Turbin gas

Turbin gas itu adalah sebuah mesin berputar yang mengambil energi dari arus gas pembakaran. Dia memiliki kompresor naik ke-atas dipasangkan dengan turbin turun ke-bawah, dan sebuah bilik pembakaran di-tengahnya.
Energi ditambahkan di arus gas di pembakar, di mana udara dicampur dengan bahan bakar dan dinyalakan. Pembakaran meningkatkan suhu, kecepatan dan volume dari aliran gas. Kemudian diarahkan melalui sebuah penyebar (nozzle) melalui baling-baling turbin, memutar turbin dan mentenagai kompresor.
Energi diambil dari bentuk tenaga shaft, udara terkompresi dan dorongan, dalam segala kombinasi, dan digunakan untuk mentenagai pesawat terbang, kereta, kapal, generator, dan bahkan tank.

Pendahuluan

Gas-turbine engine adalah suatu alat yang memanfaatkan gas sebagai fluida untuk memutar turbin dengan pembakaran internal. Di dalam turbin gas energi kinetik dikonversikan menjadi energi mekanik melalui udara bertekanan yang memutar roda turbin sehingga menghasilkan daya. Sistem turbin gas yang paling sederhana terdiri dari tiga komponen yaitu kompresor, ruang bakar dan turbin gas.

Turbin Gas Poros Tunggal (Single Shaft)

Turbin jenis ini digunakan untuk menggerakkan generator listrik yang menghasilkan energi listrik untuk keperluan proses di industri.

Turbin Gas Poros Ganda (Double Shaft)

Turbin jenis ini merupakan turbin gas yang terdiri dari turbin bertekanan tinggi dan turbin bertekanan rendah, di mana turbin gas ini digunakan untuk menggerakkan beban yang berubah seperti kompresor pada unit proses.

Siklus-Siklus Turbin Gas

Tiga siklus turbin gas yang dikenal secara umum yaitu:

Siklus Ericson

Merupakan siklus mesin kalor yang dapat balik (reversible) yang terdiri dari dua proses isotermis dapat balik (reversible isotermic) dan dua proses isobarik dapat balik (reversible isobaric). Proses perpindahan panas pada proses isobarik berlangsung di dalam komponen siklus internal (regenerator), di mana effisiensi termalnya adalah: hth = 1 – T1/Th, di mana T1 = temperatur buang dan Th = temperatur panas.

Siklus Stirling

Merupakan siklus mesin kalor dapat balik, yang terdiri dari dua proses isotermis dapat balik (isotermal reversible) dengan volume tetap (isokhorik). Efisiensi termalnya sama dengan efisiensi termal pada siklus Ericson.

Siklus Brayton

Siklus ini merupakan siklus daya termodinamika ideal untuk turbin gas, sehingga saat ini siklus ini yang sangat populer digunakan oleh pembuat mesin turbine atau manufacturer dalam analisis untuk performance upgrading. Siklus Brayton ini terdiri dari proses kompresi isentropik yang diakhiri dengan proses pelepasan panas pada tekanan konstan. Pada siklus Bryton tiap-tiap keadaan proses dapat dianalisis secara berikut:
Proses 1 ke 2 (kompresi isentropik). Kerja yang dibutuhkan oleh kompresor: Wc = ma (h2 – h1). Proses 2 ke 3, pemasukan bahan bakar pada tekanan konstan. Jumlah kalor yang dihasilkan: Qa = (ma + mf) (h3 – h2). Proses 3 ke 4, ekspansi isentropik di dalam turbin. Daya yang dibutuhkan turbin: WT = (ma + mf) (h3 – h4). Proses 4 ke 1, pembuangan panas pada tekanan konstan ke udara. Jumlah kalor yang dilepas: QR = (ma + mf) (h4 – h1)

Perkembangan Gas Turbin

Disain pertama turbin gas dibuat oleh John Wilkins seorang Inggris pada tahun 1791. Sistem tersebut bekerja dengan gas hasil pembakaran batu bara, kayu atau minyak, kompresornya digerakkan oleh turbin dengan perantaraan rantai roda gigi. Pada tahun 1872, Dr. F. Stolze merancang sistem turbin gas yang menggunakan kompresor aksial bertingkat ganda yang digerakkan langsung oleh turbin reaksi tingkat ganda. Tahun 1908, sesuai dengan konsepsi H. Holzworth, dibuat suatu sistem turbin gas yang mencoba menggunakan proses pembakaran pada volume konstan. Tetapi usaha tersebut dihentikan karena terbentur pada masalah konstruksi ruang bakar dan tekanan gas pembakaran yang berubah sesuai beban. Tahun 1904, “Societe des Turbomoteurs” di Paris membuat suatu sistem turbin gas yang konstruksinya berdasarkan disain Armengaud dan Lemate yang menggunakan bahan bakar cair. Temperatur gas pembakaran yang masuk sekitar 450 C dengan tekanan 45 atm dan kompresornya langsung digerakkan oleh turbin.
Selanjutnya, pada tahun 1935 sistem turbin gas mengalami perkembangan yang pesat di mana diperoleh efisiensi sebesar kurang lebih 15%. Pesawat pancar gas yang pertama diselesaikan oleh “British Thomson Houston Co” pada tahun 1937 sesuai dengan konsepsi Frank Whittle (tahun 1930).

