Thermal Engineering-II

Question Bank

UNIT – I Basic Concepts: Rankine cycle - Schematic layout, Thermodynamic Analysis, Concept of Mean Temperature

of Heat addition, Methods to improve cycle performance – Regeneration & reheating. Combustion: fuels and

combustion, concepts of heat of reaction, adiabatic flame temperature, stoichiometry, and flue gas analysis

1. (a) Describe the different processes of Rankine cycle. Derive the expression for its efficiency and show them

on P-v and T-s

Diagrams?

(b) A simple Rankine cycle works between pressure of 30 bar and 0.04 bar, the initial condition of steam

being dry saturated, calculate the cycle efficiency, work ratio and specific steam consumption. [8+8]

2 (a) How does a modified Rankine cycle differ from a Rankine cycle? Write also the expression of modified

Rankine cycle

efficiency.

(b) Compare the Rankine cycle efficiency of a high pressure plant operating from 80 bar and 400 0C and a

low pressure plant

operating from 40 bar and 400 0C, if the condenser pressure in both cases is 0.07 bar. [8+8]

3.. (a) State the methods of improving the thermal efficiency of a Rankine cycle.(b) In a Rankine cycle the

steam at inlet to turbine is

saturated at a pressure of 30 bar and the exhaust pressure is 0.25 bar. Determine i). The pump work ii).

Turbine work iii). Rankine

efficiency iv). Condenser heat flow v. dryness at the end of expansion [4+12]

4. (a) Describe the working of Orsat apparatus for determining the volumetric com-position of dry flue gases

with the help of neat

sketch.

(b) The dry exhaust gases from a petrol engine contained 2 percent by volume of CO and negligible

hydrogen. If the fuel contained

84% carbon and 16% hydrogen by weight, all hydrogen is burnt and all carbon may be assumed to burn

either to CO2 or to CO

Calculate i). mass of air supplied per kg of fuel. ii). proportion of carbon burn to CO2. [8+8]

5. The composition by weight of fuel is 65% hexane (C6H14) having a net calorific value of 43080 kJ/kg and

35% Benzene (C6H6)

having a net calorific value of 38900 kJ/kg. Determine (a) Air fuel ratio for stoichiometric mixture and the

calorific value of 1 m3 of

the mixture at STP treating the fuels as gases. 1 kg-mol of fuel has volume 22.42 m3 at STP.

(b) The CO2 % by volume in the dry products of combustion from a 30% rich mixture. Assume complete

combustion of H2. [16]

6. (a) Draw the T-S and H-S diagrams of reheat cycle representing all the salient points.

(b) In a steam power plant the condition of steam at inlet to the turbine is 20 bar, 300 0C and the condenser

pressure is 0.1 bar. Two

feed-water heaters operate at optimum temperatures of 1500C and 100

0C. Determine the quality of steam

at turbine exhaust,

cycle efficiency and fraction of steam bleed into heaters. [6+10]

UNIT II Boilers : Classification – Working principles – with sketches including H.P.Boilers – Mountings and

Accessories – Working principles, Boiler horse power, equivalent evaporation, efficiency and heat balance –

Draught, classification – Height of chimney for given draught and discharge, condition for maximum

discharge, efficiency of chimney – artificial draught, induced and forced.

1. (a) State which type of boiler is used for power generation and why?

(b) Explain the working of stirling boiler with the help of neat sketch. What arethe advantages of using bent

tubes over straight

tubes? [6+10]

2 (a) What is a fusible plug? State, where it is located in a boiler?

(b) During a boiler trail the following observations were made:

Duration of trial =1 hour, steam generated = 35500 kg, steam pressure 12 bar, steam temperature= 250

0C, temperature of water

entering economizer = 17 0C, temperature of water leaving economizer = 77

0C, Oil burnt = 3460 kg,

calorific value of oil

= 39500 kJ/kg. Calculate i. equivalent evaporation per kg of fuel ii. thermal efficiency of plantiii. % heat

energy of the fuel energy

utilized by the economizer. [4+12]

3. (a) Give relative merits and demerits of natural draught over artificial draught,(b) A boiler is equipped with a

chimney 25 meters high.

The temperature ofoutside air is 25 0C and the average temperature of flue gases in the chimneyis 320

0C.

If the boiler is supplied

with 20 kg of air per kg of fuel burnt, calculatethe theoretical draught created in terms of i) mm of water

column

ii). meter of column of hot gas. Also calculate the velocity of flue gases in chimney, if 60% of the

draught is lost in friction at

grate and passages.[4+12]

4. A chimney 30 m high is discharging hot gases at 360 0C when the outside temper-ature is 23 0C. The coal

burnt on the grate is

supplied with 16 kg of air per kg ofcoal. Determine the following:(a) Draught in mm of water(b) Equivalent

draught head h in meters

of hot gases(c) Volume of hot gases passing through chimney per second if 1400 kg of coal is burnt per hour

over the grate(d) The

base diameter of the chimney in meters, if the velocity v of the gases at the base of the chimney is given by

the relation h = 16 v2 / 2g

= equivalentdraught head in meters of hot gases. [16]

5. (a) A turbine is supplied with steam at a pressure of 32 bar and a temperature of 4100C. The steam then

expands isentropically to a

pressuere of 0.08 bar. Find the dryness fraction at the end of expansion and thermal efficiency of the cycle.

If the steam is reheated

at 5.5 bar to a temperature of 3950C and then expanded isentropically to a pressure of 0.08 bar, what will

be the dryness fraction

and thermal efficiency of the cycle? (b) What are the factors to be considered while selecting a boiler?

[10+6]

6 (a) A steam turbine operating on the Rankine cycle receives steam from the boiler at 3.5 MN/m2 and 3500C

and exhaust to the

condenser at 10 kN/m2.The condensate is then returned to the boiler by the feed pump. Determine the

following considering pump

work also.

i. the energy supplied in the steam generator

ii. the dryness fraction of the steam entering the condenser,

iii. the Rankine

efficiency.

