PART A ( SMALL QUESTION)1. State the materials used for boiler tubes in an auxiliary boiler.

Ans. The boiler tube materials common used are SA -178 as it is economical cost wise. This standard of tubes are used for aux boiler and they are known as low carbon steel where carbon is 0.18 max or medium carbon steel of carbon 0.35 max.

2. Why end plate are spherical preferred over flat ends?

Ans. Dished or spherical end-plates give a higher strength than flat end-plates of similar thickness.

3.What are the dangers of low water level ?

Ans:-Low water level: Boiler surfaces gets overheated / collapse and if we pump in more feedwater it will lead to explosion due to large amount of steam being produced. To avoid this we must switch off the boiler and allow it to cool.

4. What are the dangers of high water level?

Ans:-High water level: due to high water the amount of steam being produced will become less and water will be carried to the system. To avoid this feed water pump to be stopped.

5. What is the role of FD fan in boiler firing?

Ans:-The Forced draft fan purges all explosives gas present inside the furnace before starting and after completion of firing, as these gas are dangerous for boiler front explosion. The FD fan supplies oxygen continuously during firing and is responsible for complete combustion of fuel.

6.Name the different types in Foster boiler?

Ans:-1. Foster tube D type boiler

2.Foster wheeler ESD I boiler

3.Foster wheeler ESD II boiler

4.Foster wheeler ESD III boiler

5.Foster wheeler ESD IV boiler

6.Foster wheeler ESRD boiler

7.Foster wheeler D type reheat boiler

8. Foster wheeler controlled superheat boiler

9.Foster wheeler DSD boiler

10. Foster wheeler ESD & D type boiler.

7. State the various types of Babcock boilers installed on board ship.

Ans:-1.Babcock & Wilcox header boiler.

2. Babcock selectable super heater boiler

3. Babcock MR type boiler

4. Babcock & wilcox integral furnace boiler

8. What are the uses of steam on board ship?Ans:-Use of steam on board ship 1. To drive main propulsion steam turbine 2. To run cargo pump turbines in tanker.3. Heating duties. Me fuel oil heater, purifier heaters, oil tank heating, cargo heating, air conditioning and heating plant, calorifier, galley supply, sea chests, tracer lines for for pipe line heating etc4. To run turbine generators.5. To run cargo pump turbines. 6. To drive deck machineries like winches.7. to drive steam driven bilge. stripping and other Steam driven pumps.8. To drive boiler feed pump turbine. 9. Tank washing in tanker ships.10. For boiler soot blowers and steam atomized burners. 9. Why is gauge glass fitted on the boiler and how will you check its working condition?

Ans:-The gauge glass is fitted on the boiler to check the water level in the boiler. Two gauge glasses are fitted in most boilers. The gauge glass may mal-function if the steam or water passages, blocked by scales or deposits formed in the boiler. The working condition can be checked by blowing down the gauge glass periodically to confirm the steam and water side are clear.

10. How many safety valves are there in an auxiliary boiler?

Ans:- There are two safety valves fitted for safety purpose as one does not open, the other valves will open avoid explosion of boiler. The lifting pressure are set 3% above the working pressure.

11.Name the different types of boiler burners fitted in oil fired boilers

Ans:- There are six main types of burner in common use Pressure jet Spill type pressure jet Variable orifice pressure jet Spinning cup Steam assisted Ultrasonic 12. What is gland-sealing steam with reference to a turbine?Answer: Low-pressure steam is led to a sealing gland. The steam seals the gland, which may be a carbon ring or of the labyrinth type, against air at the vacuum end of the shaft.

13. Which pump is used to circulate water to the economizer and when do you start/stop this pump?

Ans:- Boiler water circulating pump is used to circulate water to the economizer. This pump circulates from Auxiliary boiler to economizer and to be started two hours before sailing and must stop two hours after arrival at the port.

14. What action is taken when oil is found in the water level gauge glass?Answer: Stop the burner immediately. Oil present, even small quantities, in boiler water will cause foaming and moisture carry-over. It also forms a heat insulating film, sometimes a carbonized layer, over tubes or shell surfaces. Even a very thin layer may result in tube or plate material failure due to overheating. The oil manifests itself by forming an oily ring inside the water gauge glasses, at the water level. The boiler requires to cool down, blow down full water and chemically clean the internal for a day or two till all the oil is removed and such procedures are not possible to carry out at sea and carried out by shored based workshop.15. What is a stay tube?

