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What is pre-ignition ? State any two factors responsible for pre-ignition.

In S.I. engine, the spark is timed to occur at a definite point just before the end of the compression stroke. If the ignition starts, due to any other reason, when the piston is still doing its compression stroke, it is known as pre – ignition.  Following factors are responsible for Pre – ignition 1) High compression ratio 2) Overheated spark plug 3) Incandescent carbon deposit in cylinder wall 4) Overheated exhaust valve 5) It may occur due to faulty timing of spark production

Define the following terms related to compressor....

i] Compressor capacity:-  It is the volume of air delivered by the compressor in m3 per minute  It is express in m3 /min ii) FAD:-  It is the volume of air delivered by compressor under the intake conditions of temperature and pressure.  Capacity of compressor is generally given in terms of free air delivery.

State any four industrial uses of compressed air.

1) To drive air motors in coal mines. 2) To inject fuel in air injection diesel engines. 3) To operate pneumatic drills, hammers, hoists, sand blasters. 4) For cleaning purposes. 5) To cool large buildings. 6) In the processing of food and farm maintenance. 7) For spray painting in paint industry. 8) In automobile & railway braking systems. 9) To operate air tools like air guns. 10) To hold & index cutting tools on machines like milling / cnc machines.

In gas turbine plants, Brayton cycle is more suitable than otto cycle...

In gas turbine plant – it works on brayton cycle where the heat added & heat rejected at constant pressure. It consists of compressor, combustion chamber & a turbine. The efficiency of Brayton cycle rotor cycle is same for but efficiency is of gas it temperature & pressure is increasing. High temperature & pressure require for ignition & fuel consumption for bray ton cycle. It is not possible in Oto cycle because the heat added & rejected at constant volume so bray ton cycle is most suitable than Otto cycle for gas turbine plant.

Define displacement of compressor for two stage compressor...

Displacement is the product of piston displacement and working stroke per minute is bared on low pressure only and the amount air passing through the other cylinder for two stage compressor. When free air wave from low pressure cylinder to high pressure cylinder through intercooler there is reduction of volume of air because of perfect cooling so free air delivered is less than displacement of compressor. ( Pl check)


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