{"id":17677,"date":"2018-04-25T17:28:41","date_gmt":"2018-04-25T17:28:41","guid":{"rendered":"http:\/\/sitepourvtc.com\/?page_id=17677"},"modified":"2022-11-14T16:11:39","modified_gmt":"2022-11-14T16:11:39","slug":"brayton-cycle-gas-turbine-engine","status":"publish","type":"page","link":"https:\/\/sitepourvtc.com\/nuclear-engineering\/thermodynamics\/thermodynamic-cycles\/brayton-cycle-gas-turbine-engine\/","title":{"rendered":"Brayton Cycle – Gas Turbine Engine"},"content":{"rendered":"
<\/div>\n
In general, the Brayton cycle<\/strong> describes the workings of a constant-pressure heat engine<\/strong>. The Brayton cycle is one of the most common thermodynamic cycles<\/strong><\/a> found in gas turbine power plants or airplanes.\n

The\u00a0thermal efficiency<\/strong>\u00a0in terms of the compressor\u00a0pressure ratio<\/strong>\u00a0(PR = p2<\/sub>\/p1<\/sub>), which is the parameter commonly used:<\/p>\n

\"thermal<\/a><\/p>\n

In general,\u00a0increasing the pressure ratio<\/strong> is the most direct way to increase the overall thermal efficiency of a Brayton cycle.<\/p>\n<\/div><\/div>\n

In 1872, an American engineer, George Bailey Brayton,<\/strong> advanced the study of heat engines <\/a>by patenting a constant pressure internal combustion engine, initially using vaporized gas but later using liquid fuels such as kerosene. This heat engine is known as \u201cBrayton\u2019s\u00a0Ready Motor<\/strong>\u201d<\/em>. The original Brayton engine<\/strong> used a piston compressor<\/strong> and piston expander<\/strong> instead of a gas turbine and gas compressor.<\/p>\n

Today, modern gas turbine engines<\/strong> and airbreathing jet engines<\/strong> are also constant-pressure heat engines. Therefore we describe their thermodynamics by the Brayton cycle<\/strong>. In general, the Brayton cycle<\/strong> describes the workings of a constant-pressure heat engine<\/strong>.<\/p>\n

It is one of the most common thermodynamic cycles<\/strong><\/a> found in gas turbine power plants or airplanes. In contrast to the Carnot cycle<\/a>, the Brayton cycle<\/strong> does not execute isothermal processes<\/a>\u00a0because these must be performed very slowly. In an ideal Brayton cycle<\/strong>, the system executing the cycle undergoes a series of four processes: two isentropic (reversible adiabatic) processes alternated with two isobaric processes.<\/p>\n

Since Carnot\u2019s principle<\/strong> states that no engine can be more efficient than a reversible engine (a Carnot heat engine<\/strong>) operating between the same high temperature and low-temperature reservoirs, a gas turbine based on the Brayton cycle must have lower efficiency than the Carnot efficiency.<\/p>\n

A large single-cycle gas turbine typically produces 300 megawatts of electric power and has 35\u201340% thermal efficiency. Modern Combined Cycle Gas Turbine (CCGT) plants, in which the thermodynamic cycle consists of two power plant cycles (e.g.,, the Brayton cycle and the Rankine cycle), can achieve a thermal efficiency of around 55%.<\/p><\/div><\/div>

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<\/span>Brayton Cycle vs. Ericsson Cycle<\/div>
It must be noted the first Ericsson cycle<\/strong> is in fact now called the “Brayton cycle<\/strong>“, commonly applied to modern gas turbine engines and airbreathing jet engines. The second Ericsson cycle<\/strong> is similar to the Brayton cycle but uses external heat<\/strong> and incorporates a regenerator<\/strong>. An ideal Ericsson cycle consists of isothermal compression and expansion processes, combined with isobaric heat regeneration between them. Applying inter-cooling, heat regeneration, and sequential combustion significantly increases the thermal efficiency of a turbine. The thermal efficiency of the ideal Ericsson cycle<\/strong> equals the Carnot efficiency<\/strong>.<\/div><\/div>
<\/span>What is a Gas Turbine<\/div>
In general, a gas turbine<\/strong> is a rotary heat engine<\/strong> that converts the chemical energy<\/strong> of the fuel to heat<\/strong> or thermal energy<\/strong><\/a> and then to mechanical energy<\/strong><\/a> or electrical energy<\/strong><\/a>. In its simplest form, a gas turbine consist of:\n