The “Atkinson” Cycle: What Is It? To put it simply, the Atkinson cycle seeks to exhaust all of the cylinder’s energy. By keeping the intake valve open longer and shortening the compression stroke, it achieves this. An effective compression ratio of 8:1 and an expansion ratio of roughly 13:1 are the end results in the Prius engine.
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How does the Atkinson cycle in a Toyota engine operate?
The 2016 Toyota Tacoma has undergone a complete redesign and is now more potent and efficient than ever. The Toyota Tacoma now features a bolder, more commanding platform that is matched with a more potent, more effective Atkinson cycle engine thanks to the total makeover. The Atkinson cycle engine, a cutting-edge piece of automotive technology, is a key element of the 2016 Toyota Prius design and other Toyota hybrid cars. As we explain what the Toyota Tacoma Atkinson cycle engine is, take a closer look at the new powerplant.
How Do Toyota Atkinson Cycle Engines Work?
Standard Otto cycle engines run on a straightforward intake, compression, power, and exhaust sequence, which is enhanced when you use an Atkinson cycle engine. A second linkage is used in Atkinson cycle engines to enable the air intake valve to remain open for a longer period of time, resulting in a shorter and more complete compression stroke. This guarantees that the 3.5-liter Atkinson cycle V-6 engine in the new Tacoma will operate at its most powerful and efficient. Atkinson cycle engines are consequently 12 to 14 percent to 12 to 14 percent more efficient than a normal engine.
What benefit does an Atkinson cycle engine offer?
In 1957, American engineer Ralph Miller added another helpful patent. His cycle was designed to be used with gasoline, diesel, or gaseous fuels like propane powered two- and four-stroke engines. The additional component is a supercharger, which provides a pressurized and intercooled intake charge to make up for the power that the Atkinson method loses at low speeds. A “compression control valve to evacuate excess pressure from the combustion chamber at periods” was also recommended by Miller. The most noteworthy production vehicle to employ the Miller cycle was the Mazda Millenia, which started being sold here in 1994.
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By how much is the Atkinson cycle more effective?
Toyota has announced the development of two extremely fuel-efficient small-displacement petrol Atkinson cycle engines: a three-cylinder 1.0-liter and a four-cylinder 1.3-liter. Both of these engines will be available across the range starting in 14 various configurations the following year. The Toyota Aygo will get 78 mpg (US) from the smaller engine, which is a 30% increase.
Particularly impressive is the one-liter engine’s fuel efficiency. From 2007 to 2010, the engine it will replace took first place in the One Liter category of the International Engine of the Year awards four times.
Just one month ago, the award-winning three-cylinder 1.0-liter engine was announced as the drivetrain for the new Aygo at this year’s Geneva Motor Show.
The reengineered engine underwent a number of modifications, including a higher 11.5:1 compression ratio, an improved combustion chamber design, decreased frictional losses, and a lighter cylinder head with an integrated exhaust manifold.
The updated unit will now be replaced once more with an Atkinson Cycle engine that was created in collaboration with Daihatsu and has the same three cylinder, 1.0-liter layout.
Atkinson Cycle engines aren’t recognized for their low- and mid-range torque, but Toyota believes it has addressed this issue with a variety of advancements. Although Toyota has utilized Atkinson Cycle engines in its hybrids before, this is the first time the Atkinson design will be employed as a stand-alone unit.
A reshaped intake port that creates a strong tumble flow (where the air-fuel mixture flows in a vertical swirl) inside the cylinder, a cooled Exhaust Gas Recirculation (EGR) system, Toyota’s Variable Valve Timing intelligent Electric (VVT-iE) technology, an idling-stop function, a high compression ratio, and various unnamed fuel consumption reduction technologies are some of these innovations.
The end result is a maximum thermal efficiency of 37% and an improvement in fuel efficiency of “about 30% over current automobiles,” which translates to a remarkable increase in mileage from 60 to 78 mpg (US).
The Toyota Aygo is mostly purchased for usage on narrow, crowded urban roads, and owners value the car for its performance at the gas station rather in the traffic light Grand Prix. The unit will significantly boost the appeal of the Aygo and other small Toyota automobiles.
By 2015, the Japanese manufacturer intends to release 14 variants of the 1.0-liter three-cylinder and its larger 1.3-liter four-cylinder sibling.
The larger 1.3-liter Atkinson cycle engine combines the same engine advancements and a high compression ratio (13.5) to attain a thermal efficiency of 38%. Although the 1.3-liter engine’s efficiency figures aren’t quite as impressive as the one-liter engine’s, they nevertheless represent a 15% increase in fuel efficiency over current automobiles.
Atkinson cycle engine: what is it?
James Atkinson created the Atkinson-cycle engine, a type of internal combustion engine, in 1882. The Atkinson cycle’s goal is to maximize efficiency while minimizing power density.
Some contemporary automotive engines employ a variation of this strategy. Later hybrids and some non-hybrid vehicles now have engines with variable valve timing, which can run in the Atkinson cycle as a part-time operating regimen, giving good economy while running in the Atkinson cycle, and conventional power density when running as a conventional, Otto cycle engine. This technology was previously only seen in hybrid electric applications, such as the earlier generation Toyota Prius.
