POWER BEC IIEERING NOTE: ae have designed the complete course material in accordance with new | svllabus under WBSCTE. Short Answer Type and Long Answer Type Questions, | those are relevant with new syllabus, are collected from Question Papers of | old syllabus and included in the subject matter. Solutions of 2015 - 2018 | uestion papers (new syllabus) are also included chapterwise.nix POWER ENGINEERING Pe 2 Chapter 1: I.C. Engine and Pollution Contrg, Chapter at a glance: An engine is defined as a device which converts one form of energy into mecha energy because, mechanical energy can be further easily converted into electricg, tte which is most required form of energy as it is easy to transport and control, Heat ¢ “8 is a device which transforms heat energy into mechanical energy. ‘The transformaie"* one form of energy into another required — form is always associated with {°° therefore, the efficiency of conversion plays an important role. Heat is considereg form of energy where mechanical work is considered rich form of energy as jy f conversion with very high efficiency (90 — 95%) is possible. . The energy heat engine, some form of fuel (solid, liquid, gas or nuclear) is useg chemical energy or nuclear energy of fuel is converted into thermal or heat energy af that is further used to perform useful work. The heat engines are classified as (i) External combustion engine and (jj combustion engine. An external combustion engine is a thermal power plant as shown in Fig (a) where fuel, burned and its heat is given to the water to generate the steam which is further useq for power generation. The working fluid is not mixed with fuel; therefore, the same working ') Intemg fluid (water) is used again and again in the L=y system. Generar An Internal combustion engine is a machine that converts chemical energy in a fuel into mechanical energy. Fuel is bumt in a combustion chamber, releases its chemical Condenser energy into the form of heat, which is converted into mechanical energy with the help of a ae, reciprocating piston and crank mechanism. Fig £@) The principal types of reciprocating internal combustion engines are in general usé, the Otto-cycle engine and the diesel cycle engine. The otto cycle engine, named aftr is inventor, the German technician’ Nikolaus ‘august Otto, is the familiar gasoline engint used in automobiles and airplanes. The diesel engine, named after the French-bom German engineer Rodolf Christian Karl Diesel, operates on a different principle and usually uses oil as a fuel. It is employed in electric-generation and marine power plants in trucks and buses, and in other automobiles. Both Otto-cycle and diesel cycle engi are manufactured in two-strake and four stroke cycle models. poit-FELC. Engine and Polluti Control Short Answer Type Questions aon ose the correct answer from the given alternatives in each of the folowing: 4 gioichio metric Air-fuel ratio in a petrol engine is al (b) 15:1 (©) 8:1 answer (b) PE.3 IWBSCTE 2006, 2013, 2014] (4) 9:1 scavenging is the method of @ Increasing compression ratio © Lubricating the engine cylinder (d Removing the burnt gases from the engine Answer: (d) iE TWBSCTE 2006, 2009, 2011] (b) Reducing pre-ignition 3, Ina carburetor, the main nozzle tip is kept at (a) The same level of the fuel as in the float chamber (b) Lower level than the fuel in the float chamber (c) Higher level than the fuel in the float chamber (d) At any, level, because it is independent of the fuel level in float chamber Answer: (c) [WBSCTE 2006, 2009] 4, IC engine crank shaft is made of [WBSCTE 2006, 2009, 2012] (CI (b) Alloy CI (c) Allow steel (d) Forged alloy steel Answer: (d) 5, For same power production, compare to 4-stroke cycle engine a 2 stroke cycle engine have a flywheel [WBSCTE 2009] (@) Lighter (b) Heavier (c) More or less same weight Answer: 6. Incase of SI engines fresh charge may be [WBSCTE 2009] (@) Mixture of combustable gas and air (b) Mixture of petrol vapour and air (c) both of the above (d) None of the above Answer: (b) 7. InCl engines ignition of fuel starts [WBSCTE 2009, 2011] (a) Just at the end of suction stroke (b) Nearly at the end of compression stroke (©) Just after the expansion stroke (d) None of the above Answer: (b) POLY-PEnx POWER ENGINEERING ; Pe 8 When fuel cut-off is delayed in the diesel engine for fixed compression ratio, the i : MWBScTE ay oO inseees (b) Decreases (c) Remains same "3 Answer: (b) 9. In 4-stroke engine, each cylinder has rvs a MWeeCTE 2009, 2011, 2a1y ‘a) One valve a three valves (d) Four valves Answer: (b) i i trol engine and diesel engine 10. Which part is not common between a pet gil wescre a (@) Air cleaner (b) Silencer (c) Battery (d) Fuel Injector Answer: (d) i ing i BSCTE 294 11. In IC engine super charging is done : wi 03) (a) To overcome high altitude effect (b) To reduce engine weight (c) To reduce possibility of knocking (d) For all the above stated purposes Answer: (d) 12. Ina four stroke