l4-gas turbine systems ssr
DESCRIPTION
gasTRANSCRIPT
GAS POWER SYSTEMObjective: Study Gas Power Plants
in which working fluid is always a gas
Gas turbines
Internal combustion engines: spark-ignition and compression-ignition
Internal Combustion Engines
Engine Terminology
Air-Standard Cycles: Otto, Diesel and Dual Cycles
ME 306 Applied Thermodynamics
Gas Turbine Power Plants
Modelling gas turbine power plants
Air-Standard Brayton cycle
Improving performance using
Regeneration, reheating and intercooling
Gas turbines for aircraft propulsion
Combined gas turbine – vapour power cycle
Ericsson and Sterling cycles 1
GAS TURBINE POWER PLANTS
• Lighter than Vapour Power Plants
• Compact as Compared to Vapour Power Plants
• Higher Power-Output-to-Weight-Ratio
ME 306 Applied Thermodynamics 2Moran and Shapiro (2006)
• Simple Cycle based GTPP have Lower Efficiency
• 15 to 18%
• Regenerative Cycle based GTPP have Higher Efficiency
• 25 to 42%
GAS TURBINE POWER PLANTS
ME 306 Applied Thermodynamics 3
OPEN SYSTEM CLOSED SYSTEM
CYCLE ANALYSISTURBINE
COMPRESSOR
HEAT INPUT
ME 306 Applied Thermodynamics 4
HEAT REJECTED
Thermal Efficiency
Back work ratio (bwr)
higher compared to VPS
NUMERICAL PROBLEM
Air enters the compressor of an ideal air-standard Brayton cycle
at 100 kPa, 300 K, with a volumetric flow rate of 5 m3/s. The
compressor pressure ratio is 9. The turbine inlet temperature is
1500 K. Determine (a) the thermal efficiency of the cycle, (b) the
back work ratio, (c) the net power developed, in kW.
ASSUMPTIONS:
1. Each component is analyzed as a control volume at steady state.
ME 306 Applied Thermodynamics 5Moran and Shapiro (2006)
1. Each component is analyzed as a control volume at steady state.
2. The turbine and compressor processes are isentropic.
3. There are no pressure drops for flow through the heat exchangers.
4. Kinetic and potential energy effects are negligible.
5. The working fluid is air modeled as an ideal gas.
6. Specific heat is assumed to be constant.
'
0( )
( )
Tp
T
c Ts T dT
T= ∫
EFFECT OF PRESSURE RATIO
( ) ( )3 4 2 1 4 1
3 2 3 2
1T T T T T T
T T T Tη
− − − −= = −
− − ( )( 1) /
11
pRγ γ
η−
= −
ME 306 Applied Thermodynamics 6Moran and Shapiro (2006)
CONDITION FOR MAXIMUM WORK OUTPUT
( ) ( )3 4 2 1p
Wc T T T T
m= − − − �
�
γ
Differentiate and equate it to zero
ME 306 Applied Thermodynamics 7Moran and Shapiro (2006)
2( 1)3
1
p
TR
T
γ
γ − =
2 4 1 3T T TT= =
Regenerative Gas Turbines
ME 306 Applied Thermodynamics 8Moran and Shapiro (2006)
Regenerator effectiveness around 60-80%
Gas Turbines with Reheat
ME 306 Applied Thermodynamics 9
Moran and Shapiro 2006
Gas Turbines with Intercooling
ME 306 Applied Thermodynamics 10
Moran and Shapiro 2006
Regenerative gas turbine with intercooling and reheat
ME 306 Applied Thermodynamics 11
Gas Turbines for Aircraft Propulsion
ME 306 Applied Thermodynamics 12
Combined Gas Turbine–Vapor Power Cycle
ME 306 Applied Thermodynamics 13
Other Cycles
Ericsson Cycle
ME 306 Applied Thermodynamics 14Moran and Shapiro (2006)
Stirling Cycle
Condition for minimum workIf the inlet state and the exit pressure are specified for a two-stage compressor operating at
steady state, show that the minimum total work input is required when the pressure ratio is
the same across each stage. Use a cold air-standard analysis assuming that each
compression process is isentropic, there is no pressure drop through the intercooler, and
the temperature at the inlet to each compressor stage is the same. Kinetic and potential
energy effects can be ignored.
1. The compressor stages and intercooler are analyzed
as control volumes at steady state.
2. The compression processes are isentropic.
ME 306 Applied Thermodynamics 15Moran and Shapiro (2006)
2. The compression processes are isentropic.
3. There is no pressure drop for flow through the
intercooler.
4. The temperature at the inlet to both compressor stages
is the same.
5. Kinetic and potential energy effects are negligible.
6. The working fluid is air modeled as an ideal gas.
7. The specific heat cp and the specific heat ratio k are
constant.
Numerical ProblemAir enters the compressor at 100 kPa, 300K and is compressed to 1000 kPa. The temperature
at the inlet to the first turbine stage is 1400 K. The expansion takes place isentropically in two
stages, with reheat to 1400 K between the stages at a constant pressure of 300 kPa. A
regenerator having an effectiveness of 70% is also incorporated in the cycle. Determine the
thermal efficiency. Consider an isentropic efficiency of 85% for each turbine.
ME 306 Applied Thermodynamics 16Moran and Shapiro (2006)
Numerical Problem
A regenerative gas turbine with intercooling and reheat operates at steady state. Air enters
the compressor at 100 kPa, 300 K with a mass flow rate of 5.807 kg/s. The pressure ratio
across the two-stage compressor is 10. The pressure ratio across the two-stage turbine is
also 10. The intercooler and reheater each operate at 300 kPa. At the inlets to the turbine
stages, the temperature is 1400 K. The temperature at the inlet to the second compressor
stage is 300 K. The isentropic efficiency of each compressor and turbine stage is 80%. The
regenerator effectiveness is 80%. Determine (a) the thermal efficiency, (b) the back work
ratio, (c) the net power developed, in kW.
ME 306 Applied Thermodynamics 17Moran and Shapiro (2006)
Air enters a turbojet engine at 0.8 bar, 240�K, and an inlet velocity of 1000 km/h (278 m/s).
The pressure ratio across the compressor is 8. The turbine inlet temperature is 1200�K and
the pressure at the nozzle exit is 0.8 bar. The work developed by the turbine equals the
compressor work input. The diffuser, compressor, turbine, and nozzle processes are
isentropic, and there is no pressure drop for flow through the combustor. For operation at
steady state, determine the velocity at the nozzle exit and the pressure at each principal
state. Neglect kinetic energy at the exit of all components except the nozzle and neglect
potential energy throughout.
ME 306 Applied Thermodynamics18
Moran and Shapiro (2006)