QUESTIONS
Model cycles
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Otto – SIIC – gasoline engine
Diesel – CIIC – diesel engine
Dual –IC
Brayton – gas turbine & jet engine
Brayton cycle
 Gas power
 Uses
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Auxiliary power generation
Stand-alone power generation
Naval propulsion
Jet engine
Brayton cycle
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1→2 Isentropic compression
2→3 steady pressure heat addition
3→4 isentropic expansion
4→1 steady pressure heat rejection
Brayton cycle
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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
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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 airstandard 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?