petrol engine the inlet valve remains open for [WBSCTE 2009) (a) Less than 180° (b) 180° (c) More than 180° Answer: (c) 13. Voltage developed to strike spark in the spark plug of SI engine is in the range [WBSCTE 2009, 201 1] (a) 1000 to 2000 volts (b) 20000 to 25000 volts (c) 6 to 12 volts (d) Any of the above Answer: (b) F 14. The specific fuel consumption of diesel engine as compared to that for petrol engine is 2 IWBSCTE 2009] (a) Higher (b) Lower (c) Same for same output (d) Same for same speed Answer: (b) 15. Increase the coolant temperature in SI engines may [WBSCTE 2009] (a) Increase the possibility of knock (b) Decrease the possibility of knock (c) Not affect the Possibility of knock at all Answer: (a) 16. By Morse test for multi-cylinder S.1. engines it could be determined (a) Thermal efficiency (c) Volumetric efficiency [WBSCTE 2008] (b) Mechanical efficiency (d) Relative efficiency poLy-PELG. Engine and Pollution Control PE.S ener ) " ines, the method of governin; I ii or diesel engines, & 'g employed is [WBSCTE Fo ality governing (b) Quantity governing ser V é Hit & miss governing oO poset: @ dynamic cycle on which the petrol engi The thermo yn Pp engine works [WBSCTE 2010] & (@ Otto cycle (b) Joule cycle (c) Rankine cycle (@) String cycle oswer? (@) 9.Ina four stroke cycle petrol engine, the pressure inside the engine cylinder during the suction stroke is atmospheric pressure [WBSCTE 2010] (a) Equal to (b) Below (c) Above answer? (b) 49, The theoretical correct mixture of air and petrol is [WBSCTE 2010] (a) 10:1 (b) 15:1 (©) 20:1 (d) 25:1 Answer: (b) 11. Ina petrol engine, if diesel is used, then the engine will [WBSCTE 2010] (a) Not run (b) Run more efficiently (© Run at high speed (d) Explode Answer: (a) 7 2. The inlet valve of a four stroke cycle I.C. engine remains open for [WBSCTE 2010, 2011] (a) 130° (b). 180° (c) 230° (d) 270° Answer: (c) 23. A diesel engine has [WBSCTE 2010, 2014] (a) One valve (b) Two valves (© Three valves (d) Four valves Answer: (b) 44, Diesel as compared to petrol is __[WBSCTE 2010] @ Highly ignitable (b) More difficult to ignite () Less difficult to ignite (d) None of these Answer: (b) 3. Ifthe temperature of intake air in I.C. engine increases, then its efficiency will ae (a) Remain same (b) Decrease (©).ncrease (d) Unpredictable Answer: (¢) POLY-PEnk POWER ENGINEERING PE 26. A diesel engine, during suction stroke, draws WBSCTE 25, ni (a) Only air (b) Diesel only 10 (c) A mixture of diesel & Air (d) None of these Answer: (a) ‘ 27. A carburetor is used to supply [WBSCTE 2010, 2014 (a) Petrol, air and lubricating oil (c) Petrol & lubricating oil (b) air & diesel (d) Petrol & air Answer: (d) 28. Number of working stroke per minute for a two stroke cycle engine are sith speed of the engine in r.p.m. IWBSCTE 2019, (a) Equal to (b) One-half (c) Twice (d) Four times Answer: (a) 29. The brake power is the power available _ IWBSCTE 2010) (a) In the engine cylinder (b) At the crank pin (©) At the crank shaft (d) None of these Answer: (c) 30. The ratio of the volume of charge admitted at NTP to the swept volume of the piston is called ___ efficiency. IWBSCTE 2019] (a) Mechanical (b) Overall (©) Relative (d) Volumetric Answer: (d) 31. The air standard efficiency of an IC engine depends on [WBSCTE 2010] (a) Fuel used (b) Speed of engine (c) Compression ratio (d) None of these Answer: (c) 32. Morse test can be conducted for [WBSCTE 2010] (a) Petrol engine only (b) Diesel engine only (c) Multi cylinder engine (d) all of these Answer: (c) 33. The ignition quality of petrol is expressed by [wescTE 2010] (a) Cetane number (b) Octane number (©) Calorific value (d) None of these Answer: (b) 34. The loud pulsating noise heard within the cylinder of an internal combustion engi is known as wescte 201d (a) Detonation (b) Turbulence (c) Pre-ignition (d) Super charging pourLC. Engi Pollution Contro! ooo) ae 1C- engine crank shaft is made of 36) Alloy steel (b) Mild steet [WBSCTE 2011] (o) Cast iron (d) Forged steel answer? @ ich part is not common between petrol engi i i: 3 Wiles aoe C)silencer tay enact ees omzine._ DWBECTE 2011} (a) Air i (c) Battery in answer @) (d) Fuel injector , when se cut-off is delayed in the diesel engine for fixed compression ratio, thermal effici b) De [WBSCTE 2011] (a) Increases (b) Decreases (c) Remain same answer: (D) 8. Compa Sa ae engine, a 2-stroke cycle engine needs (for same power produc 5 [WBSCTE 2011] (a) Lighter (b) Heavier (c) More or less same weight Answer: (2) 39, Incase of S.I. engines fresh charge may be [wesc 2014] (@) Mixture of | combustable gas and air (b) Mixture of petrol vapour & air (c) both of the above (d) None of the above Answer: (b) 40. The specific fuel consumption of diesel engine as compared to that for petrol engine is. 3 [WBSCTE 2011] (a) Higher (b) Lower (c) Same for same output (d) Same for same speed Answer: (b) 41. Increasing the coolant temperature in S.I. engine may IWBSCTE 2011] (a) Increase the