This project involved the
designing and fabrication of gamma-type Stirling engine model. This project
development task aligns well with the ‘green-energy’ movements that insisted
using energy efficient models and system in the tasks’ execution. I thought of
working with Gamma aided configuration as they proved to be the best to achieve
my intended objective. These are solar powered low temperature differential Stirling
engines. This was the problem statement behind my project idea. This project
paper indicated that a Stirling cycle engine working with relatively low
temperature with air as working fluid is one of the potentially attractive
engines of the future, especially solar-powered low-temperature differential
engine was invented by Robert Stirling and lived up to the expectations level
to great extent. It had an easy mode of operation, was remarkably safe and
quiet and involved less maintenance cost. Various hit and trials were done to
modernize the earlier versions of the engine to upgrade the efficiency as well
as the performance parameters of the engine.it was observed that the efficiency
of an ideal Stirling engine was dependent only on temperature and no other
parameter. It showed maximum efficiency when tested under the conditions supporting
Second Law of Thermodynamics. Mechanical configurations of Stirling Engines
have three distinct arrangements: alpha, beta and gamma arrangement. Out of
these three, Gamma configuration rules out all the negative aspects observed in
other two types and seem to be mechanically simpler.
to be accomplished in this project were as below:
Devising an apt project framework to design
intended Stirling Model Engine.
Looking for the best solutions of the
existing model design presented in the previous literature reviews.
Design calculations for the entire
fabrication of this model.
Testing of the results for the performance
and heat transfer of the engine design.
Summarizing all the obtained results in a
project report by giving recommendations.
of my project position is shown below:
Figure 1: My project
I performed in this project were:
Gathering of the significant design
details from varied sources through different means.
Preparing a project framework in terms of
project milestones to be achieved at regular time intervals.
Design activity as per the requirements
and standards of design principles.
Calculation of the data values of all the
parts of the design and getting the correct output values.
Fabrication of the proposed design model by
applying mechanical engineering concepts and design standards.
Documenting a final project report
mentioning all the key design parameters and methodology followed to complete
started this project by studying a history of Stirling engine and its process
flow in all its types. I also read regarding the principles of flywheel design
principles from some reference books. I did a detailed literature survey and
tried to understand the earlier relevant work done in this respect. I
differentiated the positive and negative attributes and did my level best to
rule out the earlier discrepancies in my new design. I went through a series of
research work, papers published to ensure that I choose the best possible
design with high efficiency and technical parameters as well.
my study, I observed that gamma engine showed greater feasibility ratio when
compared to other arrangements as it involved ease in manufacturing, reduced
power losses and had suitability for multi-cylinder use. I did the fabrication
and testing of the gamma configuration Stirling engine starting with the
component description. Main components that I selected for this designing task
Heat source: kerosene oil and some
Displacer: to move the working gas back
and forth between the hot and cold heat exchangers.
Flywheel: storing mechanical energy for
continuous motion within the engine.
Piston and cylinder: transfer force from
expanding gas in the cylinder to the crankshaft via a piston rod and/or
Crankshaft: to convert the linear energy
of the pistons into rotational energy in an engine.
took into consideration material properties while selecting the component. I
also examined their properties so that the designed accessories would operate
perfectly. The material of each of these stated components was chosen after
keeping in mind their physical and chemical characteristics. In order to get an
efficient and successful design model, I tried out many ways by sketching various schematic
diagrams and after series of discussions; I came to the final design in which I
used a heat source displacer, flywheel, piston, crankshaft and cylinder.
fabrication I used the displacer cylinder which had two separate sections, one
for the higher temperature and the other for the lower temperature. I placed it
in the base plate with the help of notch support. I connected both the ends and
left few holes to place the transfer tube and the linkages. I transmitted the
pressurized air through the pipe placed from displacer to piston. The base
plate I used formed the foundation of the design. It provides the base for all
the other components like piston cylinder, displacer cylinder, flywheel. I
placed the displacer piston in the displacer cylinder to transfer air from hot
chamber to the cold chamber. I used the power piston to transmit the power to
the fly wheel through linkages. I adjusted the flywheel with the help of
supports welded to the base plate. I placed the fins in the displacer cylinder
above cold chamber to enhance heat transfer.
designing and fabrication, I analyzed the functioning by performing numerous
tests and experiments. I evaluated the swept volume, calculated ideal volume,
ratio depending on the temperature difference. I compared the network and
actual work volume. I also calculated power and torque and did the fin
calculations. I also calculated the ideal efficiency value. I carried out
series of experiments to test the engine against the theoretical calculations
we made for power and efficiency. To do this, I made use of heating the hot end
of the cylinders to required temperature and starting of the engine required
several trials of hand-cranking of the flywheel.
executing preliminary analysis and running a number of experiments, I observed
that the striling engine shows high potential for future use. For the Power and
Torque measurement, I connected the engine to a Prony Brake Dynamometer. It
measured the torque and power generated by the engine. In order to calculate
the power I must first find the torque. To do this, I used a weighted scale
that measured the force exerted by the dyno housing attempting to rotate. I
then calculated the torque by the force indicated by the scale multiplied by
the length of the torque arm. With the value of Torque, I evaluated the Power
Output of the engine.
Measured Power = 1.003 Watt with the Mean Torque = 0.095 N-m
I encountered with technical as well as manufacturing
problems while carrying out this project. They are listed below:
Selection of configuration of the proposed
Slider and linkage mechanism operation as
it can cause obstruction to the motion.
Calculation of output power given by the
Welding of piston cylinder cap to cylinder
due to high chances of melting the nylon piston inside the cylinder due to heat
The linkage was pinned off-center of the piston
head and thus alignment was improper.
Fabrication of fins and conduction losses.
Solutions derived: I applied the design selection
matrix to select the best configuration. I implemented Grashof’s law so that
sum of shortest linkage length and longest linkage length was greater than
remaining linkage length to ensure that the linkage mechanism would not be
rocker. Assuming the motion of the
engine as sinusoidal, I executed Schmidt analysis rather than idealized cycle.
Then, I replaced the loosely fit O-rings by tight fit rings and provided minor
fluid leakage. I also removed piston while welding to avoid distortion. After
this I replaced the linkage position and pinned to the center of the piston
head for proper alignment to reduce leakage. I preferred a Rectangular shape
fin to circular fin as per the fabrication point of view. To reduce conduction losses, the heat cap
and displacer cylinder were made as thin as possible.
was a challenging project in every aspect. It gave me the exposure to brush up
my skills and I was able to incorporate my technical skills with knowledge and
take up my career to new heights. This project has helped me a lot in boosting
up my confidence. Now I find myself more confident and competent to look after
new opportunities coming my way. I think I am expertise in operational
precision on pilot scale. I gained the confidence to sort out problems after
the completion of my work. I am looking forward to take up new challenges in my
life now, after the successful journey of this project work.