Thermodynamics I
Download
Report
Transcript Thermodynamics I
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
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 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?