possibility of knock (b) Decrease the possibility of knock (c) Not affect the possibility of knock at all Answer: (a) 42. By Morse test for multi-cylinder Sl engines, it could be determined [WBSCTE 2011] (a) Thermal efficiency (b) Mechanical efficiency (c) Volumetric efficiency (d) Relative efficiency Answer: (b) [WBSCTE 2012] 43. SI engine means only (a) Petrol engine (b) Constant volume combustion engine POLY-PEnik POWER ENGINEERING ‘ (d) All of these 8 (c) Spart ignition engine Answer: (d) 44, In Otto cycle combustion of fuel takes place - oe ant valine (We8scre 2g (a) Constant pressure ° None of them (c) Constant temperature d@) Answer: (b) 45. The theoretical correct mixture of air & petrol is pees 2o1y (a) 10:1 (b) 15:1 (©) 20: (4) 25:1 Answer: (b) 46. The engine which is suitable for carrying ee loa 5 ‘ih [wescte 2013) 5 et (a) Diesel engine (©) Dual combustion engine (d) None of the above Answer: (a) 47. The part which is used in an IC. engine is [WBSCTE 201 (a) Eccentric (b) Poppet valve (c) Bell crank lever (d) Intake manifold Answer: (d) 48. Which one of the following does not exists in an IC engine? IWBSCTE 2013) (a) Crank shaft (b) Cam shaft (c) Piston rod (d) Connecting rod Answer: (c) 49. ere engine has a IWBSCTE 2013, 2014) three ports (c) two valves Ody three valves Answer: (a) 50. The function of venture in the carburetor is 7 1 . IWBSCTE 2013] Qwacweaeteneiny QB Rete thar velocty Answer: (b) oo (d) to increase the manifold yacuum 51. In diesel engine, fuel consumption against brak: i (a) parabolic ‘© power is [WBSCTE 2013, 2014] (©) hyperbolic (b)linear Answer: (a) (d) non-predictable 52. Mechanical efficiency of an IC engine indicates Percentage of (a) BP converted into IP awestte 2 (©) IP converted into BP (b) Heat converted into work (d) Heat lost into exhaust POLY-PE1.C. Engine and Pollution Control : PE.9 answer? © ag pywsing lubrication, which efficiency of an IC engine improves [WBSCTE 2013] ic efficiency i ie (@) volumetric eff (b) Mechanical efficienc: (o) Charging efficiency (d) Indicated thermal efficiency Answer? ( | Inorease in compression ratio in an Otto cycle engine may cause IBSCTE 2013] (a) misfiring (b) detonation m oO knocking (d) longer ignition delay , swer: (b) Jso-octane has octane number [WBSCTE 2014] @0 (b) 50 (c) 100 (d)-1000 “answer: (C) 56. Supercharging is essential in a [WBSCTE 2014] (a) Diesel engine s (b) Gas turbine (c) Petrol engine » (d) Aircraft engine “Answer: (d) ~ ld be selected 41. Ifover head clearance is less, then the following type of engine shoul [WBSCTE 2014] (a) V-type (b) Inline (c) Radial (4) Horizontal Answer: (d) 58. A 125 cc engine means 125 ce [WBSCTE 2014] (a) Fuel tank capacity (b) Lubricating oil capacity (c) Swept volume (d) cylirider volume ‘Answer: (c) : B. State whether the following statements are True or False: . Ina'diesel engine, charge is ignited with the help of spark plug. “ [WBSCTE 2012] er: False ©, The carburetor is used for air-fuel mixture in diesel engine. [WBSCTE 2012] Answer: False 61. A two stroke engine is identified by absence of valve. : ‘ [WBSCTE 2012] Answer: True [WBSCTE 2012] . Quantity method of governing is used in diesel engine. wer: False POLY-PEnk POWER ENGINEERING PE4 63. Magneto ignition is used in motor cycle, scooter etc. (Wescte 2014 Answer: True 64. The specific fuel consumption for a petrol engine is about 0.25 ca Answer: True TE 204, 5) 65. Alcohols are emerging as main alternative fuels for I.C. engines. TWBSCTE 2, 8) Answer: False 66. Supercharging increases the power developed by the engine. MBSCTE 2015 Answer: True : 67. If petrol is used in a diesel engine then higher knocking will occur. DWBSCTE 2017 Answer: True 68. Supercharging increase the power developed by the engine. [escte 2017, Answer: True 69. The theoretically correct mixture of air & petrol is 15:1. [WescTE 2017) Answer: True : 70. I.C. engine pistons are made of alloy cast iron. MWBSCTE 2017) Answer: True 2 71. Morse test gives B.P. of the engine. [WeSCTE 2017) Answer: False 72. Constant volume cycle is the Otto cycle. (WBSCTE 2019] Answer: True 73. Pre-ignition occurs in petrol engines. [WBSCTE 2018] Answer: True 74. Detonation in petrol engine occurs before the ignition of the fuel. IWBSCTE 2018} Answer: False C. Fill in the blanks in the following statement Se anks in the following statements: 75. The Morse test is used to fine LLP of a Multi-cylinder 1.C. engine. [WBSCTE 2015, 2016] 76. If the speed of engine is increased, the LP will be increased. [WBSCTE 2015, 2016] 77, Carbon monoxide is generated when engine runs on Jean mixture. Eas [WBSCTE 2015] POLY-PELC. Engine and Po! lution Control 1g Forsame compression ratio the efficiency of diese eyce is cee tess Otto cycle, [WBSCTE 2015] . IWBSCTE 2015, 2016] g0. For same compression ratio the efficiency of diesel cycle is Higher 1. Constant volume cycle is the Orto cycle. Otto cycle. : [WESCTE 2016] st. Theoretically correct mixture of air and petrol