An Atkinson cycle engine can it turbo?
The Atkinson is intended to have a short compression stroke and a longer combustion stroke, as was previously stated (by valve timing). This concept would actually be cancelled out by a turbo, adding extra compression during the compression stroke.
What is a hybrid Atkinson cycle?
From an operational perspective, the Atkinson cycle is comparable to the Otto cycle. The intake valve opens, the exhaust valve closes, the piston lowers from the top of the cylinder, and fuel and air are driven into the cylinder during the first stroke. The pressure within the cylinder is at around one bar.
What distinguishes the Atkinson cycle from the Otto cycle?
This study examines how a conventional air Atkinson cycle’s reported thermal efficiency and net output work are affected by heat transfer. Heat transfer issues are taken into account when comparing the Atkinson and Otto cycles’ performances in normal air. Assuming adiabatic and reversible compression and power processes, we can disregard any convective, conductive, or radiative heat transfer to the cylinder wall that occurs throughout the heat rejection phase. It is assumed that the heat loss through the cylinder wall only happens during combustion and that it is proportionate to the average temperature of the working fluid and the cylinder wall. It is discovered that the amount of the heat transfer has a considerable impact on the net output work versus efficiency characteristics, the maximum net work output, and the corresponding efficiency bound. The peak temperature and pressure are decreased with increased heat transfer to the combustion chamber walls, which also affects work per cycle and efficiency. The impacts of other factors, such as combustion constants, compression ratio, and intake air temperature, on heat transfer are also discussed. At the same operating environment, an Atkinson cycle produces more work and has a higher thermal efficiency than an Otto cycle. At the same operating conditions, higher compression ratios for the Otto cycle consistently produce more work than those for the Atkinson cycle. The outcomes are crucial since they may be used to evaluate performance and make practical Atkinson engines better.
What distinguishes the Miller from the Atkinson cycle?
A Miller-cycle engine employs a supercharger or turbocharger to force air into the system, whereas an Atkinson-cycle engine uses natural aspiration. This is how an Atkinson-cycle engine differs from a Miller-cycle engine.
How does a motor using an Atkinson cycle conserve fuel?
The same principles govern an Atkinson-cycle engine, but with a twist. When the piston rises during the compression stroke of a typical engine, the intake valve remains closed, building pressure inside the cylinder. The valve remains open a little bit longer in an Atkinson-cycle engine. Fuel economy is increased because the piston doesn’t have to exert as much force to overcome friction as a result of the cylinder’s reduced pressure. Through that open valve, some gasoline vapour does escape back into the intake manifold, but nothing is lost because it is drawn back in the next time the valve opens.
When James Atkinson created his first engine back in 1882, it made use of a complex mechanical system that altered the piston’s cycle’s piston travel distance. Modern engines work their magic using electronics and software. Similar to Atkinson’s mechanical invention, keeping the valve open longer essentially raises the cylinder’s displacement, but the piston’s travel distance is unaffected.
What is the Atkinson cycle’s compression ratio?
Its expansion ratio is 10.0 to 1 and its compression ratio is 8.0 to 1. When the intake valve closes, the turbocharger releases air at 200 kPa and 40.0 °C. The fuel has a heating value of 43,300 kJ/kg and an airfuel ratio of 15.0 to 1.
What different engine cycles are there?
The four-stroke cycle used by internal combustion engines is also referred to as the engine cycle. Intake, compression, combustion expansion, and exhaust are the first four strokes of these four-stroke cycles.
What does “heat engine” mean?
A heat engine is a machine that uses heat to generate power. It draws heat from a reservoir, uses that heat to produce work, such as move a piston or lift weights, and then releases that heat energy into the sink.
What is the mechanism of a Miller Cycle engine?
Traditional reciprocating internal combustion engines have four strokes, of which the compression and power strokes (high power flow from the crankshaft to the charge) can both be regarded as high-power strokes (high power flow from the combustion gases to crankshaft).
Compared to an Otto-cycle engine, the intake valve is left open for a longer period of time in the Miller cycle. The initial phase of the compression stroke, when the intake valve is open, and the end phase, when the intake valve is closed, are actually two discrete cycles. The so-called “fifth” stroke introduced by the Miller cycle is produced by this two-stage compression stroke. The charge is partially ejected back out through the still-open intake valve when the piston rises first during what is known as the compression stroke. Normally, a loss of power would follow from this loss of charge air. However, the Miller cycle makes up for this by using a supercharger. Due to its capacity to produce boost at very low engine speeds, positive-displacement (Roots or screw) superchargers are often required. Low-rpm power will suffer otherwise. If low rpm operation is not necessary, a turbocharger can also be employed for increased efficiency, or electric motors can be added.
The intake valve closes in the Miller-cycle engine when the piston has moved a specific distance above its bottom-most position, or roughly 20 to 30% of the entire piston movement during this upward stroke. Only then does the piston start compressing the fuel-air combination. The fuel-air combination is only actually compressed by the piston in the Miller cycle engine during the last 70% to 80% of the compression stroke. The piston forces some of the fuel-air mixture through the still-open intake valve and back into the intake manifold during the first phase of the compression stroke.