ANALYZE OF KS90T SOLAR TWIN AS LOW
TEMPERATURE DIFFERENTIAL STIRLING ENGINE
By:
1.
Dama Vara : 2014990002
2.
Debby Syahera :
2014370010
3.
I Wayan Surya Aryana : 2014370006
4.
Lutfi Hidayat : 2014360006
5.
Paskah Andreas Deo
Gratias : 2014370005
FACULTY OF SCIENCE AND TECHNOLOGY
SAMPOERNA UNIVERSITY
ABSTRACT
A Stirling engine is a heat engine
operating by cyclic compression and expansion of air or other gas. KS90T Solar Twin LTD stirling engine
is a new generation of stirling engine that has been born to increase the
effectiveness of stirling engine. This engine is noted
for its high efficiency compared to another engines. This compatibility with
alternative and renewable energy sources in which it has become increasingly
significant as the price of conventional fuels rises, and also in light of concerns
such as peak oil and climate change. This paper is mainly aimed to analyze KS90T Solar Twin stirling engine as a LTD engine. As a result, this study
indicate how KS90T Solar Twin LTD stirling engine work and how this engine look like in its orthogonal views.
Keywords: Stirling engine, KS90T-LTD,
Gamma-type.
CHAPTER
I
INTRODUCTION
1.1.
Background
A Stirling engine is basically an external
heated appliance that make a use of a reversible closed cycle concept in which
the Stirling engine’s thermal efficiency is equal to that of the Carnot cycle.
Even Stirling engine was invented before the internal combustion engine in
which it is in 1816 (Karabulut, 2000, p.71), Stirling engines were not
commercialized yet at that time. The main reason avoiding Stirling engine from
being commercialized was because Stirling engine was not competitive with those
that belong to the internal combustion engine in the specs of power produced
and weight owned (Karabulut, 2000, p.71). However, even it is shown like that,
there are some aspects that successfully make Stirling engine become exist till
today, which are its high heat conversion efficiency, reliability, ability to
use many fuels, and low noise operation characteristic (Hassani, 2013, p. 1).
By those characteristics, Stirling engine have been being a demand of the
effective usage of energy and environmental preservation. In fact, reducing
environmental impacts of conventional energy resources and meeting the growing
energy demand of the global population had motivated considerable research
attention in a wide range of environmental and engineering application of
renewable form of energy, and among all possible alternative energy options,
solar energy is becoming more popular in the world. This is mainly caused by
the availability of plenty of sunlight in many countries (Sharma & Harinarayana,
2012, p. 1). By that reason, a new generation of engine called LTD-SE is being
developed. In line with LTD-SE, its differentials are
also now being researched in regarding to adjust the concept of eco-friendly to
the drive mechanism used in each kind of engine. As a result of a scientific
cooperation between Moulay Ismail University in Morocco and the University of
Technology of Dresden in Germany, an LTD γ-type Stirling engine was produced.
This engine was tested and studied under a real conditions. Based on the
conclusions of this study, a new prototype of LTD-SE with walking beam drive
mechanism called KS90T Solar Twin LTD is being developed; this is beautiful,
stable, easy built, and shown a high machine efficiency.
A new generation, LTD-SE, that is being
developed in expecting to make a better future in using the solar energy. The
Low-Temperature Differential Stirling Engine (LTD-SE) is a kind of Stirling
engine that can run with a small temperature difference between the hot and the
cold source. By that characteristic, people believe that LTD-SE can utilize the
solar energy and make benefit of that. LTD-SE firstly developed by Kolin in
1983 (Hassani, 2013, p. 1), and now, considering that todays’ trend is using eco-friendly
energy with a high efficiency owned, the LTD-SE is being developed and begin to
be manufactured in large scale. Besides that, it is also noticed that LTD-SE is
being differed between those that have been produced previously; those that
manufactured before the LTD-SE is likely prevented by being commercialized but
now LTD-SE is being popularize regarding to its eco-friendly characteristic.