Komponen Turbin Gas

Turbin gas tersusun atas komponen-komponen utama seperti air inlet section, compressor section, combustion section, turbine section, dan exhaust section. Sedangkan komponen pendukung turbin gas adalah starting equipment, lube-oil system, cooling system, dan beberapa komponen pendukung lainnya. Berikut ini penjelasan tentang komponen utama turbn gas:

Exhaust Section.

Exhaust section adalah bagian akhir turbin gas yang berfungsi sebagai saluran pembuangan gas panas sisa yang keluar dari turbin gas. Exhaust section terdiri dari beberapa bagian yaitu: (1) Exhaust Frame Assembly, dan (2)Exhaust gas keluar dari turbin gas melalui exhaust diffuser pada exhaust frame assembly, lalu mengalir ke exhaust plenum dan kemudian didifusikan dan dibuang ke atmosfer melalui exhaust stack, sebelum dibuang ke atmosfer gas panas sisa tersebut diukur dengan exhaust thermocouple di mana hasil pengukuran ini digunakan juga untuk data pengontrolan temperatur dan proteksi temperatur trip. Pada exhaust area terdapat 18 buah termokopel yaitu, 12 buah untuk temperatur kontrol dan 6 buah untuk temperatur trip.

Komponen penunjang turbin gas

Adapun beberapa komponen penunjang dalam sistem turbin gas adalah sebagai berikut:

Fuel System.

Bahan bakar yang digunakan berasal dari fuel gas system dengan tekanan sekitar 15 kg/cm2. Fuel gas yang digunakan sebagai bahan bakar harus bebas dari cairan kondensat dan partikel-partikel padat. Untuk mendapatkan kondisi tersebut diatas maka sistem ini dilengkapi dengan knock out drum yang berfungsi untuk memisahkan cairan-cairan yang masih terdapat pada fuel gas.

Maintenance Turbin Gas

Maintenance adalah perawatan untuk mencegah hal-hal yang tidak diinginkan seperti kerusakan terlalu cepat terhadap semua peralatan di pabrik, baik yang sedang beroperasi maupun yang berfungsi sebagai suku cadang. Kerusakan yang timbul biasanya terjadi karena keausan dan ketuaan akibat pengoperasian yang terus-menerus, dan juga akibat langkah pengoperasian yang salah.
Maintenance pada turbine gas selalu tergantung dari faktor-faktor perasional dengan kondisi yang berbeda disetiap wilayah, karena operasional turbine gas sangat tergantung dari kondisi daerah operasional. Semua pabrik pembuat turbine gas telah menetapkan suatu ketetapan yang aman dalam pengoperasian sehingga turbine selalu dalambatas kondisi aman dan tepat waktu untuk melakukan maintenance.
Secara umum maintenance dapat dibagi dalam beberapa bagian, diantaranya adalah:

Repair Maintenance.

Perawatan yang dilakukan terhadap peralatan yang tidak kritis, atau disebut juga peralatan-peralatan yang tidak mengganggu jalannya operasi.

Predictive Maintenance.

Kegiatan monitor, menguji, dan mengukur peralatan-peralatan yang beroperasi dengan menentukan perubahan yang terjadi pada bagian utama, apakah peralatan tersebut berjalan dengan normal atau tidak.

Corrective Maintenance.

Perawatan yang dilakukan dengan memperbaiki perubahan kecil yang terjadi dalam disain, serta menambahkan komponen-komponen yang sesuai dan juga menambahkan material-material yang cocok.

Break Down Maintenance.

Kegiatan perawatan yang dilakukan setelah terjadi kerusakan atau kelainan pada peralatan sehingga tidak dapat berfungsi seperti biasanya.

Modification Maintenance.

Pekerjaan yang berhubungan dengan disain suatu peralatan atau unit. Modifikasi bertujuan menambah kehandalan peralatan atau menambah tingkat produksi dan kualitas pekerjaan.

