draft. introduction mechanical power reciprocating engines turbines turbines are compact machines...

DRAFT

IntroductionMechanical 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

Introduction

Introduction

Examples of ApplicationImpeller 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 ApplicationReaction turbine (Francis type):

Examples of ApplicationImpulse turbine (Pelton type):

Examples of ApplicationCutaway 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.)

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Introduction

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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

Introduction