In short, considering that γ-type Stirling
engine with a walking beam drive mechanism is a new engine, so this paper aims
to study both the design of the machine and the performance of how the
low-temperature Stirling engine concept in KS90T Solar Twin LTD works. A
thermodynamic analysis of the machine is also be conducted to help in finding
the result of the purposes.
1.2. Problems
Here are the problems that built up the paper:
1.
What is KS90T
Stirling engine?
2.
How KS90T Stirling
engine work?
3.
What is the
efficiency of the engine?
4.
Is it really
work in low temperatures?
1.3. Aims
Here are the aims that we want to
achieve:
1.
To analyze how
KS90T Stirling engine work.
2.
To know the
design of the engine.
1.4. Benefit
There are some categories of benefit
in this paper considering to whom the paper is used:
1. Group
a. Apply engineering drawing technique.
b. Understanding what is KS90T Stirling engine.
c. Knowing how KS90T work.
2. Student
a. Providing
the orthogonal drawing of KS90T LTD Stirling Engine.
b. Providing
a reference to the other students about KS90T LTD Stirling Engine.
CHAPTER II
BASIC THEORY
2.1.
The Principles and Works of Stirling
Engine
Thermal
circuit with a considerable degree of simplification, consisting of a number of
thermodynamic transformations is called a theoretical circuit, the example of which
is the Carnot cycle (Fig. 1). The
implementation of this course mostly impossible, because the engine forced to
have a perfect parameters. Still, this model can help in the initial stages of
design, besides it can be a simplified description of the operation of the
engines. During subsequent cycles of thermal cycle, an ideal gas is subjected
to changes, in which heat exchange is conducted between the gas and the environment (Żmudzki,
1993):
· Cycle 1. Isothermal compression at temperature C to D, even temperature heat source, usually a factor that gives off heat to the cooler.
Cycle 2. Adiabatic compression
from point D to A is the gas heating to achieve a temperature at A equal to the
temperature of the upper heat source.
· Cycle 3. Isothermal
expansion at A temperature causing reversion of gas volume to its initial value
V1.
· Cycle 4. Adiabatic expansion
from B to C — the working factor is expanded without changing the heat until to
achieve the cooler temperature T. The
intense cooling of the cylinder during compression is necessary to the proper
working which assure isothermal transformation. Stopping the piston at top dead
point and at the same time providing heat allows to perform isochoric transformation
2–3 (Part 2). Isothermal expansion is another transformation by intense heating
of the cylinder 3–4 (Part 3). The cycle closes when the piston reaches bottom dead
point during the isochoric transformation 4–1 (Part 4). In fact, an engine can’t
work through it in practical point of view, because it would require the
application of a specific mechanisms that allow the interrupted movement of the
piston. Think based on Figure 2, the Stirling engine should fulfill this
conditions (G., 1980):
Stirling engine belongs to a group of external combustion
engines, which means that the fuel is burned outside the engine. Flammable
material or other medium are supplied to drive the system. In this particular
type of engine, temperature needed to start up the systems work. It can be electric
heating, burning candle as the application of object or a material with higher
temperature. The engine circuit may occur as a closed system, which allows for
the same mass of working gas participated in all cycles without exchanging it
with the outside, so with the gas from the outside of the engine compartment.
The system allowing to better understand the Stirling engine working is a
piston engine with a single cylinder, in which a constant mass of gas is
alternately compressed and expanded, under the influence of linear progressive
— return movement of the piston (Fig. 2).
1. Continuous movement of the piston;
2.
The full exchange of the
mass of gas from an area in the low temperature to the high temperature,
without changing its volume (closed system);
3. There is no pressure loss in the heat exchangers and there are no
internal pressure differences.
4. Conditions of the working gas are changed as an ideal gas. The expansion process and the compression process changes
isothermal.
6. There is a perfect regeneration.
7. The expansion dead space maintains the expansion gas temperature
and the compression dead space maintains the compression gas temperature during
the cycle.
