Difference between revisions of "Thareq Wibisono"

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'''Rangkuman Artikel The aerodynamic Method of Archimedes Wind Turbine'''
 
  
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Turbin Archimedes adalah turbin yang mempunyai bentuk yang sangat aneh dan tidak seperti turbin kebanyakan. Desain turbin Archimedes , atau lebih spesifik membahas rotor Archimedes, terbentuk dari ruang 2-dimensi, berbentuk lingkaran, menjadi bentuk spatial atau 3-dimensi yang mengikuti pola konikal (Lihat Gambar dibawah).
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== Date: 23 February 2021 ==
  
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[[File:Archimedes rotor.png|frameless|caption]]
 
  
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Sebelum masuk mengenai turbin Archimedes, ada baiknya kita membahas tentang tipe-tipe turbin angina. Turbin angina dibagi menjadi dua tipe yaitu tipe ''resistance'' dan tipe ''lift''. Tipe ''resistance '' biasanya terbentuk dari profil datar dan memiliki ''tip speed ratio'' lebih kecil dari 1. Dimana,
+
Today I have learn about the correlation between justice and its usage in our current mechanical knowledge. Although it is rather an odd correlation as justice refers to the socio-economic term, the meaning of justice itself express the state of equilibrium in which one does not have to do another work to balance out the inequalities. As an engineer, justice is important not only to uphold social inequalities but also, in a more technical sense, an obligatory to understand how physical system works through a mathematical equations. Any physical system will find its own way to reach a state of equilibrium by increasing its entropy. By the time it reach the state of equilibrium, the entropy will reach its maximum level and any entities within the mathematical equation will balanced out.
  
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'''TSR = (Kecepatan di ujung bilah rotor) / (kecepatan angin)'''
+
But before dwell deeper to the topic, a simple definition to energy must be provided as many still have a vague idea about the term. The energy can be explained as the ability to do work, as one of my classmate says. It is a mechanism that structured life. like the flowing water, the energy is not stagnant. It constantly deliver one self to another entities in a various form. For example when we do an activity, we tend to be in exhaustion state by running a few kilometers as the energy is flowing from the chemical energy in our body to mechanical energy by moving our leg and dissipated as heat to the environment.
  
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Tipe ''resistance'' mendapatkan energi langsung dari angin sehingga kecepatan rotor lebih pelan dibandingkan kecepatan angin. Contoh tipe ''resistance'' adalah savonius wind turbine, turby, and American turbine
 
  
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[[File:Resistance.png|frameless|caption]]
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== Date: 24 February 2021 ==
  
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Dilain sisi, turbin lift adalah turbin angin yang bergerak mengikuti prinsip lift dan memiliki ''tip speed ratio'' lebih besar dari 1. Sehingga rotor dapat berputar lebih cepat dibandingkan angin. Akan tetapi, tipe ini memiliki kekurangan yaitu sangat bising pada saat berputar dan sangat berat.
 
  
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[[File:Lift.png|frameless|caption]]
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The assignment given yesterday is to define the component of the combined cycle plant which are shown below
  
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Turbin Archimedes memiliki karakteristik dari kedua tipe turbin angin. Turbin tersebut mempunyai kesalahan margin yang besar, ringan dan memproduksi suara yang kecil (<40db). Selain itu, turbin ini juga mempunyai kapabilitas untuk mendapatkan 52% energi dari angin sehingga effisiensi yang ditawarkan cukup besar.
+
[[File:CombinedCycle Assign.PNG|center|]]
  
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Dalam praktiknya, bentuk bilah dari rotor Archimedes memastikan bilahnya untuk berputar ke arah angin yang optimum sehingga ''yawing system'' yang digunakan sangat simple.
 
  
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Generator listrik yang digunakan oleh system turbin ini juga harus mempertimbangkan effiesiensi dan copper losses sehingga untuk kasus ini, generator mempunyai kapasistas sebesar 400v.
+
== Date: 2 March 2021 ==
  
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Untuk memastikan oprasional yang aman, turbin ini dipasangkan dengan ''safety system'' dimana pada saat angin berkecepatan melebihi batas prosedur, maka system rem yang terdapat di generator akan berkerja untuk melambatkan kecepatan putar rotor.
 
