Thermal Engineering II Set 3

Answer: protect the fire tube

Explaination:
the function of the fusible plug is to protect the fire tube from burning due to excessive heating. this usually happens when the water level inside the drum becomes too low and the shell and crown plate are directly exposed to steam space.

Answer: to prevent excessive steam pressure

Explaination:
the function of safety valve is to prevent the excessive steam pressure inside the boiler drum exceeding the design

Answer: 2

Explaination:
two types of safety valves are used in practice

Answer: fuel consumption decreases

Explaination:
function of the economizer is to recover a portion of heat of the exhaust gases before the flue gases enter the chimney and discharged to the atmosphere. due to the high temperature of feed water, fuel consumption reduces. this increases the overall efficiency of the boiler.

Answer: increase the temperature of steam

Explaination:
function of the superheater is to increase the temperature of steam above its saturation temperature. as heat contained in unit mass of superheated steam is more than dry saturated or wet steam, it is extensively used in steam power plants.

Answer: recover the heat from flue gas

Explaination:
function of air preheater is to recover the heat of a portion of exhaust flue gases before the flue gases enter the chimney. it is places along the passage of the exhaust flue gases in between the economizer and the chimney.

Answer: pump water at high pressure

Explaination:
function of feed water pump is to pump water at high pressure to the water space of the boiler drum. there are many types of feed pumps, in which they are

Answer: electric motors

Explaination:
rotary pumps are driven by electric motors. water is pumped due to rotary action of the impeller. rotary pumps are invented by charles c barnes. it is a positive displacement pump. the efficiency of these pumps depends on the percentage of slip to the total quantity displaced.

Answer: coke

Explaination:
coal is prepared by heating bituminous coal continuously for 15 to 18 hours in closed chamber in the absence of air 500oc to 700oc. during this process the volatile matter is removed from the coal, leaving a dull black color to coke. it is a hard porous structure and smokeless. it contains 85 to 95% carbon. when the bituminous coal is heated between 900oc to 1000oc, hard coke

Answer: briquette coal

Explaination:
briquette coal is prepared by

Answer: pulverized coal

Explaination:
pulverized coal is prepared by powdering low grade coal with high ash content. dry coal is pulverized in pulverizing mills. it burns most efficiently when mixed with air and hence it is used in most of the power plants.

Answer: they have low ignition temperature

Explaination:
they have low ignition temperature’. ignition temperature is the minimum temperature at which a substance starts to burn. different fuels have different ignition temperature. some fuels have low ignition temperature and some have high ignition temperature. the fuels that have low ignition temperature are highly inflammable and burn quickly at the spark of fire. while some fuels that have high ignition

Answer: they produce lot of smoke

Explaination:
solid fuels tend to produce lot of smoke because they have large percentage of ash content. they are also brittle in nature and they contain some amount of ash in it when they are in ground. due to their brittleness, it is common nature of solid fuels that they break into pieces while mining and transporting and form ash.

Answer: crude petroleum

Explaination:
liquid fuels are available in nature in the form of crude petroleum. all commercial liquid fuels are derived from crude petroleum or crude oil. the crude oil, as it comes out from oil wells contains 83- 87% carbon, 10-14% hydrogen and small percentages of sulfur, nitrogen, oxygen and gases containing mainly ethane and methane.

Answer: distillation

Explaination:
the impurities present in the crude oil are eliminated by the process of refining oil by distillation. it is based on the principle that boiling points of various hydrocarbons increase with an increase in molecular weight and when distilled, the crude oil is separated into gasoline, kerosene, fuel oil or reduced crude oil.

Answer: kerosene

Explaination:
kerosene is heavier than gasoline but less volatile than it. it has a specific gravity ranging from 0.78 to 0.85. it is obtained between 150 to 300oc. it is mainly used in aviation gas turbines as jet

Answer: distillate

Explaination:
distillate is slightly heavier than kerosene and is used as fuel and

Answer: diesel

Explaination:
diesel is heavier than kerosene. it has specific gravity ranging from 0.86 to

Answer: fuel oil

Explaination:
fuel oil is similar to diesel but has wider composition than diesel. it is used in furnaces of oil fired boilers. broadly speaking, fuel oil is any liquid fuel that is burned in furnace or boiler for the generation of power, except oil is having a flash point of approximately 42oc and oils burned in cotton or wool-wick burners.

Answer: alcohol

Explaination:
alcohol is an artificial fuel obtained from vegetable matter by fermentation process. it is used in many chemical processes. the first four aliphatic alcohols (methanol, propanol, ethanol and butanol) are of interest as fuels because they can be synthesized chemically or biologically. the general chemical formula for alcohol fuel is cnh2n+1oh.

Answer: artificial solid fuels

Explaination:
artificial solid fuels need excess amount of air for complete combustion because they have low calorific value compared to liquid fuels and the rate of combustion of solid fuels cannot be easily controlled. they have tendency to form clinkers at high temperatures.

Answer: pelton wheel turbine

Explaination:
pelton wheel turbine is a water

Answer: true

Explaination:
in axial flow type turbines the steam flows over the blades in a direction parallel to the axis of the wheel. in radial flow turbines the blades are arranged radially so that the steam enters at the blade tip nearest the axis of the wheel and flows towards the circumference.

Answer: central station turbine

Explaination:
central turbines are for driving the alternator at synchronous speed. in reheating turbine steam is returned back to the boiler after partial expansion for superheating and then allowed to expand to back pressure. in extraction turbines steam leaves the turbine casing before the exhaust, for feed water heating.

Answer: back pressure steam turbine

Explaination:
the other name for non condensing turbines is back pressure turbines.