is 14: [WBSCTE 2016] 82. Compression ratio of a Diesel engine may be high. [WBSCTE 2016] 43. For same power generation two stroke engine is Jighter than four stroke engine. - [WBSCTE 2016] g4, Supercharging increases the power developed by the engine. [WBSCTE 2017] 85., Otto cycle is also known as constant volume heat addition cycle. [WBSCTE 2017] 96, The thermal efficiency of petrol engine is about 25-30%. [WBSCTE 2017] 87. Supercharging increases the power developed by the engine. [WBSCTE 2018] $8. The knocking tendency in spark ignition engines may be decreased by reducing the compression ratio (a) controlling the air-fuel mixture, (b) controlling the ignition timing, (c) reducing the compression ratio, (d) all of these. [WBSCTE 2018] 89. The function of a muffler is to reduce of the sound of the exhaust gases (a) reduce the sound of the exhaust gases, (b) start the engine, (c) screen the foreign particles, (d) none of the above. (WBSCTE 2018] 90. If.N is the r.p.m. of an engine and ‘n’ be the number of working strokes per cycle, then in 4-stroke cycle engine n=N/2. [WBSCTE 2018] 91. The ratio of indicated thermal efficiency to air standard efficiency is called relative efficiency. [WBSCTE 2018] ine gives double the number of power stroke cycle engine. 9. A two stroke engine gives por Sere weitl 93, For same compression ratio, the efficiency of diesel engine is greater than Otto cycle, (a) equal to, (b) less than, (c) greater than, 2) less shan equal WweseTE 2018] 94. The Morse test is used to determine the mechanical efficiency eee eit e seule ie evlinder 1.C. engine. : POLY-PEnk POWER ENGINEERING PE D. Answer the following question 95. Name two cycles which have the same efficiency as Carnot. (WBSCTE 2013) Answer: Erricsion Cycle and Sterling Cycle 96. What is brake specific fuel consumption of an IC engine? [WBSCTE 2013) ‘Answer: It is the consumption of fuel in Kg/BP/hr. k i y ine? WBSCTE 2013 i ing is required for a diesel engine? TE 2013) Sete PE arnieg required for a diesel engine is qualitative governing, i [WBSCTE 2013, 2014) ii ctane? M 0 fae aeiticotins is a very good anti-knock fuel, therefore it is assigned a rating of 109 octane number. i tion takes place in dual combustion cycle engine. 99. In which process combustion pl ee Answer: Y In dual combustion cycle engine, combustion takes place at constant pressure and at constant volume. 100. | What is scavenging? [WBSCTE 2013, 2014] Answer: The process of removing buint gases, from the combustion chamber of the engine cylinder, is known as scavenging, 101, What is brake specific fuel consumption of IC engine? IWBSCTE 2014] Answer: Itis the mass of fuel consumed per kw power developed per hour, i.e. M, bs.fic= Sp kekwh where M, is the fuel consumption is kg/hour. 102. _In which process combustion takes place in diesel cycle. [WBSCTE 2014] Answer: In diesel cycle, combustion takes place at constant pressure, 18. hich type of governing is required of an IC engine? [WBSCTE 2014] nswer: The type of governing required for an IC engine is qualitative governing. 104. Draw the P-V and T-S diagram for Otto eycle. SIWBSCTE 2016] POLY-PE.C. ine ai ft apse PE.13 rive the efficiency of. es caicimioer od [WESCTE 2016] Temperature —>. Pressure —> Volume ——> Entropy —> | The efficiency of a Brayton cycle is the ration of net work done by a turbine to the heat supplied. Network done by: the turbine =c,{(%-%)-(i- Ta} and heat supplied =c, (7 - i) ee ep{(-1)-G-T)} _(B-%)-(i-T) ¢p(%2-i) h-T 106, Name the different methods of governing of IC engine. [WBSCTE 2016] Answer: (@) Hit and miss s method (b) Quality method () Quantity method () Combination method 107. What is detonation? IWBSCTE 2016] Answer: The loud pulsating noise heard within the engin called knocking. Itis occur due to the propagatic the un but fuel. e cylinder is-known as detonation, also con of high speed pressure waves created by end portion of POLY-PEChapter 2: Nozzles / Diffusers and Steam Turbines Chapter at a glance: a high-pressure, high temperature steam Prod m turbine converts the energy of 4 . ; sees generator into shaft work. The energy conversion is brought abou ma i ays: ‘ poe hana high-temperature steam first expands in the nozzles ¢ = as a high velocity fluid stream. sae © The Ae welecity steam coming out of the nozzles impinges on the by mounted on a wheel. The fluid stream suffers a loss of momentum while flowin, past the blades that is absorbed by the rotating wheel entailing Production ie torque. ; e The moving blades move as 4 result of the impulse of steam (caused by change of momentum) and also as a result of expansion and acceleration Of the steam relative to them. In other words they also act as the nozzles. A steam turbine is basically an assembly of nozzles fixed to a stationary casing and rotating blades mounted on the wheels attached on a shaft in a row-wise manner. In 1878, Swedish engineer, Carl G. P. de Laval developed a simple impulse turbine, using