  
 +
Last session of the class we are given a task to learn the open-modelica software as to get the general workflow of the software and its feeling. The main learning source for my learning journey is via youtube and a website titled "Modelica by Example" created by Dr. Michael M. Tiller. I began my journey with the familiarity of modelica language which is the driving program for the software. The syntax of the program, like most of the available high-language program, contain a familiar properties such as the if, elif, and else statement, iteration with for and while loop, variable declaration, array, etc. I tried to play around with the language and manage to write several interesting program. One of those is a function that return a calculation of a polynomial algebaric expression. The script is shown below
  
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----
+
[[File:Polynomial evaluator.PNG|800px|thumb|center|'''Figure 2.''' Code script for polynomial evaluator function]]
  
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== Parameter yang Bersangkutan dengan Permodelan Design Turbine ==
+
As you can see form the script, the function takes x as the input and return fx as the output. The parameter (variable that remain constant through out the simulation) is written below the protected statement which include the polynomial constant a, b, and c. Because we are dealing with the Real number, we must specified it after typing the parameter. The algorithm statement will carry out the actual evaluation which in this case will return fx as the output
  
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Desain turbin memiliki bentuk yang komplek dan sangat rumit jika kita perhatikan dengan seksama. Akan tetapi beberapa parameter bisa menjadi faktor dalam menentukan geometri dan dimensi akan sebuah turbin. Parameter pertama yang paling penting dalam permodelan turbin adalah ''velocity triangle'' yang menghubungkan kecepatan absolute sebuah fluid ''V'', kecepatan relative ''W'' dan kecepatan putar turbin ''U''. Hubungan antara ketiga parameter tersebut dapat di nyatakan pada rumus dibawah ini
+
Because it is a function, it cannot be simulated directly. So I create a new class, which are able to call and simulate the function, with the following script
  
−
[[File:Velocity triang.png|frameless|caption]]
+
[[File:Polynomial checker.PNG|800px|thumb|center|'''Figure 3.''' Code script for simulating polynomial evaluator]]
  
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Untuk sebuah turbin, Velocity triangle untuk inlet dan outlet dapat di gambarkan pada gambar dibawah. Jika diperhatikan, kecepatan absolute inlet tangensial (''V1'') dari fluid memiliki nilai 0 atau kecepatan inlet hanya berfokus pada komponen axial. Akan tetapi, setelah melewati turbine terdapat komponen axial dan tangensial untuk kecepatan absolut fluid yang berlawanan arah dengan gerakan turbin. Berdasarkan hukum newton ke-3, jika ada aksi maka akan ada reaksi yang dihasilkan dengan nilai yang sama. Reaksi inilah yang membuat turbine bergerak.
+
which will return the following result
  
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[[File:Veltriang turbin.png|frameless|caption]]
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[[File:Result polyEval.PNG|800px|thumb|center|'''Figure 4.''' Result for polynomial evaluator function]]
  
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The aforementioned parameter also applied in the analysis of the Archimedes wind turbine. The detailed view of the Archimedes win turbine's velocity triangle can be seen below
+
Another program that I write is the bouncing ball program which calculate the bouncing trajectory of a free falling ball when hitting the ground. The script to the program is shown below
  
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lll
+
[[File:Bouncing ball.PNG|800px|thumb|center|'''Figure 5.''' Code script for simulating the trajectory of a bouncing ball]]
  
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From the velocity triangle above, the tangential absolute velocity have an opposite direction relative to the direction of the turbines. Thus from the previous statement we can conclude that the system is indeed a turbines
+
In short the program will try to calculate the trajectory and the velocity of the ball. When the ball is bounced back, the velocity is decrease by a constant e. When the ball reach 0 m in height, the program will terminate. The resulting plot is shown below
  
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Another term that need to be considered is the direction of the torque produced by the wind and the direction of the angular velocity. The formula for calculating the power is
+
[[File:Bouching ball result.png]]
  
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'''Power = Torque x angular velocity'''
+
== Date: 9 March 2021 ==
  
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For turbines, the power have a negative sign indicating that the system extracting the energy from the fluid or in this case the wind. This negative sign comes from the fact that the direction of the torque is opposite from those of the angular velocity. To confirm the theory with the system, a simulation is needed to be conducted. This simulation result will be presented later in this report.  
+
Last week, we are given an assignment to investigate the parameter used for a gas turbine cycle in Open-Modelica software. My journey started by investigating the main component of the the gas turbine cycle which include the compressor, the combustion turbine, and the combustion chamber. Albeit the initial plan to investigate all of the component, I only able to investigate the input and output parameter of the compressor that are specific for the ThermoSysPro libraries which will be discussed below.
  
