Question bank - sitams

SREENIVASA INSTITUTE OF TECHNOLOGY AND MANAGEMENT STUDIES (Autonomous)

DEPARTMENT of MECHANICAL ENGINEERING

QUESTION BANK THERMAL ENGINNERING –II (16MEC311)

SREENIVASA INSTITUTE of TECHNOLOGY and MANAGEMENT STUDIES (Autonomous)

(THERMAL ENGINEERING -II)

Question bank

III - B.TECH / I - SEMESTER regulation: r16

PREPARED BY FACULTY INCHARGE : Mr.R.Satheesh

Mr.K.Sanjeeviraj Designation : Associate professor

Assistant professor Department : mechanical




III B.Tech I Semester L T P C

3 1 - 3

16MEC311 THERMAL ENGINEERING -II

Pre-requisites: Course on Engineering Mechanics.

Course Educational Objectives:

CEO1: To acquire knowledge on analysis of stages in steam power cycles

CEO2: To apply the thermodynamic concepts for systems like boilers and draughts.

CEO3: To acquire knowledge on analysis of nozzles and condensers

CEO4: To interpret the principle of steam turbines, velocity diagrams and governing.

CEO5: To gain basic knowledge on gas turbines and jet propulsion.

UNIT – 1: STEAM POWER CYCLE

Rankine cycle – Schematic layout, comparison between Rankine cycle and Carnot cycle.

Thermodynamic analysis, concept of mean temperature of heat addition, methods to improve

cycle performance: Reheat cycle – Regenerative cycle – Binary vapour cycle.

UNIT – 2: BOILERS AND DRAUGHT Boilers: Classification of steam boilers – Modern high pressure boilers – Boilers mountings and - Accessories – Methods of feed water treatment – Equivalent evaporation – Boiler efficiency –Heat losses in a boiler – Heat Balance sheet.Draught: Classification – Natural draught: Chimney height and diameter – Condition for maximum discharge through a chimney – Artificial draught: Forced draught, induced draught and balanced draught.

UNIT – 3 STEAM NOZZLES AND CONDENSERS

Steam Nozzles: Introduction - Steam flow through nozzles – Nozzle efficiency –

Supersaturated flow in a nozzle. Steam Condensers: Requirements of steam condensing plant

– Classification of condensers – Sources of air in condensers – Effects of air leakage in a

condenser – Vacuum measurement – Vacuum efficiency and condenser efficiency – Edwards

air pump – Cooling towers.

UNIT – 4: STEAM TURBINE

Classifications – Compounding – Velocity diagrams for impulse and reaction turbine –

Condition for maximum efficiency in De-Laval impulse turbine and Parsons reaction turbine –

Degree of reaction – State point locus and reheat factor – Bleeding – Governing and control.

UNIT – 5: GAS TURBINES AND JET PROPULSION

Gas Turbines: Constant pressure gas turbine – Methods improvement of thermal efficiency –

Effects of operating variables – Constant volume gas turbines. Jet Propulsion: Classification –

Working principles of turbo jet, turbo prop, ram jet, pulse jet engine and rocket engine.




QUESTION NO

QUESTION BLOOMS

LEVEL

UNIT – I STEAM POWER CYCLE

PART-A (Two Marks Questions)

1 State the essential differences between Carnot and Rankine cycles. BT2

2 What are the limitations on increasing the mean temperature of heat addition in

a Rankine cycle? BT4

3 Explain the concept of Mean temperature of heat addition. BT2

4 What is the purpose of reheating? BT2

5 Define the term Degree of super heat and degree of sub cooling. BT2

6 Why reheat cycle is not used for low boiler pressure? BT6

7 Mention the improvements made to increase the ideal efficiency of Rankine

cycle. BT4

8 What are the effects of condenser pressure on the Rankine Cycle? BT3

9 Define specific steam consumption of an ideal Rankine cycle. BT2

10 What are the advantages of super heating of steam? BT3

11 Why Rankine cycle is modified? BT6

12 Draw the P-V diagram and T-s diagram of Reheat cycle. BT2

13 Explain why a condenser is placed in a Rankine cycle. BT2

14 What are the difficulties experienced in carrying out Carnot cycle in steam

power plants? BT2

15 Draw the different processes of Rankine cycle on a T-S diagram. Mention the

Different operations of Rankine cycle. BT2

16 Draw diagram of ‘reheat cycle’ and state the advantages and disadvantages of

reheating. BT2

17 Mention the advantages and disadvantages of regenerative cycle. BT2

18 What is the difference between an open and a closed feed water heater? BT2

19 Regeneration employed in Rankine Cycle consumes some Steam mass tapped

from Steam turbine/engine thereby resulting in Loss of Work output? How

does Regeneration improve the performance of Rankine cycle?

BT2

20 State the essential differences between Carnot and Rankine cycles. BT2

21 What is binary Vapour power cycle? BT2

22 How do binary cycle power plants work? BT2

PART-B (Ten Marks Questions)

1 With neat block diagrams, explain clearly the various methods to improve

Rankine cycle performance. Draw the T-s and h-s diagrams for each category BT4, BT6

2 Explain regeneration cycle with the help of neat sketches of layout, p-v and T-s

plots. BT4

3 What are the different thermodynamic variables affecting efficiency and

output of Rankine Cycle. Explain their influence on Rankine cycle BT4

4 Draw the configuration diagram, p-v and T-s diagram of a Simple Rankine

Steam Power cycle and explain its working principle. BT2, BT4

5 Steam is supplied from a boiler to a steam engine at a pressure of 1.1 MN/m2

and at a temperature of 250. It is expanded isentropically to a release pressure

of 0.28 MN/m2. Its pressure then falls at constant volume to 35 kN/m2 at which

pressure it is exhausted to a condenser. Determine: (i) Rankine efficiency. (ii)

Specific steam consumption in kg/k Wh. (iii) The Carnot efficiency for same

temperature limits.

