Briefly discuss the following, a) Give three reasons why diesel engine is prefer

Question

Briefly discuss the following, a) Give three reasons why diesel engine is preferred in b) What are two main advantages & disadvantages of a c) How a petrol engine speed is controlled and how a trains, buses, lorries and trucks two stroke engine compare to a four stroke engine diesel engine speed is controlled. Why a fuel injection engine is cleaner in terms of NOx gas emission compare to carburetted engine. e) What the advantages and disadvantages using turbo charging in a petrol engine. (Total: 25 marks)

Explanation / Answer

a)

i) Diesel engine produces more power, compared to petrol engine

ii) compressio ratio is high in diesel engine, so provide higher energy thus torque.

iii) effecieny of diesel engine is better compared to petrol engine.

iv) Diesel is cheaper than petrol engine.

b)

i) Two stroke engine have lesser part and simple design than four stroke engine.

ii) Two stroke engine gives power output in every one revolution, whereas four stroke engine gives power output in every two revolution.

iii) Easier lubrication in two stroke engine.

iii) It is compact, cheaper and easier to maintain.

Disadvantages-

i) Fuel effeciency is less of two stroke engine.

ii) Incomplete combustion Of air-fuel mixture due to trapped air inside combustion chamber.

iii) Wastage of fuel due to simultaneous openings of inlet and exhaust port during suction stroke.

c) Petrol engine- In petrol engine air-fuel are mixed in carburetor. Engine speed is controlled by controlling the air-fuel mixture in carburetor by means of throttle valve, which controls flow of air-fuel mixture into combustion chamber, thus controlling speed.

Diesel engine-

In Diesel engine fuel is directly injected to combustion chamber, so regulating the amount of fuel regulate the speed. Amount of fuel injected is controlled by governer.

d) A fuel injected system is more effecient because the injection of fuel is controlled for each engine as per the basis of load and air present, by a central controlling system and amount of air can be totally released from cylinder and then injected according to load condition so less NOx formation. In carburated engine controlling of each engine is not possible so more NOx formation due to less effecient combustion.

e) Advantage of turbo charging-

i) Increase in power of engine

ii) Fuel economy get better because fuel for idling is reduced.

iii) Improves overall effecieny by better burning of fuel.

iv) Less smoke during low speed.

v) Smoother and quiter operation.

Disadvantage-

i) It requires frequent cooling so uses major amount of coolant.

ii) Design becomes expensive and complicated

iii) Due to more mechanical part wear and tear is rapid

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