8. The regenerator gas temperature is an average of the expansion gas
temperature and the compression gas temperature.
Meanwhile, to get perfect regeneration can be achieved by using a
material that can absorb heat which has high heat capacity. The material used
to absorb that heat called by regenerator. The regenerator might place between
cold and hot space that located inside the cylinder, however it can placed
outside. The use of this element to reduce the loss of heat energy when doing
exchange and thus increases the efficiency of the whole system.
2.2.
Types of Stirling Engine
There are three types of Stiring engine
based on the configuration and how it work.
2.2.1.
Alpha Stirling Engine
This
type of engine has two power pistons at a phase difference of 90 deg. There is
a high temperature (expansion) space and low temperature (compress) space
attached to each other. As the two pistons make the gas between both spaces go
and return, the same two pistons output power.
2.2.2.
Beta Stirling Engine
In a beta type Stirling engine the displacer and power piston
share a single cylinder. Therefore, a displacer piston and power piston is
supposed to have a bore of the same diameter. By overlapping between each
movement of both pistons, a compression ratio of the engine raises and can
obtain higher output than gamma type Stirling engine. However, the shaft of the
displacer and the power piston are on the same axis, therefore driving
mechanism gets complicated.
2.2.3. Gamma Stirling Engine
The Gamma engine is the simplest and easiest type of Stirling
engine. This type of configuration with double-acting piston arrangement has
theoretically the highest possible mechanical efficiency and also shows good
self-pressurization (Senft, 1993). The kinematic engine
with a normal 90° phase angle is a specific characteristic of gamma
configuration engine. Like a Beta system, the Gamma system has two cylinders
(sometimes there is one large and one small), which it built-in in the
different cylinder (Rizzo, 1997). Cylinders must not
be parallel, but it depend on the construction solutions. They can be construct
in an oblique or perpendicular surface. With its configuration, this type of
engine can work with low heat, as compared with conventional Beta and Alpha system.
The sufficient source of heat to run the machine can be a cup of hot water.
2.3.
Low Temperature Differential Engine
A low temperature
differential (LTD) Stirling engineis an engine that can be run with small temperature
difference between the hot and cold edge of the displacer cylinder (Rizzo, 1997). It is different
from other types of Stirling-cycle engines, mostly Stirling engine has a
greater temperature difference between the two edges. However, the power output
from the engine can be greater because it has greater temperature difference
that affect the pressure power. Some characteristics of the LTD Stirling engine (Rizzo, 1997) described as
follows.
LTD
engines might become in two designs generally. The first design uses
single-crank operation where only the power piston is connected to the flywheel
that called the Ringbom engine. This type of engine, has been commonly spread
to use, is based on the Ringbom principle. A short, large-diameter displacer
rod in a precise-machined fitted guide has been used to replace the displacer
connecting rod (Rizzo, 1997).
The other design called by a kinematic engine, where both the displacer and the
power piston are connected to the flywheel. The kinematic engine with a normal
90° phase angle is a gamma configuration engine (Rizzo, 1997).
1. Displacer
to power piston swept volumes ratio is large;
2. Diameter
both of displacer cylinder and displacer are large;
3. Displacer
size is short;
4. Effective
heat transfer surfaces on both end plates of the displacer cylinder are large;
5. Displacer
stroke commonly small;
6. Displacer
period at the end of the displacer stroke is rather longer than the normal
Stirling engine;
7. Speed
operating system is low.
LTD
Stirling engines provide mostly as demonstration units, but they immediately
become most interest when considering the possibility of power generation.
Because the system work from low temperature, means that’s only need heat
sources less than 100 °C (B. H. Van Arsdell. . In:
Zumerchik J, 2001).
A calculation using the Carnot cycle formula shows that an engine operating
with a source temperature of 100 °C and a sink temperature of 35 °C gives a
maximum thermal efficiency of about 17.42%. If an engine could be built for
achieving 50% of the maximum thermal efficiency, it would have about 8.71%
overall Carnot efficiency. Even the calculated thermal efficiency seems rather
low, but LTD Stirling engines could be used with free or cheap low temperature
sources. Therefore, this engine become recommend to selected when the low cost
engines are put into consideration.