Shut Down Maintenance.

Kegiatan perawatan yang dilakukan terhadap peralatan yang sengaja dihentikan pengoperasiannya.
       *****Engineering*****
Engineering is the discipline, art, skill and profession of acquiring and applying scientific, mathematical, economic, social, and practical knowledge, in order to design and build structures, machines, devices, systems, materials and processes.
The American Engineers' Council for Professional Development (ECPD, the predecessor of ABET)[1] has defined "engineering" as:
the creative application of scientific principles to design or develop structures, machines, apparatus, or manufacturing processes, or works utilizing them singly or in combination; or to construct or operate the same with full cognizance of their design; or to forecast their behavior under specific operating conditions; all as respects an intended function, economics of operation and safety to life and property.[2][3]
One who practices engineering is called an engineer, and those licensed to do so may have more formal designations such as Professional Engineer, Chartered Engineer, Incorporated Engineer, Ingenieur or European Engineer. The broad discipline of engineering encompasses a range of more specialized sub disciplines, each with a more specific emphasis on certain fields of application and particular areas of technology.
Contents [hide]
1 History
1.1 Ancient era
1.2 Renaissance era
1.3 Modern era
2 Main branches of engineering
3 Methodology
3.1 Problem solving
3.2 Computer use
4 Social context
5 Relationships with other disciplines
5.1 Science
5.2 Medicine and biology
5.3 Art
5.4 Other fields
6 See also
7 References
8 Further reading
9 Pranala luar
[edit]History
Engineering has existed since ancient times as humans devised fundamental inventions such as the pulley, lever, and wheel. Each of these inventions is consistent with the modern definition of engineering, exploiting basic mechanical principles to develop useful tools and objects.
The term engineering itself has a much more recent etymology, deriving from the word engineer, which itself dates back to 1325, when an engine’er (literally, one who operates an engine) originally referred to “a constructor of military engines.”[4] In this context, now obsolete, an “engine” referred to a military machine, i.e., a mechanical contraption used in war (for example, a catapult). Notable exceptions of the obsolete usage which have survived to the present day are military engineering corps, e.g., the U.S. Army Corps of Engineers.
The word “engine” itself is of even older origin, ultimately deriving from the Latin ingenium (c. 1250), meaning “innate quality, especially mental power, hence a clever invention.”[5]
Later, as the design of civilian structures such as bridges and buildings matured as a technical discipline, the term civil engineering[3] entered the lexicon as a way to distinguish between those specializing in the construction of such non-military projects and those involved in the older discipline of military engineering.
[edit]Ancient era
The Pharos of Alexandria, the pyramids in Egypt, the Hanging Gardens of Babylon, the Acropolis and the Parthenon in Greece, the Roman aqueducts, Via Appia and the Colosseum, Teotihuacán and the cities and pyramids of the Mayan, Inca and Aztec Empires, the Great Wall of China, among many others, stand as a testament to the ingenuity and skill of the ancient civil and military engineers.
The earliest civil engineer known by name is Imhotep.[3] As one of the officials of the Pharaoh, Djosèr, he probably designed and supervised the construction of the Pyramid of Djoser (the Step Pyramid) at Saqqara in Egypt around 2630-2611 BC.[6] He may also have been responsible for the first known use of columns in architecture[citation needed].
Ancient Greece developed machines in both the civilian and military domains. The Antikythera mechanism, the first known mechanical computer,[7][8] and the mechanical inventions of Archimedes are examples of early mechanical engineering. Some of Archimedes' inventions as well as the Antikythera mechanism required sophisticated knowledge of differential gearing or epicyclic gearing, two key principles in machine theory that helped design the gear trains of the Industrial revolution, and are still widely used today in diverse fields such as robotics and automotive engineering.[9]
Chinese, Greek and Roman armies employed complex military machines and inventions such as artillery which was developed by the Greeks around the 4th century B.C.,[10] the trireme, the ballista and the catapult. In the Middle Ages, the Trebuchet was developed.
[edit]Renaissance era
The first electrical engineer is considered to be William Gilbert, with his 1600 publication of De Magnete, who was the originator of the term "electricity".[11]
The first steam engine was built in 1698 by mechanical engineer Thomas Savery.[12] The development of this device gave rise to the industrial revolution in the coming decades, allowing for the beginnings of mass production.
With the rise of engineering as a profession in the eighteenth century, the term became more narrowly applied to fields in which mathematics and science were applied to these ends. Similarly, in addition to military and civil engineering the fields then known as the mechanic arts became incorporated into engineering.
[edit]Modern era
The International Space Station represents a modern engineering challenge from many disciplines.
Electrical engineering can trace its origins in the experiments of Alessandro Volta in the 1800s, the experiments of Michael Faraday, Georg Ohm and others and the invention of the electric motor in 1872. The work of James Maxwell and Heinrich Hertz in the late 19th century gave rise to the field of Electronics. The later inventions of the vacuum tube and the transistor further accelerated the development of electronics to such an extent that electrical and electronics engineers currently outnumber their colleagues of any other Engineering specialty.[3]
