sir James achieved a decrease in pumping losses. For this, the piston reaches the bottom of the dead point, then rises, leaving the intake valve by an open approximately half of the piston stroke. The part of the fuel mixture returns to the intake manifold. It increases pressure that makes it possible to enable throttle valve on small and medium turns.

But in the series, Atkinsonian motor was not released due to interruptions in the work. The fact is that, in contrast to the engine, the motor only works on high revs. At idle it can stumble. But this problem was solved in the production of hybrids. At low speeds, such machines are driving on the elector, and the gasoline engine is transmitted only in case of overclocking or under loads. A similar model, as removing the shortcomings of the Atkinson engine, emphasizes its advantages in front of the other DVS.

Advantages and disadvantages of the Atkinson cycle

Atkinson's engine has several advantagesMixing it in front of the other DVS: 1. Reducing fuel loss. As mentioned earlier, due to the change in the duration of the clocks, it became possible to maintain fuel using exhaust gases and reducing pumping losses. 2. Small probability of detonation combustion. The degree of fuel compression decreases from 10 to 8. This allows you to not increase the rotation of the motor switching to reduced transmission due to the increase in the load. Also, the probability of detonation combustion is less due to the heat outlet from the combustion chamber in the intake manifold. 3. Little gasoline consumption. In new hybrid models, gasoline consumption is 4 liters per 100 km. 4. Efficiency, environmental friendliness, high efficiency.

But atkinson's engine has one significant drawback that did not allow it to apply it to mass production machines. Due to low power indicators, the engine can stumble on small revs. Therefore, Atkinson's engine worked on hybrids very well.

Application of the Atkinson's cycle in the automotive industry

By the way, about the machines on which Atkinson engines are put. In the mass release of this modification of DVS Appeared not so long ago. As mentioned earlier, the first users of the Atkinson cycle were Japanese firms and Toyota. One of the most famous machines – Mazdaxedos 9 / Eunos800which was produced in 1993-2002.

Then, DVS Atkinson took the manufacturers of hybrid models. One of the most famous companies using this motor is Toyota.producing Prius, Camry, Highlander Hybrid and Harrier Hybrid. The same engines are used in Lexus RX400H, GS 450H and LS600H, and "Ford" and "Nissan" have developed Escape Hybrid. and Altima Hybrid..

It is worth saying that in the automotive industry there is a fashion for ecology. Therefore, hybrids working on the Atkinson cycle completely satisfy customer needs and environmental standards. In addition, progress does not stand still, the new modifications of the Atkinsonian motor improve its advantages and destroy cons. Therefore, it is confidently said that the engine based on the Atkinson cycle has a productive future and hope for a long existence.

The internal combustion engine is very far from the ideal, at best reaches 20 - 25%, diesel 40 - 50% (that is, the rest of the fuel is burned almost into an empty). To increase efficiency (respectively increase the efficiency), it is required to improve the engine design. Many engineers are fighting on it, and to this day, but the first were only a few engineers, such as Nicalas August Otto, James Atkinson and Ralph Miller. Everyone contributed certain changes, and tried to make motors more economical and more productive. Each offered a certain cycle of work, which could radically differ from the design of the opponent. Today I will try simple words, explain what kind of basic differences are in dVS work, well, of course video version at the end ...

The article will be written for newbies, so if you are a silent engineer, you can not read it, written to the general understanding of the cycles of the engine.

It also wants to note that variations of various designs are a lot, the most famous which we can still know, the cycle of diesel, stirling, carno, Ericonna, etc. If you calculate the designs, then they can get about 15. And not all internal combustion engines, and for example, in stirling external.

But the most famous, which are used to this day in cars, is Otto, Atkinson and Miller. That's about them and we will talk.

In fact, it is the usual thermal internal combustion engine with the forced ignition of a combustible mixture (via a candle) that is used now in 60 - 65% of cars. Yes - yes, it is the one that you have under the hood, works on the cycle Otto.

However, if you hit the story, the first principle of such an economist suggested in 1862 the French engineer Alphonse Bo de Roche. But it was the theoritic principle of work. Otto in 1878 (16 years later) embodied this engine in the metal (in practice) and patented this technology

In essence, this is a four-stroke motor, which is characteristic:

• Inlet . Filling fresh air-fuel mixture. The inlet valve opens.
• Compression . The piston goes up, squeezing this mixture. Both valves are closed
• Working . Candle sets on a compressed mixture, fired gases pushing the piston down
• Distribution of exhaust gases . The piston goes up, pushing the burnt gases. Opened exhaust valve

I would like to note that intake and exhaust valves, work in a strict sequence - equally at high and at low revs. That is, changes in work at various revs are not observed.

In its engine, Otto, the first applied the compression of the working mixture to raise the maximum cycle temperature. Which was carried out by Adiabat (simple words without heat exchange with an external environment).

