The Comparison for Different Type of Drive Mechanism for Small Solar Stirling Engine 500 W in Thailand. ISEC 2007

1. The Comparison for Different Type of Drive Mechanism for Small Solar
Stirling Engine 500 W in Thailand.
Eng’r. Suravut, Snidvongs*1 and Dr. Sirinuch, Chindaruksa*2
*1
Vice President, Asian Renewable Energy Development and Promotion Foundation, Bangkok, 10400, Thailand ,
airscan@cscoms.com, PhD Students, School of Renewable Energy Technology (SERT), Naresuan University,
Pitsanulok, THAILAND.
*2
Physic Department, Faculty of Science, Naraesuan University, Pitsanulok, THAILAND.
Abstract The Author tries to develop the Drive Mechanism
A purpose of this research is to compare the for Stirling engine which has the lowest friction. This
different type of drive mechanism for Small Gamma may cause to increase the performance of the Stirling
Type Solar Stirling Engine. This system was direct engine up to 30 %.
equipped with asynchronous motor, 500 W, as In this research the author will compare 3 different
generator. There are three type of daisy chain drive mechanism Stirling engines, with the same
mechanism to compare, Gear drive, Swash Plate Drive condition, four cylinders, power piston diameter,
Type I (Whisper Tech), Swash Plate Drive Type II displacement diameter, regenerator, pressure, cooler,
(Rotary Drive). This system will compare in term of generator, heat exchanger, and stroke. The Daisy
cost, performance, and efficiency. Chain Drive Mechanism has three different types, Gear
Drive, Swash Plate Drive Type I (Whisper Tech),
1. Introduction Swash Plate Drive Type II (Rotary Drive).
It will compare cost of manufacture, performance,
The Author had found out from his past and efficiency.
experience of Stirling Engine experiments. The
performance of the Stirling engine depend on the fluid 2. Engine Specification
type, pressure, efficiency of heater tube, efficiency of
cooler tube, efficiency of regenerator and friction etc. The Stirling Steele engine was redesigned by
Friction is the most critical for Stirling engine. The enlarges. The power piston size changes from 22 mm
more friction in the system it will be less power output. to 48 mm, Stroke from 25 mm to 40 mm, and Volume
If we can reduce the friction of the engine it will from 37.6 cc to 289.4 cc. The power changed from 20
increase the efficiency of the Stirling engine greatly. W at 20 psi Air to 215 W at 20 psi Air. The engine
Insolation in Thailand is varying between in 450 specifications shown in Table 1.
to 550 W/m2 daily whole year round, and the average The piston sets of this engine was linked with
value is at 550 W/m2 daily over the year. Friction of three different type daisy chain drive mechanism, Gear
Stirling engine may not have direct effect to the Drive, Swash Plate Drive Type I (Whisper Tech),
insolation, but if the Stirling engine has less friction, Swash Plate Drive Type II (Rotary Drive). As the
Stirling engine will require less power to overcome the engine has less crank case along with a simpler crank.
friction and could produce more power output. This It permits for a more cost effective engine to
will gain the performance of the Stirling engine up. manufacture. Building four cylinders instead of single
Thus, with medium insolation as Thailand, Stirling cylinder units has several strong advantages such as
engine could perform better. easy starting, good balance, smooth running even at
Lot of researchers tries to improve the efficiency very low speeds, increased heater and cooler surface
of the heater tube, cooler tube, regenerator, and seal to area, and good low end torque.
adopt higher pressure. All of these reach to maximum Since this Stirling engine is a closed cycle device,
criterion already but to reduce the friction of the it runs very quiet. It also has no cam shaft, lifters, push
engine still far away. Stirling engine friction may come rods, valves, spring, intake or exhaust manifold,
from Power Piston Seal, Connecting Rod Seal, Shaft complex spark ignition or carburetor. [1]
Seal, Displacer Seal, and Type of Drive Mechanical
etc.
Copyright© 2007 by the Japan Society of Mechanical
Engineers. All rights reserved.
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2. Table 1 Engine Specification bearing system. The rotation, Clock-wise or counter
Type Gamma clock-wise, can be done by adjust a little phase angle,
Acting Double positive or negative, different.
Working Gas Air
Max. Expansion space gas 650 C (+/- 5 C) 2.2 Swash Plate Type 1 Drive Mechanisms
temp The four pistons gamma type Stirling engine, are
Compression space gas temp 40 – 50 C (+/- 5 daisy chained together with Whisper Tech
C) Technology, Swash Plate, Figure 2. [2] This is done by
Ambient Temperature 40 C (+/-5 C) driving the displacer via linear drive rods which are
Thermal Efficiency 60 % attached to the top of power pistons. The rods pass
Power Control Variable Pressure through a sealed bulkhead and the displacer cylinders
No. of Cylinders 4 are ported to power piston cylinders that are phased
Means Pressure 0.5 MPa behind them 90°. This allows an engine that only
requires one crank through per piston where other
Maximum Pressure 1 Mpa
Stirling engine requires two.