CHAPTER
III
METHOD
3.1. Method
We decide to use
qualitative way as the method to study about KS90T Stirling Engine. Because the
main idea we get, come from problems that come up around us. Those attract us
to study about KS90T to solve the issues. Moreover the qualitative way be an
effective way to us for collecting data and the information needed.
3.2. Collecting
Data
To take some information
from the system, we decide to use case study with existed product. We make
analyze with the system to improve the KS90T performance. Meanwhile, we also
look up with the design. We observe the KS90T to know every detail of the
component. Furthermore, we can involve to redesign the system to get more
effectiveness.
3.3. Location
and Schedule
We decide to use Sampoerna University to
make analyzing with the KS90T. We think of the environment support to do
analyzing and Sampoerna University might give the facilities to support us to
work. Besides, we also look at our schedule to work effectively and due in the
proper time. We use timeline to summarize every work to do. The schedule of
activities detail shows as (Fig. 3) follows:
CHAPTER
IV
RESULT
AND DISCCUSSION
4.1. Result
Here the result we get when open the case
from KS90T Stirling Engine. The data we get come from analyze the system and
study literature from existed journal.
|
Main
Design Parameters
|
Dimension
|
|
Plates
|
|
|
Flywheel
|
|
|
Power
Piston
|
|
|
Displacer
|
|
Table 1: Main engine design
parameters
Main engine design
parameters are shown in Table 1.
KS90T LTD Stirling engine is designed in single-acting which is in gamma
configuration. Since the gamma configuration Stirling engine provides a
relatively large regenerator heat transfer area and it is easy to be constructed,
this configuration act as a basic configuration in this engine KS90T LTD-SE.
The power cylinder are directly connected to the cooler plate to minimize the
cold-space and transfer-port dead volume in which, in KS90T LTD-SE the cooling
water pan is a part of the cooler plate.
KS90T Solar Twin LTD Stirling engine basically make up by the acrylic
plates. This acrylic plate gives a special ability to the engine in the field
of how it uses the heat supplies. This special property let the engine to be
transparent to the infra-red, in which it means that the heat source (sunlight)
can directly heat the air inside the main chamber without having to firstly
heat the plate. In line with the hot side, on the cool side, the heat can also
directly radiate away into without firstly having to pass through the cool
plate.
The process of KS90T Solar Twin LTD Stirling engine in which it is cyclically
heat and cools the air inside can be shown in the cut-away diagrams below (Fig. 4 and Fig. 5) (Kontax Engineering Ltd Company, 2012). In
this case, it is important to remember that the large blue displacer disk is
moving (displacing) the air from the top of the plate to the bottoms and
precisely back again, and there is also a small black piston that actually
drives the flywheel. The figure provided also explain a different chamber; one
of those chambers is the right chamber and the other is the left chamber.
Figure 4. Hot condition
With the large blue displacer disk at the top, it is reasonable to
state that, most of the air inside the main chamber is at the bottom. By the
expanding air caused by the source of heat (sunlight), the black piston is
pushed upward, in which automatically cause the flywheel to turns around (Fig. 5).
Figure 5. Cold Condition
As the flywheel turns, the displacer disk in the other chamber is moved
(by means of a crank and a connecting rod flow) to the bottom of the chamber.
As the displacer move down, the air that was initially at the bottom of the
chamber rushes around the outside of the displacer to the top of the chamber. So with the displacer at the bottom, most of the air
is at the top, where it is cooled by the cool top plate (Fig.5). As it cools, it contracts, which pulls the small black
piston downwards, and drives the flywheel around some more, and so the cycle
continues.
