space
space
austin clean energyenergy conservation, clean energy
  www.austincleanenergy.com
space
space
space
homeglobal warmingaboutsitemapcontact usblogs - energy conservationwsn links
space
Stirling engine
The engine cycle
The Stirling cycle
Engine configurations
Wind Power
Wind energy
Turbine placement & Installation
Ecology and pollution
PV Power (Photovoltaics)
Working of PV Cells
Environmental impacts
Jet Turbine Power
Types of jet engines
Turbojet engines
Gas Turbine
Gas turbines in vehicles
Microturbines
 
 
 
Affilliate Links:
Jlove:
Click here to meet Jewish Singles!
 
Mothernature:
Shop for all-natural products at MotherNature.com
 

Gas Turbine

A gas turbine, also called a combustion turbine, is a rotary engine that extracts energy from a flow of hot gas produced by combustion of gas or fuel oil in a stream of compressed air. It has an upstream air compressor (radial or axial flow) mechanically coupled to a downstream turbine and a combustion chamber in between. Gas turbine may also refer to just the turbine element.

Energy is released when compressed air is mixed with fuel and ignited in the combustor. The resulting gases are directed over the turbine’s blades, spinning the turbine, and, mechanically, powering the compressor. Finally, the gases are passed through a nozzle, generating additional thrust by accelerating the hot exhaust gases by expansion back to atmospheric pressure.

Energy is extracted in the form of shaft power, compressed air and thrust, in any combination, and used to power aircraft, trains, ships, electrical generators, and even tanks.

Theory of operation

Gas turbines are described thermodynamically by the Brayton cycle, in which air is compressed isentropically, combustion occurs at constant pressure, and expansion over the turbine occurs isentropically back to the starting pressure.

In practice, friction, and turbulence cause:

a) non-isentropic compression: for a given overall pressure ratio, the compressor delivery temperature is higher than ideal.

b) non-isentropic expansion: although the turbine temperature drop necessary to drive the compressor is unaffected, the associated pressure ratio is greater, which decreases the expansion available to provide useful work.

c) pressure losses in the air intake, combustor and exhaust: reduces the expansion available to provide useful work.

As with all cyclic heat engines, higher combustion temperature means greater efficiency. The limiting factor is the ability of the steel, nickel, ceramic, or other materials that make up the engine to withstand heat and pressure. Considerable engineering goes into keeping the turbine parts cool. Most turbines also try to recover exhaust heat, which otherwise is wasted energy. Recuperators are heat exchangers that pass exhaust heat to the compressed air, prior to combustion. Combined cycle designs pass waste heat to steam turbine systems. And combined heat and power (co-generation) uses waste heat for hot water production.

Mechanically, gas turbines can be considerably less complex than internal combustion piston engines. Simple turbines might have one moving part: the shaft/compressor/turbine/alternative-rotor assembly (see image above), not counting the fuel system.

More sophisticated turbines (such as those found in modern jet engines) may have multiple shafts (spools), hundreds of turbine blades, movable stator blades, and a vast system of complex piping, combustors and heat exchangers.

As a general rule, the smaller the engine the higher the rotation rate of the shaft(s) needs to be to maintain tip speed. Turbine blade tip speed determines the maximum pressure that can be gained, independent of the size of the engine. Jet engines operate around 10,000 rpm and micro turbines around 100,000 rpm.

Thrust bearings and journal bearings are a critical part of design. Traditionally, they have been hydrodynamic oil bearings, or oil-cooled ball bearings. This is giving way to foil bearings, which have been successfully used in micro turbines and auxiliary power units.



Back to Blogs Index

Other Useful Links: Search The Web:
Low cost health care solutions

California lawyer and attorney directory

Chula vista real estate attorneys

San Diego Law Schools

San Diego Business Directory

Internet Marketing Consultants

Legal Commentary Blog

California Unpublished Legal Decisions

Judicial Misconduct Resources

California Apartment Manager

Search Engine Optimization (SEO)

Posting Images Online

City Defense Campaign
Google
             
Web
www.fearnotlaw.com
www.sandiegodirectory.net
www.sandiegohealthdirectory.com
 
Copyright 2007-2009 , Result Oriented Marketing, Inc.
For Further Assistance Visit : www.mcmillanlaw.us and www.fearnotlaw.com