(b) What is the difference between economizer and superheater? Why are they used in a boiler? [12+4]

7. (a) Give the detailed classification of boilers?

(b) Write short notes on any one Boiler accessory with the schematic sketch.[6+10]

8. (a) Establish a condition for maximum discharge of flue gases through chimney.

(b) Calculate the draught in mm of water column produced by a chimney 30 m high when the average

temperature of hot gases is 225

0C and the temperature of outside air is 20

0C. The quantity of air supplied is 18 kg/kg of fuel. [8+8]

9 A boiler uses coal having the following % composition by mass: Carbon = 80%, H2 = 6.5%, O2 = 4.5%,

Moisture = 2.0% and the

remaining 7% being ash and incombustible matter. Calculate:(a) the stoichiometric air required for complete

combustion of 1 kg of

this fuel (b) If the actual air supplied is 17 kg / kg of coal, hydrogen is completely burnt,80% of carbon burns

to CO2 and the

remainder 20% to CO. Determine the volumetric analysis of the products of combustion. Assume aircontains

23% of Oxygen by

mass. [16]

10.(a) Show that for maximum discharge from a chimney, gas temperature is nearly twice the atmospheric

temperature.

(b) Find the height of a chimney to get net draught of 13 mm, temperature of chimney gases 320 0C,

temperature of air 30 0C and the

mass of air used per kg of fuel 20 kg. One kg of air occupies a volume of 0.7734 m3 at NTP. [8+8]

11. (a) What is a steam trap? Explain expansion type of steam trap with a neat sketch.

(b) What is the function of a steam separator? Discuss with a neat sketch any one type of steam separators.

[8+8]

12. (a) Derive an expression connecting the height of a chimney and the draught it produces in terms of

temperature of outside air and

the mean temperature of the flue gases.

(b) How much air is used per kg of coal burnt in a boiler having a chimney of 35 m height to create draft of

20 mm of water, when the

temperature of the flue gases in the chimney is 370 0C and the temperature of the boiler house is 34

0C. Take

volume of 1 kg of air

at NTP as 0.7734 m3.

13. (a) Give the detailed classification of boilers?

(b) Write short notes on any one Boiler accessory with the schematic sketch.[6+10]

14.Steam is supplied to a two-stage turbine at 40 bar and 3500C. It expands in the first turbine until it is just dry

saturated, then it is re-

heated to 3500C and expanded through second stage turbine. The condenser pressure is 0.035 bar. Calculate

the work output and the

heat supplied per kg of steam for the plant, assuming ideal processes and neglecting the feed pump work.

Calculate also the specific

stream consumption and cycle efficiency.

15. (a) Explain the working principle of any one of horizontal fire tube boiler.

(b) A chimney is 60 m high and the temperature of atmospheric air is 270C. If 15 kg of air per kg of fuel is

used find the temperature

of hot gases for maximum discharge. [10+6]

16. (a) Explain the operation of any one type of modern high pressure boiler with a neat sketch.

(b) Define equivalent evaporation of a boiler. [12+4]

17. (a) Explain the working of i. water level indicator ii. high steam and low water safety valve with the help of

neat sketches. (b)

Describe briefly the advantages which you would expect to be gained from incorporating an economizer,

an air pre-heater and

super heater in a steam generating plant and indicate their positions in a typical boiler plant. [8+8]

18. (a) What is the use of cooling tower in a steam power plant? Mention the different types of cooling towers.

(b) With the neat sketch explain the operation of Benson boiler. [4+12]

19. (a) With the neat sketch explain stinling boiler.

(b) Explain various heat losses in a boiler. [10+6]

20. (a) Explain fusible plug used as boiler mounting with the neat sketch.

(b) Calculate the mass of flue gases flowing through the chimney when the draught produced is equal to 2

cm of water.

Temperature of flue gases is 2900C and ambient temperature is 25

0C. the flue gases formed per kg of fuel

burnt are 23 kg. Neglect

the losses and take the mean diameter of the chimney as 2 m.[8+8]

UNIT – III

Steam Nozzles : Function of nozzle – applications - types, Flow through nozzles, thermodynamic analysis –

assumptions -velocity of nozzle at exit-Ideal and actual expansion in nozzle, velocity coefficient, condition for

maximum discharge, critical pressure ratio, criteria to decide nozzle shape: Super saturated flow, its effects,

degree of super saturation and degree of under cooling - Wilson line.

1. (a) What do you mean by choked flow in nozzles? (b) Steam at 10 bar and 0.96 dryness fraction is to be

discharged at a rate of 100

kg/hr through a convergent divergent nozzle to a back pressure of 1.4 bar, Find suitable diameters for

throat and exit assuming

10% of the overall isentropic enthalpy drop reheats the steam in the divergent portion of the nozzle.

[4+12]

2 (a) Explain the terms“over expanding” and “under expanding” as applied to a fluid flow through a nozzle.

(b) Describe the changes which occur in a convergent divergent nozzle as the back pressure is slowly

increased from the design

pressure up to the pressure at entry. [8+8]

3. (a) Explain the terms“over expanding” and “under expanding” as applied to a fluid flow through a nozzle.

(b) Describe the changes which occur in a convergent divergent nozzle as the back pressure is slowly

increased from the design

pressure up to the pressure at entry. [8+8]

4. A steam turbine develops 185 KW with a consumption of 16.5 Kg/KWh. Pressure and temp. of the steam at

inlet of nozzle are 12 Bar

and 2200 C respectively. The steam leaves the nozzle at 1.2 Bar. The diameter of nozzle at throat is 7 mm.

Find the no of nozzles.[16]

5. A convergent-divergent nozzle for a steam turbine has to deliver 400 Kg of steam per hour under a supply

condition of 10 Bar dry

and saturated ,and a back pressure of 0.1 Bar Initial velocity of steam is 150 m/s. Neglect friction.Find throat

and outlet areas.

