Previous year question paper for AT (B-TECH automobile engineering 3rd)

Air Compressors

Introduction; Classification; Application of compressors and use of compressed air in industry

and other places; Complete representation of compression process on P-v and T-s coordinates

with detailed description of areas representing total work done and polytropic work done; Areas

representing energy lost in internal friction, energy carried away by cooling water and extra flow

work on T-s coordinates for un-cooled and cooled compression; Definitions of isentropic,

polytropic and isothermal efficiencies and their representation in terms of ratio of areas

representing various energy transfers on T-s coordinates.

Reciprocating Air Compressors

Single stage single acting reciprocating compressor (with and without clearance volume):

construction, operation, work input and best value of index of compression, heat rejected to

cooling medium, isothermal, overall thermal, isentropic, polytropic, mechanical, and clearance

volumetric efficiency, overall volumetric efficiency, effect of various parameters on volumetric

efficiency, free air delivery; Multistage compressors: purpose and advantages, construction and

operation, work input, heat rejected in intercoolers, minimum work input, optimum pressure

ratio, isothermal, overall thermal, isentropic, polytropic and mechanical efficiency.

Positive Displacement Rotary Compressors

Introduction; Classification; Comparison of rotary compressors with reciprocating compressors;

Construction, operation, work input and efficiency of rotary compressors like roots blower,

Lysholm compressor and Vane type Blower.

Centrifugal Compressors

Construction and operation; Applications of Steady Flow Energy Equation and thermodynamics

of dynamic compressors; Stagnation and static values of pressure, Temperature and enthalpy for

flow through dynamic machines; Complete thermodynamic analysis of centrifugal compressor

stage; Polytropic, isentropic and isothermal efficiencies; Complete representation of compression

process starting from ambient air flow through suction pipe, Impeller, Diffuser and finally to

delivery pipe on T-S coordinates; Pre-guide vanes and pre-whirl; Slip factor; Power input factor;

Various modes of energy transfer in impeller and diffuser; Energy transfer in backward, forward

and radial vanes; Pressure coefficient as a function of slip factor; Efficiency and out-coming

velocity profile from the impeller; Derivation of non-dimensional parameters for plotting

compressor characteristics; Centrifugal compressor characteristic curves; Surging and choking in

centrifugal compressors.

Axial Flow Compressors

Different components of axial flow compressor and their arrangement; Working; 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 transfer in rotor and stator blade flow passages; Detailed

discussion on work done factor, degree of reaction, blade efficiency and their derivations;

Isentropic, polytropic and isothermal efficiencies; Surging, Choking and Stalling in axial flow

compressors; Comparison of axial flow compressor with centrifugal compressor; Field of

application of axial flow compressors.

Gas Turbines

Classification on the basis of system of operation (open and closed cycles) and on the basis of

combustion (at constant volume or constant pressure); Comparison of open and closed cycles;

Comparison of gas turbine with IC engine; Fields of application of gas turbines; Position of gas 

turbine in power industry; 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 that of mass of fuel on

power and efficiency; Multistage compression and expansion; Dual Turbine system; Series and

parallel arrangements; Closed and semi-closed gas turbine cycle; Requirements of a gas turbine

combustion chamber; 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 engine components; 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.