Ans. Stay tubes : A stay tube is a thick walled tube, the end of which is usually thickened by upsetting to compensate for threading. Such tubes are used for staying tube sheets into which they are screwed and expanded. The max stress in a screwed stay tube is not to exceed 527 KG/cm2.the stay tubes are screwed with the tube plate they are to be screwed with a continuous thread not finer than 11 threads per 25.4 mm at both ends and are to be expanded in to the tube plate by roller expander.16. What is the size of a Plain tubes?

Ans: Plain tubes : Size 63.5mm to 88.9mm OD, with thickness 3 to 4.5mm.17. What are the dangers of low water level?

Ans.Low water level: the boiler surfaces gets overheated / collapse and if we pump in more feedwater it will lead to explosion due to large amount of steam being produced. To avoid this we must switch off the boiler and allow it to cool.

18. What are the dangers of high water level?

Ans:-High water level: due to high water the amount of steam being produced will become less and water will be carried to the system. To avoid this the feed water pump to be stopped.

19.Name any three mountings and explain their use for an auxiliary boiler.

MAIN STOP VALVE:This is mounted on the super heater outlet header, and enables the boiler to be isolated from the steam line. If two or more boilers are fitted supplying steam to a common line, the stop valve on each boiler must be a screw down, non-return type.This is to prevent steam from the other boilers flowing into a damaged boiler in the event of a loss of pressure due to a burst tube.In some cases the main stop valve incorporates an automatic closing device, designed to operate in emergency.AUXILIAR STOP VALVE:This is smaller version of the main stop valve isolates the boiler from auxiliary steam lines, and these are screw down non return valves to prevent steam blowing back in to the boiler. FEED CHECK VALVES These are fitted to give final control over the entry of feed water into the boiler and they must be screw down, non-return valves so that, in the event of a loss of feed the boiler water cannot blow back into the feed line.Main and auxiliary feed checks valves are fitted.Extended spindles are usually fitted so that than valves can be operated at convenient position. PART B (BIG QUESTIONS)

1.Write short notes on boiler safety valve pressure setting?

Ans. The range ofsetting ofallthe safety valves on the boiler should not exceed 10% of the working pressure. The lifting pressure is set at 3% of working pressure.

TESTING SAFETY VALVE. a)By the accumulation test, which consists of shutting off all other steam-discharge outlets from the boiler and forcing the fires to the maximum. The safety valve capacity should be sufficient to prevent a pressure in excess of 10% above the maximum allowable working pressure by continuous firing of boiler.

b) Hot setting :-One valve is gagged and the other tested for the correct pressure as required and sealed. Later the valve gagged is inter-changed and tested/sealed.

c) Cold setting:- valves normally opened for inspection and overhaul should be assembled. It is later tested hydro tested carried out with the required pressure in the workshop. The cold setting definitely is different than the hot setting, this is due to the thermal expansion of the metal in place.

2. State the advantages of corrugated furnaces in a boiler.Ans. The corrugated construction gives additional strength, flexibility and increased heating surface area. It minimizes thermal stresses and makes the furnace inherently flexible. By offering uniform stress distribution, corrugated furnaces ensure long life of the boiler. It also helps in increasing the moment of inertia for a given thickness and a consequent increase in maximum possible operating pressure. There is a slight heat absorbing over a plain furnace of same diameter and length. It is made to withstand expansion during change in load.

3. Write briefly about Cochran Boilers.

This boiler is ideal for producing low pressure steam and used as auxiliary boilers. The hot gas is contained inside tubes and the water surrounding. Cleaning the tubes is easier as no slag formation. In the case of water tube, the deposits can be formed on both the tubes and the casing, while in the fire tube it is only inside the tubes.There are two types of Cochrane boilers 1. the oil fired boiler used only in port and 2.composite boiler, where exhaust gases of main engine can be used to produce steam at sea and oil fired in ports. Various safety alarms are fitted for the safety of the crew and the boiler. These alarms are tested periodically for confirming its operation.

4.What is a spanner boiler and brief its outline?

The boiler consists of an outer shell enclosing a cylindrical furnace which is connected by vertical smoke tubes to a cylindrical smoke box at the top of the boiler. The vertical smoke tubes known as swirly flow tubes have a special twist along the greater part of their length, only a short portion at each, end being left plain to allow for expansion. These tubes are more efficient than normal plain smoke tubes in that they cause the gases passing through to swirl, so coming into more intimate contact with the tube wall and therefore increasing the rate of heat transfer. No stays are required for the outer shell and for the internals. Only the flat tube plates need to be supported; this is done by stay tubes, of plain section, expanded and then welded into the tube plates. Internal access is obtained by means of a manhole in the outer shell, and by hand holes and sight holes cut at strategic positions in the shell to allow for cleaning and inspection.