6. A convergent divergent nozzle is required to pass 1.8 kg of steam per second. At inlet the steam pressure and

actual temperature are 7

bar and 2000C respectively and the speed is 75 m/s. Expansion is stable throughout to the exit pressure of

1.1bar. There is no loss by

friction in the converging section of the section, but loss by friction between throat and outlet is equivalent

to 71 kJ/kg of steam.

Calculate (a) the required area of throat in mm2,(b) the required area of outlet in mm2and (c) the overall

efficiency of the nozzle,

based on the heat drop between the actual inlet pressure and temperature and the outlet pressure. [16]

7. A steam turbine develops 185 KW with a consumption of 16.5 Kg/KWh. Pressure and temp. of the steam at

inlet of nozzle are 12 Bar

and 2200 C respectively. The steam leaves the nozzle at 1.2 Bar. The diameter of nozzle at throat is 7 mm.

Find the no of nozzles.

8. Steam at 10 bar and 0.98 dry expands through a convergent divergent nozzle to a back pressure of 0.1 bar.

The discharge through the

nozzle is 0.55 kg/s. The enthalpy drop used for reheating the steam by friction in the divergent portion is

10% of the overall enthalpy

drop. Determine(a) the throat pressure (b) number of nozzles required if the throat area of each nozzle is 0.5

cm2 (c) exit diameter of

each nozzle m(d) cone angle of divergent portion if its length is 10 cm. [16]

9. Steam expands from a pressure of 10 bar and 300 0C to 0.5 bar in a convergent divergent steam nozzle of 1

sq.cm.of throat area.

Calculate the rate of flow and exit area when the flow is frictionless adiabatic. State whether the rate of flow

will increase or decrease

if the friction losses equal to 5% of the total heat drop are considered to take place between throat and exit.

Give reasons in support of

your answer.

10. The nozzles of a certain turbine have a throat diameter of 0.6 cm each. The power developed by the turbine

is 150 kW and the steam

consumption is about 5.25 kg/kWh. The upstream pressure is 14 bar and the temperature is 300 0C. The

back pressure is 0.05 bar.

Assuming that the flow is isentropic between entrance and exit, find the number of nozzles and the actual

steam consumption in

kg/kWh based on these conditions. Neglect the velociy of approach. If 12% of the total heat drop is wasted

between throat and exit,

find the exit diameter and final condition of steam. What will be the overall efficiency of the nozzle? [16]

11. The throat diameter of a nozzle is 5 mm. If dry and saturated steam at 10 bar is supplied to the nozzle,

calculated the mass flow rate.

The exhaust pressure is 1.5 bar. (a) Assume friction less adiabatic flow. (b) If 10 % of the isentropic heat

drop lost in friction, what

should be the correct diameter at outlet for steam to issue at the same exhaust pressure? [16]

12. (a) Discuss the effect of friction on flow through steam nozzles. Explain with the help of H-S Diagram

(b) Dry saturated steam at a pressure of 10 bar with negligible velocity expands in Convergent Divergent

nozzle to 1 Bar and

Dryness fraction 0.94.Determine the velocity of steam leaving the nozzle. [6+10]

13. A convergent divergent nozzle is required to pass 1.8 kg of steam per second. At inlet the steam pressure

and actual temperature are

7 bar and 2000C respectively and the speed is 75 m/s. Expansion is stable throughout to the exit pressure of

1.1bar. There is no loss

by friction in the converging section of the section, but loss by friction between throat and outlet is

equivalent to 71 kJ/kg of steam.

Calculate(a) the required area of throat in mm2,(b) the required area of outlet in mm2and(c) the overall

efficiency of the nozzle,

based on the heat drop between the actual inlet pressure and temperature and the outlet pressure. [16]

14. A convergent divergent nozzle is required to discharge 2 kg of steam per second. The nozzle is supplied

with a steam at 7 bar and

1800C and discharge takes place against a backpressure of 1 bar. The expansion upto throat is isentropic

and the frictional resistance

between the throat and exit is equivalent to 63 kJ/kg of steam. Taking approach velocity of 75 m/s and

throat pressure of 4 bar.

Estimate : (a) Suitable areas for the throat and exit. (b) Overall efficiency of the nozzle based on the

enthalpy drop between the

Actual inlet pressure and temperature and the exit pressure. [16]

15. Compare the mass of discharge from a convergent-divergent nozzle expanding from 8 Bar and 2100C to 0.1

bar. When the (a)

Expansion takes place under thermal equilibrium (b) The steam is super saturated condition during part of

its expansion. [16]

16. A convergent divergent nozzle is required to pass 1.8 kg of steam per second. At inlet the steam pressure

and actual temperature are

7 bar and 2000C respectively and the speed is 75 m/s. Expansion is stable throughout to the exit pressure of

1.1bar. There is no loss

by friction in the converging section of the section, but loss by friction between throat and outlet is

equivalent to 71 kJ/kg of steam.

Calculate (a) the required area of throat in mm2, (b) the required area of outlet in mm2and (c) the overall

efficiency of the nozzle,

based on the heat drop between the actual inlet pressure and temperature and the outlet pressure. [16]

UNIT – IV Steam Turbines: Classification – Impulse turbine; Mechanical details – Velocity diagram – effect of friction –

power developed, axial thrust, blade or diagram efficiency – condition for maximum efficiency. De-Laval

Turbine - its features. Methods to reduce rotor speed-Velocity compounding and pressure compounding,

Velocity and Pressure variation along the flow – combined velocity diagram for a velocity compounded

impulse turbine.

1. What is compounding? Describe various ways of compounding impulse turbines and give their merits and

demerits.

