Post on 09-Apr-2023
كلية الھندسة –الجامعة المستنصرية الميكـــــانيكيـــةالھندســــــــة قســــم
ــــةــــمحطــــــــــــات طاقــــــــــــــــــ
CHAPTER (6) Gas Turbines & Combined Cycles
د. مشعل عبد االميرأ.م.
10‐Feb‐15
Chapter6
GasTurbine&CombinedCycles
The Ideal Brayton Cycle, Example (1), The Actual Simple Gas Turbine Cycle, Example (2), Splitting the Turbine, Example (3), Modification to the basic cycle: Intercooling, Reheat, Heat-Recovery Exchanger, Example (4), Combined Cycles with Heat-Recovery Boilers, Example (5), Tutorial Sheet 6.
Power Plant Engineering TUTORIAL SHEET ‐ 6 كلية الھندسة –الجامعة المستنصرية
Gas Turbine & Combined Cycles اقةـــــــمحطات ط –قسم الميكانيك
119
Assume the following:
For compression process: ‐ 1.005.
, 1.4
For combustion and expansion processes: ‐ 1.15.
, 1.333
‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐ 1‐ A gas turbine unit has an overall pressure ratio of (5/1) and a maximum cycle
temperatureof(550Co).Theturbinedrivesthecompressorandanelectricgenerator.Themechanicalefficiencyofthedriveis(97%).Theambienttemperatureis(20Co)andtheisentropicefficienciesofthecompressorandturbineare(80and83%)respectively.Calculate the power output in kilowatt for airflow of (15 kg/s). Also, calculate thethermal efficiency and the work ratio. Neglect changes in kinetic energy and thepressurelossesinthecombustionchamber.
2‐ Inamarinegasturbineunit,aHigh‐pressureturbinestagedrivesthecompressor,and
alow‐pressureturbinestagedrivesthepropellerthroughsuitablegearing.Theoverallpressure ratio is (4/1), and the maximum temperature is (650 Co). The isentropicefficienciesofthecompressor,HPandLPturbinesare(80,83and85%)respectively,andthemechanicalefficiencyofbothshaftsis(98%).Calculatethepressurebetweenturbinestageswhentheairintakeconditionare(1.01barand25Co).Also,calculatethethermalefficiencyandtheshaftpowerwhenthemassflowis(60kg/s).Neglectchangesinkineticenergyandthepressurelossesinthecombustionchamber.
3‐ A combined power plant consisting of a simple open cycle gas turbine unit, using air as the
working fluid (neglect fuel mass flow rate), and a steam turbine is to be designed such that the heat rejected at the gas turbine unit is to be utilized to produce steam at the generator for the steam turbine. The exhaust air leaving the generator is at (200 Co). Draw a simple sketch for the plant and the (T‐s) diagram and calculate the mass flow rate of steam per (kg/s) of airflow, the total power output per (kg/s) of airflow and the overall thermal efficiency of the plant. Assume ideal cycles. Neglect the feed pump work of Rankine cycle.
Thedataofeachcycleareasfollows:‐ GasTurbineCycle SteamTurbineCycle
Pressure(bar)
Minimum 1 0.07Maximum 5 30
Temperature(Co)
Minimum 20 Maximum 830 300