5. What do you know about an aux boiler and economizer?

Ans. The economizer acts as a super heater to the aux-boiler steam. The economizer mostly uses waste exhaust gas from main engine. The aux.boiler water is circulated through the economiser with the help of a Boiler water circulating pump. The economizer should be periodically soot blown off the tubes and also manually water wash, to avoid uptake fire due to the accumulation of carbon from the flue gas. The aux boiler is an oil fired boiler. It is normally used in ports to produce saturated steam. The aux boiler water is fed through a feed water pump from a boiler cascade tank. The water is preheated to approximately 70 to 80 deg.C in the cascade tank before feeding to aux boiler. The aux boiler works either on automatic and can be operated during trouble shooting on manual mode. There are numerous burner controls installed for safety of the boiler and to the ship crew. These controls are periodically tested to ensure they are in order.

6. State the difference between fire tube boiler and water tube boiler.

Water Tube Boilers :-Suitable for high steam pressure and temperature with large capacities exceeding millions of kgs/hr of steam. Various types of fuels can be fired with ease including.If the gas side is dirty provision is made for cleaning using soot blowers. Due to low water volume, the startup time is lesser and response to load changes is faster compared to fire tube boilers. Due to higher heat transfer coefficients surface area required is lesser and hence gas pressure drop is also lower. Fire Tube Boilers:-Ideal for low pressure steam. The pressure can be nearly twice in water tube designs for the same tube thickness. Suitable for high pressures as gas is contained inside tubes. Cleaning the tubes is easier ifthere is no slag. In the case of water tube, the deposits can be formed on both the tubes and the casing, while in the fire tube it is only inside the tubes.

7. What is the difference between stay tube and plain tube?

Ans. Stay tubes : A stay tube is a thick walled tube, the end of which is usually thickened by upsetting to compensate for threading. Such tubes are used for staying tube sheets into which they are screwed and expanded. The max stress in a screwed stay tube is not to exceed 527 KG/cm2.the stay tubes are screwed with the tube plate they are to be screwed with a continuous thread not finer than 11 threads per 25.4 mm at both ends and are to be expanded in to the tube plate by roller expander.

Plain tubes: Plain tubes :Size 63.5mm to 88.9mm OD, with thickness 3 to 4.5mm.

8. What are the uses of the following in the steam system 1) reducing valve 2) steam traps and

3) steam drains.

A.Steam reducing valves are used to reduce steam pressure for using in engine room services where low pressure is required. This can be reduced from main line pressure of 6kg/cm2 to 4 kg/cm2.

B.A steam trap is a device used to discharge condensate. Nearly all steam traps are nothing more than automatic valves. They open, close or modulate automatically. Three important functions of steam traps are 1. To discharge condensate as soon as it is formed. 2. Not to allow steam to escape.

C.Steam drains are placed in the outlet and inlet line to drain the condensate to avoid steam hammering , thus causing accidents. Water in steam systems result in impingement, erosion and corrosion which can cause major damage to equipment and piping. Steam propulsion plants have various drain collecting systems which collect and gather this water for reuse. These drain collecting systems are vital in keeping the steam propulsion plant as efficient as possible. The basic steam cycle assumes nearly all steam is ultimately converted back to water and reused. When water is lost from the cycle, additional water is added to compensate for the loss. Contamination of any steam drain collecting system can prevent the reuse of those steam drains, causing a decrease in overall plant efficiency.

9. What is blow back / boiler front explosion with respect to aux. boiler?

Ans. When the flame failure alarm sound, trying out firing the boiler numerous time on manual mode without any success may cause oil injection (without ignition) inside the furnace. The oil thus collected inside the furnace, may ignite at any time during re- firing in auto or manual mode. The sudden burning of this high quantity of oil causes abnormal high pressure causing the furnace door rupture and leading burns to the ship crew. This is the reason that standing in front of the boiler furnace is prohibited for safety. This term is called blow back or boiler front explosion.