2 Steam with absolute velocity 300 m/s enters the stage of an impulse turbine pro- vided with a single row

wheel. The nozzles are

inclined at 200 to the plane of wheel and the rotor blades are equiangular. The rotor with mean diameter 100

cm rotates with speed

of 3000 rpm. Estimate the power developed in the blade if the axial thrust in the blades is 145 N. It may be

assumed that due to .

friction in the blade passages the kinetic energy due to outgoing relative velocity is only 67% of the kinetic

energy due to incoming relative velocity. [16]

3. In a two stage velocity compounded steam turbine the mean blade speed is 150 m/s while the steam velocity

as it issued from the

nozzle is 675 m/s. The nozzle angle is 200. The exit angles of first row moving blades, fixed blades and the

second

row moving blades are 250, 250 and 300 respectively. The blade friction coefficient is 0.9 for all blades.

Determine for a flow rate of 4.5 kg/s (a) the power output (b) the diagram efficiency.

4. A single row impulse turbine develops 132.4 kw at a blade speed of 175m/s, using 2kg of steam per sec.

steam leaves the nozzle at

400m/s. Velocity coefficient of the blades is 0.9.Steam leaves the turbine blades axially. Determine the

nozzle angle, Blade angles at

entry and exit, assuming no shock. [16]

5. In an impulse turbine (with a single row wheel) the mean diameter of the blades is 1.05m and speed is

3000r.p.m.The nozzle angle is

180, the ratio of the blade speed to steam speed is 0.42 and the ratio of the relative velocity at outlet from the

blades to that at inlet is

0.84.The outlet angle of the blade is to be made 30 less than the inlet angle. The steam flow is 10kg(S)s.

Draw The velocity diagram

for the blades and derive the following:

(a) Tangential thrust on the blades

(b) Axial thrust on the blades

(c) Resultant thrust on the blades

(d) Power developed in the blades

(e) Blading efficiency.

6. Steam with absolute velocity 300 m/s enters the stage of an impulse turbine pro- vided with a single row

wheel. The nozzles are

inclined at 200 to the plane of wheel and the rotor blades are equiangular. The rotor with mean diameter 100

cm rotates with speed of

3000 rpm. Estimate the power developed in the blade if the axial thrust in the blades is 145 N. It may be

assumed that due to friction

in the blade passages the kinetic energy due to outgoing relative velocity is only 67% of the kinetic energy

due to incoming relative

velocity. [16]

7. A velocity compounded impulse turbine has two rows of moving blades with a fixed row of guide blades

between them. The steam

leaves the nozzle at 900 m/s in a direction at 180 to the plane of rotation. Blade speed is 150 m/s and the

blade outlet angles for first

moving blade 240, fixed blade 260 and second moving blade 300. Friction factor is 0.9 for all rows.

Determine thrust and power

developed for the steam supply of 1.25 kg/s. [16]

8. In an impulse turbine the steam issues from the nozzle with speed of 600 m/s and blade speed is 120 m/s.

The velocity is compounded

by passing the steam through a ring of moving blades, through a ring of fixed blades and finally through a

ring of moving blades. The

nozzle angle is 180 and the blade exit angles and relative velocity coefficients are 1st row moving: 200 and

0.8 ; Fixed row: 250 and

0.85 ; 2nd row moving 300 and 0.9 Find the diagram efficiency under these conditions and the power output

for steam flow rate of 5

kg/s. [16]

9 (a) Briefly explain the classification of steam turbines.

(b) Explain briefly why in multistage impulse turbines the first stage is often Compounded for velocity and

remaining stages have

single row wheels? [6+10]

10. (a) What do you mean by compounding of steam turbines? Discuss various methods of compounding steam

turbines?

(b) Explain the difference between an impulse turbine and a reaction turbine? [10+6]

11. In a single stage impulse turbine the nozzle angle is 250. The absolute velocity of steam at exit is 300 m/sec

in a direction 1200 to

the direction of motion of the blades. Assuming equiangular blades and no axial thrust, determine

(a) the blade angles,

(b) the power developed per kg and

(c) the diagram efficiency. [16]

12. (a) Define and derive an expression for diagram efficiency incase of a steam tur- bine.

(b) In a simple impulse turbine, the nozzles are inclined at 200 to the direction

of motion of moving blades. The steam leaves the nozzles at 375 m/sec. The blade speed is 165

m/sec.Find suitable inlet and outlet angles for the blades in order that the axial thrust is zero. The

relative velocity of steam as it flows over the blades is reduced by 15% by friction. Determine the

power developedif the flow rate is 10 kg/sec. [8+8]

13. In a De Laval turbine steam issues from the nozzle with a velocity of 1200m/s.The nozzle angle is 200, the

mean blade velocity is

400m/s, and the inlet and outlet angles of blades are equal. The mass of steam flowing through the turbine

per hour is 1000 kg. Calculate:

(a) Blade angles.

(b) Relative velocity of steam entering the blades.

(c) Tangential force on the blades.

(d) Power developed.

(e) Blade efficiency.

Take velocity coefficient as 0.8 [16]

UNIT V

Reaction Turbine: Mechanical details – principle of operation, thermodynamic analysis of a stage,degree of

reaction –velocity diagram – Parson’s reaction turbine – condition for maximum efficiency.

1. In a Parson’s reaction turbine of 50% degree of reaction running at 25 r p s the available enthalpy drop for an

expansion is 62.8 kJ/kg.

If the mean diameter of the rotor is 1 m, find the number of rows of moving blades required. The outlet blade

angle is 200 and speed

ratio is 0.7. Assume that the stage efficiency is 80%. [16]

2 (a) Explain the functionality of reaction steam turbine with suitable diagram. And how it is different from the

impulse turbine?

(b) What are different losses that are occurring in reaction turbine? Explain with preventive measures. [8+8]

3. At a stage in a reaction turbine, the mean blade ring diameter is 1 m and the turbine runs at a speed of 50 rps.

The blades are designed

for 50% reaction with exit angles 300 and inlet angles 500. The turbine is supplied with a steam at a rate of 6

×105 kg/hr and stage

efficiency is 85 %, determine the power output. [16]

4. In a reaction turbine the fixed and moving blades are of the same shape but reversed in direction. The angle

of receiving tip is 350 and

the discharging tip is 200. Find the power developed per pair of blades for the steam consumption of 2.5

kg/s, when the blade speed is

50 m/s. If the enthalpy drop in the pair is 12 kJ/kg. Also find the efficiency of the pair. [16]

5. (a) Show that for a Parson’s reaction turbine the degree of reaction is 50%.