a convergent-divergent (supersonic) nozzle which ran the turbine to a maximum speed of 100,000 rpm. In 1897 he constructed a velocity-compounded impulse turbine a two-row axial turbine with a row of guide vane stators between them. Auguste Rateau in France started experiments with a de Laval turbine in 1894, and developed the pressure compounded impulse turbine in the year 1900. In the USA, Charles. G. Curtis Patented the velocity compounded de-Lavel turbine in 1896 and transferred his rights to General Electric in 1901. i England, Charles A. Parsons developed a multi-stage axial flow reaction turbiné in 884. Steam turbines are employed as the prime movers together with the electric generators it thermal and nuclear power plants to produce electricity. They are also used to prop! large ships, ocean liners, submarines and to drive power absorbing machines like larg compressors, blowers, fans and pumps. Turbines can be condensin, 8 OF non-condensi: ji the back Pressure is below or equal t ces depending on whether * io the atmosphere Pressure,Nozzles / Diffusers and leam Turbi Ste ines Short Answer Type Questions PE.63 , choose the correct answer from the given altematives in each of th 1e lowing: | et De-Laval turbine is a__ “@ multi-stage impulse turbine (c) simple impulse turbine 2 [WBSCTE 2005, (b) multi-stage reaction turbine eee Dt) (d) simple reaction turbine Answer peed in steam turbi 1, The rotor s im turbines can be reduced by — a 1 @) velocity compounding (b) pressure comp. a i E 2007, 2008] (0) velocity pressure compounding (all of these ig answer: (4) 3, The pressure velocity compounded impulse turbine allows a bigger pressure drop and hence __number of stages are required — [WBSCTE 2007, 2009, 2010] @) more (b) less ieee Answer: (b) 4 De Laval Turbine is — ‘ [WBSCTE 2009, 2010] (@) simple single wheel reaction turbine (6) simple single wheel impulse turbine (¢) velocity compounded impulse turbine Answer: (b) 5. The pressure on the two sides of impulse wheel steam turbine — [WBSCTE 2009] (@is same (b) is different (0) decreases from one side to other side (d increases from one side to the other Answer: (a) & Incase ofimpulse turbine there is enthalpy drop — (@) only is moving blades (b) only in fixed blades (©) both in fixed and moving blades Answer: (b) | [IWBSCTE 2009] 1 The ink : ine i a [WBSCTE 2009] governing of a steam turbine is done by v (@ throttle governing (b) nozzle control governing (© by-pass governing (d) all of these iswer: (d) POLY-PEnk POWER ENGINEERING P64 8. Reheat factor in steam turbine depends on — (wescTe 2009) (a) stage efficiency only (b) initial pressure and temperature only (©) exit pressure only (d) all of these Answer: (d) 9. The rotor speed inthe steam turbines can be reduced by — IWBSCTE 2099) (a) pressure compounding of steam turbines (b) velocity compounding of steam turbine (©) velocity pressure compounding of steam turbine @ all of these. Answer: (d) 10. Tip leakage is a problem in— : IWESCTE 2009) (a) reaction turbine (b) impulse turbine (c) velocity compounded turbine Answer: (a) 11. The main advantage of reaction turbine is that — TWBSCTE 2009) (a) much lower blade speed can be obtained (b) high efficiency can be obtained (c) high blade speed can be obtained ‘Answer: (a) 12. Ina steam turbine while steam is passing through nozzle, pressure of steam — IWBSCTE 2010) (a) decreases (b) increases (c) remains same Answer: (a) 13. In a reaction turbine velocity of steam changes — [WBSCTE 2010) (a) in rotor only (b) in stator only (c) in both stator and rotor Answer: (c) 14. In an impulse turbine pressure of steam — (a) changes in rotor.only —_(b) in stator only Answer: (c) [WBSCTE 2010] (c) does not change in the roto: 15. Tip leakage is a problem in— [WBSCTE 2010] (a) impulse turbine “(b) reaction turbine —_(c) velocity compound turbine. Answer: (b) B. Fill in the blanks in the following statements: 16. De Laval turbine is a simple impulse turbine. IWBSCTE 2004, 2012, 2011, 2013, 2014, 2018 } POLY-PENozzles / Diffusers and Steam Turbines Nozzles / Diffusers and Steam Turbines pin asteam turbine while steam is passing through nozzle pressure of ste - PE.65 am decreases 3 p * [WBSCTE 2011] yg. na reaction turbine velocity of steam changes on moving blades .weSCTE 2011] CTE 2011, 1p. Incase of Impulse Turbine, there is enthalpy drop in nozzle [WBSCTE 2012] , The pressure velocity compounded impulse turbine allows a bigger pressure drop and hence Jess number of stages are required. ined. (WBSCTE 2012] yJ..The rotor speed in steam turbine can be reduced by compounding [WBSCTE 201: 2] 1. In impulse turbine pressure does not change in rotor. [WBSCTE 2012] 33, The function of the reheater in a steam power plant is to reheat steam after part expansion. [WBSCTE 2013] 24, In impulse turbine impact is produced on moving blade. [WBSCTE 2013] 45, In reaction turbine number of nozzle is zero. [WBSCTE 2013] 26, The value of diagram factor is 1. In a