TURBINES

A turbine is an energy converter. It is a term used to describe a device or machine that extracts energy from a flowing fluid medium and converts it to rotating energy of a turbine rotor to generate power.

Turbines can be categorized according to the following features; the working medium (i.e. water turbine, steam turbine, gas turbine, wind turbine etc.), the principle of operation (i.e. action turbine, impulse turbine, free jet turbine, cross flow turbines etc.), the direction of flow of the fluid (i.e. axial turbine, radial turbine, diagonal turbine etc.), the external design (i.e. according to the shaft position or the type of water supply i.e.  vertical shaft turbine, spiral turbine, tube turbine etc.), the operating modes (i.e.as turbine only or as reverse turbine as a pump), the control principle (i.e. single regulated via the distributor only or  double regulated via the distributor and rotor settings).

However the most common types of turbines are; impulse, reaction, axial flow, radial flow, mixed flow, tidal, wind, hydro, gas and steam turbines.

Impulse turbines use the impulse of the fluid to generate power. The impulse turbine is driven by a high velocity jet or multiple jets of water.

Reaction turbines use the reaction of the fluid to generate power. The rotor of the reaction turbine is fully immersed in the fluid and is enclosed in a pressure casing.

Axial turbines use axial flow of the fluid to generate power.

Radial flow turbines use the radial flow of the fluid to generate power.

Mixed flow turbines use a combination of axial and radial flow of the fluid to generate power.

Tidal turbines use the kinetic energy of ocean tides to generate power.

Wind turbines use the kinetic energy of the wind to generate power.

Hydro turbines use the kinetic energy of running water to generate power.

Gas turbines are a combustion engine that converts natural gas or other fuels to generate power by the thermal expansion action of these gases or fluid to generate power.

Steam turbine is a mechanical device that converts thermal energy in pressurized steam to generate power.

The main components of the turbine consist of the following; rotor, stator, blades, nozzles, and diffuser.

The rotor is the rotating part of the turbine. It consists of a shaft and a series of blades or vanes attached to the shaft.

The stator is the stationary part of the turbine. It consists of a casing or housing that surrounds the rotor and a series of blades or vanes that are attached to the casing.

The blades are attached to the rotor and are responsible for extracting energy from the working fluid.

The nozzle is a narrow, tapered passage that slows down the fluid after it leaves the turbine.

The working principle of the turbine is based on the conversion of the energy of the fluid into rotational motion or energy. The fluid is accelerated through a nozzle which increases the velocity and reduces the pressure. The fluid then enters the turbine where it transfers its energy to the rotor. The rotor is connected to the shaft which is connected to a generator or other machinery. As the rotor spins, it drives the shaft which generates power.

The advantages of turbines are that they have or can achieve higher efficiencies compared to other types of power generation. Turbines are reliable and can operate for a long period of time with little or no maintenance. Turbines are scalable, compact with a high power to weight ratio and have lower emission and flexibility over other types of power generation.

On the other hand their main disadvantages is their high upfront cost as well a long project delivery time especially with higher capacity power plants compared to other types of power generation.

Turbines generally require specialized maintenance and are noisy especially at higher operating speeds and the often require additional equipment to regulate the power output, due to their intermittent operational nature. Their operation has disastrous consequence to the environment in terms of noise, environmental pollution and land issues like flooding as regards hydroelectric power plants.

The application of turbines is diverse and finds use across many industries; turbines are used to generate power in wind farms, tidal, steam and hydroelectric power plants. Turbines are preferred and used to propel aircrafts as jet engines and turbo prop engines in the aviation industry. Turbines are used to propel ships using either steam or gas turbines. Turbines are also used to drive machinery and equipment in industrial processes using pump, compressor and generators driven by turbine power.

The future of turbines generally is predicated on the following trends and developments; advances in materials, improvement in design and the integration with other technologies such as energy storage, and smart grid networks.

 

SOURCES:

• Turbines design and theory by David Japikse and Nicholas Braines.
• Wind turbine technology by David A. Spera.
• Gas turbine theory by H.I.H Saravanamuto and H. Cohen.
• Gas turbines: A hand book of air, land and sea applications by Claire Soares.
• Hydroelectric turbines: Design, installation and operation by P. Novak, A.I.B Moffat and R.H.J Sellin.