1BRAYTON CYCLE: THE IDEAL CYCLE FOR GAS-TURBINE ENGINESAn open-cycle gas-turbine engine. A closed-cycle gas-turbine engine.The combustion process is replaced by a constant-pressure heat-addition process from an external source, and the exhaust process is replaced by a constant-pressure heat-rejection process to the ambient air. 1-2 Isentropic compression (in a compressor2-! "onstant-pressure heat addition!-# Isentropic expansion (in a turbine#-1 "onstant-pressure heat rejection2T-s and P-v diagrams for the ideal $rayton cycle.%ressure ratioThermal e&ciency of the ideal $rayton cycle as a function of the pressure ratio.!The fraction of the turbine 'or( used to dri)e the compressor is called the bac( 'or( ratio.The t'o major application areas of gas-turbine engines are aircraft propulsion and electric power generation.The highest temperature in the cycle is limited by the maximum temperature that the turbine blades can 'ithstand. This also limits the pressure ratios that can be used in the cycle.The air in gas turbines supplies the necessary oxidant for the combustion of the fuel, and it ser)es as a coolant to (eep the temperature of )arious components 'ithin safe limits. An air*fuel ratio of +, or abo)e is not uncommon.#Development of Gas T!"#nes1. Increasing the turbine inlet (or -ring temperatures2. Increasing the e&ciencies of turbomachinery components (turbines, compressors.!. Adding modi-cations to the basic cycle (intercooling, regeneration or recuperation, and reheating.Dev#at#on of A$tal Gas-T!"#ne C%$les f!om I&eal#'e& OnesThe de)iation of an actual gas-turbine cycle from the ideal $rayton cycle as a result of irre)ersibilities.Reasons: Irre)ersibilities in turbine and compressors, pressure drops, heat lossesIsentropic e&ciencies of the compressor and turbine+THE BRAYTON CYCLE (ITH REGENERATIONIn gas-turbine engines, the temperature of the exhaust gas lea)ing the turbine is often considerably higher than the temperature of the air lea)ing the compressor. Therefore, the high-pressure air lea)ing the compressor can be heated by the hot exhaust gases in a counter-/o' heat exchanger (a regenerator or a recuperator. The thermal e&ciency of the $rayton cycle increases as a result of regeneration since less fuel is used for the same 'or( output. T-s diagram of a $rayton cycle 'ith regeneration.A gas-turbine engine 'ith regenerator.0T-s diagram of a $rayton cycle 'ith regeneration.12ecti)eness of regenerator12ecti)eness under cold-air standard assumptions3nder cold-air standard assumptionsThermal e&ciency of the ideal $rayton cycle 'ith and 'ithout regeneration.The thermal e&ciency depends on the ratio of the minimum to maximum temperatures as 'ell as the pressure ratio. 4egeneration is most e2ecti)e at lo'er pressure ratios and lo' minimum-to-maximum temperature ratios."an regeneration be used at high pressure ratios5 6THE BRAYTON CYCLE (ITH INTERCOOLING) REHEATING) AND REGENERATIONA gas-turbine engine 'ith t'o-stage compression 'ith intercooling, t'o-stage expansion 'ith reheating, and regeneration and its T-s diagram.7or minimi8ing 'or( input to compressor and maximi8ing 'or( output from turbine.9"omparison of 'or( inputs to a single-stage compressor (1AC and a t'o-stage compressor 'ith intercooling (1ABD.*lt#sta+e $omp!ess#on ,#t- #nte!$ool#n+: The 'or( re:uired to compress a gas bet'een t'o speci-ed pressures can be decreased by carrying out the compression process in stages and cooling the gas in bet'een. This (eeps the speci-c )olume as lo' as possible.*lt#sta+e e.pans#on ,#t- !e-eat#n+ (eeps the speci-c )olume of the 'or(ing /uid as high as possible during an expansion process, thus maximi8ing 'or( output.Inte!$ool#n+ an& !e-eat#n+ al'ays decreases the thermal e&ciency unless they are accompanied by regeneration. (-%/As the number of compression and expansion stages increases, the gas-turbine cycle 'ith intercooling, reheating, and regeneration approaches the 1ricsson cycle.;IDEAL 0ET-1RO1ULSION CYCLESIn jet engines, the high-temperature and high-pressure gases lea)ing the turbine are accelerated in a no88le to pro)ide thrust.tto cycle. The ideal cycle for spar(-ignition engines?iesel cycle. The ideal cycle for compression-ignition engines=tirling and 1ricsson cycles$rayton cycle. The ideal cycle for gas-turbine enginesThe $rayton cycle 'ith regenerationThe $rayton cycle 'ith intercooling, reheating, and regenerationIdeal jet-propulsion cycles=econd-la' analysis of gas po'er cycles