BT4, BT5

6 Steam at a pressure of 15 bar and 250oC is expanded through a turbine at first BT4, BT5




to a pressure of 4 bar. It is then reheated at constant pressure to the initial

temperature of 250oC and finally expanded to 0.1 bar. Using Mollier chart,

estimate the work done per kg of steam flowing through the turbine and

amount of heat supplied during the process of reheat. Assume all expansion

process to be isentropic.

7 In a Rankine cycle, the steam at inlet to turbine is saturated at pressure of 30

bar and 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. Assume flow rate of 10 kg/s.

BT4, BT5

8 A power generating plant uses steam as working fluid and operates at boiler

pressure of 50 bar, dry saturated and condenser pressure of 0.5 bar. Calculate

for these limits i) the cycle efficiency and ii) the work ratio and iii) specific

steam consumption for Carnot cycle and Rankine cycle.

BT4, BT5

9 A smaller power plant produces 25 kg/s steam at 3 MPa and 600oC, in the

boiler. It cools in the condenser with ocean water so that the condenser exit is

at 45oC. There is reheat done at 500 kPa upto 400oC, and then expansion takes

place in the low-pressure turbine. Find the net power output and the total heat

transfer in the boiler.

BT4, BT5

10 Steam is the working fluid in an ideal Rankine Cycle. Saturated vapour enters

the turbine at 10 MPa and saturated liquid exits the condenser at a pressure of

0.010 MPa. The net power output of the cycle is 110 MW. Determine the

following for the cycle.

(a) The thermal efficiency

(b) The back work ratio

(c) Steam mass flow rate in kg/hr

(d) Rate of heat added to the working fluid in the boiler

(e) Heat removed from the working fluid in the condenser

BT4, BT5

11 The steam is supplied to a steam turbine at a pressure of 32 bar and a

temperature 410°C. The steam then expands isentropically to a pressure of

0.08bar. Find the dryness fraction of steam at the end of expansion and

thermal efficiency of the cycle. If the steam is reheated at 5.5 bar to a

temperature of 395° C and then expands isentropically to 0.08 bar, what will be

the dryness fraction at the end of final expansion and the thermal efficiency of

the cycle?

BT4, BT5

12 A power generating plant uses steam as a working fluid and operates at a

boiler pressure of 80 bar and a condenser pressure of 0.075 bar. Assuming the

operating cycle to be ideal, determine i) The heat transfer per unit mass of

steam in the boiler and condenser; ii) The specific work output; iii) The cycle

efficiency; iv) The required rate of steam flow to provide a specified power

output of 10000 kW and v) Work ratio if the plant operates on The Rankine

cycle, taking the pumping work into account

BT4, BT5

13 Steam at 70 bar and 4500C is supplied to a steam turbine. After expanding to

25bar in high pressure stages, it is reheated to 4200C at the constant pressure.

Next; it is expanded in intermediate pressure stages to an appropriate

minimum pressure such that part of the steam bled at this pressure heats the

feed water to a temperature of 1800C. The remaining steam expands from this

pressure to a condenser pressure of 0.07bar in the low pressure stage. The

isentropic efficiency of HP stage is 78.5%, while that of the intermediate and

LP stage is 83% each. Determine the minimum pressure at which bleeding is

necessary, the quantity of steam bled per kg of flow at the turbine inlet and the

efficiency of the cycle.

BT4, BT5

14 A steam power plant operates on a theoretical reheat cycle. Steam at boiler at

1500c expands through the high pressure turbine. It is reheated at a constant BT4, BT5




pressure of 40bar to 5500C and expands through the low pressure turbine to a

condenser at 0.1bar. Draw T-S and h-s diagrams and find the Quality of steam

at turbine exhaust, cycle efficiency and steam rate in kg/kWh.

15 Steam used in a reheat cycle for the working of steam engine. The steam leaves

the boiler and enters the turbine at 3 MPa and 3500C. After expansion in the

turbine to 500 kPa, the steam is reheated to 5000C and then expanded in the

low pressure turbine to 20 kPa. Determine the efficiency of the reheat cycle.

BT4, BT5

16 In a single-heater regenerative cycle the steam enters the turbine at 30 bar,

4000C and the exhaust pressure is 0.10 bar. The feed water heater is a direct

contact type which operates at 5 bar. Find: (i) The efficiency and the steam rate

of the cycle. (ii) The increase in mean temperature of heat addition, efficiency

and steam rate as compared to the Rankine cycle (without regeneration). Pump

work may be neglected.

BT4, BT5,

BT6

17 Consider a regenerative vapour power cycle with a feed water heater. The

steam enters the first stage turbine at 8 MPa, 500oC and expands to 0.7 MPa,

where some of the steam is extracted and diverted to feed water heater

operating at 0.7 MPa. The remaining steam expands through the second stage

turbine to a condenser pressure of 0.008 MPa. The saturated liquid exits the

feed water heater at 0.7 MPa. The isentropic efficiency of each turbine is 85%,

while each pump operates isentropically. If the net power output of the cycle is

105 MW, determine i) Thermal efficiency of the cycle ii) The mass flow rate of

steam entering the first turbine stage.

BT4, BT5

18 Discuss the advantages of reheating the steam in high pressure steam plants. BT2, BT4

19 A steam power plant running on Rankine cycle has steam entering HP turbine

at 20 MPa , 5000C and leaving LP turbine at 90% dryness. Considering

condenser pressure of 0.005 MPa and reheating occurring upto the

temperature of 5000C determine, i) The pressure at which steam leaves HP

turbine ii) The thermal efficiency.

BT4, BT5

20 In a single regenerative heater system, the steam is supplied to the turbine at a

rate of 68000 kg/hr and 15420 kg of steam is blowed per hour at 10 bar and the

remaining is passed to the condenser. Determine the enthalpy of steam at entry

of regenerative heater and entry condition at the entry of the condenser.

