DESIGN AND FABRICATION OF ALPHA STIRLING ENGINE

International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056
Volume: 09 Issue: 11 | Nov 2022 www.irjet.net p-ISSN: 2395-0072
© 2022, IRJET | Impact Factor value: 7.529 | ISO 9001:2008 Certified Journal | Page 697
DESIGN AND FABRICATION OF ALPHA STIRLING ENGINE
Tharun Amgothu1, Rohith Reddy Katta2
1B.E Mechanical Engineering (2022), Chaitanya Bharathi Institute of Technology(A)
2B.E Mechanical Engineering (2022), Chaitanya Bharathi Institute of Technology(A)
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Abstract - This paper describes a method for designingand
fabricating an Alpha Stirling enginewiththe goalofbuildinga
working prototype. The Stirling cycle is a dynamic system
which have one hot and one cold cylinders. Standard
dimensions are used to calculate all design parameters and
control tools. This type of engine has a high-volume ratio, but
becomes unstable on reaching high temperature. Stirling
engines convert heat energy into electricity without polluting
the environment using solar energy as a primarysource. Solar
energy is one of the world's fastest-growing renewableenergy
sources. The ideal Stirling engine would be as efficient as a
Carnot engine, so it can generate more power than normal
solar panels. Stirling engine won’treleaseanykindofpollution
into the environment. Fabricating of Stirling engine required
low cost than compared to another engines. We used
SolidWorks to design the engine parts with standard
dimensions for specific power output. After designing, the
parts were fabricated using CNC machining and surfacefinish
is done to avoid friction between the parts. We calculated the
theoretical power output of the engine is 0.785kWat300rpm
with cylinder diameter of 36mm. The theoretical efficiency is
around 40%.
Key Words: Alpha Stirling engine, heat energy, Carnot
engine, SolidWorks, CNC, Solar energy
1.INTRODUCTION
The Stirling engines works on a closed thermodynamic cycle
as they are external heat engines, so we maintain
temperature difference between the two cylinder one is hot
cylinder and other is cold cylinder. Solar Stirling engineuses
solar radiation energy as external heat source for heating
working fluid (gas) to convert thermal energy into electrical
energy. There is an ideal Stirlingenginethathasanefficiency
of 40%, in contrast to others engines like the otto engine,
which has 25% and the diesel engine, which has 35%.
Stirling engine work by isochoric and isothermal processes.
Stirling engines have a higher capital cost and are heavier
than internal combustion engines; however, they require a
lower maintenance cost. It is more efficient than other
engines, but controlling it at high temperatures can be
challenging.
1.1 Literature Review
• B. Kongtragool Et Al, 2003 [1] reviewed on
solar Stirling engine and low temperature
differential Stirling engine to find feasible design
and workable solar-powered low temperature
Stirling engine. This paper results shown low
temperature air are given more energy.
• Krissadang Sookramoon Et Al, 2022 [2]
describes in paper about using of biomass
incineration to heat Stirling engine to produce
electric power.
• K.G. Maheswaran Et Al, 2017 [3] provides an
explanation of how a beta type Stirling engine is
constructed and they are external combustion
engines that run on Stirling cycles. They use heat
sources such as solar energy and agricultural
waste like paddy straw, sugarcane leaves, wheat
stalk, groundnut shell, coconut husk, etc. The
efficiency of these engines is comparable to the
theoretical Carnot efficiency, making them
suitable for stationary power generation.
• K. Dinesh Et Al, 2014 [4] describes how low-
cost Stirling engines can be built and utilized for
green energy application, including theoretical
background, various designs and parameters.
• Mohamed Abbas Et Al, 2008 [5] proposed
thermal analysis of Stirling engine using
parabolic concentrator in paper. This paper
shows various energy loses that engine does
when converting heat into electrical energy.
• Muhammad Hassan Et Al, 2021 [6] paper
showcases that using CAD tools, the design and
fabrication of a 90-degree alpha Stirling engine
were performed, and the power outputsfromthe
Stirling engine were analyzed at every different
temperature. At various points, external heat
input was increased to observe the engine’s
stability.
• Najafi. G Et Al, 2015 [7] paper describes about
design of gamma Stirling engine and using
biomass energy as heat source of the engine.This
shows gamma Stirling engine behavior at
different temperatures.
• Snyman. H Et Al, 2008 [8] published paper on
design analysis of Stirling engine, made attempts
to create new design of engine whicharefeasible,
low cost and produces more power.