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The parameter of the Archimedes wind turbine's design is derived from the aforementioned theory which is a little bit different because the theory of momentum and mass equilibrium play a handy role to calculating the torque and the power. Before proceeding to the derivation of the equation, a few assumption is made in regards to the analysis of the wind turbine. These assumption include:
+
'''Compressor'''
  
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1. Incompressible and steady flow
+
Compressor is a device that are responsible to compress air to increase the pressure and temperature of the upstream air up to a certain point depending on the compressor unit specification. Because we idealized the system to be isentropic (adiabatic and reversible), there exist isentropic efficiency (''tau'') to relate the actual power and the idealized power. In ThermalSysPro system, there are several input that must be considered which are:
  
−
2. The fluid move to the control volume parallel to the rotating axis of the wind turbines.
+
1. Inlet and outlet pressure ('''''Pi''''' and '''''Po''''')
  
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3. The quantities of the mass flow in the three outlet boundaries are the same
+
2. Inlet mass flow rate ('''''m_dot''''')
  
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There are several parameter that are used for the sake of analyzing the design of the Archimedes turbines. Which are:
+
3. Nominal compression rate
  
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L1 : The distance between the  back-end of the spiral shape to the x point located perpendicular to the tip of the outer blade.  
+
4. Inlet and outlet air temperature ('''''Ti''''' and '''''To''''')
  
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L2 : The distance between the  back-end of the spiral shape to the x point located perpendicular to the tip of the inner blade
+
5. Air composition ('''''XCO2''''', '''''XO2''''', '''''XH20''''', '''''XSO2''''')
  
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R1 : The length from the rotating axis to the outer blade
+
6. Nominal isentropic efficiency
  
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R2 : The length from the rotating axis to the inner blade
+
It is worth mention, that the air composition will remain constant through out the process as there are no chemical reaction (combustion) occurring within the compressor. The parameter mention above will be used to calculate the power required for the compressor which have the following governing equation
  
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Gamma : The angle between the outer blade relative to the rotational axis
 
  
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S1 : The total length of the turbine relative to the rotational axis.
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'''''W_cp = m_dot * (hi - ho)'''''
  
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The above nomenclature can be clearly seen in the picture below
 
  
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iii
+
As we can see from the equation above, we do not know the inlet and outlet specific enthalpy ('''''hi''''' and '''''ho'''''). The inlet specific enthalpy can be calculated by taking the '''''Pi''''', '''''Ti''''', and the air composition ('''''XCO2''''', '''''XO2''''', '''''XH20''''', '''''XSO2''''') using the following governing equation:
  
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The parameter above is essential to find the torque in which later crucial to find the power through the equation mentioned before. The equation of the torque is presented below (the derivation of the equation is not mentioned in this report in regard to the reference)
 
  
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iii
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'''''h = u * (Pi / rho_i)'''''
  
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From the equation, the shape parameter which are R1, R2, L1, and L2 can be found by trial and error to find the best geometry. The problem is how to find the tangential absolute velocity. Because it is not known and depended on the absolute velocity itself which are presented in the equation below
 
  
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iii
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in which '''''u''''' is the specific energy and '''''rho_i''''' is the inlet density which can be calculated by taking into account the inlet temperature ('''''Ti''''') and the air composition which will not be discussed in this today's wiki. Meanwhile, the oulet specific enthalpy can be calculated by using the relation between the specific enthalpy and the isentropic efficiency ('''''tau''''') by using the following equation:
  
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The absolute velocity of the wind is depended on the relative and rotational velocity of the turbine which can be found using the relation below
 
  
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iii
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'''''tau = (his - hi) / (ho - hi)'''''
  
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The rotational velocity is the product of the angular velocity of the turbine and the overall radius of the turbine.The angular velocity can be found using simulation and the radius is based on the shape requirements. The relative velocity in the other hand can be found using the equation below:
 
  
 +
which can be modified as:
  
−
iii
 
  
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Thus from the equation above we can find the tangential absolute velocity which later essential to find the torque
+
'''''ho = hi + ((his - hi) / tau)'''''
  
  
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== Progress Turbin Archimedes Semester 2 ==
+
in which his '''''his''''' is the isentropic specific enthalpy that take into account the outlet pressure '''''Po''''', the isentropic temperature ('''''Tis''''') and the air composition.
  