Bore, mm. 48
This engine was replace bronze bushing sealed
Stroke, mm. 40 bulkhead as guide bearing with rubber seal, and
Engine Displacement, cc. 72 x 4 replace the Mitter gear with Whisper Tech
Speed, rpm 500 - 1200 Technology, Swash Plate. This could call Positive
Cooling type Ethyl glycol Swash plate. It also added more bearing and universal
Mechanical Output Power 215 W @ 20 psi joint. The rotation, Clock-wise or counter clock-wise,
Mechanical Output Power 550 W @ 60 psi can be done by adjust a little phase angle, positive or
Heat Source, Electric Heater 700 W x 4 negative, different.
Source : By Author
2. Drive mechanism
2.1 Gear Drive Mechanisms
Figure 2 Swash Plate Type 1
Souce : By Author
Figure 1 Gear Drive Mechanism
Source : By author 2.3 Swash Plate Type 2 Drive Mechanisms
The four pistons gamma type Stirling engine, are
The four pistons gamma type Stirling engine, are daisy chained together with Rotary Air Compressor
daisy chained together with Mitter gear, Figure 1. This Swash Plate, Figure 3. [3] This is done by driving the
is done by driving the displacer via linear drive rods displacer via linear drive rods which are attached to the
which are attached to the top of power pistons. The top of power pistons. The rods pass through a sealed
rods pass through a sealed bulkhead and the displacer bulkhead and the displacer cylinders are ported to
cylinders are ported to power piston cylinders that are power piston cylinders that are phased behind them
phased behind them 90°. This allows an engine that 90°. This allows an engine that only requires one crank
only requires one crank through per piston where other through per piston where other Stirling engine requires
Stirling engine requires two. two.
This engine still has the same bronze bush sealed The ideal of this engine mechanism was come
bulkhead as original designed. But at the Mitter gear from Rotary Air condition. The bronze bushing sealed
instead using of bronze bushing it was changed to bulkhead was replaced with guide bearing with rubber
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3. seal, and replace the Mitter gear with Rotary Drum. Table 2 Performance
This could call Negative Swash plate. It also added Gear Drive, Figure 4
more bearing and universal joint. The rotation, Clock- Friction @ 1800 RPM (W) 8.9
wise or counter clock-wise, can be done by adjust a Cost USD 950.00
little phase angle, positive or negative, different. Mean Time Between Fail (hrs) 2,500
How to make Easy
Maintenance Time (hrs) 150
Torque (N-m) 8
Carnot Eff. % 60
Thermal Eff. % 28
Mechanical Eff. % 44
Easy to start (Count as 10) 7
Swash Plate Drive Type I, Figure 5
Friction @ 1800 RPM (W) 7.6
Cost USD 1500.00
Mean Time Between Fail (hrs) 15,000
How to make Accurate
Maintenance Time (hrs) 2,500
Torque (N-m) 9.8
Carnot Eff. % 60
Thermal Eff. % 29
Mechanical Eff. % 56
Easy to start (Count as 10) 8
Figure 3 Swash Plate Type 2 (Rotary)
Souce : By Author Swash Plate Drive Type II, Figure 6
Friction @ 1800 RPM (W) 6.1
3. How to test Cost USD 1280.00
Friction test, Use DC motor, Minertia Encoder Mean Time Between Fail (hrs) 18,000
Motor 200 W torque 3.5 N-m, direct connects to the How to make Very Accurate
shaft of the Stirling engine without load and Power Maintenance Time (hrs) 3,500
piston connected. Supply the motor with DC power, Torque (N-m) 10.2
measure volt and current every 100 RPM until reach to Carnot Eff. % 60
maximum 1,800 RPM. Stop measurement. Thermal Eff. % 30
Connect Power piston, Displacer Cylinder, Mechanical Eff. % 58
Connecting rof, all other components. Release pressure Easy to start (Count as 10) 9
value of Stirling engine to atmospheric pressure. Source : By Author
Supply the motor with DC power, measure volt and
current every 100 RPM until reach to maximum 1,800
RPM. Stop measurement. Gear Drive Friction Test
Power test, connect Stirling Engine with Torque 12
indicator. Supply AC volt to Electric Heater, supply
10
Air up to 0.5 MPa measure Torque, Temperature,
Power. 8
4. Results 6
Table 2 shown the performance of each type of V
4 A
mechanism, Gear Drive, Swash Plate Type I, Swash
W
plate Type II. This performance from the experiment at 2
AREF laboratory, Bangkok, Thailand.