3.2. Discussion
Basically, the working of
this machine is quite similar with the other gamma type Stirling engine. The
gamma type Stirling engine use two tube or chamber which are connected, one of
them for the piston and the other one for the displacer. The tube of displacer
has different temperature of each edge, hot and cold. Firstly, when the seesaw
moves the displacer up to the upper of the tube, the air in the tube move to
the bottom of the plate. In the bottom, the temperature of the air is
increasing as the hot plate. As the air become hot, then it will expand and
push the piston so that the piston goes up. Continuously, the piston that goes
up will make the flywheel rotate, and the rotating flywheel will make the
seesaw moves, then the seesaw will make the displacer goes down. As the
displacer goes to the bottom of the tube, the hot air is moved to the upper of
the tube. Next, the temperature of the air will be decreased by the upper plate,
which is the cold plate. Because the temperature of the air is decreasing, so
the air will be constructed and pull the piston down. This cycle is working
continuously as long as there are temperature difference in the end of plate.
Unlike the other Stirling machine that only can move with the temperature
difference around 200K-400K, this machine can work and move with minimum
temperature different of 25K only. This can be happened because of the tiny
size of the machine and also the super low friction of the machine. As shown in
the calculation:
KS90T
is a gamma type Stirling engine that use walking beam model. Walking beam model
is model of engine that use seesaw and connect with the crank, flywheels, and
also the piston. It connect the seesaw to the piston vertically to the side
tube of the piston. It to minimize the friction and maximize the movement of
the piston. Like KS90T machine was made with very high precision, moreover it
chosen from high material in order to make frictionless. It important because
the system has function to convert energy from a small temperature difference
to mechanical energy—energy of movement. In
the calculation shown that the difference of pressure only
, a very small pressure.
Use
weight of the whole system and assumed that friction near to zero, the equation
will show as follow:
As shown in the calculation above, the
area of the piston tube will cover 1.3*
or
the diameter is only 14 millimeter. It has very small size of piston, mean that
the system cover very small machine with low friction. In the end, efficiency
of this machine can be gotten with the Carnot efficiency. Minimum efficiency of
this machine is 3.4% and it can be increased depend on the temperature
difference.
Besides,
here Beale Formula is created to help to calculate the power output of KS90T
Solar Twin LTD Stirling engine (Kongtragool
& Wongwises , 2002, p. 141).
Beale Formula
P = 0.0015 pm f
VP
Where
P is the engine power output in Watt,
pm is the mean
cycle pressure in bar, f is the cycle
frequency in Hz, and Vp is
displacement of power piston in cm3.
The
resulting dimensionless parameter
is
called the Beale number. This number is basically a function of both source and
sink temperatures. The graph (Fig. 6)
indicates the relationship between the Beale number and source temperature. The
upper bound represent the high efficiency, well-designed engines with low sink
temperatures, while the lower bound represents the moderate efficiency, less
well-designed engine with high sink temperatures.
CHAPTER V
CONCLUSION AND SUGGESTION
The KS90T Solar Twin LTD
Stirling Engine are being analyzed. It is basically made up by 28 different
kind of part in which each of them are having their specific roles within the
engine. There are three main aspects that having an important roles in how the
engine works, they are the acrylic plate, temperature, and the fluid (air)
inside the chamber. The power output of KS90T Solar Twin LTD Stirling Engine
can also be gotten. It is calculated by using the Beale formula.
The Carnot thermal
efficiency of KS90T Solar Twin LTD Stirling Engine is experimentally not going
to reach that of the high temperature differential Stirling engine. However
apart of that this LTD Stirling engine can use many different kind of heat
source in which they are usually ignored by human, solar heat is the example.
While making this paper,
It would be advisable if:
1.
There is a lab provided to support in
collecting the data and making the prototype.
2.
There are enough funding to create a
prototype.
References
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Senft, J. R. (1993). Ringbom Stirling Engines. New
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Żmudzki, S. (1993). Silniki Stirlinga. Warszawa:
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Stirling engine driven. International Journal of Energy and
Environmental Engineering, 1-11.
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