Post on 06-Jan-2016
description
STIRLING ENGINE
The Analysis of a…
WHY A STIRLING ENGINE?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.jpghttp://www.dansdata.com/images/blog/msiairpowerfan2_s.jpg
DEMONSTRATION
WHAT IS A STIRLING ENGINE?
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?
Invented in 1816 by Robert Stirling
First used in Dundee Foundry in Scotland for power generation
Applications include mechanical and electrical power generation, cryogenic cooling and HVAC.
Typical efficiency is 30-50% of Carnot cycle (15-30% overall)
BACKGROUND
SOLAR POWER
approximately 31% efficient
We measured… System dimensions Temperature difference RPM
EXPERIMENT
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
CALCULATIONS
V1 = minimum volume V2 = maximum volume
POWER
qin = 12.50 Watts
Work = 0.14 Wattsqout = 12.36 Watts
Material Thot °C Tcold °C T(delta) RPMTime to
Stop(sec)
Power output (Watts)
Power Water
(Watts)qconv qin Efficiency
Aluminum 67 2 65 87 0.14 20 6.8 13.4 1.0%Aluminum 60 3 57 108 0.17 18 5.7 12.1 1.4%Aluminum 44 4 40 46 70 0.07 12 3.1 9.3 0.8%Aluminum 25 -3 28 39 0.06 9 0.0 8.6 0.7%Aluminum 93 -3 96 127 0.20 30 10.9 18.9 1.1%Aluminum 85 -4 89 132 0.21 28 9.7 18.0 1.2%Aluminum 59 22 37 58 0.09 12 5.5 6.1 1.5%
Steel 50 -3 53 84 0.13 16 4.1 12.4 1.1%Steel 64 0 64 100 380 0.16 20 6.3 13.6 1.2%
Average 59 87 0.14 18 5.8 12.5 1.1%
RESULTS
20 30 40 50 60 70 80 90 1000.00
0.05
0.10
0.15
0.20
0.25
f(x) = 0.00252506106685977 xf(x) = 0.002313346706129 x
Power vs Temperature Difference
Aluminum Linear (Aluminum)Steel Linear (Steel)
Temperature Difference (C)
Pow
er
(Watt
s)
qin Work qout0
2
4
6
8
10
12
14
Power
Watt
s
RESULTS
OVERVIEW 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: 12% - 20%- 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!
Questions?