De Laval turbine, the steam enters the wheel through a nozzle, with a velocity of 500 m/s and at an angle of 20° to the direction of motion of the blade. The blade speed is 200 m/s & the exit angle of the moving blade is 25°. Find (i Inlet angle of the moving blade (ii) Exit velocity of the steam & its direction (ii) Work done per Kg of steam, assuming friction less process (use graphical method). [WBSCTE 2004] OR, “Ina single impulse turbine, the velocity of steam at exit of nozzle is 500 m/s and the nozzle angle is 20°. The blade speed is 200 m/s and the exit angle of the moving blade is 25°. Determine i) intet angle of the moving blade ii) exit velocity of steam and its direction and iii) work done per kg of steam. : [WBSCTE 2015, 2016] Answer: Given: V =500 m/s; @ =20°; V, =200 m/s; $= 25° Now draw the combined velocity triangle. Scale: 1 Cm = 100 m/sec. POLY-PEChapter 3: Gas Turbine & Jet Propulsio in chapter at a glance: concept of gas turbine is old one, derived from Te fom the well. The modem gas turbine is us edotary IC engine. jpworks on the same principle as steam turbine, onl; (hot gas) used to operate the turbine. It consi quid fi y compressors combustion chamber, turbine and c ycle aiid mill used to grind corn and lift ‘or various applications and also ye nerences is in the type of working ‘sts of four major components that is a ‘ooling chamb: a used for operation of the gas turbine is Brayton or Joule a ie thermodynamic f gas turbine, closed cycle gas turbi cation and US inet . : gas turbine, open cycle gas turbine, having specific wpe power from the turbine is obtained by utilizing the ener; j fa hich is made to flow over the turbine blades wheie it ae ee ie Voter s motion to the turbine shaft. The part of the power developed by the tuing is utilized in running the compressor and rest is used for the specific purposes. There are numerous pplication of gas turbine like power generation, aircrafts propulsion, marine, locomotive and several industrial usage. ° Short Answer Type Questions A. Choose the correct answer from the given alternatives in each of the following: 1. Thermal efficiency of closed cycle gas turbine compared to that of open cycle gas turbine is [WBSCTE 2008] (a) less (b) more (c) same (d) unpredictable Answer: (b) 2. Thermal efficiency of gas turbine depends only on [WBSCTE 2009] (a) inlet temperature of air (b) compression ratio or expansion ratio (c) maximum pressure attained (d) index of compression & expansion Answer: (b) 3. Gas turbine compared to IC & SI engines gives IWBSCTE 2009, 2011] (a) higher thermal efficiency (b) lower thermal efficiency (©) same thermal efficiency (d) unpredictable » Answer: (b)nx POWER ENGINEERING 4. Gas turbine compared to 4-stroke diesel engine gives (a) higher mechanical energy (b) lower mechanical efficiency (c) more or less same mechanical efficiency (d) unpredictable Answer: (a) PE MWBSCTE 2095 an my WBSCTE 2099, ant 5. Gas turbine cycle with regenerators (b) increase work ratio (a) improves thermal efficiency (©) avoids pollution (d) none of the above Answer: (a) 6. A closed cycle gas turbine works on MESCTE 29, (a) Carnot cycle (b) Rankine cycle 0) (c) Ericsson cycle (d) Joule cycle Answer: (d) 7.. A closed cycle gas turbine consists of a DWBSCTE 294 (a) compressor (b) heating chamber ") (©) cooling chamber (d) all of these Answer: (d) 8. A open cycle gas turbine gives efficiency as compared to a Closed cycle gas turbine. [WBscTE 2010) (a) same (b) lower (c) higher Answer: (b) 9. The ratio of net work obtained from the gas turbine plant to the turbine work is known as = : DWBSCTE 2019] (a) compression ratio (b) work ratio (c) pressure ratio (d) none of the above Answer: (b) 10. Gas turbine as compared to I.C. engine [WBSCTE 2010] (a) can be driven at a very high speed (b) produces uniform torque (c) has more efficiency (d) all of these Answer: (d) 11. Mechanical efficiency of a gas turbine as compared to IC engine is : [WBSCTE 2014] (a) higher + (b)lower (c) same (d) unpredictable Answer: (a) POLY-PEGas Turbine & Jet Propulsion PE.95 sp, openccycle gas turbine works on [wescre 2014] ) Atkinson cycle (b) Rankine cycle (c) Carnot cycle (d) Ericsson cycle answer: (4) d cycle gas turbine maximum pressure attained is abs 3, In close ed is about [WBSCTE 2014] ' (a) I-bar (b) 50-bar (c) 20-bar (d) 28-bar Answer: (C) g, Fill in the blanks in the following statements: 44. Aclosed cycle gas turbine works on Bra yton cycle. [WBSCTE 2015, 2016] 45, The efficiency of Jet engine is higher at high speeds, [WBSCTE 2016] 46. The gas turbine cycle with regenerator Improve thermal efficiency. [WBSCTE 2016] 17. Ramjet engine.is a simplest type of jet engine. [WBSCTE 2017] 48. Basic working principle of gas turbine based on Brayton cycle. [WBSCTE 2017] 19. Inter-cooling is a method to improve efficiency of gas turbine. IWBSCTE 2017] 20. In a gas turbine, reheating increases the thermal efficiency (a) increases thermal efficiency, (b) increases