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----
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Although there are a lot of things I have been learn about the compressor, I still have a confusion regarding the calculation of the isentropic efficiency for the compressor in the ThermoSysPro libraries.
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Tanggal 25 April 2020
 
  
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'''Desain dan proses manufaktur turbin'''
 
  
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Pada semester ini saya ditugaskan untuk membuat komponen turbin dari turbin Archimedes dengan menggunakan metode 3d printing sehingga turbin tersebut dapat muat dalam pipa. Pipa yang dipilih berukuran 4 inc. Desain dan dimensi sudah dibuat terlebih dahulu oleh Andrew. Tetapi perlu penyesuaian ukuran dikarenakan ukuran turbin yang dibuat Andrew lebih besar dari pipa. Setelah melakukan scaling dengan menggunakan software solidworks, turbin sekarang memiliki panjang 238 mm dan diameter maximum 41.4 mm. Gambar turbin setelah di scaling dapat ditunjukan pada gambar dibawah
+
== Date: 10 March 2021 ==
  
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[[File:Turbin_hasil_scaling.JPG|frameless|caption]]
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In the last class session, we have a change to practice OpenModelica to simulate and interpret the result combustion chamber simulation. The simulation procedure is similar to those in compressor but the difference lies in the components used.  
  
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Untuk memudahkan proses 3d printing, turbin dibagi menjadi 2 bagian yaitu bagian atas dan bagian bawah. Hal ini dikarenakan jika proses 3d printing dilakukan untuk satu keutuhan turbin, maka akan banyak terjadi ''failure printing'' yang sangat memakan waktu dan biaya. Proses penyambungan kedua komponen tersebut dilakukan dengan menggunaan super glue. Untuk memudahkan penyambungan, sebuah sistem coupling dibutuhkan untuk memudahkan lem mengering. Komponen turbin dan sistem coupling-nya dapat dilihat pada gambar dibawah.
+
There are several components that plays an important role in the simulation listed below:
  
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[[File:Turbin_siap_3d_print.JPG|frameless|caption]]
+
1. The ''GT(Gas Turbine)CombustionChamber''
  
−
Setelah desain dari turbin selesai, file turbin saya ubah menjadi format STL untuk dikirim ke vendor 3d printing. Proses 3d printing dilakukan dengan keakuratan (''layer height'') sebesar 0.2 mm. Lama pengerjaan 3d printing adalah 6 hari dekarenakan terjadi 2 kali kegagalan dalam proses printing. Hasil 3d printing sangat mulus dan hanya terdapat cacat sedikit. Gambar dibawah memperlihatkan turbin yang selesai di 3d print
+
2. ''SourcePQ (Pressure and mass flow is fixed)'' component for the flue gasses
  
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[[File:Hasil_3d_print_turbin.jpg|frameless|caption]]
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3. ''Sink'' component for the flue gasses
  
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'''Proses assembly turbin'''
+
4. ''SourcePQ (Pressure and mass flow is fixed)'' for the water steam
  
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Setelah proses desain selesai dilakukan oleh masing-masing teman yang mengerjakan mounting turbin. Semua komponen kami list beserta vendor pembeliannya. gambar dibawah menunjukan list komponen komponen yang harus di 3d print maupun yang harus dibeli.
+
5. ''FuelSourcePQ (Pressure and mass flow is fixed)'' for the fuel
  
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[[File:List_komponen_yang_harus_dibeli.JPG|frameless|caption]]
+
Unlike the compressor where the air composition remain the same as discussed in 9 March 2021 wiki, the component model of combustion chamber involve the chemical reaction between the air composition from the flue gasses source and the fuel source. Thus, the outlet air composition that will be feed to the combustion turbine will differ from the initial value.  
  
