The gas turbine engine is one of the most widely used technologies in the world today. Its uses range from powering aircraft, seacraft and some military vehicles (e.g. M-1 tank) to generating electricity.

The basic principle of a gas turbine engine is a very simple thermodynamic cycle. It comprises of 3 main parts. First is a compressor which takes air from the atmosphere and compresses it to a high pressure increasing its velocity, This high-pressure air then enters the combustion area where fuel (generally jet fuel, propane or n�atural gas) is injected and combusted. This gives the air more energy by further increasing its velocity and also in the form of thermal energy. The air finally enters the turbine stage. Here the hot air turns the turbine blades and we obtain energy in the form of shaft work. Part of this goes back to powering the compressor and the rest is the useful output.

The concept of a turbine engine goes back much further in time than one would imagine. The first model was developed as far back as 150 AD by Hero of Alexandria. This model used steam to make a wheel turn. Leonardo Da Vinci also invented a device which used the same principles to turn a roasting spit. The hot air rising from the chimney turned a fan which through a series of gears was connected to a spit which turned. Various models of turbines (mostly steam turbines) were invented in the 16^th and 17^th centuries. But the biggest breakthrough was in 1791 when John Barber obtained a patent for his design of a gas turbine engine which had most of the elements present in modern gas turbines. After making various improvements to his design, it was used to power one of the earlier automobiles which were known as a ‘horseless carriages’. Since then gas turbine design has improved with advancing technology and we now have the turbines that we can see in our modern aircraft and power plants.

In this discussion the focus will be on the turbines that are used in power plants. This is an inherently political technology. It is part of a process and system that distributes electricity to a mass populace so it can be called a democratic technology. However it is not completely democratic as for example solar power (Winner) since it is very much an elitist technology which is why we don’t see people trying to build a turbine in their backyard and generate electricity. It requires large centralized power plants to generate and distribute electricity. And it requires a certain management and power structure to run. In most cases the government owns and ensures the running of power plants.

Even though the gas turbine is one of the most useful technologies today, it has its drawbacks. The main one being emissions which has become quite an ethical issue of recent times. The combustion process of the gas turbine engine results in gases such as carbon monoxide (CO) and nitrogen oxides (NO_x) being released into the atmosphere. Statistics by the Environmental Protection Agency have shown that electricity generation and fossil fuel combustion are two of the biggest contributors to this problem. Continued emissions at the current rates would result in more formation of smog, acid rain and increased global warming.

Now a question that has been raised a lot in the recent times is if there is any alternate form of energy we can use? There exist many forms of alternate energy like solar, wind, geothermal etc. but the fact of the matter is that none of these can fully replace a gas turbine engine. Nuclear power plants use steam turbines which have similar issues as gas turbine engines do. And the other forms of energy mentioned have issues with storing the acquired energy which is a critical factor to consider since energy cannot always be harnessed from those sources (e.g. solar panels cannot do anything at nighttime). Research into alternative forms of energy will go on but in addition to that universities like Penn State and gas turbine manufacturers like GE are looking into finding methods of building low emissions gas turbine engines. The main way they hope to achieve this is by using a more lean mixture (more air than fuel) during the combustion process. Of course this method has its issues too like pressure oscillations and heat fluctuations that occur when the fuel and air don’t mix uniformly. Researchers are working to find ways of predicting and preventing these phenomena. The issue of emissions is one that needs a solution soon or the future of the gas turbine industry as well as our environment will be at risk.

 

References

Langdon Wagner, Do artifacts have politics

National nitrogen oxides emissions by source sector from http://www.epa.gov/cgi-bin/broker?_service=data&_program=dataprog.dw_12cat_nat.sas&pol=227