3. • INTRODUCTION
• APPLICATIONS OF GAS TURBINES
• CLASSIFICATION OF GAS TURBINES
• COMPARISON OF GAS TURBINE AND IC ENGINES
• COMPARISON OF GAS TURBINE AND STEAM ENGINES
4. INTRODUCTION
• GAS TURBINE IS A ROTARY INTERNAL COMBUSTION ENGINE. IT CONSISTS
OF COMPRESSOR, A COMBUSTION CHAMBER AND A TURBINE. THE GAS
TURBINE USES CONTINUOUS GAS FLOW AS THE WORKING MEDIUM BY
WHICH HEAT ENERGY IS PARTIALLY CONVERTED INTO MECHANICAL
ENERGY.
5.
6. APPLICATIONS OF GAS TURBINES
• THESE ARE WIDELY USED IN THE AIRCRAFT FIELD, i.e., FOR
PROPULSION OF TURBO JET AND TURBO PROPELLER ENGINES.
• WITH AVAILABILITY OF GAS FUEL, THE GAS TURBINES ARE
INCREASINGLY BEING USED FOR ELECTRIC POWER GENERATION.
• THEY ARE ALSO USED IN MARINE PROPULSION.
• THE GAS TURBINES ARE USED IN HIGH SPEED RACING CARS.
• THE GAS TURBINES ARE ALSO USED TO RUN THE RAILWAY
LOCOMOTIVES.
• THEY ARE USED TO OPERATE HOVERCRAFTS.
• THEY ARE USEDTO RUN ROTARY COMPRESSORS
7. CLASSIFICATION OF GAS TURBINES
I. ACCORDING TO CYCLE OF OPERATION
A. OPEN CYCLE GAS TURBINE- THE FRESH CHARGE IS SUPPLIED TO
THE COMPRESSOR IN EACH CYCLE. THE COMPRESSED AIR IS MIXED
WITH FUEL AND COMBUSTION OCCURS IN THE COMBUSTION
CHAMBER THE COMBUSTION GASES LEAVING THE TURBINE AFTER
EXPANSION ARE EXPELLED TO THE ATMOSPHERE. THUS, THE CYCLE BECOMES
AN OPEN CYCLE.
B. CLOSED CYCLE GAS TURBINE- IN ACLOSED CYCLE GAS TURBINES, THE WORKING
SUBSTANCE AIR UNDERGOES THE CYCLE, REPEATEDLY. THE COMBUSTION PROCESS
IS REPLACED BY HEAT ADDITION FROM EXTERNAL SOURCE AND EXHAUST PROCESS
IS REPLACED BY HAEAT REJECTION PROCESS TO THE SURROUNDINGS.
9. I. ACCORDING TO COMBUSTION PROCESS
A. CONSTANT-PRESSURE COMBUSTION GAS TURBINE-
THEORETICALLY, IT OPERATES ON AIR STANDARD BRAYTON
CYCLE IN WHICH THE COMBUSTION TAKES PLACE AT CONSTANT
PRESSURE BY SLOW BURNING FUEL.
B. CONSTANT-VOLUME GAS TURBINE –
IT IS ALSO CALLED EXPLOSIVE GAS TURBINE AND
THEORITICALLY, IT OPERATES ON THE ATKINSON POWER CYCLE.
10.
11. COMPARISON OF GASTURBINE AND IC ENGINES
• MERITS-
1. SINCE THE GAS TURBINE IS A ROTARY ENGINE, ITS MECHANICAL
EFFICIENCY APPROACHES 95% QUITE HIGH COMPARED WITH IC ENGINES
2. THE WEIGHT OF THE GAS TURBINE PER KW POWER IS LESS THAN IC
ENGINE
3. POWER DEVELOPED BY GAS TURBINE PER KG OF AIR IS MORE THAN OF IC
ENGINE
4. THE SPEED OF THE GAS TURBINE IS HIGHER THAN THE IC ENGINES
5. THE COMBUSTION IS COMPLETE IN A GAS TURBINE, THUS EXHAUST IS
LESS POLLUTING AS COMPARED TO IC ENGINES.
12. • DEMIRITS-
1. THERMAL EFFICIENCY OF THE GAS TURBINE POWER PLANT IS
LOWER(15 TO 20%) AS COMPARED WITH IC ENGINES.
2. IT IS DIFFICULT TO START A GAS TURBINE AS COMPARED TO
AN IC ENGINE.
3. THE GAS TURBINE BLADES REQUIRE A SPECIAL COOLING
SYSTEM.
4. THE MANUFACTURING OF GAS TURBINE IS DIFFICULT AND
COSTLY.
5. FOR THE SAME POWER OUTPUT, THE GAS TURBINE
PRODUCES EXHAUST GAS APPROXIMATELY FIVE TIMES MORE
THAN THAT OF IC ENGINE.
13. COMPARISON OF GASTURBINE AND STEAMTURBINES
1. STEAM TURBINES USE STEAM AS WORKING FLUID. STEAM IS THE CHEAPEST
MEDIUM AND CAN BE GENERATED WITH THE HELP OF EASILY AVAILABLE FUELS.
THE GAS TURBINES ARE USING COSTLY FUEL WHICH CAN BURN EFFICIENTLY IN
ITS COMBUSTION CHAMBER
2. STEAM IS PRODUCED OUTSIDE THE TURBINE, THUS IT IS AN EXTERNAL
COMBUSTION ENGINE, WHILE THE COMBUSTION CHAMBER IS AN INTEGRAL PART
OF GAS TURBINE, THUS IT IS AN INTERNAL COMBUSTION ENGINE.
3. A GAS TURBINE USES LOWER PRESSURE RATIO OF THE WORKING FLUID AS
COMPARED TO STEAM PRESSURE IN STEAM TURBINE.
4. GAS TURBINE RUNS AT HIGHER SPEED THAN STEAM TURBINE.
5. A GAS TURBINE PLANT CAN EASILY BESTARTED OR STOPPED AS COMPARED TO
STEAM POWER PLANT.
6. THE NUMBER OF SKILLED MAN POWER REQUIRED TO OPERATETHE GAS TURBINE
POWER PLANT IS COMPARATIVELY MUCH LESS THAN FOR STEM POWER PLANT.
