Brayton & Otto Cycle

Javier Estrada
ENG 1223

Brayton and Otto Cycle
When you talk about the Brayton cycle, gas turbine engines should come up and when you’re talking about the Otto cycle, piston engines should also come up. These two cycles are the backbone of power generation. The theory of the two cycles goes all the way back to the 18th century. The Name Brayton comes from the American inventor George Brayton and Otto comes from German engineer Nikolaus Otto. Both these men changed the world and how we live life now a day.
The Brayton cycle was first proposed by George Brayton for use in the reciprocating oil burning engine that he developed around 1870. Today, it is used for gas turbines only where both the compression and expansion processes take place in rotating machinery. In order for a plane to fly or move it needs some kind of propulsion system to provide for thrust. A propulsion system is a machine that pushes an object forward, based on Newton’s third law. The gas turbine engine substitutes for the propulsion system. The two important areas of gas turbine engines are aircraft propulsion and electric power generation. When it is used for aircraft propulsion, the gas turbine produces just enough power to drive the compressor and a small generator to power the auxiliary equipment. Turbine engines are not only for airplanes. Gas turbines are also used as stationary power plants to generate electricity as stand-alone units. The first gas turbine for an electric utility was installed in 1949 in Oklahoma as part of a combined cycle power plant. It was built by General Electric and produced 3.5 MW of power.
The author of Thermodynamics and Thermal Engineering by J. Selwin Rajadurai explains in his words how the Brayton Cycle works:
"Fresh air in an ambient condition is thrown into the compressor, and the air gets compressed isentropically. During this stage, work is done on the system. During this process, the pressure and temperature of the working substance increases, whereas the volume is reduced. The high pressure proceeds into the combustion chamber, where the fuel is burned at constant pressure. Due to constant pressure heating, the temperature and the volume of the working substance increases. The resulting high temperature gases then enter the turbine, where they expand to the atmospheric pressure isentropically, this producing the power"(qtd. in Butterman)
So in other words, air is sucked into the compressor. The Compressor is the first set of blades on a turbine engine This section is called the cold section because of the cool air coming in. Afterwards this air goes into the combustion where it’s mixed with the burning gas and produces very high pressure and temperature. This section is called the hot section. After the combustion the high pressure air is released to produce power. An Otto Cycle has four stages: expansion, cooling, compression, and combustion. In the expansion stage fuel is burned to heat the compressed air and the hot gas that expands forces the piston to travel up in the cylinder moving from bottom dead center to top dead center. The cooling stage is where the expanded air is cooled and when the piston is at the top dead center. Next stage is the compression where the piston moves down and compresses the air. In this part of the cycle it contributes work to the air.

Work Cited

Butterman, Eric. "George Brayton." ASME.org. ASME, Apr. 2012. Web. 29 April 2013.

Cengal, Yunus A., and Michael A. Boles Thermodynamics: An Engineering Approach. Boston: McGraw Hill, 2006. Print.

Moyer, Michael. “Internal-Combustion Engine. (Cover Story).” Scientific American 301.3 (2009): 97. Mas Ultra – School Edition. Web. 1 May 2013.

Sharke, Paul. “Otto or Not, Here It Comes.” Mechanical Engineering 122.6 (200): 62. Master File Premier. Web. 30 April 2013.

Whaley, P.B. Basic Engineering Thermodynamics. New York: Oxford University Press, 1992. Print.

Cited: Butterman, Eric. "George Brayton." ASME.org. ASME, Apr. 2012. Web. 29 April 2013. Cengal, Yunus A., and Michael A. Boles Thermodynamics: An Engineering Approach. Boston: McGraw Hill, 2006. Print. Moyer, Michael. “Internal-Combustion Engine. (Cover Story).” Scientific American 301.3 (2009): 97. Mas Ultra – School Edition. Web. 1 May 2013. Sharke, Paul. “Otto or Not, Here It Comes.” Mechanical Engineering 122.6 (200): 62. Master File Premier. Web. 30 April 2013. Whaley, P.B. Basic Engineering Thermodynamics. New York: Oxford University Press, 1992. Print.