BT4, BT5

21 Consider a water-ammonia binary vapor cycle consisting. In the steam cycle,

superheated vapor enters the turbine at 7 MPa, 450 oC, and saturated liquid

exits the condenser at 55 oC. The heat rejected from the steam cycle is

provided to the ammonia cycle, producing saturated vapor at 45 oC, which

enters the ammonia turbine. Saturated liquid leaves the ammonia condenser at

1 MPa. For a net power output of 24 MW from the binary cycle, determine (a)

the mass flow rates for the steam and ammonia cycles, respectively, in kg/s, (b)

the power output of the steam and ammonia turbines, respectively, in MW. (c)

the rate of heat input to the ammonia cycle, in MW, (d) the rate of heat

addition to the binary cycle, in MW, and (e) the thermal efficiency of the

binary vapor cycle. (f) Show the cycle on T-s diagram with respect to

saturation lines.

BT4, BT5,

BT6

22 A binary vapor cycle operates on mercury (Hg) and steam. Standard mercury

vapor at 4.5 bar is supplied to the mercury turbine, from which it exhausts at

0.04 bar. The mercury condenser generates saturated steam at 15 bar, which is

expanded in a steam turbine to 0.04 bar. a) Determine the efficiency of the

Mercury cycle b) Determine the efficiency of the Steam cycle c) Determine the

overall efficiency of the Binary cycle d)Re-do c) if the steam leaving the

mercury condenser is superheated to a temperature of 300 C in a superheater

located in the mercury boiler and if the efficiencies of the mercury and steam

turbines are 84% and 88%, respectively.

BT4, BT5,

BT6




UNIT II BOILERS AND DRAUGHT


1 Explain the use of following: (i) Blow off cock. (ii) Fusible plug BT2

2 What are the requirements of a good steam boiler? BT2

3 What is the difference between subcritical and supercritical boiler? BT2

4 Name some mountings used in boilers for the control of Pressure in Boiler BT2, BT3

5 How boilers are classified on different accounts with examples for each

category. BT2, BT4

6 Write the basic functions of a chimney in a natural draught. BT2

7 Explain why air preheaters are used in a high pressure boiler? BT6

8 What is artificial draught in thermal power plant? BT2

9 Explain the difference between a fire tube and water tube boiler. State which

type of boiler is used for power generation. BT2

10 How are the steam boilers classified? BT2

11 Compare force and induced draught. BT2

12 What is FD fan in boiler? BT2

13 Why are ID fans bigger than FD fans? BT2

14 What is meant by evaporation ratio in case of steam boiler? BT2

15 What are the effects of evaporation? BT2

16 Write the significance of mountings of a boiler. Plain `Boiler Draught`? BT2

17 What are the functions of a boiler chimney? Why chimney is not provided in a

locomotive boiler? BT6

18 What are the major differences between mountings and accessories? Give

three examples of each. BT4

19 What is the function of fusible plug? BT2

20 Write any six comparisons between fire tube and water tube boilers. BT2


1 Explain the working of a Lamont boiler with a neat sketch. BT2, BT4

2 Describe the working of a Lancashire boiler with the aid of a neat sketch. Show

the path of flue gasses to stack and the relative position of economizer and

super heater.

BT2, BT4

3 Describe the working of a locomotive boiler with the aid of a neat sketch. Show

the position of various mountings. Explain the method of obtaining draught in

the absence of a chimney of appreciable height in these boilers. How is the

draught maintained when the locomotive engine is stationary?

BT2, BT4,

BT6

4 A coal fire boiler plant consumes 400kg of coal per hour. The boiler evaporates

3200 kg of water at 44.5oC into superheated steam at a pressure of 12 bar and

274.5oC. If the calorific value of fuel is 32760 kJ/kg of coal. Determine

equivalent evaporation from and at 100oC and the thermal efficiency of the

boiler. Assume specific heat of superheated steam as 2.1 kJ/kg.K.

BT4, BT5

5 What do you mean by high pressure boilers? How do they differ in

construction and Working from an ordinary boiler? BT4, BT5

6 Estimate the height of the chimney to produce a static draught of 20 mm of

water if the mean temperature of the hot gases is 250ºC and ambient

temperature is 20ºC. Assume the density of air and hot gases as 1.293 kg/m3

and 1.34 kg/m3 respectively at NTP. Also estimate the mass of flue gases

formed per kg of fuel. Barometer reads 760 mm of Hg.

BT4, BT5

7 Derive an expression for maximum discharge rate of gases through the

chimney for a given height of the chimney. b) Calculate the height of a chimney

required to produce a draught equivalent to 1.7cm of water if the flue gas

temperature is 2700C and ambient temperature is 220C and minimum amount

of air per kg of fuel is 17kg

BT4, BT5

8 A boiler is to provide 7000 kg/hr of steam with superheated by 40ºC at a BT4, BT5




pressure of 20bar. The temperature of water is 60ºC. If the thermal efficiency

of the boiler is 75%, how much fuel oil will be consumed in one hour? The

calorific value of oil used is 45000 kJ/kg. Take specific heat of superheated

steam as 2.093 kJ/kg K and also calculate the equivalent evaporation from and

at 100ºC.

9 Calculate the height of chimney required to produce a draught equivalent to

1.7cm of water if the flue gas temperature is 270°C and ambient temperature is

22°C and minimum amount of air per kg of fuel is 17kg.

BT4, BT5

10 Discuss the advantages and disadvantages of artificial draught system over

natural draught system? BT2

11 The equivalent evaporation of boiler from and at 1000C is 1300kg/hr.

Calculate the actual evaporation if the feed water is supplied at 1100C and the

steam is generated at a pressure of 15bar and temperature 2000C. if the

efficiency of this boiler is 72%, find i) The fuel consumption per hour taking

calorific value of coal as 25500 kJ/kg, and ii) The grate area if the rate of

evaporation is 100kg/m2 per hour.

BT4, BT5

12 A thermal power station works on natural draught. The height of the chimney

is restricted to 40 m. The ambient temperature of the air is 20oC and the

temperature of the flue gas passing through the chimney at its base is 300oC.

The air fuel ratio is 17:1. Calculate the diameter of the chimney at the base, if

head due to friction is 25% of the ideal draught.