compression efficiency, (c) increases turbine work, (d) none of these. [WBSCTE 2018] C. State whether the following statements are True or False: U1, Ina closed cycle gas turbine, the air is cooled as it enters the compressor. [WBSCTE 2007, 2012] Answer: True 2. Thermal efficiency of a gas turbine as compared to diesel plant is lower. (WBSCTE 2012] Answer: True 33, The efficiency of a jet engine is higher at high altitude. [WBSCTE 2015] Answer: False 4, The maximum temperature in a gas turbine is 400°C. [WBSCTE 2015] Answer: False 48, Reheating in a gas turbine decreases thermal efficiency. IWBSCTE 2017] Answer: False %6. Jet ion is based on the principle of third law of thermodynamics. propulsion is base TescTe 2017 POLY-PEni POWER ENGINEERING PE.9g Answer: False 27. Turbojet engine is same as Ramjet engine. IWBSCTE 2017) Answer: False 28. Nitroglycerine is an example of solid propellant. IWBSCTE 2017) Answer: True 29. Rocket engine is an example of air breathing engine. [WBSCTE 2017, Answer: False 30. In air-craft, Turbo-jet engine is used. (WBSCTE 2019) Answer: False 31. A closed cycle gas turbine works on Joule’s cycle. [IWBSCTE 2018] Answer: True D. Answer the following questions: 32. On which cycle the gas turbine works. IWBSCTE 2013] ‘Answer: Brayton cycle 33. Write two uses of Gas Turbine. [WBSCTE 2013, 2014] ‘Answer: a) Electric power generation b) Ship propulsion 34, Define Ram jet. [WBSCTE 2016] Answer: A ramjet is a form of air-breathing jet engine that uses the engine’s forward motion to compress incoming air without an axial compressor. Long Answer Type Questions > 1. Deduce the expression for thermal efficiency for Brayton cycle in terms of pressure ratio, showing flow diagram, p-v and T-s diagrams. [WBSCTE 2006, 2018] OR, Prove that the thermal efficiency. of a constant pressure gas turbine depends only on the compression or expansion ratio. [WBSCTE 2008, 2014] OR, Deduce the expression of thermal efficiency for Brayton cycle in terms of pressure ratio, showing p-v and T-s diagrams along with flow diagram. : [WBSCTE 2007] POLY-PEChapter 4: Hydraulic Turbines | Chapter at a glance: Hydraulic turbines are defined as the hydraulic machines by which hydraulic energy i converted into mechanical energy. A egnaaearaaeiei wi fetke fay ba or ica ic generator which is directly c bine shan, acne tas paved from hydraulic energy is called hydro-electric power” Me There are many types of hydraulic | turbines used in hydro-electric Power plant . impulse turbine (Pelton wheel), Francis turbine (it is so called, because it was invented by Francis, an American Engineer and Kaplan turbine). : : Hydraulic turbine are classified as (a) Impulse turbine and (b) Reaction turbine, The hydraulic turbine works on the impulse-momentum principle. : The potential energy of water which are stored in a dam built across a river is conv. into kinetic energy by allowing the water to flow through nozzles. This high Velocity is made to strike over a series a vanes or blades mounted on the rotor ofthe turbine produce impulsive force while passing over the blade due to change in momentum, Thi impulsive force gives rotary motion to the turbine rotor. Hydraulic turbines has man: advantages over other types of power generating unit like steam turbine, 28S turbine exe it is produce green energy and does not pollute the environment and Tenewable source of energy. Moreover cost of production of hydro-electric power is minimum compared to thermo-electric or thermo-nuclear power. Short Answer Type Questions A. Choose the correct answer from the 2 given altematives in each of the following: ; 1. The specific speed of a turbine is [WBSCTE 2014) @ ro) ae (©) MP (@ XP HA He We Answer: (c) 2. An impulse turbine is used for (a) Low head of water ©) High head of water Answer: (c) * [WBSCTE 2014] (b) Medium head of water (d) Any one of theseHydraulic Turbines gquble overhung pelton wheel has : Coe 4 To jets (b) Two runners. (WescTE 2014] oO Four jets (d) Four runners ste (b) is turbine runner, numb: ina Francis a er of blades are generall 4 ated (6) 4t08 ©@8wie (Oneneree eer @ (d) 16 to 24 «, Suge tanks ae provided to protect the | (a) Pen stocl (b) Tail stock te - agswer’ (8) “A iilin the blanks in the following statements: +g, specific speed of pelton wheel varies from 30-85 for single nozzle (WBSCTE 2006, 2014] 4, Kaplan turbine is suitable for Low head & high discharge. [WBSCTE 2006, 2014] q. InKaplan turbine, number of vanes varies from 4 to 8 [WBSCTE 2007, 2009] g, The shaft of the axial flow turbine is Vertical. [WBSCTE 2009] 1), Radial flow turbine is best suited for medium discharge and large head. [WBSCTE 2009] 11, Ina draft tube, pressure at the inlet is lessithan Atmospheric pressure. TWBSCTE 2009] 1, Kaplan turbine is a Axial flow reaction turbine. : [WBSCTE 2009, 2010, 2012, 2013, 2014] 13, Pelton wheel is a High head impulse turbine. [WBSCTE 2010] 14. Draft tube is used in Reaction turbine. [WBSCTE 