The Atkinson cycle, invented in 1882 by James Atkinson, is designed for efficiency at the expense of power density, making it suitable for hybrid electric applications. Compared to the Otto cycle, it features a longer combustion stroke and modified valve timing, resulting in greater fuel efficiency but lower peak power. Modern uses of the Atkinson cycle can be found in various hybrid vehicles, including the Toyota Prius and Honda Accord.

2. 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).

3. 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.

4. 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)

5. 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

6. 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.

7. 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

8. COMPARISON OF OTTO AND ATKINSON CYCLES

9. 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

10. 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

11. ATKINSON-CYCLE ENGINES TODAY

12. TODAY ATKINSON CYCLE ENGINE