(b) In a 50% reaction turbine stage running at 3000rpm, the exit angles are 300and the inlet angles are 500.

The mean diameter is

1m.The steam flow rate is 10000kg/minute and the stage efficiency is 85%.

Determine:

i. Power output of the stage.

ii. The specific enthalpy drop in the stage.

iii. The percentage increase in the relative velocity of the steam when it flowsover the moving

blades. [8+8]

6. (a) Define the term degree of reaction for the reaction turbine and show that its value is 0.5 for the Parson’s

reaction turbine. (b) In a

reaction turbine, both the fixed and moving blades have same tip angles of 300 and 220 for inlet and

outlet respectively. The mean

blade speed is 90 m/s and steam consumption is 8 kg/s. Determine the power required if isentropic heat

drop in a pair is 23.5

kJ/kg. [8+8

7. (a) Show that for maximum diagram efficiency of a reaction turbine blade steam speed ratio is equal to cosα,

where α is angle of

absolute inlet velocity. (b) What are the assumptions used in the above problem? And also derive the

expression for maximum

efficiency. [8+8]

8. (a) Draw the schematic and combined velocity triangle of a Parson’s reaction turbine and explain its working

principle along with

pressure variations. (b) Explain the performance of the reaction turbine if degree of reaction is zero and

one. [8+8]

9 (a) What are the differences between impulse and reaction turbines? Explain.

(b) A reaction turbine has a speed of 3000 rpm and the mean diameter of blading at a certain pair is 750 mm.

The exit angle of the

blade is 200, both fixedand moving blades being identical. The steam flow rate is 810 kg/min. If

thepower developed per pair is

220 kW and the steam pressure is 2.74 bar and saturated, calculate the inlet blade angle and blade height.

[8+8]

10. In a stage of impulse reaction turbine provided with single row wheel, the mean diameter of the blades is

1metre.it turns at

3000r.p.m.the steam issues from the nozzle at a velocity of 350m/sec and the nozzle angle is 200. The rotor

blades are equiangular.

The blade friction factor is 0.86.determine the power developed if the axial thrust on the end bearing of a

rotor is 118N. [16]

11. A closed cycle gas turbine using Argon as the working fluid has a two compression with perfect inter

cooling. The overall pressure

ratio is 9 and pressure ratio in each stage is equal. Each stage has an isentropic efficiency of 85%. The

turbine is also two stage with

equal pressure ratio with inter change reheat to original temperature. Each turbine stage has an isentropic

efficiency of 90%. The

turbine inlet temperature is 1100K and the compressor inlet is 303K. Find (a) work done per kg of fluid

flow (b) work ratio (c) The

overall cycle efficiency.The properties of argon are Cp= 0.5207kJ/kg 0K,γ =1.667 and R=0.20813kJ/kg0K

[16]

12. (a) The following data refers to a particular stage of a Parsons Reaction turbine:

Speed of the turbine = 1500r.p.m

Mean diameter of the rotor = 1metre

Stage efficiency=80 percent

Blade outlet angle=200

Speed ratio= 0.7

Determine the available isentropic enthalpy drop in the stage.

(b) What do you mean by combined velocity diagram with reference to steam turbines? [10+6]

13. (a) What do you mean by compounding of steam turbines? Discuss various methods of compounding steam

turbines?

(b) Explain the difference between an impulse turbine and a reaction turbine? [10+6]

14. (a) what is the Parson’s Reaction turbine?

(b) A 50% reaction turbine (with symmetrical velocity triangles) running at 400 rpm has the exit angle of the

blades as 20o and the

velocity of steam relative to the blades at the exit is 1.35 times the mean blade speed. The steam flow rate

is 8.33 kg/s and at a

particular stage the specific volume is 1.381 m3/kg.

Calculate for this stage:

i. The suitable blade height, assuming the rotor mean diameter as 12 times the blade height, and

ii. The diagram work. [6+10]

15. (a) Show that optimum pressure ratio for maximum specific output for a gas tur- bine plant is rp ( optimum)

={η turbine × η

compressor × (T3/T1)}/2(−1) where T3 is Maximum temperature of cycle T1 is Minimum

temperature of of cycle

(b) List out any four applications of gas turbines. [12+4]

16. (a) Define and derive an expression for stage efficiency incase of a steam turbine.

(b) In an impulse turbine the nozzles are inclined at 240 to the plane of rotation of the blades. Steam speed

is 1000

m/sec and blade speed is 400 m/sec. Assuming equiangular blades, determine

i. blade angles,

ii. axial thrust,

iii. force on the blades in the direction of motion,

iv. power developed for a flow rate of 1000 kg/hr. [8+8]

UNIT VI

Steam Condensers : Requirements of steam condensing plant – Classification of condensers – working

principle of different types – vacuum efficiency and condenser efficiency – air leakage, sources and its affects,

air pump- cooling water requirement.

1. (a) What are the principal requirements of steam condensing plant in power gen-eration unit? Explain.

(b) What are the advantages obtained by incorporating the condenser in a steam power plant? Explain. [8+8]

2 In a surface condenser the vacuum reading is 721 mm of Hg. The barometric reading is 758 mm of Hg. The

amount of air leakage in

the condenser amounts to 6 kg/hr. The temperature at inlet to the air cooler section is 30 0C and at the outlet

is 26 0C. Calculate (a)

mass of steam condensed in the air cooler section (b) reduction in the air pump capacity following the

cooling air. [16]

3. (a) Draw the schematic diagram of low level counter flow jet condenser and explain its working principle.

(b) What are the advantages and limitations of surface condensers over jet con-densers?

4. (a) What are different types of cooling towers? Explain with suitable figures.

