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Introduction Mechanical Power Reciprocating Engines Turbines Turbines are compact machines (high power to weight ratio, having less balancing problems and less oil consumption. Turbines Hydraulic turbines Steam turbines Gas turbines The performance of these machines depend on compressor efficiency, pressure ratio and turbine inlet temperature.
Introduction • Gas Turbine versus Steam turbine • Steam turbine plants are utilized for producing large power 1000 MW per unit. Gases are used to heat water and steam. Then steam is used in turbines to produce power. • In gas turbines gas is directly used to produce power • Power cycles are simple, complex and combined (steam and gas) • Simple and combined gas turbines • Use of turbines • Electrical power generation • Jet propulsion • Supply of compressed air/ gas • Mechanical power generation
Examples of Application Impeller of a compressor
Examples of Application • Vaned diffuser for centrifugal compressor
Examples of Application • Turbo charger
Examples of Application • Schematic of flow in an axial turbine. Contours of pressure are from a CFD calculation
Examples of Application Reaction turbine (Francis type):
Examples of Application Impulse turbine (Pelton type):
Examples of Application Cutaway view of the GE90 turbofan engine designed for long-range commercial aircraft
Introduction • Description of simple cycle • Specific work, w; thermal efficiency, η= w/q • Assumptions: • Both compressor and turbine are isentropic (reversible adiabatic, η= 100 %) • Pressure losses in both of combustion chamber and heat exchanger are negligible. • Working fluid is air. It behaves as an ideal gas • Mass flow rate is constant and combustion process is replaced by heat addition process.
Introduction • First law of thermodynamics (conservation of energy) • q – w = Δh • Compressor (adiabatic, q=0.) • Turbine
Introduction • Combustion chamber
Introduction • Open cycle single shaft and twin-shaft arrangements • Complex with inter-cooling, heat exchange and reheat • Multi-spool arrangements • Typical gas turbine design procedures