BT4, BT5

13 A 30 m high chimney discharges flue gases at 357oC in to an atmosphere at

27oC. Consider the air-fuel ratio required to burn the coal on the grate is 16.

Calculate:

(a) Volume of flue gases passing through the chimney per sec if 1360 kg of

coal is burnt per hour over the grate.

(b) The base diameter of the chimney if the velocity of the flue gases at the

base of the chimney is given by, H1=K C2/2 where the value of K =

1.627

BT4, BT5

14 A chimney of 24 m height is used to produce a natural draught when flue gas

temperature is 300oC and ambient temperature is 25oC. The air supplied is 20

kg/kg of fuel burned. Find (i) theoretical draught produced in mm of water (ii)

velocity of the hot gases passing through the chimney if 50% of theoretical

draught is lost in friction.

BT4, BT5

UNIT III STEAM NOZZLES AND CONDENSERS


1 What is the effect of friction on the flow through a steam nozzle? BT2

2 What is the function of steam nozzle? BT2

3 How does a spray nozzle work? BT2

4 What are the various types of nozzles and their functions? BT2

5 How does nozzle size affect velocity? BT2

6 What is divergent nozzle? BT2

7 What is critical pressure in nozzle? BT2

8 What is back pressure in nozzle? BT2

9 Define nozzle efficiency and critical pressure ratio. BT2

10 What are the parameters affect the nozzle efficiency? BT2

11 Why there is a need of an air extraction pump in the condenser? BT6

12 Explain the phenomenon of super saturated expansion in steam nozzle. or

What is metastable flow? BT2

13 Define nozzle velocity coefficient and how it is related to nozzle efficiency. BT2

14 Explain the term nozzle efficiency, velocity coefficient and discharge coefficient

as applied to nozzles. BT2

15 What are the effects of friction on the flow through a steam nozzle? Explain BT2




with the help of diagram.

16 Explain the terms “over expanding” and under expanding” applied to a fluid

flow through a nozzle. BT2

17 What are the sources of air leakages into a condenser? Briefly state the effects

of air leakage on the performance of a condenser. BT2

18 Mention various types of nozzles and distinguish their features. BT2

19 Explain the working principle of a nozzle. BT2

20 What do you mean by vacuum efficiency of a condenser? On what factors does

this efficiency depend? BT2


1 Air expands under reversible adiabatic conditions in a nozzle form 4 bar and

725 to a final pressure of 1 bar. Determine: (i) Type of nozzle required. (ii)

Critical velocity. (iii) Air flow rate if the minimum nozzle diameter is 1.25 cm.

BT4, BT5

2 In a convergent-divergent nozzle, the steam enters at 15 bar and 3000C and

leaves at a pressure of 2 bar. The inlet velocity to the nozzle is 150 m/s. Find the

required throat and exit areas for a mass flow rate of 1 kg/s. Assume nozzle

efficiency to be 90 percent and Cps = 2.4 kJ/kg.K

BT4, BT5

3 A set of 16 nozzles for an impulse turbine receives steam at 16 bar and 300oC.

The pressure of steam at exit is 10 bar. If the total discharge is 245 kg/min and

efficiency of nozzle is 90%, calculate the cross sectional area at the exit of each

nozzle. If the steam has a velocity of 100 m/sec at the entry to the nozzles,

calculate the percentage increase in discharge.

BT4, BT5

4 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 30ºC and at the

outlet is 26ºC. Calculate: (i) mass of steam condensed in the air cooler section

(ii) reduction in the air pump capacity following the cool air From the

fundamentals deduce expressions for mass discharge and critical pressure ratio

for maximum discharge in the case of flow through nozzles.

BT4, BT5

5 A surface condenser is to be introduced to handle 14000 kg of steam per hour.

The steam enters the condenser at 0.07 bar, 0.81 dry and the condensate leaves

the condenser at the corresponding saturation temperature. Determine the rise

in cooling water temperature, if the cooling water flow rate is 8.30 x 105 kg/hr.

It is assumed that the pressure is same throughout the condenser.

BT4, BT5

6 In a nozzle steam expands from 12 bar and 3000C to 6 bar with flow rate of 5

kg/s. Determine throat and exit area if exit velocity is 500 m/s and velocity at

inlet to nozzle is negligible. Also find coefficient of velocity at exit. Coefficient

of velocity is the ratio of actual velocity of fluid at nozzle exit to the velocity at

exit considering isentropic flow through nozzle

BT4, BT5

7 Steam enters a group of nozzles of a steam turbine at 12bar and 2200C and

leaves at 1.2bar. The steam turbine develops 220kW with a specific steam

consumption of 13.5kg/kWh. If the diameter of nozzles at throat is 7mm,

calculate the number of nozzles.

BT4, BT5

8 Dry saturated steam at a pressure of 8bar enters a convergent divergent nozzle

and leaves it at a pressure of 1.5 bar. If the flow is isentropic and the

corresponding expansion index is 1.135. Find the ratio of cross sectional area at

exit and throat for maximum discharge.

BT4, BT5

9 A convergent- divergent steam nozzle is required to deliver 2 kg of steam per

second. The nozzle is supplied with steam at 10 bar (abs) and temperature

200oC, while discharge takes place against a back pressure of 0.34 bar (abs).

Calculate the throat and exit areas of the nozzle. Assume the flow of steam

through the nozzle to be isentropic and the index of expansion to be 1.3. If the

nozzle efficiency is assumed to be 85 %, calculate the exit area of the nozzle.

BT4, BT5




10 The observations recorded during the trail on steam condenser are given

below: Condenser vacuum = 685 mm of Hg; Barometer reading = 765 mm of

Hg; Mean condenser temperature = 34oC; Hot well temperature is 28oC;

Condensate formed per hour = 1750 kg; Circulating cooling water inlet

temperature is 18oC; Outlet temperature is 30oC; Quantity of cooling water is

1300 kg/min. Calculate: (i) Vacuum efficiency. (ii) Under-cooling of

condensate. (iii) Efficiency of condenser. (iv) Condition of steam as it enters the

condenser. (v) Mass of air present per kg of uncondensed steam.