The inventions of Thomas Savery and the Scottish engineer James Watt gave rise to modern Mechanical Engineering. The development of specialized machines and their maintenance tools during the industrial revolution led to the rapid growth of Mechanical Engineering both in its birthplace Britain and abroad.[3]
Chemical Engineering, like its counterpart Mechanical Engineering, developed in the nineteenth century during the Industrial Revolution.[3] Industrial scale manufacturing demanded new materials and new processes and by 1880 the need for large scale production of chemicals was such that a new industry was created, dedicated to the development and large scale manufacturing of chemicals in new industrial plants.[3] The role of the chemical engineer was the design of these chemical plants and processes.[3]
Aeronautical Engineering deals with aircraft design while Aerospace Engineering is a more modern term that expands the reach envelope of the discipline by including spacecraft design.[13] Its origins can be traced back to the aviation pioneers around the turn of the century from the 19th century to the 20th although the work of Sir George Cayley has recently been dated as being from the last decade of the 18th century. Early knowledge of aeronautical engineering was largely empirical with some concepts and skills imported from other branches of engineering.[14]
The first PhD in engineering (technically, applied science and engineering) awarded in the United States went to Willard Gibbs at Yale University in 1863; it was also the second PhD awarded in science in the U.S.[15]
Only a decade after the successful flights by the Wright brothers, there was extensive development of aeronautical engineering through development of military aircraft that were used in World War I . Meanwhile, research to provide fundamental background science continued by combining theoretical physics with experiments.
In 1990, with the rise of computer technology, the first search engine was built by computer engineer Alan Emtage.
[edit]Main branches of engineering
Main article: List of engineering branches
Engineering, much like other science, is a broad discipline which is often broken down into several sub-disciplines. These disciplines concern themselves with differing areas of engineering work. Although initially an engineer will usually be trained in a specific discipline, throughout an engineer's career the engineer may become multi-disciplined, having worked in several of the outlined areas. Engineering is often characterized as having four main branches:[16][17]
Chemical engineering – The exploitation of both engineering and chemical principles in order to carry out large scale chemical process.
Civil engineering – The design and construction of public and private works, such as infrastructure (airports, roads, railways, water supply and treatment etc.), bridges, dams, and buildings.
Electrical engineering – a very broad area that may encompass the design and study of various electrical and electronic systems, such as electrical circuits, generators, motors, electromagnetic/electromechanical devices, electronic devices, electronic circuits, optical fibers, optoelectronic devices, computer systems, telecommunications, instrumentation, controls, and electronics.
Mechanical engineering – The design of physical or mechanical systems, such as power and energy systems, aerospace/aircraft products, weapon systems, transportation products engines, compressors, powertrains, kinematic chains, vacuum technology, and vibration isolation equipment.
Beyond these four, sources vary on other main branches. Historically, naval engineering and mining engineering were major branches. Modern fields sometimes included as major branches include aerospace, systems,architectural, biomedical,[18] industrial, materials science[19] and nuclear engineering.[20][citation needed]
New specialties sometimes combine with the traditional fields and form new branches. A new or emerging area of application will commonly be defined temporarily as a permutation or subset of existing disciplines; there is often gray area as to when a given sub-field becomes large and/or prominent enough to warrant classification as a new "branch." One key indicator of such emergence is when major universities start establishing departments and programs in the new field.
For each of these fields there exists considerable overlap, especially in the areas of the application of sciences to their disciplines such as physics, chemistry and mathematics.
[edit]Methodology
Design of a turbine requires collaboration of engineers from many fields, as the system is subject to mechanical, electro-magnetic and chemical processes. The blades, rotor and stator as well as the steam cycle all need to be carefully designed and optimized.
Engineers apply the sciences of physics and mathematics to find suitable solutions to problems or to make improvements to the status quo. More than ever, engineers are now required to have knowledge of relevant sciences for their design projects, as a result, they keep on learning new material throughout their career.
If multiple options exist, engineers weigh different design choices on their merits and choose the solution that best matches the requirements. The crucial and unique task of the engineer is to identify, understand, and interpret the constraints on a design in order to produce a successful result. It is usually not enough to build a technically successful product; it must also meet further requirements.
Constraints may include available resources, physical, imaginative or technical limitations, flexibility for future modifications and additions, and other factors, such as requirements for cost, safety, marketability, productibility, and serviceability. By understanding the constraints, engineers derive specifications for the limits within which a viable object or system may be produced and operated.