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Butuh waktu sekitar 1-2 minggu agar semua komponen terkumpul dikarenakan faktor logistik dan kegagalan 3d printing. Setelah semua komponen terkumpul, semua komponen dikirim ke rumah saya untuk proses assembly. Proses assembly sampai tanggal ini baru selesai pada pemasangan kedua komponen turbin (bagian atas dan bawah) dengan menggunakan super glue dan penyambungan turbin tersebut ke mountingnya beserta bearingnya. Hasil assembly untuk saat ini dapat ditampilkan pada gambar dibawah.
+
The components mention before can be found in the ThermoSysPro libraries which can be drag and drop to the diagram view of the model and connected to each other to closed the equation inside the ''GT(Gas Turbine)CombustionChamber''. It is worth noting, however, that each ''GT(Gas Turbine)CombustionChamber'' input correspond to a different source type. There are 3 source type which is the flue gasses, the water steam, and the fuel source as mention in the component list and each of the source type is connected to the corresponding inlet within the combustion chamber as shown in Figure 7 below
  
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[[File:Assembly_mounting_turbin.jpg|frameless|caption]]
+
[[File:Combustion chamber.PNG|800px|thumb|center|'''Figure 7.''' The diagram view of the combustion chamber system including the water steam source (''Top left''), the flue gasses source (''centre left''), and the fuel source (''bottom left'')]]
  
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Yang harus dilakukan oleh saya untuk progress berikutnya adalah untuk menyelesaikan proses assembly. Proses assembly yang dimaksud adalah menggabungkan mounting turbin dengan sistem ''power transmission'' yang tersambung ke generator via bevel gear. Setelah itu menggabungkan mounting turbin yang sudah lengkap dengan mekanisme tersebut ke pipa 4 inc
+
Because the simulation involve 3 different source, the input of the simulation also differ from those in compressor which are summarized below:
 +
 
 +
- Flue gases temperature at the outlet of the boiler = 386.16 K
 +
 
 +
- Flue gases pressure at the outlet of the boiler = 14.1e+5 Pa
 +
 
 +
- Thermal power losses = 106 W
 +
 
 +
- Air pressure at the inlet of the combustion chamber = 15e+5 Pa
 +
 
 +
- Air temperature at the inlet = 680 K
 +
 
 +
- Air mass flow rate at the inlet = 415 kg/s
 +
 
 +
- CO2 mass fraction in the air at the inlet = 0
 +
 
 +
- H2O mass fraction in the air at the inlet = 0.01
 +
 
 +
- O2 mass fraction in the air at the inlet = 0.23
 +
 
 +
- SO2 mass fraction in the air at the inlet = 0
 +
 
 +
- Fuel temperature at the inlet = 410 K
 +
 
 +
- Fuel mass flow rate at the inlet = 9.3 kg/s
 +
 
 +
- Lower heating value of the fuel = 47.5e+6 J/kg
 +
 
 +
- Fuel humidity = 0
 +
 
 +
- C mass fraction in the fuel = 0.755
 +
 
 +
- H mass fraction in the fuel = 0.245
 +
 
 +
- Fuel specific heat capacity = 2255 J/kg/K
 +
 
 +
- Fuel density = 0.838 kg/m3.
 +
 
 +
The result of the simulation with the aforementioned input is shown below
 +
 
 +
[[File:Combustion chamber R1.PNG|800px|thumb|center|'''Figure 8.''' The first attempt result of the combustion chamber simulation]]
 +
 
 +
It worth noting that the above simulation runs with zero mass flow rate of the water steam to the combustion chamber. Thus, I try to make an experiment out of it to see whether the result will change particularly the air composition, the temperature and the flue gasses mass flow rate. The second attempt result is shown below where I increase the mass flow rate of the water steam to 50 Kg/s
 +
 
 +
[[File:Combustion chamber R2.PNG|800px|thumb|center|'''Figure 9.''' The second attempt result of the combustion chamber simulation]]
 +
 
 +
The second attempt result clearly show that the air composition is changing. The mass flow rate of the flue gasses also shows a slight increase from 424 Kg/s to 474 Kg/s. In contrast, the temperature of the flue gasses is decreasing significantly which shows that increasing the water steam mass flow rate will decrease the outlet flue gasses temperature.
 +
 
 +
There are a lot of things that needs to be learn from the experiment above because I only change only one parameter from one type of the source. Thus, the knowledge of the governing GT combustion chamber equation is needed to find more correlation between each parameter and its output which is still in the process so I can not write it down yet.

