Skip to main content

SINGLE AND TWO SHAFT GAS TURBINES

There are basically two gas turbine driving methods, known as ‘single-shaft’ and ‘two (or twin) shaft’ drives. In a single-shaft gas turbine, all the rotating elements share a common shaft. The common elements are the air compressor, the compressor turbine and the power turbine. The power turbine drives the generator.

In some gas turbines, the compressor turbine and the power turbine are an integral component. This tends to be the case with heavy-duty machines.

The basic arrangement is shown in Figure 2.3.





In a two-shaft gas turbine the compressor is driven by a high pressure turbine called the compressor turbine, and the generator is driven separately by a low pressure turbine called the power turbine

The basic arrangement is shown in Figure 2.4.

Two-shaft systems are generally those which use aero-derivative engines as ‘gas generators’, i.e. they produce hot, high velocity, high pressure gas which is directed into the power turbine. Some light industrial gas turbines have been designed for either type of drive. This is achieved by fitting a removable coupling shaft between the two turbines. Some points to consider with regard to the two types of driver are:-

a) High speed of rotation tends to improve the compressor and turbine efficiency. Hence, with two separate shafts, the best thermodynamic performance from both turbines and the compressor is obtainable.

b) Using aero-derivative machines means that a simple ‘add on’ power turbine can be fitted in the exhaust streams of the aero engine. This enables many manufacturers to design a simple power turbine and to use a particular aero engine.

c) Two-shaft machines are often criticized as electrical generators because of their slower response to power demands in comparison with the single-shaft machines. This can be a problem when a two-shaft machine may have to operate in synchronism with other single-shaft machines or steam turbine generators. Sometimes the slower response may affect the power system performance during the starting period of large motors. A power system computerized stability study should be carried out to investigate these types of problem.

Some of the recent aero engines could be called ‘three-shaft’ arrangements because within the gas generator there are two compressor turbines and two compressors.

Comments

D'Killest_Striker said…
Hye Engineer, thank you a lot. Very appreciate.
Thursday, 02 March, 2017
Post a Comment

Popular posts from this blog

Advantages of Per Unit System in Power System Analysis | Electrical Engineering

  Advantages of Per Unit System in Power System Analysis In electrical power engineering, the per unit (p.u.) system is one of the most widely used techniques for analyzing and modeling power systems. It is a method of expressing electrical quantities — such as voltage, current, power, and impedance — as fractions of chosen base values rather than their actual numerical magnitudes. This normalization technique provides a universal language for system calculations, minimizing errors, simplifying transformer modeling, and enabling consistency across multiple voltage levels. Because of these benefits, the per unit system is essential in fault analysis, load flow studies, transformer testing, and short-circuit calculations . ⚡ What is the Per Unit System? The per unit system is defined as: Q u a n t i t y ( p u ) = A c t u a l   V a l u e B a s e   V a l u e Quantity_{(pu)} = \dfrac{Actual \ Value}{Base \ Value} Q u an t i t y ( p u ) ​ = B a se   ...
6 comments
Read more

BREAKDOWN VOLTAGE AND DIELECTRIC STRENGTH

An insulator or dielectric is a substance within which there are no mobile electrons necessary for electric conduction. However, when the voltage applied to such an insulator exceeds a certain value, then it breaks down and allows a heavy electric current (much larger than the usual leakage current) to flow through it. If the insulator is a solid medium, it gets punctured or cracked. The disruptive or breakdown voltage of an insulator is the minimum voltage required to break it down. Dielectric strength of an insulator or dielectric medium is given by the maximum potential difference which a unit thickness of the medium can withstand without breaking down. In other words, the dielectric strength is given by the potential gradient necessary to cause breakdown of an insulator. Its unit is volt/meter (V/m) although it is usually expressed in KV/mm. For example, when we say that the dielectric strength of air is 3 KV/mm, then it means that the maximum PD which one mm thickness of ...
Read more