(b) The air entering a steam condenser with steam is estimated at 6 kg/hr. The temperature at the inlet to air

cooler section is 30 0C

and at the outlet is 260C. The vacuum in the shell is essentially constant throughout and is 721 mm of Hg,

while the barometer

reads 758 mm of Hg. Calculate i. the volume of air entering the cooling section per hour ii. the mass of

moisture contained in the

air iii. the mass of steam condensed per hr in the cooling section. [16]

5. (a) Draw the schematic diagram of low level counter flow jet condenser and explainits working principle.

(b) What are the advantages and limitations of surface condensers over jet con-densers? [8+8]

6. (a) Draw the schematic diagram of parallel flow jet condenser and explain its working principle. (b) Explain

the advantages and

limitations of surface condensers over jet con-densers.

7. (a) What are the functions of condensers in a steam power plant? Explain with a simple diagram. (b) A

surface condenser is designed

to handle 10,000 kg of steam per hr. The steam enters at 0.08 bar and 0.9 dry and the condensate leaves at

the corresponding

saturation temperature. The pressure is constant throughout the condenser. Estimate cooling water flow

rate per hr, if the cooling

water temperature rise is limited to 10 0C. [8+8]

8. (a) Differentiate between wet air pump and dry air pump and also derive the equation for volumetric

efficiencies for both the cases.

(b) A surface condenser deals with 2100 kg of steam per hour and the air leakage amounts to 0.8 kg per hour.

The temperature of air

pump suction is 35 0C and the vacuum is 680 mm of Hg when the barometer reads 760 mm of Hg.

Determine the capacity of wet

air pump which has a volumetric efficiency of75%. [8+8]

9. The air leakage into a surface condenser operating with a steam turbine is estimated as 84 Kg/hr. The

vacuum near the inlet of air

pump is 700 mm of Hg. When Barometer reads 760 mm of Hg. The temp. at the inlet of vacuum pump

is200C.Calculate

(a) Min. capacity of air pump in m3/hr.

(b) The dimensions of the reciprocating air pump to remove the air if it run at 200 RPM and L/D

ratio=1.5 and volumetric

efficiency =100%.

(c) The mass of vapour extracted per minute. [16]

10. (a) What are the objectives of a steam condenser in a steam power plant?

(b) Explain the working of high level jet condenser, with the help of a neat sketch.[6+10]

11. (a) With the help of a neat sketch. Explain the working of counter flow jetcondenser.

(b) The following data were obtained from the test of a surface condenser :Condenser vacuum =711 mm of

Hg; Hot water

Temp=320C; Inlet temp ofcirculating water = 140C Outlet temp of circulating water is 280C,

Barometer reading is 760 mm of

Hg. Calculate the vacuum efficiency and efficiency of condenser. [8+8]

12. (a) With help of neat sketch explain the working principle of Barometric jet con-denser.

(b) With a line diagram explain the working of natural draught cooling tower.[8+8]

13. The following observations were recorded during test on a steam condenser.

Recorded condenser vacuum =710 mm of Hg

Barometer reading =765 mm 0f Hg

Mean condenser temperature =340 C

Temp. of hot well =28.50 C

Condensate collected =1800 Kg/hr

Weight of cooling water =57,500 Kg/hr

Inlet temp. of cooling water =8.50 C

Outlet temp. of cooling water =260 C

Calculate:

(a) Vacuum corrected to the Std. Barometer reading

(b) Vacuum efficiency of the condenser

(c) Under cooling of the condenser

(d) Condenser efficiency

(e) Quality of steam entering the condenser.

(f) Mass of air per Kg of uncondensed steam

(g) Mass of air per m3 of condenser volume. [16]

14. The air leakage into a surface condenser operating with a steam turbine is estimated as 84 Kg/hr. The

vacuum near the inlet of air

pump is 700 mm of Hg. When Barometer reads 760 mm of Hg. The temp. at the inlet of vacuum pump is

200C.Calculate (a) Min. capacity of air pump in m3/hr. (b) The dimensions of the reciprocating air pump to

remove the air if it run

at 200 RPM and L/D ratio=1.5 and volumetric efficiency =100%. (c) The mass of vapour extracted per

minute. [16]

UNIT – VII Gas Turbines : Simple gas turbine plant – Ideal cycle, essential components – parameters of performance –

actual cycle – regeneration, inter cooling and reheating –Closed and Semi-closed cycles – merits and demerits,

Brief concepts about compressors, combustion chambers and turbines of Gas Turbine Plant.

1. (a) What are different operating variables affect the thermal efficiency of gas tur-bine power plant? Explain.

(b) The minimum and

maximum temperature limits in a gas turbine plant are288 K and 1100 K. The pressure limits are 1 bar and

8 bar. Determine the

thermal efficiency and work ratio. [8+8]

2 (a) What are different parameters influence the performance of gas turbine cycle.Explain.

(b) In a gas turbine power cycle, the pressure ratio is 6 and the maximum cycle temperature is 650 0C. The

air enters to the cylinder at

15 0C and the flow rate of air is 12 kg/s. Determine the power developed and thermal efficiencyof cycle.

[8+8]

3. A Brayton cycle works between 1 bar, 300 K and 5 bar, 1250 K. There are two stages of compression with

perfect inter cooling and

two stages of expansion with reheating. The work output of first expansion stage being used to drive the two

compressors, where the inter-stage pressure is optimized for the compressor. The air from the first stage

turbine is again heated to

1250 K and expanded. Calculate the power output of free power turbine and cycle efficiency without and

with perfect

heat exchanger and compare them. Also calculate the percentage improvement in the efficiency because of

the addition of heat

exchangers. [16]

4. (a) Draw the schematic diagram of open cycle gas turbine unit and explain its working along with its merits

and demerits.

