ME-603-A Turbo Machinery - May 2024 Question Paper

Under each question, How to answer lists the points an answer should cover, outlined by CampusPrep from the syllabus. Check the details against your textbook.

1. 7 Marks
   aExplain the application of the second law of thermodynamics to the turbo machines.
   How to answer

   • State second law in entropy / exergy form
   • Application to steady flow turbomachines: irreversibility and losses
   • Isentropic vs actual work, adiabatic efficiency
   • Example: turbine/compressor T-s diagram
2. 7 Marks
   bDerive the moment of momentum and Euler turbine equation for turbo machine.
   How to answer

   • Consider control volume with angular momentum
   • Moment of momentum about axis
   • Euler turbine equation: $E = U_1V_{w1} \pm U_2V_{w2}$
   • Sign convention for turbine / compressor
3. 14 Marks
   The velocity of steam at inlet to a simple impulse turbine is $1000$ m/s and nozzle angle is $20^\circ$. The blade speed is $400$ m/s and the blades are symmetrical. Calculate blade angles, tangential force on blade, diagram power, axial thrust and diagram efficiency for a mass flow rate of $0.75$ kg/s. Neglect friction losses.
   How to answer

   • Draw inlet/outlet velocity triangles with $V_1=1000$ m/s, $\alpha_1=20^\circ$, $U=400$ m/s
   • Symmetrical blades: $\beta_1=\beta_2$, no friction $V_{r1}=V_{r2}$
   • Calculate $V_{w}$, $V_f$, tangential force $F=m(V_{w1}+V_{w2})$
   • Diagram power $F\cdot U$, axial thrust, $\eta_d$
4. 7 Marks
   aDerive an expression for optimizing blade efficiency in an impulse steam turbine.
   How to answer

   • Blade efficiency expression in terms of $U, V_1, \alpha_1, \beta$ and friction factor
   • Differentiate w.r.t. $U/V_1$ for maximum
   • Condition $U/V_1 = \cos\alpha_1/2$ for optimum
   • Maximum efficiency value
5. 7 Marks
   bExplain various losses in turbine.
   How to answer

   • Nozzle, blade friction, disc windage losses
   • Leaving, leakage, mechanical losses
   • Effect on T-s diagram and efficiency
   • Brief means to reduce losses
6. Marks
   aWhat is a draft tube? Explain the different types of draft tubes.
   How to answer

   • Definition and function of draft tube
   • Pressure recovery at turbine exit
   • Types: conical, elbow, Moody spreading
   • Sketches and applications
7. 7 Marks
   bA Pelton wheel is to be designed for a head of $60$ m when running at $200$ r.p.m. The Pelton wheel develops $95.6475$ kW shaft power. The velocity of the buckets $= 0.45$ times the velocity of the jet, overall efficiency $= 0.85$ and coefficient of the velocity is equal to $0.98$.
   How to answer

   • Jet velocity $V = C_v\sqrt{2gH}$
   • Bucket speed $U=0.45V$, wheel diameter from $U=\pi DN/60$
   • Discharge from overall efficiency and shaft power
   • Jet diameter and number of jets
8. 7 Marks
   aDefine the specific speed of a turbine. Derive an expression for the specific speed.
   How to answer

   • Definition of specific speed $N_s$
   • Similarity laws: $P \propto N^3D^5$, $H \propto N^2D^2$
   • Eliminate D to get $N_s = N\sqrt{P}/H^{5/4}$
   • Significance for turbine selection
9. 7 Marks
   bWith the help of neat sketch discuss the main parts of a centrifugal pump.
   How to answer

   • Neat labelled sketch of centrifugal pump
   • Impeller, casing, suction/delivery pipes
   • Function of each main part
   • Working flow path
10. 7 Marks
    aDescribe Surging and Choking in compressor.
    How to answer

    • Definition of surging: flow reversal and pressure fluctuation
    • Causes and effects on compressor operation
    • Definition of choking: sonic condition, max mass flow
    • Characteristics on compressor map
11. 7 Marks
    bCompare the axial flow and centrifugal compressor.
    How to answer

    • Working principle: axial vs radial flow
    • Pressure ratio, efficiency, size comparison
    • Tabular comparison on construction and application
    • Suitability for different duties
12. 7 Marks
    aWhat is a torque converter? Explain the working principle of a converter with the help of a neat sketch.
    How to answer

    • Definition of torque converter and components
    • Neat sketch: pump, turbine, stator
    • Working principle with oil circulation
    • Torque multiplication and applications
13. Marks
    bA hydraulic press has a ram of $200$ mm diameter and a plunger of $30$ mm diameter. It is used for lifting of $3$ kN. Find the force required at the plunger.
    How to answer

    • Pascal law: $F_1/A_1 = F_2/A_2$
    • Areas from $D=200$ mm and $d=30$ mm
    • Force at plunger for $3$ kN load
    • Result in N
14. 14 Marks
    Write short notes on any three of the following:

    1. a)Velocity and pressure compounding in steam turbines
    2. b)Degree of reaction of turbo machinery
    3. c)Various efficiencies of hydraulic turbines
    4. d)Governing of steam turbines
    How to answer

    • Select any three topics
    • Definition, working / classification with sketch
    • Key formulas / advantages / applications
    • Brief conclusion for each note