TYPES OF SINGLE PHASE MOTORS

Single phase motors are manufactured in fractional kilowatt range to be operated on single phase supply and for use in numerous applications like ceiling fans, refrigerators, food mixers, hair driers, portable drills, vacuum cleaners, washing machines, sewing machines, electric shavers, office machinery etc. Single phase motors are manufactured in different types to meet the requirements of various applications. Single phase motors are classified on the basis of their construction and starting methods employed. The main types of single phase motors are: (a) Induction motors (b) Synchronous motors (c) Commutator motors The various types of motors under each class are shown as under: Repulsion, repulsion induction and reluctance start motors are not used these days, they have been largely replaced by split phase motors with special capacitors which can be designed to perform equally well as repulsion types. In addition they offer such advantages as lower cost and trouble fr...
Post a Comment
Read more

PRINCIPLE OF OPERATION OF UNIFIED POWER FLOW CONTROLLER UPFC

UPFC consist of two back to back converters named VSC1 and VSC2, are operated from a DC link provided by a dc storage capacitor. These arrangements operate as an ideal ac to ac converter in which the real power can freely flow either in direction between the ac terminals of the two converts and each converter can independently generate or absorb reactive power as its own ac output terminal. Figure: Basic UPFC scheme One VSC is connected to in shunt to the transmission line via a shunt transformer and other one is connected in series through a series transformer. The DC terminal of two VSCs is coupled and this creates a path for active power exchange between the converters. VSC provide the main function of UPFC by injecting a voltage with controllable magnitude and phase angle in series with the line via an injection transformer. This injected voltage act as a synchronous ac voltage source. The transmission line current flows through this voltage source resulting in reactive an...
5 comments
Read more

AC Transmission Line and Reactive Power Compensation: A Detailed Overview

  Introduction The efficient operation of modern power systems depends significantly on the management of AC transmission lines and reactive power. Reactive power compensation is a vital technique for maintaining voltage stability, improving power transfer capability, and reducing system losses. This article explores the principles of AC transmission lines, the need for reactive power compensation, and its benefits in power systems. Keywords: Reactive Power Compensation Benefits, STATCOM vs SVC Efficiency, Power Transmission Stability Solutions, Voltage Stability in Long-Distance Grids, Dynamic Reactive Power Compensation.      Fundamentals of AC Transmission Lines AC transmission lines are the backbone of modern power systems, connecting generation stations to distribution networks. They have distributed electrical parameters such as resistance ( R R R ), inductance ( L L ), capacitance ( C C ), and conductance ( G G ) along their length. These parameters influence ...
Post a Comment
Read more

TYPES OF DATA FLOW IN COMMUNICATION SYSTEM

Communication between two devices can be simplex, half-duplex, or full-duplex. SIMPLEX : In simplex mode, the communication is unidirectional, as on a one-way street. Only one of the two devices on a link can transmit; the other can only receive. Keyboards and traditional monitors are examples of simplex devices. The keyboard can only introduce input; the monitor can only accept output. The simplex mode can use the entire capacity of the channel to send data in one direction. HALF-DUPLEX : In half-duplex mode, each station can both transmit and receive, but not at the same time. When one device is sending, the other can only receive, and vice versa The half-duplex mode is like a one-lane road with traffic allowed in both directions. When cars are traveling in one direction, cars going the other way must wait. In a half-duplex transmission, the entire capacity of a channel is taken over by whichever of the two devices is transmitting at the time. Walkie-talkies and CB (...
Post a Comment
Read more

THE HISTORY OF PHOTOVOLTAIC TECHNOLOGY

The first solar cell was created in 1883. It was inefficient by today’s standards, converting only 1–2% of sunlight into electricity. The breakthrough in solar cell technology came in 1954 when researchers at Bell Laboratories stumbled across the photo voltaic (or PV) properties of silicon while experimenting with new transistor technologies. Three years later, PV research began in earnest to develop an independent solar energy source for space technologies. Thanks to continuing research, modern commercial PV cells have improved to 11–15% efficiency. Historically, PV has been used extensively in areas that are not served by a power grid. As PV prices have dropped, and grid energy has become more expensive, PV systems are increasingly used in grid-tied applications. A solar electric or PV cell uses a semiconductor material similar to that used in computer chips to absorb sunlight and convert it into electricity. Multiple solar cells are linked together to form a module or panel. Multipl...
Post a Comment
Read more