(b) What is the effect of pressure ratio during compression on the performance of gas turbine cycle. [8+8]

5. A closed cycle gas turbine using Argon as the working fluid has a two compression with perfect inter

cooling. The overall pressure

ratio is 9 and pressure ratio in each stage is equal. Each stage has an isentropic efficiency of 85%. The

turbine is also two stage with

equal pressure ratio with inter change reheat to original temperature. Each turbine stage has an isentropic

efficiency of 90%. The

turbine inlet temperature is 1100K and the compressor inlet is 303K. Find

(a) work done per kg of fluid flow

(b) work ratio

(c) The overall cycle efficiency.

The properties of argon are Cp= 0.5207kJ/kg 0K,γ =1.667 and R=0.20813kJ/kg0K [16]

6. (a) Explain with neat sketch open cycle gas turbine plant.

(b) Enumerate the differences between open cycle gas turbine plant and closed Cycle turbine plant. [8+8]

7. (a) How the gas turbine cycles classified?

(b) A Gas turbine plant works between the temperature limits of 11520K and 2880 K Isentropic efficiency

for compressor and

turbines are 0.85 and 0.8 respec- tively. Determine the optimum pressure ratio for maximum work output

and also for maximum

Cycle thermal efficiency. [6+10]

8. Compare the maximum work delivered by an air craft gas turbine which works with two stage compression

with inter cooling. The

compressor pressure ratio is 4 and the temperature limit is 1000 K, for the given ambient condition 1 bar and

301 K. If the

temperature and pressure at 6000 m altitude is -25 0C and 0.5 bar, find the percentage change in network

output, efficiency and

exhaust gas temperature if the volume flow rate is 2.5 m3/s. [16]

9 (a) Draw the schematic layout of gas turbine cycle with regenerator, intercooler and reheating. Explain salient

features.

(b) Derive the thermal efficiency of gas turbine unit with multi stage compression with inter-cooling. [8+8]

10. (a) What is the influence of isentropic efficiency of compressor and turbine on thermal efficiency of gas

turbine unit? Explain with

suitable diagrams.

(b) Explain the working of regenerative gas turbine cycle with p-V and T-s dia-grams. [8+8]

11. (a) What are essential components required for the operation of gas turbine cycleand explain their

functionality.

(b) What are the advantages and limitations of gas turbine power generation units in comparison with other

power generating units.

[8+8]

12. (a) Explain with neat sketch open cycle gas turbine plant.

(b) Enumerate the differences between open cycle gas turbine plant and closed Cycle turbine plant. [8+8]

13. In gas turbine plant, operating on joules cycle, maximum and minimum temperatures of 8250C and 27 0C .

The pressure ratio is 4.5.

Calculate the specific work output , cycle efficiency and work ratio. Assume isentropic efficiency of

compressor and turbine

85%and 90% respectively. What is the heat rate in kJ / kW-hr. If the rating of the turbine is 1300kW, what

is the mass flow in kg/s.

Neglect the mass of fuel. Cp=1.005 kJ/kg 0K. [16]

14. (a) What are the Principal components in closed cycle gas turbine and Explain them briefly, show the cycle

on T-S diagram

(b) Derive the expression for thermal efficiency of a simple gas turbine plant. [8+8]

15. In gas turbine plant, operating on joules cycle, maximum and minimum tempera-tures of 8250C and 27 0C .

The pressure ratio is

4.5. Calculate the specific work output , cycle efficiency and work ratio. Assume isentropic efficiency of

compressor and turbine

85%and 90% respectively. What is the heat rate in kJ / kW-hr. If the rating of the turbine is 1300kW, what

is the mass flow in kg/s.

Neglect the massof fuel. Cp=1.005 kJ/kg 0K. [16]

UNIT – VIII Jet Propulsion : Principle of Operation –Classification of jet propulsive engines – Working Principles with

schematic diagrams and representation on T-S diagram - Thrust, Thrust Power and Propulsion Efficiency –

Turbo jet engines – Needs and Demands met by Turbo jet – Schematic Diagram, Thermodynamic Cycle,

Performance Evaluation Thrust Augmentation – Methods.

Rockets : Application – Working Principle – Classification – Propellant Type – Thrust, Propulsive Efficiency

– Specific Impulse – Solid and Liquid propellant Rocket Engines.

1. (a) Explain the essential differences between rocket propulsion and turbojet propul-sion?

(b) What is the importance of specific impulse in rocket engines? [8+8]

2 (a) Explain clearly the various factors affecting the performance of different propul-sive devices.

(b) Explain the working principle of solid propellant rocket engine with suitablesketch. [8+8]

3. (a) Discuss the advantages and limitations of turboprop engine over turbo jet engine.

(b) What is the operating principle of a rocket engine. Discuss the advantages and disadvantages of rocket

engines. [8+8]

4. (a) How to classify the jet propulsive engines? What are different applications of jet propulsions.

(b) Explain the operating principles of rocket engine with a neat diagram? [8+8]

5. (a) Describe a solid propellant rocket engine with a neat sketch.

(b) What are the advantages and disadvantages of rocket engine? [10+6]

6. (a) What is ramjet? Explain the working of a ramjet with a neat sketch.

(b) Explain the following terms

i. Isentropic Compressor efficiency

ii. Isentropic Turbine efficiency

iii. Propelling nozzle efficiency

iv. Transmission efficiency. [8+8]

7. (a) Where is rocket propulsion is used? What are the kinds of rocket propellants?

(b) Describe a liquid propellant rocket engine with a neat sketch. [12+4]

8. (a) Explain with a neat sketch a Turbo-Prop System.

(b) Explain with a sketch a rocket propulsion unit. [8+8]

9 (a) What do you mean by jet propulsion? Explain the Various devices in a jet propulsion unit.

(b) Prove that the propulsion of a rocket motor is obtained is

ηp = 2(Ca/Cje)/(1 + (Ca/Cje)2)

Where Ca=flight speed

Cje=effective jet velocity of rocket motor. [6+10]

10. A turbo-jet has a speed of 750 km/hr, while flying at an altitude of 10000m. The propulsive efficiency of

the jet is 50% and the

overall efficiency of the turbine plant is 16%. The density of air at 10000m altitude is 0.173 kg/m3. The

drag of the

plant is 6250 N. The calorific value of the fuel is 48,000 KJ/kg. Calculate:

(a) Absolute velocity of the jet.

