The Cheng cycle is a
thermodynamic cycle
A thermodynamic cycle consists of a linked sequence of thermodynamic processes that involve transfer of heat and work into and out of the system, while varying pressure, temperature, and other state variables within the system, and that eventuall ...
which uses a combination of two working fluids, one gas and one steam. It can therefore be considered a combination of the
Brayton cycle
The Brayton cycle is a thermodynamic cycle that describes the operation of certain heat engines that have air or some other gas as their working fluid. The original Brayton engines used a piston compressor and piston expander, but modern gas tur ...
and the
Rankine cycle
The Rankine cycle is an idealized thermodynamic cycle describing the process by which certain heat engines, such as steam turbines or reciprocating steam engines, allow mechanical work to be extracted from a fluid as it moves between a heat sourc ...
. It was named for Dr. Dah Yu Cheng.
The company founded by Dr. Cheng has developed systems in partnership with both GM and GE turbine manufacturers to take advantage of the Cheng cycle by modification of existing turbine designs before construction. The Cheng cycle involves the heated
exhaust gas
Exhaust gas or flue gas is emitted as a result of the combustion of fuels such as natural gas, gasoline (petrol), diesel fuel, fuel oil, biodiesel blends, or coal. According to the type of engine, it is discharged into the atmosphere through an ...
from the turbine being used to make steam in a heat recovery steam generator (HRSG). The steam so produced is injected into the gas turbine's combustion chamber to increase power output. The process can be thought of as a parallel combination of the gas turbine
Brayton cycle
The Brayton cycle is a thermodynamic cycle that describes the operation of certain heat engines that have air or some other gas as their working fluid. The original Brayton engines used a piston compressor and piston expander, but modern gas tur ...
and a steam turbine
Rankine cycle
The Rankine cycle is an idealized thermodynamic cycle describing the process by which certain heat engines, such as steam turbines or reciprocating steam engines, allow mechanical work to be extracted from a fluid as it moves between a heat sourc ...
. The cycle was invented by Prof. Dah Yu Cheng of the
University of Santa Clara
Santa Clara University is a private Jesuit university in Santa Clara, California. Established in 1851, Santa Clara University is the oldest operating institution of higher learning in California. The university's campus surrounds the historic Mis ...
who patented it in 1976.
Cen, Ke-fa Yong Chi, Jianhua Yan (2007) ''Challenges of Power Engineering and Environment: Proceedings of the International Conference on Power Engineering'', Springer
(Accessed August 2012)[Cheng, D.Y. and A.L.C. Nelson (2002) ''Chronological development of the Cheng cycle steam injected gas turbine during the past 25 years''. in: Anon (Ed.), ''Proceedings of ASME Turbo Expo'' 2002, Amsterdam, ASME Paper No. GT-2002-30119 (2002), pp. 421–428]
A fully Cheng Cycle design Gas/Steam two fluid flow turbine can achieve a theoretical thermal efficiency of 60% matching or even exceeding many traditional Combined Cycle Gas Turbines that keep the steam Rankine Cycle
The Rankine cycle is an idealized thermodynamic cycle describing the process by which certain heat engines, such as steam turbines or reciprocating steam engines, allow mechanical work to be extracted from a fluid as it moves between a heat sourc ...
and gas Brayton Cycle
The Brayton cycle is a thermodynamic cycle that describes the operation of certain heat engines that have air or some other gas as their working fluid. The original Brayton engines used a piston compressor and piston expander, but modern gas tur ...
as separate loops.
See also
* Combined cycle
A combined cycle power plant is an assembly of heat engines that work in tandem from the same source of heat, converting it into mechanical energy. On land, when used to make electricity the most common type is called a combined cycle gas turb ...
* Brayton cycle
The Brayton cycle is a thermodynamic cycle that describes the operation of certain heat engines that have air or some other gas as their working fluid. The original Brayton engines used a piston compressor and piston expander, but modern gas tur ...
* Rankine cycle
The Rankine cycle is an idealized thermodynamic cycle describing the process by which certain heat engines, such as steam turbines or reciprocating steam engines, allow mechanical work to be extracted from a fluid as it moves between a heat sourc ...
* Cogeneration
Cogeneration or combined heat and power (CHP) is the use of a heat engine or power station to generate electricity and useful heat at the same time.
Cogeneration is a more efficient use of fuel or heat, because otherwise- wasted heat from elect ...
References
Power engineering
Thermodynamic cycles
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