• Vishal Gehlot Et Al, 2014 [9] discussed an
alpha Stirling engine prototype is built with an
emphasis on developing a new approach to
development and fabrication. For maintaining
control of dynamic systems, the Stirling cycle is
recast in this paper.
• Yaseen H. Mahmood Et Al, 2018 [10] this
paper investigated the properties of Gamma
Stirling engines produced using low-cost
materials, and their efficiency in relation to
temperatures and pressure.
1.2 Research Gaps
Many researchers in the past had performed experiments on
the Stirling engine and proposed design adjustments and
fabrications methods. Most of them have analyzed Stirling
engines in Ansys, but we, in this paper, are designing and
fabricating Stirlingengines withdifferentdesigndimensions.
Most researchers have made studies on beta and gamma
Stirling engines. Here, we are studying the range of output
electricity for various inputs of temperatures to an alpha
Stirling engine. i.e., when the temperature parameter is
varied, electricity output at the outlet is noted.
2. MATERIALS AND METHODS
In the present chapter the various components were
designed to fabricate the parts and has been discussedalong
with their specifications and the working process of the
prototype has also been discussed. Parts were designed
using Solid Works.
Design of Parts: We designed 23 parts of Stirling engine
and some of them are
1.Crank Shaft: Fig-1 shows the design view of the crank shaft
with length 35mm and diameter 5mm. crank shaft is
responsible for converting a linear motion to a rotational
motion.
Fig-1: Crank Shaft
2. Counter Weight-A and Counter Weight-B: Fig-2 shows the
design view of the counter weight-A and counter weight-B.
Counter weights are used for applying an opposite force,
provides balance and stability of a mechanical system.
Fig-2: Counter Weights A&B
3. Cylinder: Fig-3 shows the designviewofthecylinder.Here
the air is compressed and expanded.
Fig-3: Cylinder
4. Flywheel: Fig-4 shows the design view of the flywheel.
Flywheel is a circular disc which rotates when shaft and
counter weights rotates. Flywheel is fixed to delivery power
from an engine to machine.
Fig-4: Flywheel
5. Piston: Fig-5 shows the design view of piston which has
diameter of 30mm. Piston is used to compress the air inside
the cylinder and transfer energy.

Fig-5: Piston
6. Cross Head: Fig-6 shows the design view of cross head.
Cross head is a mechanism used as part of slider-crank
linkages of long reciprocating engines to eliminatesideways
pressure on the piston.
Fig-6: Cross Head
7. Crank Rod: Fig-7 shows the design view of crank rod.
Crank rod is a part of piston engine which connects the
piston to the crankshaft. It transfers the force of expanded
air to crank shaft via a piston.
Fig-7: Crank Rod
8. Heat Exchanger Piston Tube: Fig-8 shows the designview
of the heat exchange piston tube with diameter 35mm and
length 87.50mm. This piston tube exchange heat from one
body to another.
Fig-8: Heat Exchanger Piston Tube
9. Heat Exchange Cylinder: Fig-9 shows the design view
of heat exchange cylinder. The cylinder has fins
around it to exchange heat.
Fig-9: Heat Exchanger Cylinder
Fabrication:
Our projectinvolvedthedesignofa 90-degreeAlpha
Stirling engine usingSolidWorkssoftware,andall partswere
designed in line with standard dimensions to fit together.
The engine parts were manufactured utilizing CNC Machine
techniques after they were designed using operations such
as Machining, Milling, Lathe, Cutting, etc. In order to achieve
good heat transfer, corrosion resistance and high ductile
nature, we found copper as an ideal material forengineparts
like heat exchanger piston head, crank rod and piston tube.
During fabrication, rest of the parts were constructed using
mild steel since it is inexpensiveandweldable.Eachhole was
drilled with a drill machine, and the internal thread was
dyed by hand using an iron. A surface finish improvement
was achieved by treating all parts with emery paper
following fabrication.
According to the standard dimensions for engine design,the
theoretical calculations were done before fabrication in
order to determine how much power the Stirling engine
would produce. As a solar parabolictroughforconcentrating
solar energy was unavailable, we had to calculate power
output with theoretical calculations and test the engine
theoretically.

