Transcript Stirling Engine

The Analysis of a…
Here is what we wanted to learn:
 How do stirling engines work?
 Which design aspects have the greatest effect on their performance?
 How do they compare to more common engines?
 Where would a stirling engine be used?
http://i.ytimg.com/vi/osNluWPOpJ0/0.jpg
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Gamma type stirling engine
A stirling engine uses heat flux
from a temperature differential to
create a cycle of expanding and
contracting air
The expansion and contraction
causes a pressure change which
moves the green piston
The green piston rotates the shaft
and the flywheel which moves the
displacer
Why are they 90° out of phase?
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Invented in 1816 by Robert Stirling
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First used in Dundee Foundry in Scotland for power
generation
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Applications include mechanical and electrical power
generation, cryogenic cooling and HVAC.
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Typical efficiency is 30-50% of Carnot cycle (15-30% overall)
approximately 31% efficient
We measured…
 System dimensions
 Temperature difference
 RPM
We assumed…
 Steady state heat reaction for
engine
 Laminar flow
 Insulated cylinder
 No loss through bottom of coffee
cup or sides of plate
 Frictionless
Significant calculations:
 Work output per cycle
 Heat loss from mug
V1 = minimum volume
V2 = maximum volume
qin = 12.50 Watts
Work = 0.14 Watts
qout = 12.36 Watts
Material
Thot °C
Tcold °C
T(delta)
RPM
Aluminum
Aluminum
Aluminum
Aluminum
Aluminum
Aluminum
Aluminum
Steel
Steel
Average
67
60
44
25
93
85
59
50
64
2
3
4
-3
-3
-4
22
-3
0
65
57
40
28
96
89
37
53
64
59
87
108
46
39
127
132
58
84
100
87
Time to
Stop(sec)
70
380
Power
output
(Watts)
Power
Water
(Watts)
qconv
qin
Efficiency
0.14
0.17
0.07
0.06
0.20
0.21
0.09
0.13
0.16
0.14
20
18
12
9
30
28
12
16
20
18
6.8
5.7
3.1
0.0
10.9
9.7
5.5
4.1
6.3
5.8
13.4
12.1
9.3
8.6
18.9
18.0
6.1
12.4
13.6
12.5
1.0%
1.4%
0.8%
0.7%
1.1%
1.2%
1.5%
1.1%
1.2%
1.1%
14
12
y = 0.0025x
0.20
10
y = 0.0023x
Watts
Power (Watts)
0.25
0.15
8
6
0.10
4
0.05
2
0.00
0
0
20
40
60
80
Temperature Difference (C)
Aluminum
Steel
100
120
qin
Work
qout
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Plate properties and dimensions have no effect on power output for steady-state
A larger diameter cylinder can operate on a smaller temperature difference
Gases with large (m*R) J/kg, such as helium, are the best working fluids
Temperature difference is directly proportional to power output
Efficiency comparison:
- Stirling engine: 15% - 30%
- Steam engine: 8%
- Internal combustion: 35%
Stirling engines are increasingly being used in solar power applications.
They are useful because they are extremely low maintenance and do not
require fuel to run. Renewable energy!