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The first person to build a working four-stroke engine, a stationary engine using a coal gas-air mixture for fuel (a gas engine), was German engineer Nicolaus Otto. [4] This is why the four-stroke principle today is commonly known as the Otto cycle and four-stroke engines using spark plugs often are called Otto engines.
The gas temperature fluctuations are caused by the effects of compression and expansion in the engine, together with non-ideal heat exchangers which have a limited rate of heat transfer. When the gas temperature deviates above and below the heat exchanger temperature, it causes thermodynamic losses known as "heat transfer losses" or "hysteresis ...
The steam so produced is injected into the gas turbine's combustion chamber to increase power output. [3] The process can be thought of as a parallel combination of the gas turbine Brayton cycle and a steam turbine Rankine cycle. [4] [5] The cycle was invented by Prof. Dah Yu Cheng of the University of Santa Clara who patented it in 1976. [6] [1]
Because of lagging characteristics of fuel this cycle is invariably used for Diesel and hot spot ignition engines. It consists of two adiabatic and two constant volume and one constant pressure processes. Pressure-Volume diagram of Sabathe cycle Temperature-Entropy diagram of Sabathe cycle. The dual cycle consists of following operations:
The Diesel engine is a heat engine: it converts heat into work. During the bottom isentropic processes (blue), energy is transferred into the system in the form of work W i n {\displaystyle W_{in}} , but by definition (isentropic) no energy is transferred into or out of the system in the form of heat.
If at every point in the cycle the system is in thermodynamic equilibrium, the cycle is reversible. Whether carried out reversible or irreversibly, the net entropy change of the system is zero, as entropy is a state function. During a closed cycle, the system returns to its original thermodynamic state of temperature and pressure.
Here, is the overall mass transfer coefficient, which could be determined by empirical correlations, is the surface area for mass transfer (particularly relevant in membrane-based separations), and ˙ is the mass flowrate of bulk fluid (e.g., mass flowrate of air in an application where water vapor is being separated from the air mixture). At ...
The gas turbine cycle is used for all modern gas turbine and turbojet engines, however simple cycle turbines are often recuperated to improve efficiency and these recuperated turbines more closely resemble Ericsson's work. Ericsson eventually abandoned the open cycle in favor of the traditional closed Stirling cycle.