APPLIED THERMODYNAMICS – II

IC Engines

Classification. Two stroke and four stroke engines, rotary engines and their comparison, Principle of Carburation, Essential requirements for petrol and diesel fuels ; R.A.C. rating of petrol engines, Theory of combustion in SI and CI engines, pressure time diagram, various phenomenon such as turbulence squish and swirl, dissociation and pre ignition, Theory of detonation (knocking) for SI and CI engines, effect of engine variables on Delay period in SI and CI Engines, effect of various engine parameters on knock (detonation) in SI and Diesel engines ; effect of detonation on engine performance and methods employed to reduce detonation. Octane and Cetane rating of fuels, octane and cetane number knockmeter and doping of fuels. Combustion chambers and cylinder heads for SI and CI engines. Methods of governing and cooling of IC Engines. Performance curves of SI and CI engines, performance maps, effect of compression ration and of air fuel ratio on power and efficiency of an engine. Variation of engine power with altitude ; supercharging its advantages and application ; supercharging of IC engines ; types of superchargers. High speed engine indicators, logarithmic plotting of PV diagrams

Rotary Compressors

Introduction and general classification of rotary compressors; comparison of rotary compressors with reciprocating processors; operation of positive displacement type of rotary compressors like roots blower, Lysholm compressor and Vane type Blower. Applications of Steady Flow Energy Equation and thermodynamics of Rotary compressors; stagnation and static values of pressure, temperature and enthalpy etc. for flow through rotary machines. Complete representation of compression process on T-S coordinates with detailed description of areas representing total work done and Polytropic work done, area representing energy lost in internal friction, energy carried away by cooling water etc. on T-S coordinates for uncooled and cooled compression, Isentropic, polytropic and isothermal efficiencies as ratios of areas representing various energy transfers T-S coordinates.

Centrifugal Compressors

Complete thermodynamic anlysis of centrifugal compressor stage, polytropic, isentropic and isothermal efficiencies; complete representation of compression process starting from ambient air to flow through suction pipe, impeller, diffuser and finally to delivery pipe on T-S coordinates; preguide vanes and prewhirl; Slip factor, power input factor; various modes of energy transfer in impeller and diffuser; Degree of reaction and its derivation; energy transfer in backward, forward and radial vanes; pressure coefficient as a function of slip factor, efficiency and outcoming velocity profile from the impeller. Derivation of non-dimensional parameters for plotting compressor characteristics; centrifugal compressor characteristics curves; surging and choking in centrifugal compressors.

Axial Flow Compressors

Different components of axial flow compressors and their arrangement; discussion on flow passages and simple theory of aerofoil blading; angle of attack; coefficients of lift and drag; turbine versus compressor blades; velocity vector vector diagrams, thermodynamic analysis and power calculations; modes of energy trasfer in rotor and stator blade flow passages. Detailed discussion on work done factor; Degree of reaction and Blade efficiency and their derivations; Isentropic, polytropic and Isothermal Efficiencies. Surging, choking and stalling in axial flow compressors, characteristics curves for axial flow compressor, flow parameters of axial flow compressor like pressure coefficient, flow coefficient, work coefficient and temperature rise coeffieicnt specific speed etc. Comparison on axial flow compressor with centrifugal compressor and reaction turbine; field of application of axial flow compressors.

Gas Turbines

Comparison of open and closed cycles; comparison of gas turbine with a steam turbine and IC engine. Fields of application of gas turbine. Position of gas turbine in power industry; classification on the basis of system of operation (open and closed cycles) and on the basis of combustion (at constant volume or constant pressure) Thermodynamics of constant pressure gas turbine cycle (Brayton cycle); calculation of net output, work ratio and thermal efficiency of ideal and actual cycles; cycle air rate, temperature ratio; effect of changes in specific heat and of mass of fuel on power and efficiency; Operating variables and their effects on thermal efficiency and work ratio. Thermal refinements and their effects on gas turbine cycle i.e. gas turbine cycle with regeneration, intercooling and reheating; multistage compression and expansion; Dual Turbine system; Series and parallel arrangements, closed and semiclosed gas turbine cycle; requirements of a gas turbine combustion chamber. Blade materials and selection criteria for these materials and requirements of blade materials. Gas turbine fuels.

Jet propulsion

Principle of jet propulsion, description of different types of jet propulsion system like Rockets and thermal jet engines like (I) athodyds (ramjet and pulsejet), (ii) turbojet engine, (iii) turboprop engine. Thermodynamics of turbojet engines components; development of thrust and methods for its boosting/augmentation; thrust work and thrust power, propulsion energy, propulsion and thermal (internal) efficiencies, overall thermal efficiency. Specific fuel consumption. Rocket propulsion, its thrust and thrust power; propulsion and overall thermal efficiency, types of rocket motors (e.g. solid propellant and liquid propellant systems); various common propellant combinations (i.e. fuels) used in rocket motors; cooling of rockets Advantages and disadvantages of jet propulsion over propulsion systems; Brief introduction to performance characteristics of different propulsion systems; fields of application of various propulsion units.