The Cheng cycle is a
thermodynamic cycle
A thermodynamic cycle consists of linked sequences of thermodynamic processes that involve heat transfer, transfer of heat and work (physics), work into and out of the system, while varying pressure, temperature, and other state variables within t ...
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, also known as the Joule cycle, is a thermodynamic cycle that describes the operation of certain heat engines that have air or some other gas as their working fluid.
It is characterized by isentropic process, isentropic compre ...
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 sour ...
. 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 ...
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, also known as the Joule cycle, is a thermodynamic cycle that describes the operation of certain heat engines that have air or some other gas as their working fluid.
It is characterized by isentropic process, isentropic compre ...
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 sour ...
. The cycle was invented by Prof. Dah Yu Cheng of the
University of Santa Clara 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
In thermodynamics, the thermal efficiency (\eta_) is a dimensionless performance measure of a device that uses thermal energy, such as an internal combustion engine, steam turbine, steam engine, boiler, furnace, refrigerator, ACs etc.
For ...
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 sour ...
and gas Brayton Cycle
The Brayton cycle, also known as the Joule cycle, is a thermodynamic cycle that describes the operation of certain heat engines that have air or some other gas as their working fluid.
It is characterized by isentropic process, isentropic compre ...
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, also known as the Joule cycle, is a thermodynamic cycle that describes the operation of certain heat engines that have air or some other gas as their working fluid.
It is characterized by isentropic process, isentropic compre ...
* 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 sour ...
* 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 elec ...
References
Power engineering
Thermodynamic cycles
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