[edit]Problem solving
Engineers use their knowledge of science, mathematics, logic, economics, and appropriate experience or tacit knowledge to find suitable solutions to a problem. Creating an appropriate mathematical model of a problem allows them to analyze it (sometimes definitively), and to test potential solutions.
Usually multiple reasonable solutions exist, so engineers must evaluate the different design choices on their merits and choose the solution that best meets their requirements. Genrich Altshuller, after gathering statistics on a large number of patents, suggested that compromises are at the heart of "low-level" engineering designs, while at a higher level the best design is one which eliminates the core contradiction causing the problem.
Engineers typically attempt to predict how well their designs will perform to their specifications prior to full-scale production. They use, among other things: prototypes, scale models, simulations, destructive tests, nondestructive tests, and stress tests. Testing ensures that products will perform as expected.
Engineers take on the responsibility of producing designs that will perform as well as expected and will not cause unintended harm to the public at large. Engineers typically include a factor of safety in their designs to reduce the risk of unexpected failure. However, the greater the safety factor, the less efficient the design may be.
The study of failed products is known as forensic engineering, and can help the product designer in evaluating his or her design in the light of real conditions. The discipline is of greatest value after disasters, such as bridge collapses, when careful analysis is needed to establish the cause or causes of the failure.
[edit]Computer use
A computer simulation of high velocity air flow around the Space Shuttle during re-entry. Solutions to the flow require modelling of the combined effects of the fluid flow and heat equations.
As with all modern scientific and technological endeavors, computers and software play an increasingly important role. As well as the typical business application software there are a number of computer aided applications (Computer-aided technologies) specifically for engineering. Computers can be used to generate models of fundamental physical processes, which can be solved using numerical methods.
One of the most widely used tools in the profession is computer-aided design (CAD) software which enables engineers to create 3D models, 2D drawings, and schematics of their designs. CAD together with Digital mockup (DMU) and CAE software such as finite element method analysis or analytic element method allows engineers to create models of designs that can be analyzed without having to make expensive and time-consuming physical prototypes.
These allow products and components to be checked for flaws; assess fit and assembly; study ergonomics; and to analyze static and dynamic characteristics of systems such as stresses, temperatures, electromagnetic emissions, electrical currents and voltages, digital logic levels, fluid flows, and kinematics. Access and distribution of all this information is generally organized with the use of Product Data Management software.[21]
There are also many tools to support specific engineering tasks such as Computer-aided manufacture (CAM) software to generate CNC machining instructions; Manufacturing Process Management software for production engineering; EDA for printed circuit board (PCB) and circuit schematics for electronic engineers; MRO applications for maintenance management; and AEC software for civil engineering.
In recent years the use of computer software to aid the development of goods has collectively come to be known as Product Lifecycle Management (PLM).[22]
[edit]Social context
This section may contain original research. Please improve it by verifying the claims made and adding references. Statements consisting only of original research may be removed. More details may be available on the talk page. (July 2010)
Engineering is a subject that ranges from large collaborations to small individual projects. Almost all engineering projects are beholden to some sort of financing agency: a company, a set of investors, or a government. The few types of engineering that are minimally constrained by such issues are pro bono engineering and open design engineering.
By its very nature engineering is bound up with society and human behavior. Every product or construction used by modern society will have been influenced by engineering design. Engineering design is a very powerful tool to make changes to environment, society and economies, and its application brings with it a great responsibility. Many engineering societies have established codes of practice and codes of ethics to guide members and inform the public at large.
Engineering projects can be subject to controversy. Examples from different engineering disciplines include the development of nuclear weapons, the Three Gorges Dam, the design and use of Sport utility vehicles and the extraction of oil. In response, some western engineering companies have enacted serious corporate and social responsibility policies.
Engineering is a key driver of human development.[23] Sub-Saharan Africa in particular has a very small engineering capacity which results in many African nations being unable to develop crucial infrastructure without outside aid. The attainment of many of the Millennium Development Goals requires the achievement of sufficient engineering capacity to develop infrastructure and sustainable technological development.[24]
All overseas development and relief NGOs make considerable use of engineers to apply solutions in disaster and development scenarios. A number of charitable organizations aim to use engineering directly for the good of mankind:
Engineers Without Borders
Engineers Against Poverty
Registered Engineers for Disaster Relief
Engineers for a Sustainable World
Engineering for Change