Latest revision as of 15:34, 10 March 2021

Date: 23 February 2021

Today I have learn about the correlation between justice and its usage in our current mechanical knowledge. Although it is rather an odd correlation as justice refers to the socio-economic term, the meaning of justice itself express the state of equilibrium in which one does not have to do another work to balance out the inequalities. As an engineer, justice is important not only to uphold social inequalities but also, in a more technical sense, an obligatory to understand how physical system works through a mathematical equations. Any physical system will find its own way to reach a state of equilibrium by increasing its entropy. By the time it reach the state of equilibrium, the entropy will reach its maximum level and any entities within the mathematical equation will balanced out.

But before dwell deeper to the topic, a simple definition to energy must be provided as many still have a vague idea about the term. The energy can be explained as the ability to do work, as one of my classmate says. It is a mechanism that structured life. like the flowing water, the energy is not stagnant. It constantly deliver one self to another entities in a various form. For example when we do an activity, we tend to be in exhaustion state by running a few kilometers as the energy is flowing from the chemical energy in our body to mechanical energy by moving our leg and dissipated as heat to the environment.


Date: 24 February 2021

The assignment given yesterday is to define the component of the combined cycle plant which are shown below

CombinedCycle Assign.PNG


Date: 2 March 2021

Last session of the class we are given a task to learn the open-modelica software as to get the general workflow of the software and its feeling. The main learning source for my learning journey is via youtube and a website titled "Modelica by Example" created by Dr. Michael M. Tiller. I began my journey with the familiarity of modelica language which is the driving program for the software. The syntax of the program, like most of the available high-language program, contain a familiar properties such as the if, elif, and else statement, iteration with for and while loop, variable declaration, array, etc. I tried to play around with the language and manage to write several interesting program. One of those is a function that return a calculation of a polynomial algebaric expression. The script is shown below

Figure 2. Code script for polynomial evaluator function

As you can see form the script, the function takes x as the input and return fx as the output. The parameter (variable that remain constant through out the simulation) is written below the protected statement which include the polynomial constant a, b, and c. Because we are dealing with the Real number, we must specified it after typing the parameter. The algorithm statement will carry out the actual evaluation which in this case will return fx as the output

Because it is a function, it cannot be simulated directly. So I create a new class, which are able to call and simulate the function, with the following script

Figure 3. Code script for simulating polynomial evaluator

which will return the following result

Figure 4. Result for polynomial evaluator function

Another program that I write is the bouncing ball program which calculate the bouncing trajectory of a free falling ball when hitting the ground. The script to the program is shown below

Figure 5. Code script for simulating the trajectory of a bouncing ball

In short the program will try to calculate the trajectory and the velocity of the ball. When the ball is bounced back, the velocity is decrease by a constant e. When the ball reach 0 m in height, the program will terminate. The resulting plot is shown below

Bouching ball result.png

Date: 9 March 2021

Last week, we are given an assignment to investigate the parameter used for a gas turbine cycle in Open-Modelica software. My journey started by investigating the main component of the the gas turbine cycle which include the compressor, the combustion turbine, and the combustion chamber. Albeit the initial plan to investigate all of the component, I only able to investigate the input and output parameter of the compressor that are specific for the ThermoSysPro libraries which will be discussed below.

Compressor

Compressor is a device that are responsible to compress air to increase the pressure and temperature of the upstream air up to a certain point depending on the compressor unit specification. Because we idealized the system to be isentropic (adiabatic and reversible), there exist isentropic efficiency (tau) to relate the actual power and the idealized power. In ThermalSysPro system, there are several input that must be considered which are:

1. Inlet and outlet pressure (Pi and Po)

2. Inlet mass flow rate (m_dot)

3. Nominal compression rate

4. Inlet and outlet air temperature (Ti and To)

5. Air composition (XCO2, XO2, XH20, XSO2)

6. Nominal isentropic efficiency

It is worth mention, that the air composition will remain constant through out the process as there are no chemical reaction (combustion) occurring within the compressor. The parameter mention above will be used to calculate the power required for the compressor which have the following governing equation


W_cp = m_dot * (hi - ho)


As we can see from the equation above, we do not know the inlet and outlet specific enthalpy (hi and ho). The inlet specific enthalpy can be calculated by taking the Pi, Ti, and the air composition (XCO2, XO2, XH20, XSO2) using the following governing equation:


h = u * (Pi / rho_i)


in which u is the specific energy and rho_i is the inlet density which can be calculated by taking into account the inlet temperature (Ti) and the air composition which will not be discussed in this today's wiki. Meanwhile, the oulet specific enthalpy can be calculated by using the relation between the specific enthalpy and the isentropic efficiency (tau) by using the following equation:


tau = (his - hi) / (ho - hi)


which can be modified as:


ho = hi + ((his - hi) / tau)


in which his his is the isentropic specific enthalpy that take into account the outlet pressure Po, the isentropic temperature (Tis) and the air composition.