BT4, BT5

11 What is compounding of turbines? Discuss in brief with relevant sketches. BT3, BT4

12 A convergent nozzle is used to expand ethane gas at 780 kPa and 3500K

isentropically into a chamber at 370 kPa. Find the nozzle exit area for a mass

flow rate of 1400 kg/s. Assume the initial velocity is zero, C p=1.9 kJ/kgK,

R=277 J/kg K and _=1.17.

BT4, BT5

13 The air entering a steam condenser with steam is estimated at 6kg per hour.

The temperature at inlet to air cooler section is 30oC and at the outlet 26oC.

The vacuum in the shell is essentially constant throughout and is 721mm of Hg,

while the barometer reads 758 mm of Hg. Calculate the volume of air entering

the cooling section per hour, the mass of moisture contained in the air and the

mass of steam condensed per hour in the cooling section.

BT4, BT5

14 Surface condenser is designed to handle 10000 kg of steam per hour. The steam

enters at 0.08 bar abs. and 0.9 dryness and the condensate leaves at the

corresponding saturation temperature. The pressure is constant throughout

the condenser. Estimate the cooling water flow per hour, if the cooling water

temperature rise is limited to 100C.

BT4, BT5

15 A steam engine using 4500 kg of steam per hour exhaust into a jet condenser

where the vacuum is 68.5 cm of Hg(barometer reading being 760 mm of Hg).

Cooling water with initial temperature of 25 is injected into the condenser at an

hourly rate of 350 m3. Air enters the condenser along with steam at the rate of

1 kg for every 3,000 kg of steam. The injection water has also air dissolved in it

which is 6% of the volume of water at atmospheric pressure. The temperature

of condensate is 35. Assuming the volumetric efficiency of air extraction pump

to be 85%, determine its capacity to remove water and air from the condenser.

Take atmospheric conditions of 0.98 bar and 27.

BT4, BT5

16 Steam enters an impulse wheel having a nozzle angle 200 at a velocity of 450

m/sec. The exit angle of moving blade is 200 and the relative velocity of steam

may be assumed to remain constant over the moving blades. If the blade speed

is 180m/sec; Calculate i) Blade angle at inlet, ii) Work done per kg of steam, iii)

Power developed if rate of steam flow is 1.6 kg/sec.

BT4, BT5

17 Explain the phenomenon of meta stable flow of steam through a nozzle. What

is the significance of Wilson’s line in it? BT2, BT4

18 Discuss the process of super saturation in steam nozzles with the help of

enthalpy entropy diagram. Define degree of super-saturation and degree of

under-cooling. Explain in detail the physical significance of abrupt change at

Wilson`s line.

BT2, BT4

19 Derive the condition of maximum blade efficiency in single-stage impulse

turbine? What is its value? Sketch how efficiency varies with blade-steam

velocity ratio.

BT2, BT4

20 A condensing plant condenses 13750kg of steam per hour and the leakage of air

in the system is 1kg per 2500kg of steam. The vacuum in the air pump suction

is 71.5cm (barometer 76cm) and the temperature 32.90C. Compute the

capacity of the air pump which removes both air and water in m3/min, taking

the volumetric efficiency as 80%.

BT4, BT5

21 Steam at 15 bar and 300oC expanded in a nozzle till its pressure falls to 1 bar. BT4, BT5




If the12% of isentropic heat drop is lost in friction; find out the mass of steam

passing through the nozzle of exit diameter = 1.5 cm. Neglect initial velocity of

the steam.

22 The following data relate to a compound impulse turbine having two rows of

moving blades and one row of fixed blades in between them. Steam velocity

coming out of nozzle = 450 m/sec., Nozzle angle = 15o, Moving blades tip

discharge angles = 30o, Fixed blade discharge angle = 20

o , Friction loss in each

blade rows = 10% of the relative velocity. Find the blade velocity, blade

efficiency and specific steam consumption for the turbine.

BT4, BT5

23 The vacuum at the bottom of a surface condenser is 65.4 cm of mercury

(barometer 75.7cm), the temperature at the air pump suction is 36.20C. If the

rate of air leakage into the condenser is 1kg per 1000 kg of steam, estimate the

mass of air and vapour removed by the air pump per minute when the engine

consumption is 136000 kg of steam/hr.

BT4, BT5

24 In a surface condenser a section of tubes near the air pump section is screened

off so that the air is cooled to a temperature below that of the condensate,

separate extraction pumps being provided to deal with air and condensate

respectively. The steam condensed per hour is 15000 kg, and air leakage is 12

kg/hr. The temperature of the steam entering the condenser is 32.550C, the

temperature of condensate at entrance at entrance to the air cooler is 30.690C,

and the temperature at the air pump suction is 250C. Assuming a constant

vacuum throughout the condenser, find: (i) The weight of steam condensed in

the cooler per hour. (ii) The volume of air in m3/hr to be dealt with by the air

pump. (iii) The percentage reduction in the air pump capacity following the

cooling of the air.

BT4, BT5

25 The air entering a steam condenser with steam is estimated at 6kg per hour.

The temperature at inlet to air cooler section is 30oC and at the outlet 26oC.

The vacuum in the shell is essentially constant throughout and is 721mm of Hg,

while the barometer reads 758 mm of Hg. Calculate the volume of air entering

the cooling section per hour, the mass of moisture contained in the air and the

mass of steam condensed per hour in the cooling section.

BT4, BT5

26 A surface condenser is designed to handle 10000 kg of steam per hour. The

steam enters at 0.08 bar abs. and 0.9 dryness and the condensate leaves at the

corresponding saturation temperature. The pressure is constant throughout

the condenser. Estimate the cooling water flow per hour, If the cooling water

temperature rise is limited to 100C. b) Define the term Degree of Reaction used

in Reaction Turbines. Prove that moving and fixed blades should have the

same shape for 50% reaction.