10. How are soot blowers operated and where are they located?

When burning heavy fuel the heating surfaces are subjected to due to deposits .Soot blowers are fitted in suitable position for blowing out the deposits by jets of high pressure steam or air .The jet being caused to move through an arc while in operation. These are situated in the combustion chambers and the nozzles of special heat resisting steel are so arranged that while not actually in operation they are drawn back within a protective housing. The efficiency of the blower depends upon the conversion of pressure energy of the blowing medium to kinetic energy this results in high velocity of the jet impinging upon the fouled surface. The water should be drained prior to soot blowing to avoid acid attack if it comes in contact with carbon.

11. How will you prepare Aux. boiler for survey ?

Ans.

Boiler to be shut down, cooled and ventilated.

All Boiler mountings to be dismantled, cleaned, overhauled and exhibit.

Water side manhole doors to be opened up and if any water present to be removed and kept dry.

All hand hole doors to be opened, cleaned and kept ready with gaskets.

Furnace side to be cleaned dry.

Both safety valves to dismantle overhauled and kept ready.

Boiler burners to be kept overhauled and ready.

Boiler is ready for survey.

12. How will you overhaul a fuel oil burner of an aux.boiler?

Shut off the boiler completely and switch off the circuit breaker.

Place a placard MEN AT WORK.

Shut off all fuel valves right from the tank to the main burner.

Disconnect burner and transport to workshop for overhauling.

Overhaul burner by lapping orifice plate/ seat.

All parts to wash thoroughly with clean diesel oil and blow through with air.

Clean and assemble all parts in order.

Main burner after overhaul to fix it in position by tightening the holding bolt.

Connect all connections and purge system. Start the forced draft fan and purge all explosive gases from the furnace. Start the boiler firing by keeping off from the front to avoid blow back.

Finally adjust the air/fuel ratio for low and high combustion.

13. Explain primary flame of a main burner of an oil fired boiler.

Primary Flame-To burn oil the temperature must be raised to vaporization temperature, this cannot be done in heaters due to gassing but is done by radiant heat in the flame. The lighter hydrocarbons in the atomized spray are rapidly heated and burnt in the primary flame. The heavier fractions pass through this achieving their vaporization temperature. The primary flame is essential to good combustion. By design the primary flame exists where it receives maximum reflected heat from the shape of the quarl. The size of the primary flame just fills the quarl space. Too large and impingement leads to carbon deposits building up. Too small unheated secondary air reduces combustion efficiency. The tip plate creates vortices reducing the mixing time for the air/fuel and reduces the forward speed of the flame 14. Discuss briefly about Clarkson timble tube boiler.

Ans:- This type of boiler will generate steam by means of exhaust gas and oil firing, many different arrangements are possible, the one shown is the Clarkson composite boiler which makes use of thimble tubes for heat steam generation. The only restriction is that it must not be possible to have oil firing and exhaust gas firing on the same heating surface at the same time. If this were the case there would be the possibility of exhaust gas entering the engine room through the burner section or of blowback due to the action of exhaust gas and oil firing. There would also be a risk of poor engine performance due to exhaust back pressure, in order to avoid problems and ensure that full use is made of exhaust gases even at slow speeds it is usual to have completely separate oil and exhaust fired heating sections.

15. What is an Aalborg boiler and how does it produce steam?

Ans:- The fuel is burnt in a furnace surrounded by water wall, which by receiving radiant heat from the furnace flame increases the evaporation rate of the boiler. It greatly reduces the amount of refractory material for the furnace. The hot gases from furnace flows over the vertical water filled generating tubes, giving up heat finally entering the boiler uptake..Positive circulation of water is assisted by a number of external down comers taking water from the stearn drum to a header. This header then distributes the water to the water wall tubes,around the flue pipe. The water passes through numerous generating tubes to enter finally to a cylindrical steam drum at the top of the boiler.16.Write short notes on Babcock MR type boiler.

