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QUESTIONS. Model cycles. Otto – SIIC – gasoline engine Diesel – CIIC – diesel engine Dual –IC Brayton – gas turbine & jet engine. Brayton cycle. Gas power Uses Auxiliary power generation Stand-alone power generation Naval propulsion Jet engine. Brayton cycle.
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Model cycles • Otto – SIIC – gasoline engine • Diesel – CIIC – diesel engine • Dual –IC • Brayton – gas turbine & jet engine
Brayton cycle • Gas power • Uses • Auxiliary power generation • Stand-alone power generation • Naval propulsion • Jet engine
Brayton cycle • 1→2 Isentropic compression • 2→3 steady pressure heat addition • 3→4 isentropic expansion • 4→1 steady pressure heat rejection
Brayton cycle • Working fluid – air • Ideal gas • High AFR – air as working fluid • Complete combustion • Temperature limits • Thermal reservoirs • Open or closed model • Steady pressure heat exchange
Brayton cycle • Work in & work out • Heat in & heat out • Thermal efficiency • Pressure ratio • Back work ratio
Brayton cycle • Variable specific heat – isentropic processes of ideal gas • Constant specific heats - k
Cycles • Otto – r • Diesel – r & rc • Brayton -rp
Example • The rate of heat addition to an air-standard Brayton cycle is 3.4X109 Btu/hr. The pressure ratio is 14; the minimum and maximum cycle temperatures are 520oR and 3000oR respectively. • Find the thermal efficiency, mass flow rate, and net power.
Example • A gas turbine power plant opeating on an ideal Brayton Cycle has a pressure ratio of 8. Tha gas temperature is 300K at the compressor inlet and 1300K at the turbine inlet. Find the bwr and thermal efficiency of the cycle.
Example • Use the preceding data and modify for an compressor isentropic efficiency of 80% and a turbine isentropic efficiency of 85%. How is the thermal efficiency affected?