BT4, BT5

UNIT IV STEAM TURBINE


1 Distinguish between impulse and reaction turbine. BT2

2 State the function of fixed blades. BT2

3 Explain degree of reaction. BT2

4 The blade height in an axial flow turbine is increased towards the low pressure

end why? BT2

5 Classify steam turbines. BT2

6 How does impulse work? BT2

7 What is meant by carry over loss? BT2

8 State the function of moving blades. BT2

9 What is the fundamental difference between the operation of impulse and

reaction steam turbines? BT2

10 What are the different methods of governing steam turbines? BT2

11 How is throttle governing done? BT2




12 Where nozzle control governing is used? BT2

13 Where by - pass governing is more suitable? BT2

14 What are the different losses in steam turbines? BT2

15 Write the expression for blade efficiency for a single stage reaction turbine for

getting the maximum blade efficiency. BT2

16 Explain the essential differences in the functioning of moving blades in impulse

and reaction turbines. BT2

17 Explain the terms blade speed ratio and blade velocity coefficient in a steam

turbine. BT2

18 Draw velocity diagram at inlet for impulse turbine. BT2

19 Write the expression for blade efficiency for a single stage reaction turbine for

getting the maximum blade efficiency. BT2

20 Why does steam expand in a turbine? BT2


1 In a Delaval turbine, the steam issues from the nozzles with a velocity of 850

m/s. The nozzle angle is 20oC. Mean blade velocity 350 m/s. The blades are

equiangular. The mass flow rate is 1000 kg/min. Friction factor is 0.8.

Determine: (i) Blade angles. (ii) Axial thrust on the bearing. (iii) Power

developed. (iv) Blade efficiency. (v) Stage efficiency if nozzle efficiency is 93%.

BT4, BT5

2 The outlet angle of the blade of a Parson’s turbine is 20oC and axial velocity of

flow of steam is 0.5 times the mean blade velocity. If the diameter of the ring is

1.25 m and the rotational speed is 3000 rpm. Calculate: (i) Inlet angles of the

blades. (ii) Power developed if dry saturated steam at 5 bar passes through the

blade whose height may be assumed as 6 cm. Neglect the effect of blade

thickness.

BT4, BT5

3 Derive the expression for maximum blade efficiency for a Parson’ 50-50

reaction turbine. BT3, BT4

4 Explain the working of a single-stage reaction turbine. Sketch pressure and

velocity variations along the axis of the turbine. Show the expansion on h-s

chart.

BT4

5 What do you mean by compounding of steam turbine? Discuss various

methods of compounding steam turbines? BT3, BT4

6 A single stage impulse turbine rotor has a diameter of 1.2 m running at 3000

rpm. The nozzle angle is 18, blade speed ratio is 0.42. The ratio of relative

velocity at out let to inlet is 0.9. The out let angle of blade is 3 smaller than the

inlet. The steam flow ratio is 5 kg/sec. Draw the velocity diagram and find: (i)

Velocity of whirl. (ii) Blade angle. (iii) Axial thrust (d) Power developed.

(a) the diagram efficiency

(b) power developed by the turbine if the flow of steam

is 5 kg/sec

BT4, BT5

7 At a certain pair in a reaction turbine, the steam leaves the fixed blade at a

pressure of 3bar with a dryness fraction of 0.98 and a velocity of 130m/sec. The

ratio of axial velocity of 130m/sec. The blades are 20mm high and discharge

angle for both the rings is 200. The ratio of axial velocity of flow to the blade

velocity is 0.7 at inlet and 0.76 at exit from the moving blade. If the turbine uses

4kg of steam per second with 5% tip leakage. Find the mean blade diameter

and the power developed in the ring. Draw the free hand sketch and explain

velocity compounded impulse turbine.

BT4, BT5,

BT6

8 In a single stage impulse turbine the isentropic enthalpy drop of 200 kJ/kg

occurs in the nozzle having efficiency of 96% and nozzle angle of 150. The

blade velocity co efficiency is 0.96 and ratio of blade speed to steam velocity is

0.5. The steam mass flow rate 20 kg/s and velocity of steam entering is 50 m/s.

determine

BT4, BT5,

BT6




i) The blade angles at inlet and outlet if the steam enters blades smoothly and

leaves axially.

ii) The blade efficiency

iii) The power developed in Kw

iv) The axial thrust.

Solve using velocity diagram.

9 A Parson’s reaction turbine has mean diameter of blades as 1.6 m and rotor

moving at 1500 rpm. The inlet and outlet angles are 800 and 200 respectively.

Turbine receives steam at 12 bars, 2000C and has isentropic heat drop of 26

kJ/kg. 5% of steam supplied is lost through leakage. Determine the following

considering horse power developed in stage to be 600 hp.

i) The stage efficiency

ii) The blade height.

BT4, BT5,

BT6

10 A 50% reaction turbine running at 400 rpm has the exit angle of blades as 20°

and the velocity of steam relative to the blade at the exit is 1.35 times mean

speed of the blade. The steam flow rate is 8.33 kg/s and at a particular stage

the specific volume is 1.38m3/kg .Calculate, suitable blade height, assuming

the rotor mean diameter 12 times the blade height, and diagram work.

BT4. BT5.

BT6

11 A reaction turbine having identical blading delivers dry saturated steam at 3

bar. The velocity of steam is 100 m/s. The mean blade height is 4 cm and the

exit angle of the moving blade 20. At the mean radius the axial flow velocity

equals ¾ blade speed. For steam flow rate of 10,000 kg/hour. Calculate: (i) The

rotor speed rev/min. (ii) The power output of stag. (iii) The diagram efficiency.

(iv) The percentage increase in relative velocity in the moving blades due to

expansion in these blades. (v) The enthalpy drop of the steam in stage.

