Fundamentos de Los Ciclos Termodinamicos

TAREA #1

FUNDAMENTOS DE LOS CICLOS

KARIM ORTIZ ALDACO

PLANTAS TERMICAS Y USO RACIONAL DE LA ENERGIA

Profeso: Dr. ALEJANDRO ZALETA AGUILAR

5 DE FEBRERO DE 2016

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Universidad de Guanajuato. División de ingenierías Campus Irapuato – Salamanca


ALUMNO: KARIM ORTIZ ALDACOPROFESOR: Dr. ALEJANDRO ZALETA AGUILAR

TAREA #1 FUNDAMENTOS DE LOS CICLOS

TAREA 1: CICLOS TERMODINAMICOS

Ciclo de Rankine:El ciclo de Rankine es un ciclo termodinámico que tiene como objetivo la conversión de calor en trabajo, constituyendo lo que se denomina un ciclo de potencia. Como cualquier otro ciclo de potencia, su eficiencia está acotada por la eficiencia termodinámica de un ciclo de Carnot que operase entre los mismos focos térmicos (límite máximo que impone el Segundo Principio de la Termodinámica). Debe su nombre a su desarrollador, el ingeniero y físico escocés William John Macquorn Rankine.

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CICLO DIESSEL

The Diesel cycle is a combustion process of a reciprocating internal combustion engine. In it, fuel is ignited by heat generated during the compression of air in the combustion chamber, into which fuel is then injected. This is in contrast to igniting the fuel-air mixture with a spark plug as in the Otto cycle (four-stroke/petrol) engine. Diesel engines are used in aircraft, automobiles, power generation, diesel-electric locomotives, and both surface ships and submarines.[dubious – discuss]

The Diesel cycle is assumed to have constant pressure during the initial part of the "combustion" phase (V_2 to V_3 in the diagram, below). This is an idealized mathematical model: real physical diesels do have an increase in pressure during this period, but it is less pronounced than in the Otto cycle. In contrast, the idealized Otto cycle of a gasoline engine approximates a constant volume process during that phase.

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Otto cycleAn Otto cycle is an idealized thermodynamic cycle that describes the functioning of a typical spark ignition piston engine.[1] It is the thermodynamic cycle most commonly found in automobile engines.

Pressure-Volume diagram

Temperature-Entropy diagram

The Otto cycle is a description of what happens to a mass of gas as it is subjected to changes of pressure, temperature, volume, addition of heat, and removal of heat. The mass of gas that is subjected to those changes is called the system. The system, in this case, is defined to be the fluid (gas) within the cylinder. By describing the changes that take place within the system, it will also describe in inverse, the system's effect on the environment. In the case of the Otto cycle, the effect will be to produce enough net work from the system so as to propel an automobile and its occupants in the environment.

The Otto cycle is constructed from:

Top and bottom of the loop: a pair of quasi-parallel and isentropic processes (frictionless, adiabatic reversible).

Left and right sides of the loop: a pair of parallel isochoric processes (constant volume)

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Mixed/dual cycle

The dual combustion cycle (also known as the limited pressure or mixed cycle, Trinkler cycle, Seiliger cycle or Sabathe cycle) is a thermal cycle that is a combination of the Otto cycle and the Diesel cycle, first introduced by Russian-German engineer Gustav Trinkler. Heat is added partly at constant volume and partly at constant pressure, the advantage of which is that more time is available for the fuel to completely combust. Because of lagging characteristics of fuel this cycle is invariably used for diesel and hot spot ignition engines. The P-V diagram is given below:

The dual cycle consists of following operations:

1-2 Adiabatic compression 2-3 Addition of heat at constant volume. 3-4 Addition of heat at constant pressure. 4-5 Adiabatic expansion. 5-1 Rejection of heat at constant volume.

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Brayton cycleThe Brayton cycle is a thermodynamic cycle that describes the workings of a constant pressure heat engine. Gas turbine engines and airbreathing jet engines use the Brayton cycle. Although the Brayton cycle is usually run as an open system (and indeed must be run as such if internal combustion is used), it is conventionally assumed for the purposes of thermodynamic analysis that the exhaust gases are reused in the intake, enabling analysis as a closed system.

The engine cycle is named after George Brayton (1830–1892), the American engineer who developed it, although it was originally proposed and patented by Englishman John Barber in 1791.[1] It is also sometimes known as the Joule cycle. The Ericsson cycle is similar to the Brayton cycle but uses external heat and incorporates the use of a regenerator. There are two types of Brayton cycles, open to the atmosphere and using internal combustion chamber or closed and using a heat exchanger.

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Ericsson cycleThe Ericsson cycle is named after inventor John Ericsson, who designed and built many unique heat engines based on various thermodynamic cycles. He is credited with inventing two unique heat engine cycles and developing practical engines based on these cycles. His first cycle is now known as the closed Brayton cycle, while his second cycle is what is now called the Ericsson cycle.

Ideal Ericsson cycle

The following is a list of the four processes that occur between the four stages of the ideal Ericsson cycle:

Process 1 -> 2: Isothermal compression. The compression space is assumed to be intercooled, so the gas undergoes isothermal compression. The compressed air flows into a storage tank at constant pressure. In the ideal cycle, there is no heat transfer across the tank walls.

Process 2 -> 3: Isobaric heat addition. From the tank, the compressed air flows through the regenerator and picks up heat at a high constant-pressure on the way to the heated power-cylinder.

Process 3 -> 4: Isothermal expansion. The power-cylinder expansion-space is heated externally, and the gas undergoes isothermal expansion.

Process 4 -> 1: Isobaric heat removal. Before the air is released as exhaust, it is passed back through the regenerator, thus cooling the gas at a low constant pressure, and heating the regenerator for the next cycle.

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The Stirling cycle

The Stirling cycle is a thermodynamic cycle that describes the general class of Stirling devices. This includes the original Stirling engine that was invented, developed and patented in 1816 by Reverend Dr. Robert Stirling with help from his brother, an engineer.

Documents

Fundamentos de Los Ciclos Termodinamicos