File Name: gas turbine question and answer .zip
The combustion gas turbines being installed in many of today's natural-gas-fueled power plants are complex machines, but they basically involve three main sections:. Land based gas turbines are of two types: 1 heavy frame engines and 2 aeroderivative engines.
The work produced by a turbine can be used for generating electrical power when combined with a generator. Moving fluid acts on the blades so that they move and impart rotational energy to the rotor. Early turbine examples are windmills and waterwheels.
Gas , steam , and water turbines have a casing around the blades that contains and controls the working fluid. Credit for invention of the steam turbine is given both to Anglo-Irish engineer Sir Charles Parsons — for invention of the reaction turbine, and to Swedish engineer Gustaf de Laval — for invention of the impulse turbine. Modern steam turbines frequently employ both reaction and impulse in the same unit, typically varying the degree of reaction and impulse from the blade root to its periphery.
A working fluid contains potential energy pressure head and kinetic energy velocity head. The fluid may be compressible or incompressible. Several physical principles are employed by turbines to collect this energy:. Impulse turbines change the direction of flow of a high velocity fluid or gas jet.
The resulting impulse spins the turbine and leaves the fluid flow with diminished kinetic energy. There is no pressure change of the fluid or gas in the turbine blades the moving blades , as in the case of a steam or gas turbine, all the pressure drop takes place in the stationary blades the nozzles.
Before reaching the turbine, the fluid's pressure head is changed to velocity head by accelerating the fluid with a nozzle. Pelton wheels and de Laval turbines use this process exclusively. Impulse turbines do not require a pressure casement around the rotor since the fluid jet is created by the nozzle prior to reaching the blades on the rotor.
Newton's second law describes the transfer of energy for impulse turbines. Impulse turbines are most efficient for use in cases where the flow is low and the inlet pressure is high. Reaction turbines develop torque by reacting to the gas or fluid's pressure or mass.
The pressure of the gas or fluid changes as it passes through the turbine rotor blades. The casing contains and directs the working fluid and, for water turbines, maintains the suction imparted by the draft tube. Francis turbines and most steam turbines use this concept. For compressible working fluids, multiple turbine stages are usually used to harness the expanding gas efficiently. Newton's third law describes the transfer of energy for reaction turbines.
Reaction turbines are better suited to higher flow velocities or applications where the fluid head upstream pressure is low. In the case of steam turbines, such as would be used for marine applications or for land-based electricity generation, a Parsons-type reaction turbine would require approximately double the number of blade rows as a de Laval-type impulse turbine, for the same degree of thermal energy conversion.
Whilst this makes the Parsons turbine much longer and heavier, the overall efficiency of a reaction turbine is slightly higher than the equivalent impulse turbine for the same thermal energy conversion. In practice, modern turbine designs use both reaction and impulse concepts to varying degrees whenever possible. Wind turbines use an airfoil to generate a reaction lift from the moving fluid and impart it to the rotor. Wind turbines also gain some energy from the impulse of the wind, by deflecting it at an angle.
Turbines with multiple stages may use either reaction or impulse blading at high pressure. Steam turbines were traditionally more impulse but continue to move towards reaction designs similar to those used in gas turbines. At low pressure the operating fluid medium expands in volume for small reductions in pressure.
Under these conditions, blading becomes strictly a reaction type design with the base of the blade solely impulse. The reason is due to the effect of the rotation speed for each blade. As the volume increases, the blade height increases, and the base of the blade spins at a slower speed relative to the tip.
This change in speed forces a designer to change from impulse at the base, to a high reaction-style tip. Classical turbine design methods were developed in the mid 19th century.
Vector analysis related the fluid flow with turbine shape and rotation. Graphical calculation methods were used at first. Formulae for the basic dimensions of turbine parts are well documented and a highly efficient machine can be reliably designed for any fluid flow condition.
Some of the calculations are empirical or 'rule of thumb' formulae, and others are based on classical mechanics. As with most engineering calculations, simplifying assumptions were made. Velocity triangles can be used to calculate the basic performance of a turbine stage. Gas exits the stationary turbine nozzle guide vanes at absolute velocity V a1. The rotor rotates at velocity U.
Relative to the rotor, the velocity of the gas as it impinges on the rotor entrance is V r1. The gas is turned by the rotor and exits, relative to the rotor, at velocity V r2. However, in absolute terms the rotor exit velocity is V a2. The velocity triangles are constructed using these various velocity vectors.
Velocity triangles can be constructed at any section through the blading for example: hub, tip, midsection and so on but are usually shown at the mean stage radius. Mean performance for the stage can be calculated from the velocity triangles, at this radius, using the Euler equation:. Modern turbine design carries the calculations further. Computational fluid dynamics dispenses with many of the simplifying assumptions used to derive classical formulas and computer software facilitates optimization.
