BRIEF HISTORY OF ATKINSON CYCLE

Invented in 1882 by

British engineer James

Atkinson

Patents for the existing Otto

cycle engine presented a need

for a new crankshaft design

The Atkinson cycle is designed to

provide efficiency at the expense

of power density, and is used in

some modern hybrid electric

applications. Also called the

Barta engine in (1884).

ATKINSON-CYCLE ENGINES

Operates on a four-stroke cycle

Intake

Compression

Combustion

exhaust

Its Combustion stroke is longer than compression

stroke allowing more expansion of combustion

gases.

These are all strokes complete in one revolution

of crankshaft.

THERMODYNAMICS OF ATKINSON-CYCLE

ENGINE

The ideal Atkinson cycle consists of following

operations:

1-2 Isentropic or reversible adiabatic compression

2-3 Isochoric heat addition (Qin)

3-4 Isentropic expansion

4-1 Isobaric heat rej (Qout)

ATKINSON ENGINE V/S OTTO ENGINE

Atkinson and Otto engines are very similar.

Atkinson uses slightly different timing for valve

opening and closing events

In particular, the intake valve stays open as the

compression stroke begins.

This difference results in increased fuel

efficiency, but decreased peak power

ATKINSON ENGINE V/S OTTO ENGINE

From a mechanical standpoint, the only thing

that needs to change between an Otto cycle and

an Atkinson cycle is the camshaft(s)

The power of the engine can be supplemented by

an electric motor during times when more power

is needed.

ATKINSON CYCLE V/S OTTO CYCLE

the Atkinson cycle has an efficiency advantage

over the Otto cycle.

Atkinson cycle has a larger expansion ratio than

compression ratio.

The power output would be lower in Atkinson

cycle engine as compared to a similar sized Otto

cycle en

COMPARISON OF OTTO AND ATKINSON CYCLES

ADVANTAGE AND DISADVANTAGE OF ATKINSON

CYCLE ENGINE

The main advantage of the Atkinson cycle is that

it is much more efficient than the Otto cycle.

But the Biggest disadvantage is reduction in

power density (power/unit volume) arising from

the reduction in air intake

However Atkinson cycle engine can be supplemented with electric motor to provide more power if needed

Electric motors can be used in combination or independent of Atkinson cycle engines to provide the desired power output most efficiently

USES OF ATKINSON CYCLE ENGINE

Today Atkinson cycle engine used in many cars

such as

Toyota Prius hybrid electric

Ford Escape/Mercury Mariner/Mazda Tribute

hybrid electric

Toyota Camry hybrid electric

Honda Accord Plug-in Hybrid

Lexus CT 200h

ATKINSON-CYCLE ENGINES TODAY

TODAY ATKINSON CYCLE ENGINE