Fabricated Parts:
Fig-10: Cylinder Fig-11: Crank Rod
Fig-12: Flywheel
Fig-13: Stirling Engine
Fig -14: Stirling Engine
3. WORKING PROCEDURE
Solar Stirling engine process
● An engine starts when an external heatsource,such
as solar energy, is provided at the end of a hot
cylinder.
● Stirling engine utilizes gas as a working fluid. As
when the external heat source was activated, heat
transfer increased to the hot cylinder, which
increased the temperature of the gas molecules.
During the heating process, gas molecules expand
inside the hot cylinder as the temperature rises.
● By expanding the gas, the piston is pushed away by
the pressure, which starts the flywheel in motion.
● The power piston is linked with crank shaft and
displacer piston is connected with crankshaft. As
crankshaft moves the displacerpistondrivestocold
cylinder.
● Displacer piston movement causes gas to move
from a cold cylinder to a hot cylinder andviceversa.
● Through the gas exchange tube, expanded gas or
heated gas molecules move from the hot cylinderto
the cold cylinder. Cooling the hot gas is
accomplished by the fins in a cold cylinder.
● When the gas has been cooled, the piston
compresses it in the cold cylinder, allowing it to
move to the hot cylinder, where the cycle repeats.
This causes the flywheel to rotate through the
motion of piston expansion and compression.
● A flywheel is attached to the motor which rotatesto
generate the electro flux and to produce the
electricity.
4. CALCULATIONS
The present chapter discusses the calculations obtained
from the theoretical values.
THEORETICAL CALCULATIONS:
▪ Swept volume = (π ÷ 4 × D² × L)
= (π ÷ 4 × 0.036 × 0.124)
= 129.747 × 10-6 m3
▪ Clearance volume = 5% of swept volume
= 5 × 129.747 × 10-6
V₂= 6.487 × 10-6 m³
▪ Volume of air admitted