Although there are a lot of things I have been learn about the compressor, I still have a confusion regarding the calculation of the isentropic efficiency for the compressor in the ThermoSysPro libraries.


Date: 10 March 2021

In the last class session, we have a change to practice OpenModelica to simulate and interpret the result combustion chamber simulation. The simulation procedure is similar to those in compressor but the difference lies in the components used.

There are several components that plays an important role in the simulation listed below:

1. The GT(Gas Turbine)CombustionChamber

2. SourcePQ (Pressure and mass flow is fixed) component for the flue gasses

3. Sink component for the flue gasses

4. SourcePQ (Pressure and mass flow is fixed) for the water steam

5. FuelSourcePQ (Pressure and mass flow is fixed) for the fuel

Unlike the compressor where the air composition remain the same as discussed in 9 March 2021 wiki, the component model of combustion chamber involve the chemical reaction between the air composition from the flue gasses source and the fuel source. Thus, the outlet air composition that will be feed to the combustion turbine will differ from the initial value.

The components mention before can be found in the ThermoSysPro libraries which can be drag and drop to the diagram view of the model and connected to each other to closed the equation inside the GT(Gas Turbine)CombustionChamber. It is worth noting, however, that each GT(Gas Turbine)CombustionChamber input correspond to a different source type. There are 3 source type which is the flue gasses, the water steam, and the fuel source as mention in the component list and each of the source type is connected to the corresponding inlet within the combustion chamber as shown in Figure 7 below

Figure 7. The diagram view of the combustion chamber system including the water steam source (Top left), the flue gasses source (centre left), and the fuel source (bottom left)

Because the simulation involve 3 different source, the input of the simulation also differ from those in compressor which are summarized below:

- Flue gases temperature at the outlet of the boiler = 386.16 K

- Flue gases pressure at the outlet of the boiler = 14.1e+5 Pa

- Thermal power losses = 106 W

- Air pressure at the inlet of the combustion chamber = 15e+5 Pa

- Air temperature at the inlet = 680 K

- Air mass flow rate at the inlet = 415 kg/s

- CO2 mass fraction in the air at the inlet = 0

- H2O mass fraction in the air at the inlet = 0.01

- O2 mass fraction in the air at the inlet = 0.23

- SO2 mass fraction in the air at the inlet = 0

- Fuel temperature at the inlet = 410 K

- Fuel mass flow rate at the inlet = 9.3 kg/s

- Lower heating value of the fuel = 47.5e+6 J/kg

- Fuel humidity = 0

- C mass fraction in the fuel = 0.755

- H mass fraction in the fuel = 0.245

- Fuel specific heat capacity = 2255 J/kg/K

- Fuel density = 0.838 kg/m3.

The result of the simulation with the aforementioned input is shown below

Figure 8. The first attempt result of the combustion chamber simulation

It worth noting that the above simulation runs with zero mass flow rate of the water steam to the combustion chamber. Thus, I try to make an experiment out of it to see whether the result will change particularly the air composition, the temperature and the flue gasses mass flow rate. The second attempt result is shown below where I increase the mass flow rate of the water steam to 50 Kg/s

Figure 9. The second attempt result of the combustion chamber simulation

The second attempt result clearly show that the air composition is changing. The mass flow rate of the flue gasses also shows a slight increase from 424 Kg/s to 474 Kg/s. In contrast, the temperature of the flue gasses is decreasing significantly which shows that increasing the water steam mass flow rate will decrease the outlet flue gasses temperature.

There are a lot of things that needs to be learn from the experiment above because I only change only one parameter from one type of the source. Thus, the knowledge of the governing GT combustion chamber equation is needed to find more correlation between each parameter and its output which is still in the process so I can not write it down yet.

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