Boiler consists of a fully water cooled furnace and a fully water cooled chamber containing the integral convection heating surfaces. These two are separated by a membrane screen wall which is gas tight. The oil burners are mounted in the roof of the furnace. The combustion gas pass down the whole height of the furnace giving long flame travel and extended furnace time. The gases leaving the furnace pass through over super heater and economiser. The super heating surface consists of primary and secondary system. Final steam temperature is controlled by attemperator. 17.Draw a simple diagram showing a steam turbine and gravity lubricating tank. Ans:- All flat surfaces in the Scotch Boiler are supported by stays. 1. The front and back top plates are stayed together by long bars screwed at each end and fitted with washers and nuts inside and outside the plate. These are called steam space stays. 2. Flat back of the combustion chamber are stayed to the back plate of the boiler by bars which are continuously screwed into both plates and thin nuts fitted at both ends. These are called Combustion chamber stays. 3. The combustion chamber sides are also supported in the same manner by stays, as No: 2.4. The front plate of the combustion chamber is stayed to the tube plate by stay tubes. One third of total numbers of tubes are stay tubes. Stay tubes are thicker than normal tubes. Screwed through the plates and fitted with thin nuts. The other end expanded.5. Flat top of combustion chamber is strengthened by number of girders which are stayed by studs screwed through the top of the wrapper plate and fitted with nuts. 19. What is attemperator and explain with a simple sketch?

One of the methods used to control the final steam temperature is by using attemperation. Feed water of having nearly the same TDS as the final steam is injected in between two stages of a superheater system as shown above. The uncontrolled final steam temperature decreases as the load decreases, while with a radiant superheater system, the uncontrolled steam temperature decreases as the load increases. Injecting the feed water achieves the desired final steam temperature at a given load. The load range over which the steam temperature can be maintained depends on the boiler from 50 to 100 %.

20. Explain the term de superheater and its advantages in the steam system.

Desuperheaters remove the superheat in the steam that is to be used for auxiliary purposes, the reason is that if high temperature steam was used for auxiliaries then the materials used would have to be capable of withstanding high temperatures, this leads to increased initial cost. Desuperheaters are generally coils situated in the water spaces that are supplied with steam from the superheated section outlet; this type of desuperheater is generally called as internal desuperheaters. Such an internal desuperheater is shown down below.If this type of desuperheater develops a leakage then water loss from the boiler occurs since boiler pressure is greater than steam pressure in the desuperheater coil. This water loss could result in water hammer and subsequent damage in the auxiliary system.

21.Write short notes on economizer construction of an exhaust gas economizer.

Cast iron gills are shrunk onto mild steel tubes. These tubes are supplied as U-bend elements which are welded to stub tubes on the inlet & outlet headers and are interconnected by welded on ends to form the required number of feed water paths. The stub tubes are integral part of each header. Hand holes are located opposite to each tube end to allow internal inspection and emergency plugging of a water path should an element fail in service.22. Describe the various procedure for maintaining the boiler feed water before and after to avoid corrosion and failure.Ans:- A total water treatment program should follow these four-points:

1. Maintenance of free caustic corrosion potential, accomplished by eliminating free hydroxide (caustic) though the addition of various phosphate salts.

2. Minimize caustic deposit formation due to scale and suspended solids and sludge conditioners so that blowdown will remove this potential problem.

3. Eliminate oxygen content through deaeration or other mechanical means and chemical scavenging.

4. Prevention of carryover and foaming.

The above generally requires treatment before and after introduction of water into the boiler.The selection of pre-treatment processes depends upon water source, chemical characteristics, amount of make-up water needed, plant operating practices. These treating methods include filtering, softening, de-mineralizing, deaerating, and preheating.

After-treatment involves the addition of chemicals into the boiler water. This after-treatment is required to compensate for any variations in the pre-treatment of the boiler feedwater system and for protection of the boiler.

23. What happens if sea water enters the boiler and action taken?Answer: The salinity will rise rapidly since the salt remains in the boiler, while the water boils off. Salt will soon precipitate and accumulate on the bottom and also on the heating surface. Just as boiler-scales disrupts heat transmission to the water and causes the metal to overheat and can burst. It may also get foam in the boiler that will cause difficulties to maintain the water level and water droplets might follow with the steam, causing problems with turbines and engines.It is very dangerous to operate a boiler with salt in it, and you have to control by frequently blowing off from the bottom of the boiler and maintain salinity below 9.5%. It is wise to stop operation and to open up the boiler for inspection.

24. Name the safety devices and various alarms fitted to the auxiliary boiler.

Ans:-

FunctionAudible and visualAction

Low water levelAlarm

Low Low water level *AlarmBurner stop

High water levelAlarm

High High water levelAlarmFeedwater pump stop

Low steam pressureAlarm (overridden on slave boiler?)

High steam pressureAlarmBurner stop

Low feedwater pressureAlarmStand-by pump start

Low fuel oil pressureAlarmStand-by pump start

Low fuel oil temperatureAlarm

High fuel oil temperatureAlarm

Low combustion air pressureAlarmBurner stop

Low atomizing steam pressureAlarmBurner stop

Flame failure **Alarm (overridden during light-up)Burner stop

Burner not in firing positionAlarmBurner stop

*This function requires two independent level switches connected electrically in series.One of the switches may be a limit switch on thelevel controltransmitter's measuring signal.