2010] Reversible to each other. [WBSCTE 2011] 15, The function of turbine and pump are 16, For a semicircular vane as used in Pelton turbine, the maximum efficiency 1+cos0, 4 [WBSCTE 2011] Nex 2 Reaction. n, i i i (b) There are two basic type of turbine (a) impulse ( ) [WBSCTE 2011, 2013] POLY-PEnk POWER ENGINEERING PE.106 nan pais bine with low flow rate ‘elton wheel is a high head Jmpulse turbine wi (WBSCTE 2011, 2012, 2013, 045 NAP 19. The specific speed of turbine is expressed as Ny = = [WBSCTE 2011, 2012, 2013) Reaction. [WBSCTE 2012, 20. There are two basic types of turbine (a) Impulse and (b) 21. A Kaplan turbine best suited at part loads. [WBSCTE 2008, 2010, 2011, 2012, 2013) 22. For a semicircular vane as used in Pelton turbine, 9 = 0°, 7m. = 50% eor 23. In reaction turbine spiral casting serves to water into guide blade. [WBSCTE 2014) 24, Mixed flow turbines are partly Radial & partly Axial. [WBSCTE 2014] 25. Cavitations in hydraulic turbine occurs at rotor blades. [WBSCTE 2014) 26. The jet ratio of a pelton wheel lies between LI to 16 (12 for most cases). Tazo 27. Impulse turbine is suitable for small discharge & high head. (WBSCTE 2006, 2014) NVP 28. The specific speed of turbine is given by N, sNAES [WBSCTE 2017] Ht 29. Penstock is a part of hydraulic turbine. (WBSCTE 2017) 30. The speed ratio of a Pelton wheel operating under a head of 500 m is 0.46. The velocity of the wheel is 45.46 m/s. [WBSCTE 2018] Answer: True 31. Draft tube exit in hydraulic turbines most susceptible for cavitation. [WBSCTE 2018} Answer: False 32. The function of a governor is to maintain constant speed at varying loads. Answer: True [WBSCTE 2018] C. State whether the following statements are True or False: 33. Pelton wheel is recommended for use in those places where head of water is low. [WBSCTE 2008, 2009] POLY-PEHydraulic Turbines PE.107 net False 4, Angle of deflection in bucket varies from 160° to 165°, [Wascte 2008, 2009] es Trae : «, Reaction turbines are also called pressure turbine. IWBSCTE 2008, 2009, 2010] srswers TUE 36. Kaplan turbine is a radial flow reaction turbine. IWBSCTE 2008, 201! 0) ower: False 31, Speed ratio of a pelton wheel is always less than the hydraulic efficiency. [WBSCTE 2009] ‘Answer? True 38, Overall efficiency of pelton wheel is always less than the hydraulic efficiency. [WBSCTE 2009] ‘Answer: True 39. Outward flow reaction turbines is axial flow turbine. [WBSCTE 2009] ‘Answer: False 40. Draft tube is used in an impulse turbine. [WBSCTE 2009] Answer: False 41, In reaction turbine the runner runs full of water. [WBSCTE 2009, 2010, 2011, 2012, 2013] Answer: True : 42. In pelton wheel angle of deflection in buckets varies from 160° to 165°. IWBSCTE 2010] Answer: True 43. For high head, pelton wheel is most suitable. [WBSCTE 2010] Answer: True 44, Draft tube is used in pelton wheel. IWBSCTE 2010] Answer: False 45. Modern Francis turbine is an inward flow reaction turbine. [WBSCTE 2010] Answer: True 46. Francis turbine is a high head impulse turbine. [WBSCTE 2011] Answer: False 47. Draft tube is used in reaction turbine. [IWBSCTE 2011] Answer: True : POLY-PEnv POWER ENGINEERING , . E19 48. Kaplan turbine is an axial flow high head reaction turbine. IWBSCTE 2014, 201 i Answer: False 21 49. The furiction of surge tank is to control the flow of liquid. IWBSCTE a4 Answer: True 50. The function of surge tank is to control the flow of liquid. IWBSCTE 2012, 2013) Answer: True 51. Throttle governing is done in impulse turbine. IWBSCTE 2013, 2014) Answer: True 52. Draft tube used in pelton wheel. (WBScTE 2014) Answer: False z 53. Reaction turbine is also called pressure turbine. (WBScTE 2014) Answer: True 54, The gross or total head of the turbine is the sum of the water levels at the head race and tail race. DWBSCTE 2015) Answer: True 55. A draft tube is used with impulse turbines. (WBSCTE 2015) Answer: False Answer the following questions 56. Define Draft tube. DWBSCTE 2016] Answer: ‘A pipe gradually increasing area is used for discharging water from the exit of the turbine to the tail race. This pipe is called Draft tube. One end of the draft tube is connected to the outlet-of the runner while the other end is submerged below the level of water in the tail race. 57. Define specific speed of turbine. [WBSCTE 2016] Answer: It is defined as the speed of a turbine which is identical in shape, geometrical dimensions, blade angles, gate opening etc, with the actual turbine but of such a size that it will develop unit power when working under unit head. 58. Explain Working principle of Pelton wheel. [WBSCTE 2016] Answer: Pelton wheel is an impulse turbine which is suitable for high head & low discharge. It consists of a wheel, called runner, which is fixed on a horizontal shaft. A number of curved vanes, called buckets, are fixed to the periphery of the runner. Water from the head race is supplied through a large diameter pipe, called penstock, the nozzle is fitted at POLY-PE