(b) Volume of air compressed per minute.

(c) Diameter of the jet.

(d) Power output of the unit in KW.

(e) Air-fuel ratio. [16]

11. A turbo-jet engine consumes air at the rate of 60.2 kg/s when flying at a speed of 1000 km/hr. Calculate:

(a) Exit velocity of the jet when the enthalpy for the nozzle is 230 KJ/kg. and velocity coefficient of the

jet is 0.96

(b) Fuel flow rate in kg/s when air-fuel ratio is 70:1

(c) Thrust specific fuel consumption

(d) Thermal efficiency of the plant when the combustion efficiency is 92% and the calorific value of the

fuel is 42000 KJ/kg

(e) Propulsive power

(f) Propulsive efficiency

(g) Overall efficiency. [16]

12. A jet propulsion unit consists of compressor, combustion chamber, turbine and nozzle. The air at 0.65 bar

and 272K is compressed in the compressor to 3 bar. η c =0.85.The temperature of the gases at inlet to the

turbine is 7000 C , and the

ηt =0.80. The gases coming out of the turbine are expanded in a nozzle to a pressure 0.564 bar. The η of the

nozzle is 0.90. Neglecting the pressure and mechanical losses and fuel mass, find the following:

(a) A:F ratio used assuming C.V. of fuel 44000 KJ/ Kg and the η com.=0.90.

(b) Power required to run the compressor

(c) Pressure of the gases entering the nozzle

(d) The thrust developed per kg of air per sec.

Take Cp=1.005 KJ/Kg-K, γ = 1.4 for air and Cp=1.005 KJ/Kg-K, γ = 1.4 for air and Cp=1.1514 KJ/Kg-

K, γ = 1.33 for gases.

Speed of the jet propulsion unit is 720 Km/h. [16]

13. (a) Draw the neat sketch of Turboprop engine and explain its working principle. (b) What are the important

elements used in rocket

engines? Explain their func-tions. [8+8]

14. (a) What are the advantages and limitations of Ram jet engine over turbojet engine? Explain them briefly.

(b) Discuss the relative merits and demerits of gas pressurization system over the pump pressurization

system? [8+8]

15. (a) Define and explain terms relevant to turbojet engine i. Ram efficiency ii. propeller efficiency iii.

transmission efficiency

iv. propeller efficiency v. propulsive efficiency vi. overall efficiency.

(b) Explain the working principle of a hybrid rocket engine with a neat diagram?List its applications. [8+8]

16. (a) Define and explain the terms:

i. Thrust

ii. Thrust power,

iii. Effective jet exit velocity,

iv. Propulsive efficiency related to turbojet engines.

(b) Describe the nuclear rocket engine with a neat sketch and explain its merits and demerits. [8+8]

17. (a) Explain the significance of effective speed ratio on Specific thrust and overall thermal efficiency in a

turbojet engine.

(b) Briefly explain the needs and demands to be met by a modern turbo-jet engine. [8+8]

18. (a) Why liquid propellants are preferred in rocket propulsion?

(b) A simple turbojet unit operates with a turbine inlet temperature of 11000K, a pressure ratio is 4:1 and a

mass flow of 22.7

Kg/Sec. under design conditions. The following component efficiencies may be assumed: Isentropic

Compressor

efficiency - 0.85

Isentropic Turbine efficiency - 0.90

Propelling nozzle efficiency - 0.95

Transmission efficiency - 0.99

Combustion chamber loss - 0.21 bar

Calculate the design thrust and specific fuel consumption when the unit is stationary at sea level where

the ambient conditions may be taken as 1.013 bar and 288K. [6+10]

19. (a) What are the important properties of a good propellant? (b) In a jet propulsion cycle air enters the

compressor at 1 bar, 150 C.

The pressure leaving the compressor is 5 bar and the maximum temperature is 9000 C. The air expands

in the turbine to such a

pressure that the turbine work is just equal to the compressor work. On leaving the turbine, the air

expands in a reversible

adiabatic process in a nozzle to 1 bar. Calculate the velocity leaving the nozzle. Take Cp=1.0035 andγ =

1.4 for compressor and

expansion processes. [4+12]

20. (a) Explain with a neat sketch a Screw Propeller Unit.

(b) What are the fundamental differences between jet propulsion and rocket propul-sion? [8+8]

21. (a) Describe the effect of altitude on turbo jet unit.

(b) How do the thrust and thrust power of a turbojet engine vary with flight speed? Compare these with

a reciprocating engine. How thrust is augmentedfor the off and climb? [6+10]

22. A turbo-jet engine flying at a speed of 960 km/hr consumes air at the rate of 54.5 kg/s. Calculate

(a) Exit velocity of jet when the enthalpy change for the nozzle is 200 KJ/kg and velocity coefficient is

0.97.

(b) Fuel flow rate in kg/s when air-fuel ratio is 75:1.

(c) Trust specific fuel consumption.

(d) Thermal efficiency of the plant when the combustion efficiency is 93% and calorific value of the

fuel is 45000 KJ/kg.

(e) Propulsive power.

(f) Propulsive efficiency.

Overall efficiency. [16]

23. Discuss the theory of the rocket engine. [16]

24. (a) What are the important properties of a good propellant?

(b) In a jet propulsion cycle air enters the compressor at 1 bar, 150 C. The pressure leaving the compressor

is 5 bar and the maximum

temperature is 9000 C. The air expands in the turbine to such a pressure that the turbine work is just

equal to the compressor

work. On leaving the turbine, the air expands in a reversible adiabatic process in a nozzle to 1 bar.

Calculate the velocityleaving

the nozzle. Take Cp=1.0035 andγ = 1.4 for compressor and expansion processes. [4+12]