**This function requires two independent flame detectors and their switches connected electrically in series.Possibility to distinguish between flame failures occurring during the burner's start-up sequence and flame failures that occur during normal firing would be a great advantage.

25. Draw a neat sketch of a boiler fuel oil system and name its parts.

26. Describe the Requirements for testing of boiler/ feed water.

Ans:-For prolonged boiler life, a water treatment program recommended by a water consultant is a must. Steam boilers are sensitive to even minor deposits on tube walls. Therefore, most feedwater treatment programs are oriented toward scale control. However, internal corrosion control cannot be ignored. Scald with locally high caustic concentrations can develop on metal components, strip away the protective magnetite film, and attack the base metal. This attack is characterized by gouging of the metal and its severity is directly proportional to increasing operating pressures.

Oxygen is highly corrosive when dissolved in water, and can result in corrosion pitting of heat transfer surfaces. Mechanical deaeration of the feed water using a deaerator is the typical first step in eliminating dissolved oxygen and other gases such as ammonia and carbon dioxide. Mechanical deaeration will reduce oxygen to as low as 0.005 cc/liter. In boilers below 1,000 psig, the oxygen-scavenging chemical is fed continuously, preferably at the storage compartment of deaerator or at suction of boiler feed pump, to provide turbulence and time for mixing. Specification of chemicals and dosages should be in accordance with the recommendations of the Owner's water consultant.

27. Draw a neat flow chart showing the automatic combustion control of an oil fired boiler. 0o start 6.0kg/cm2 1 to 1.5 differential pressure FD FAN

Minutes transmitter signal ABNORMAL

FD FAN STARTS

(Pre purging)

After 30sec PILOT BURNER+SPARK IGNITION

(DIESEL OIL PLUG ON AT 10000V) FAILURE

Flame eye sensitivity FLAME FAILURE

After 30 sec set normally (80-85%) HFO TEMP LOW

main burner on HFO PRESSURE LOW

(H.F.O)

After 30 sec

5.5 5.15 kg/cm2 (pilot burner off)

Air fuel ratio controller

change to high combustion / low combustion

6.5 Kg/cm2 Main burner off (Post purging starts)

1 to 1.5 minutes

360ostop FD FAN STOPS

28. How is velocity compounding accomplished?

Answers: 1.This is accomplished by an arrangement with alternate rows of fixed blades and moving blades. These are mounted on the casing, while the moving blades are keyed in series on a common shaft. The function of the fixed blades is to correct the direction of entry of steam to the next row of moving blades.

2.The high velocity steam leaving the nozzles passes on to the 1st row of moving blades where it suffers a partial velocity drop.

3.Its direction is then corrected by the next row of fixed blades and then it enters the 2nd row of moving blades. Here the steam velocity is again partially reduced. Since only part of the velocity of the steam is used up in each row of the moving blades, a slower turbine results. This is how velocity compounding works.

29. How is pressure-velocity compounding accomplished?

Answers: It is a combination of pressure compounding and velocity compounding.

1.Steam is expanded partially in a row of nozzles whereupon its velocity gets increased. This high velocity steam then enters a few rows of velocity compounding whereupon its velocity gets successively reduced.

2.The velocity of the steam is again increased in the subsequent row of nozzles and then again it is allowed to pass onto another set of velocity compounding that brings about a stage-wise reduction of velocity of the steam. Thus the system is continued.

30. What is the operating principle of an impulse turbine and reaction turbine?

Answer:The basic idea of an impulse turbine is that a jet of steam from a fixed nozzle pushes against the rotor blades and impels them forward. The velocity of the steam is about twice as fast as the velocity of the blades. Only turbines utilizing fixed nozzles are classified as impulse turbines.A reaction turbine utilizes a jet of steam that flows from a nozzle on the rotor. Actually, the steam is directed into the moving blades by fixed blades designed to expand the steam. The result is a small increase in velocity over that of the moving blades. These blades form a wall of moving nozzles that further expand the steam. The steam flow is partially reversed by the moving blades, producing a reaction on the blades. Since the pressure drop is small across each row of nozzles (blades), the speed is comparatively low. Therefore, more rows of moving blades are needed than in an impulse turbine.