BT4, BT5,

BT6

12 The blade angle of a single ring of an impulse turbine is 300m/s and the nozzle

angle is 200.Theisentropic heat drop is 473kJ/kg and nozzle efficiency is

85%.Given the blade velocity coefficient is 0.7and the blades are symmetrical,

Draw the velocity diagram and calculate for a mass flow of 1 kg/s i)

axial thrust on balding ii) steam consumption per BP hour if the mechanical

efficiency is 90% iii) blade efficiency and stage efficiency.

BT4

13 In a surface condenser test the following observations were made : Vacuum 70

cm of Hg; barometer 76.5 cm of Hg; mean temperature of condensate 35.820C;

hot well temperature 300C; weight of cooling water 47500 kg/h; inlet

temperature of cooling water 170C; outlet temperature of cooling water 320C;

weight of condensate 1500 kg/h. Calculate: (i) The mass of air present per m3

of condenser volume; (ii) The state of steam entering the condenser, and (iii)

The vacuum efficiency.

BT4, BR5,

B56

14 Deduce an expression for work done per stage of a reaction turbine. BT3, BT4

15 Following particulars refer to a compound turbine: Inlet pressure and

temperature to the first stage are: 20 bar and 2500C, pressure at entrance to

next stage is 1.5 bar and exhaust pressure is 0.05 bar. Stage efficiency is 0.77.

Determine i) Internal heat drop, ii) If external losses are 4% of total isentropic

heat drop, Calculate overall efficiency ratio, iii) Reheat factor.

BT4, BT5

16 16. A single state impulse turbine rotor has a diameter of 1.1 m and running at

3200 rpm. The nozzle angle is . The blade speed ratio is 0.45. The ratio of the

blade velocity at outside to the relative velocity at inlet is 0.95. The outlet angle

of the blade is 10 smaller than the inlet angle. The steam flow rate is 2 kg/sec.

Draw the velocity diagram and estimate:

(a) Velocity of whirl

(b) Axial thrust on the bearings

(c) Blade angles

(d) Power Developed

BT4, BT5




17 In a reaction turbine, the tips are inclined at 40 and 25 to the direction of

motion. The guide blades are of the same shape as the moving blades, but

reverse in direction. At some point in the turbine, the drum diameter is 1.2 m

and blades are 100 mm high. At this place, the steam has a pressure of 2 bar

and dryness fraction 0.9. If the speed of this machine is 300 rpm and the steam

passes through the blades without shock, find the mass flow rate of steam and

power developed in the ring of moving blades.

BT4, BT5

18 300 kg/min of steam (2 bar, 0.98 dry) flows through a given stage of reaction

turbine. The exit angle of fixed blades as well as moving blades is 200 and 3.68

kW of power is developed. If the rotor speed is 360 rpm and the tip leakage is 5

percent, calculate the mean drum diameter and the blade height. The axial

flow velocity is 0.8 times the blade velocity.

BT4, BT5

19 A Parson’s turbine has the following data for a particular group of blading :

Mean diameter of the blades = 100 cm, RPM = 300, Number of stages = 4,

Ratio of blade speed to steam speed = 0.75, Blade outlet angle = 200, Carry

over factor = 0.75, Efficiency of conversion of heat into kinetic energy in fixed

as well as moving blades = 90 %, Steam flow rate through the turbine = 20

kg/s. Find: (i) The total heat drop. (ii) The power developed. (iii) Gross stage

efficiency

BT4, BT5

UNIT V GAS TURBINES AND JET PROPULSION


1 State the assumptions made for thermal efficiency of a gas turbine plant. BT2

2 Draw the line diagram of a closed cycle gas turbine. BT2

3 What are the different rocket propulsion systems? BT2

4 Define the terms thrust power and propulsion efficiency. BT2

5 What is meant by thrust augmentation? When is it necessary? BT2

6 What are the different methods to improve the efficiency of gas turbines? BT2

7 What are the basic requirements of a combustion chamber used in Gas

Turbine Plant? BT2

8 List out the factors which are to be considered for the comparison of different

types of rockets? BT2

9 Draw the T-s diagram of a reheat gas turbine cycle. BT2

10 Define propulsive efficiency and thermal efficiency of jet propulsion system. BT2

11 What are the requirements of a good combustion chamber for a gas turbine? BT2

12 What is the essential difference between rocket propulsion and turbo-jet

propulsion? BT2

13 What are the different methods to improve the efficiency of gas turbines? BT2

14 Write the principle of jet propulsion and classify the Jet propulsive engines. BT2

15 Inter-cooling does not improve the thermal efficiency of the plant always.

Mention the reasons and explain when it is preferable. BT2

16 List out the differences between the open cycle gas turbines and closed cycle

gas turbines. BT2

17 Brief the working differences between the propeller-jet, turbojet and turbo-

prop. BT2

18 What do you mean by propulsive power and propulsive efficiency? BT2

19 What is meant by thrust? BT2

20 Explain briefly about pulse jet. BT2

21 Enumerate the requirements of ideal rocket propulsion. BT2

22 What is the purpose of inter cooling in gas turbine. BT2

23 Draw two combustion chambers of gas turbine plant. BT2

24 Write equations for propulsive efficiency and thermal efficiency of jet

propulsion engine. BT2

25 Explain solid propellant rocket engine. BT2





1 Determine the efficiency of a gas turbine plant fitted with a heat exchanger of

75% effectiveness. The pressure ratio is 4:1 and the compression is carried out

in two stages of equal pressure ratio with intercooling back to initial

temperature of 290K. The maximum temperature is 925K. The turbine

isentropic efficiency is 88% and each compressor’s isentropic efficiency is 85%.

For air _=1.4 and cp=1.005kJ/kg K.

BT4, BT5

2 A gas turbine unit receives air at 100kPa and 300K and compresses it

adiabatically to 620kPa with efficiency of the compressor 88%. The fuel has a

heating value of 44,180kJ/kg and the fuel/air ratio is 0.017kg fuel/kg air. The

turbine internal efficiency is 90%. Calculate the compressor work, turbine

work and thermal efficiency.