After compressing the mixture, it flammped from the candle, after that the process of heat removal began, which proceeded almost on the isohod (that is, with a constant volume of the engine cylinder).

Since Otto patented its technology, its industrial use was not possible. To circumvent Patents James Atkinson in 1886, decided to modify the Otto cycle. And offered its type of engine internal combustion engine.

He proposed to change the ratio of times of clocks, thanks to which the work move was increased due to the complication of the crank-connecting structure. It should be noted that the test copy which he built was a single-cylinder, and did not get much distribution due to the complexity of the design.

If in a nutshell to describe the principle of operation of this engine, then it turns out:

All 4 clocks (injection, compression, work move, release) - occurred in one rotation of the crankshaft (Otto rotations - two). Thanks to the complex levers, which were attached next to the "crankshaft."

In this design, it turned out to implement certain ratios of levers. If you say simple words - the stroke of the piston on the intake and release tact is greater than the stroke of the piston in also compression and working stroke.

What does it give? Yes, what can be "played" by the degree of compression (changing it), due to the ratio of the lengths of the levers, and not at the expense of "throttling" inlet! From this output the advantage of the Aktinsson cycle, on pumping losses

Such engines turned out to be quite effective with high efficiency and low fuel consumption.

However, there were also a lot of negative points:

• Complexity and bulky design
• Low-speed
• Poorly controlled throttle damn, whether ()

Stubborn rumors go that the Atkinson principle was used on hybrid cars, in particular, Toyota. However, this is a bit of the wrong, only his principle was used there, but the design was used by another engineer, namely Miller. In its pure form, Atkinson's motors were rather a partial character than the massive.

Ralph Miller also decided to play with the degree of compression, in 1947. That is, he will continue to work at the Atkinson, but it took not his complex engine (with levers), but the usual OI OTO.

What he suggested . He did not make compression tact mechanically shorter than the stroke tact (as Atkinson offered, his piston moves faster upwards than down). He came up with cut the compression tact at the expense of the intake tact, keeping the movement of pistons up and down the same (classic OTTO motor).

It was possible to go in two ways:

• Close the inlet valve before the end of the intake tact - this principle was called "shortened inlet"
• Either close the inlet valve later input tact - this option received the names of "shortened compression"

Ultimately, both principles give the same thing - a decrease in the degree of compression, the working mixture relative to the geometric! However, the degree of expansion is preserved, that is, the beat of the working stroke is preserved (as in the OTC OTO), and the compression tact is reduced (as in the FRO Akinson).

Simple words - The air-fuel mixture of Miller is compressed much less than it was suppressed in the same motor from Otto. This allows you to increase the geometric degree of compression, and accordingly the physical degree of expansion. Much greasome than the detonation properties of fuel (i.e., gasoline can not be compressed infinitely, detonation will begin)! Thus, when the fuel is flammable in the NWT (more than a dead point), it has a much greater degree of expansion than the design of Otto. This gives much more use the energy expanding in the gas cylinder, which increases the thermal efficiency of the structure, which entails high savings, elasticity, etc.

It is also worth considering that the pump losses are reduced on the compression tact, that is, compress the fuel in Miller is easier, less energy is required.

Negative sides - This is a decrease in peak output power (especially on high revs) due to the worst filling of cylinders. To remove the same power as O Otto (at high speed), the motor needed to build more (volume cylinders) and massive.

On modern motors

So what is the difference?

The article turned out more difficult than I assumed, but if you sum up. It turns out:

Otto - This is the standard principle of the usual motor, which are now standing on most modern cars.

Atkinson - offered more efficient DVS, By changing the degree of compression with the help of a complex design of the levers that were connected to the crankshaft.

Pros - fuel economy, more elastic motor, less noise.

Cons - bulky and complex design, low torque on low revs, poorly controlled by throttle valve

It is practically no applied in its pure form.

Miller - proposed to use a reduced compression ratio in the cylinder, using the late closure of the intake valve. The difference with Atkinson is huge, because he used not his design, but Otto, but not in its pure form, but with a modified timing system.

It is assumed that the piston (on the compression tact) comes with less resistance (pump losses), and it is better to geometrically compressing the air-fuel mixture (excluding its detonation), but the degree of expansion (when inflammation from the candle) remains almost the same as in the OTO cycle) .

Pros - fuel economy (especially on low revs), elasticity of work, low noise.

Cons - a reduction in power at high revs (due to the worst filling of cylinders).

It is worth noting that now the Miller principle is used on some cars at low revs. Allows you to adjust the inlet and release phases (expanding or narrowing them with

Slide 2.

Classic DVS

The classic four-stroke motor was invented back in 1876 by one German engineer named Nicaus Otto, the cycle of such an internal combustion engine (DVS) is simple: inlet, compression, work move, release.

Slide 3.

Indicator chart of Otto and Atkinson cycle.