These tools have led to steady improvements in turbine design over the last forty years. The primary numerical classification of a turbine is its specific speed.
This number describes the speed of the turbine at its maximum efficiency with respect to the power and flow rate. The specific speed is derived to be independent of turbine size.
Given the fluid flow conditions and the desired shaft output speed, the specific speed can be calculated and an appropriate turbine design selected. The specific speed, along with some fundamental formulas can be used to reliably scale an existing design of known performance to a new size with corresponding performance. Off-design performance is normally displayed as a turbine map or characteristic.
The number of blades in the rotor and the number of vanes in the stator are often two different prime numbers in order to reduce the harmonics and maximize the blade-passing frequency. A large proportion of the world's electrical power is generated by turbo generators. Turbines are used in gas turbine engines on land, sea and air.
Turbochargers are used on piston engines. Gas turbines have very high power densities i. The Space Shuttle main engines used turbopumps machines consisting of a pump driven by a turbine engine to feed the propellants liquid oxygen and liquid hydrogen into the engine's combustion chamber. Turboexpanders are used for refrigeration in industrial processes. From Wikipedia, the free encyclopedia. Rotary mechanical device that extracts energy from a fluid flow.
For other uses, see Turbine disambiguation. This section relies largely or entirely on a single source. Relevant discussion may be found on the talk page. Please help improve this article by introducing citations to additional sources. Balancing machine Euler's pump and turbine equation Helmholtz's theorems Rotordynamics Rotor—stator interaction Secondary flow Segner wheel Turbo-alternator Turbodrill Turbofan Turbojet Turboprop Turboshaft Turbine-electric transmission.
Online Etymology Dictionary. Okiishi, and Wade W. Hoboken, NJ: J. See: Annales de chimie et de physique , vol. Burdin titled: Hydraulic turbines or high-speed rotary machines , Annales de chimie et de physique , vol.
ASME-sponsored booklet to mark the designation of Turbinia as an international engineering landmark. Archived from the original PDF on 28 September Retrieved 13 April Categories : Turbines Jet engines Power engineering Gas technologies. Namespaces Article Talk. Views Read Edit View history.
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Covering basic theory, components, installation, maintenance, manufacturing, regulation and industry developments, Gas Turbines: A Handbook of Air, Sea and Land Applications is a broad-based introductory reference designed to give you the knowledge needed to succeed in the gas turbine industry, land, sea and air applications. Providing the big picture view that other detailed, data-focused resources lack, this book has a strong focus on the information needed to effectively decision-make and plan gas turbine system use for particular applications, taking into consideration not only operational requirements but long-term life-cycle costs in upkeep, repair and future use. With concise, easily digestible overviews of all important theoretical bases and a practical focus throughout, Gas Turbines is an ideal handbook for those new to the field or in the early stages of their career, as well as more experienced engineers looking for a reliable, one-stop reference that covers the breadth of the field. Engineers involved with gas turbines in contexts including aerospace engineering, marine engineering and energy systems; especially recent graduates and those new to the field. Manufacturers, maintenance and reliability professionals involved with the production, upkeep and repair of gas turbine engines.
The work produced by a turbine can be used for generating electrical power when combined with a generator. Moving fluid acts on the blades so that they move and impart rotational energy to the rotor.
Solved examples with detailed answer description, explanation are given and it would be easy to understand. Here you can find objective type Mechanical Engineering Compressors, Gas Dynamics and Gas Turbines questions and answers for interview and entrance examination. Multiple choice and true or false type questions are also provided.
Study the top Gas Turbine Interview Questions and Answers useful to review the basics and prepare for common technical questions on Gas Turbine. It is a thermic machine running according to the admission-compression-combustion-exhaust 4 step cycle. All combustion chambers are interconnected by means of crossfire tube. This tube enables flame from the fired chambers to propagate to the unfired chambers. After the turbine rotor approximates operating speed, combustion chamber pressure causes the spark plugs to retract to remove their electrodes from the hot flame zone.
Wind turbines c. The result is a system tainted with uncertainty that is constraining the policy space of countries and consequently hindering sustainable development. Non-renewable resources cannot be regenerated in a reasonable enough time frame and have a limited quantity as a result. Most of these renewable energies depend in one way or another on sunlight. It wakes us up in the morning, lights up our homes, cooks our food, powers our computers, tv sets and other appliances. Each time you take the quiz, ten questions are drawn from our database on renewable energy - so you get a different revision quiz each time to help test your knowledge and understanding of renewable energy. Energy Transfer.
What is Gas turbine? It is a thermic machine running according to the admission-compression-combustion-exhaust 4 step cycle.
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