BT4, BT5

3 In an air standard regenerative gas turbine cycle the pressure ratio is 5. Air

enters the compressor at 1 bar, 300 K and leaves at 490 K. The maximum

temperature in the cycle is 1000 K. Calculate the cycle efficiency, given that the

efficiency of regenerator and the adiabatic efficiency of the turbine are each

80%. Assume for air, the ratio of specific heats is 1.4. Also show the cycle on T-

S diagram.

BT4, BT5

4 The following description pertains to a certain gas turbine unit: Inlet condition

to compressor = 1 kgf/cm2 and 300 K, efficiency of compressor = 80%,

pressure ratio = 4, turbine inlet temperature = 850 K, turbine expansion

efficiency = 85%. Heat value of fuel used = 10,500 k.cal/kg, for an air flow ratio

of 80 kgs/min, determine: (i) Air fuel ratio of the turbine plant. (ii) Net horse

power of the installation. (iii) Overall efficiency of the plant (iv) Back work

ratio. It may be assumed that for air Cp = 0.238 and Cv = 0.17 and for gases

Cp = 0.25 and Cv = 0.185.

BT4, BT5

5 A gas turbine unit receives air at 1 bar and 300 K and compresses it

adiabatically to 6.2 bar. The compressor efficiency is 88%. The fuel has a

heating value of 44186 KJ/kg and the fuel air ratio is 0.017 KJ/kg of air. The

turbine efficiency is 90 %. Calculate the work of turbine and compressor per

kg of air compressed and thermal efficiency. Take Cp=1.005 KJ/kg K, γ=1.4

for the compression process, Cp=1.147 KJ/kg, γ=1.33 for the expansion process

BT4, BT5

6 In an open cycle constant pressure gas turbine, air enters the compressor at 1

bar and 300 K. The pressure of air after the compression is 4 bar. The

isentropic efficiencies of compressor and turbine are 78% and 85%

respectively. The air-fuel ratio is 80: 1. Calculate the power developed and

thermal efficiency of the cycle if the flow rate of air is 2.5 kg / sec. Take Cp =

1.005 kJ / kg-K ;ɣ = 1.4 for air and Cp = 1.14 kJ / kg-K ; ɣ = 1.33 for gases. R =

0.287 kJ/kg-K. Calorific Value of fuel = 42,000 kJ/kg.

BT4, BT5

7 A gas turbine has an overall pressure ratio of 6 and a maximum cycle

temperature of 600. The turbine drives the compressor and an electric

generator, the mechanical efficiency of the drive being 90% the ambient

temperature 17 and air enters the compressor at the rate of 12 kg/s. The

isentropic efficiencies of compressor and turbine are 85% and 91%

respectively. Neglecting changes in kinetic energy, mass flow rate of fuel and all

pressure losses, calculate: the power output (a) the cycle efficiency, (b) work

ratio ɣ =1.35, Assume for both expansion and compression and Cp=1.005

KJ/Kg K

BT4, BT5

8 Air is drawn in a gas turbine unit at 170 C and 1.01 bar and the pressure ratio

is 8:1. The compressor is driven by the H.P turbine and the L.P. turbine drives

a separate power shaft. The isentropic efficiencies of the compressor and the

H.P. and L.P turbine are 0.8, 0.85 and 0.83, respectively. Calculate the pressure

and temperature of the gases entering the power turbine, the net power

BT4, BT5




developed by the unit per kg/s of mass flow, the work ratio and the thermal

efficiency of the unit. The maximum cycle temperature is 6500C. For the

compression process take cp = 1.005 kJ/kg K and = 1.4 For the combustion

process and expansion process, take Cp = 1.15 kJ/kgK and ɣ = 1.333 neglect the

mass of fuel.

9 In a gas turbine plant, air is drawn at 1 bar, 150 C and the pressure ratio is 6.

The expansion takes place in two turbines. The efficiency of compressor is 0.82,

high pressure turbine is 0.85 and low pressure turbine is 0.84. The maximum

cycle temperature is 6250 C. Calculate i) Pressure and temperature of gases

entering the low pressure turbine. ii) Net power developed iii) Work ratio iv)

Thermal efficiency. Work output of high pressure turbine is equal to

compressor work

BT4, BT5

10 With the help of a neat diagram explain the working of a regenerative cycle gas

turbine also compare the performance with simple cycle BT4, BT5

11 Derive an equation for thermal efficiency of a simple gas turbine cycle in terms

of pressure ratio and specific heat ratio. BT4, BT5

12 A gas turbine unit receives air at 2 bar, 300 k and compresses it adiabatically

to 6.2 bar. The compressor efficiency is 88%. The fuel has a heating value of

44186 kJ/kg and fuel- air ratio is 0.017 kg fuel/kg of air. The turbine internal

efficiency is 90%. Calculate the work of turbine and compressor per kg of air

compressed and thermal efficiency. For products of combustion Cp=1.147

kJ/kg K, ɣ =1.33.

BT4, BT5

13 A gas turbine unit receives air at 100kPa and 300K and compresses it

adiabatically to 620kPa with efficiency of the compressor 88%. The fuel has a

heating value of 44,180kJ/kg and the fuel/air ratio is 0.017kg fuel/kg air. The

turbine internal efficiency is 90%. Calculate the compressor work, turbine

work and thermal efficiency.

BT4, BT5

14 A gas turbine plant receives air at 1 bar and 290K and compresses it to 5bar. If

the temperature of air after compression is 1000K. Find the thermal efficiency

of the turbine. Take γ=1.4 for air.

BT4, BT5

15 Explain the working difference between propeller jet, turbojet and turbo

propeller. BT2, BT4

16 Describe the working of Rocket engine with neat sketch. BT2, BT4

17 Explain the Ram-Jet engine with neat sketch. BT2, BT4

18 Explain the turbo prop with a neat sketch BT2, BT4

19 Explain the working of a turbojet with a schematic diagram indicating various

components and with the help of pressure and velocity curves. Also explain the

advantages of a turbojet engine over the multi cylinder piston engine.

BT2, BT4

20 Give the differences between jet thrust and propeller thrust. BT2, BT4

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