0
500 700 900 1100 1300 1500 1700 1900
RPM
Figure 4 Daisy Chain Gear Drive Mechanism, Friction
Test
Source : By Author
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4. accurate workmanship to make but it operates quite.
Swash Plate Friction Test
As the parts are precision it helps the maintenance time
12
increase up to 15,000 hrs.
10
As the weight of swash plate is in balance so it
creates less vibration. This type of Drive Mechanism
8 had lot of parts and complicates to make. The cost to
make this system is quite high. The friction is about
6 7.6 W. The engine torque 9.8 N-m is quite good.
Carnot efficiency is 60 %. Thermal Efficiency is 29 %
4 V and Mechanical Efficiency is 56 %. The friction test
A shown as Figure 5.
2 W The Swash Plate Drive Mechanism Type 2
(Rotary Drive), all piston rods install with guide
- bearing on both side to reduce the friction. This type of
500 700 900 1100 1300 1500 1700 1900
Mechanism needs very accurate workmanship to
make. It is very quite during the operation. The Stirling
Figure 5 Daisy Chain Wisper Tech Swash Plate, engine can be rotate clockwise or counter clockwise by
Friction Test adjust a little phase angle, positive or negative,
Source : By Author different. The maintenance time are high, 18,000 hrs.
As the weight of Rotary drum is in balance so this
Rotary Drive Friction Test type of mechanism create much lower vibration than
other system. This type of Drive Mechanism has fewer
12
parts than Daisy Chain Gear Drive but complicate to
10 make. The cost of the system is medium high. The
friction is about 6.1 W. The engine torque 10.2 N-m is
V quite good. Carnot efficiency is 60 %. Thermal
8
A Efficiency is 30 % and Mechanical Efficiency is 58 %.
6 W The friction test shown as Figure 6.
The Swash Plate Drive Type I (Whisper Tech) can
4 be improved mechanical efficiency 27 % from Gear
Drive Mechanism. The Swash Plate Drive Type II
2
(Negative Rotary) can be improved mechanical
- efficiency 31 %.
500 700 900 1100 1300 1500 1700 1900 Some modification may improve better efficiency,
such as weight of linkage arm, weight of piston, type
Figure 6 Daisy Chain Rotary, Friction Test of piston seal.
Source : By Author Friction of Stirling engine may not have direct
effect to the insolation, but if the Stirling engine has
5. Conclusions less friction, Stirling engine will require less power to
overcome the friction. This will gain the performance
All three Daisy Drive Mechanisms work well in of the Stirling engine up. Thus, with medium
the test bench. All Stirling engine can be rotate Clock- insolation as Thailand, average 550 W/m2 daily,
wise or counter clock-wise by adjust a little phase Stirling engine could perform better.
angle, positive or negative, different.
The Gear Drive Mechanism is easy to make but ACKNOWLEDGMENTS
very noisy during the operation. As the weight of gear This research was prepared by Mr. Suravut
not easy to balance so this type of mechanism can SNIDVONGS, Vice President, Asian Renewable
create a lot of vibration. This type of Mechanism is the Energy Development and Promotion Foundation, EIT
cheapest one to make. The maintenance time too low, member, a PhD Student, School of Renewable Energy
150 hrs as the screw holding the bearing, and axial Technology, Naraesuan University, Pitsanulok,
shaft always loose from vibration. The friction is Thailand. The author would like to acknowledge the
about 8.9 W. The engine torque 8 N-m is quite good. assistance and guidance of Asian Renewable Energy
Carnot efficiency is 60 %. Thermal Efficiency is 28 % Development and Promotion Foundation Dr. Sub.Lt.
and Mechanical Efficiency is 44 %. The friction test Prapas Limpabandhu Deputy Minister of Foreign
shown as Figure 4. Affair, Mr. Sutas AROONPAIROJ and staffs, the
All piston rod of Swash Plate Drive Mechanism Engineering Institute of Thailand members who
was installed with guide bearing on both sides to provided a critical review of this research through its
reduce friction. This type of Mechanism needs various stages, including Asist. Prof. Dr. Sirinuch,
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5. Chindaruksa, Physic Department, Faculty of Science
Naraesuan University, as Advisor, Dr. Vichit,
Yamboonrung, Assoc. Prof. Dr. Wattanapong
Rakwichien, Asist. Prof. Dr. Mathanee
Sanugansermsri, as Co-Advisor and the Naraesuan
University Staffs, Pitsanulok, Thailand. Especially the
Don Bosco Technical School staffs for their
fabrication and construction work on the prototype.
Finally, the author would like to thank the numerous
industries to provide information for this research.
References
[1]. The Stirling Steele engine, Ronald J. Steele, 1994.
[2]. Development of Stirling Engine Generator,
Whisper Tech, 2006
[3]. Mitsubishi Air-condition Swash Plate, Rotary
compressor, 2004.
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