V₁ = Swept + Clearance
V₁=129.747 × 10-6 m³ + 6.487 × 10-6 m³
= 136.234 × 10-6 m3
▪ Compression ratio
r = V₁ ÷ V₂
= (136.234 × 10-6 ÷ 6.487 × 10-6)
= 21.001
▪ 1-2 isentropic process
T₂ ÷ T₁ = (V₁ ÷ V₂) ‫ﻻ‬-1
= (136.234 × 10-6 ÷ 6.487 × 10-6)1.4-1
= 1057 K
According to ideal gas equation, P₁×V ₁ =m × R × T₁
Mass of air (m) =0.001kg,
Temperature of air = 313 K
P₁ × 136.234 × 10-6 =0.00159 × 0.287 × 313
P₁ = 0.659 × 10⁶ kPa
P₂ ÷ P₁ = (1 ÷ r‫ﻻ‬
)
P₂ =1 ÷ (211.4) × (0.659 × 10⁶)
= 9.284 × 10⁶ Pa
▪ 2-3 Constant Volume Process
V₃ = V₂
P₃ × V₃ = m × r × T ₃
P₃ × 6.487 × 10-6 = 0.001 × 0.287 × 500
Supply Heat temperature (T₃), assume T₃ = 500k
P₃ = 22.12 × 10⁶ Pa
▪ Heat supplied = m × Cv × (T₂ - T₃)
= 0.001 × 0.707 × (10547-500)
= 0.39 kJ/kg
▪ 3-4 isentropic process P₃ ÷ P₄ = r‫ﻻ‬
P₄ = 22.12 × 10⁶ ÷ 211.4
P₄ = 31.16 × 104
▪ 4-1 Constant volume process T₄ ÷ T₁ = P₄ ÷ P₁
T4 = 31.16 × 104 × 313 ÷ (0.659 × 10⁶)
T4 = 147.99 K
▪ Heat Rejected = m × Cv × (T₁ - T₄)
= 0.001 × 0.707 × (313 – 147.9)
= 0.11 kJ/kg
▪ Work done = Heat Supplied – Heat Rejected
= 0.39 - 0.11 = 0.28 kJ/kg
▪ %Efficiency = (work done/Heat supplied)
= (0.28 ÷ 0.39) × 100 % = 71.7 %
▪ Performance calculation
1) Area = π × D × L
= 3.14 × 0.036 × 0.124
= 0.014 m2
2) Force = Pressure × Area
Assume, P = 1 bar
Force = 1 × 105 × 0.014
= 1.4 kN
3) Torque = Force × Radius
Radius of flywheel = 18 mm
= 0.018 m
Torque = 1.4 × 0.018
= 0.025 kN-m
4) Power = (2π × N × T) ÷ 60 KW
= (2π × 300 × 0.025) ÷ 60 KW
= 0.785 kW
Therefore, Power generated from heat supply 500K with
cylinder diameter 36mm is 0.785kw.
5. RESULT
The results obtained from the theoretical calculations of the
solar Stirling engine are discussed in this chapter. The
Stirling engine was designed in SolidWorks with assumed
dimensions. The designed parts were fabricated by
performing CNC machining, CNC turning, drilling, wire
cutting. The theoretical calculationstofindthepoweroutput
from specific heat supply was performed assuming the heat
supply as 500K with our cylinder diameter of 36mm. The
theoretical power output is 0.785 kW at 300rpm.Because of
fabrication difficulties while machining the Stirling engine
was not performing. An attempt was made to design and
fabricate the Stirling engine where designofthe enginewent
well but, due to fabrication errors the engine is not working.
6. CONCLUSIONS
The following conclusions can be derived from the design
and fabrication:

● The design of the Stirling engine provides the
necessary data for the comparison of several
aspects of the Stirling-cycle engine.
● The Stirling engine parts were fabricated
according to dimensions in CNC machines.
● The theoretical efficiency is more than 70% for
respective supplied heat.
REFERENCES
[1] B. Kongtragool, A review of solar-powered Stirling
engines and low temperature differential Stirling
engines, 2003, Vol. 7, pp. 131 – 154.
[2] Krissadang Sookramoon, Updraft gasifier-Stirling
engine biomass incineration system power
generation, 2022, vol 19, pp. 1-11.
[3] K. G. Maheswaran, Design and Manufacturing of
Beta Stirling engine, 2017, vol 6, pp. 1-9.
[4] K. Dinesh, Design and Fabrication of low-cost
Stirling engine, 2014, vol 3, pp. 75-78.
[5] Mohamed Abbas, Thermal performances of Stirling
engine solar driven, 2008, vol 8, pp. 1-10.
[6] Muhammad Hassan, Design and Fabrication of
Stirling engine for solar power application, 2021,
vol 143, pp. 1-7.
[7] Najafi. G, Design, Fabrication and Evaluation of
Gamma type Stirling engine, 2015, vol 7, pp. 137-
143.
[8] Snyman. H, Design analysis methods for Stirling
engines, 2008, vol 19, pp. 4-19.
[9] Vishal Gehlot, Development and Fabrication of
Stirling engine, 2014, vol 11, pp. 69-71.
[10] Yaseen H. Mahmood, Fabrication of Stirling engine
and study of its characteristics, 2018, vol 8, pp. 96-
100.

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