Atkinson Cycle, Ericsson Cycle and Stirling Cycle

-by Group 11 [Dhaval Shukla, Abhishek Singh R., Abhishek Singh Aman Singh]-Engineering Thermodynamics-A.C.E.T.

Atkinson CycleThe Atkinson cycle was

conceived and developed by a British engineer, Dr. James Atkinson.

This cycle consists of two adiabatic processes, a constant volume and a constant pressure processes.

Atkinson CycleFig. 1.1, shows the Atkinson cycle

plotted on p-V and T-s diagram.

Atkinson CycleThe point 1 represents that the cylinder is

full of air with volume V₁, pressure p₁, and absolute temperature T₁.

a) Process 1-2: This process represents the isentropic compression of air from state-1 to state-2.

b) Process 2-3: Heat is supplied to the compressed air at constant volume from an external source. The pressure rises and the ratio α=p₃/p₂ is called the explosion ratio.

Atkinson Cyclec) Process 3-4: The increased high pressure

exerts a greater amount of force on the piston and pushes it forward. Expansion of working fluid takes place isentropically up to the lowest pressure p₁=p₄ of the cycle, and work is done by the system.

d) Process 4-1: This process represents the rejection of heat by air at constant pressure. Hence volume and temperature of air decreases to initial value. Therefore, a cycle is completed.

Atkinson CycleCalculation of air standard

efficiency Consider ‘m’ kg of air in the

cycle.3 2

4 1

3 2 4 1

Heat supplied at constant volume, ( )

Heat rejected at constant pressure, ( )

Net work done, Heat supplied - Heat rejected

= ( ) - ( )

S v

R p

net

v p

Q mC T T

Q mC T T

WmC T T mC T T

Atkinson Cycle

3 2 4 1

3 2

4 1

3 2

Air standard efficiency,work done η=

Heat supplied( ) ( )

=( )

γ( ) =1 1

v p

v

mC T T mC T TmC T T

T TT T

Atkinson Cycle

γ-1

γ-112 1 1

2

γ-133 2 2 1

2

From isentropic compression process 1-2,

From constant volume process 2-3,

α=α

From isentropic expansion process 3-4,

VT T T rV

pT T T T rp

Atkinson Cycle

γ-1 γ-1

3 3 14 3 3

4 1 4

γ-1

2 13 2 3

1 4

γ-1

3 1γ-1

4

44 1

1

=

=

From constant pressure process 4-1,

V V VT T TV V V

V VT V VV V

T Vr V

VT TV

Atkinson Cycle

1γ

1 1

γ-1 γ-11 1

1γ

γ-1

Substituting the value of temperaturesin equation 1 , we get

1 γ α -

ηα

γ α 1η 1 2α -1

T T

T r T r

r

Atkinson CycleWhich is the required equation for air

standard efficiency of the cycle.The idea of the Atkinson cycle is to get

more work than that given by Otto cycle.The area 4 onwards represents this

increased work. Further it is to be noted that heat

rejection occurs at lower average temperature (T₅ being higher than T₁).

Atkinson CycleThis aspects make Atkinson cycle

more efficient than Otto cycle.However, it is very difficult to

construct an engine working on Atkinson cycle.

Atkinson CycleApplication of Atkinson Cycle:

Atkinson Differential Engine(Opposed Piston Engine)

Atkinson Gas Engine with Intake

Atkinson CycleApplication of Atkinson Cycle:

Rotary Atkinson Cycle Engine

Ericsson CycleThe Ericsson cycle is named

after inventor John Ericsson, who designed and built many unique heat engines based on various thermodynamic cycles.

He is credited with inventing two unique heat engine cycles and developing practical engines based on these cycles.

Ericsson CycleHis first cycle is now known as

the closed Brayton cycle, while his second cycle is what is now called the Ericsson cycle.

The Ericsson cycle consists of two isothermal and two constant pressure processes.

The p-V and T-s diagram with the mainframe structure of Ericsson Cycle is shown in Fig.1.2:

Ericsson Cycle

Ericsson CycleThe processes taking place in

Ericsson cycle is given below:a) Process 1-2: At a constant

temperature the pressure of air is increased, therefore the compression takes place.

b) Process 2-3: The increased pressure during this process is maintained and further heat is added to the cylinder.

Ericsson Cyclec) Process 3-4: Now, the temperature is

again maintained constant and the volume of air increases. Therefore the expansion takes place.

d) Process 4-1: Again maintaining the pressure constant, heat is removed from the cylinder system. Hence the process reaches to its initial state, making the process reversible cyclic process.

Ericsson CycleThe thermal efficiency of Ericsson

Cycle is given below:

thη

1

,

H L

H

L

H

H

L

T TTTT

where T Higher Temperatureand T Lower Temperature

Ericsson CycleApplication of Ericsson Cycle:

Ericsson Engine Ericsson Cycle

Engine

Stirling CycleThe Stirling cycle was

introduced by Dr. Robert Stirling over the improvement of ideal Otto and Diesel cycles.

The Stirling cycle is a thermodynamic cycle that describes the general class of Stirling devices.

Stirling CycleThe Stirling cycle consists of two

isothermal and two isochoric processes.

The p-V and T-s diagrams of Stirling cycle has been given below:

Stirling CycleThe processes occurring in a Stirling

Cycle is given below:a) Process 1-2: The volume of gas increases

at a constant temperature. Therefore, the process is called isothermal expansion process.

b) Process 2-3: The increased volume now is maintained constant and heat removal is offered. Therefore, the process is called Isochoric heat-removal process.

Stirling Cyclec) Process 3-4: In this process again

temperature is maintained constant and pressure increases. Therefore, isothermal compression takes place.

d) Process 4-1: Now, the heat is added at a constant volume. Therefore, the process is called isochoric heat addition process. Hence, the process reaches to its initial state. Therefore, cycle is completed.

Stirling CycleThe thermal efficiency of Stirling

Cycle is given below:

thη

1

,

H L

H

L

H

H

L

T TTTT

where T Higher Temperatureand T Lower Temperature

Stirling CycleApplication of Stirling Cycle:

Stirling Engine

Alpha Stirling Engine

Stirling CycleApplication of Stirling Cycle:

Four phase Stirling Cycle Engine(Ideal Stirling Engine)

Thank you!