Mechanical Interview Questions 13 contains questions...
121. What is the function of EGR valve?
122. What do you mean by super critical above 500MW in
Thermal power plant?
123. What is the purpose of scrapper ring?
124. How catalyst converter works?
125. What will happen if relief valve in Hydraulic system
fails?
126. What does CC Stand for?
127. What is the difference between S.S to EN8
128. The Compression ratio of Petrol engine is always
less than Compression Ratio of Diesel engine why?
129. What is the temperature of space ?
130. How to calculate the speed of conveyer in Meter Per
Minute
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121. What is the function of EGR valve?
EGR means Exhaust Gas Recirculation.
The main function of EGR is to control NOx emission from the engine. At elevated temperature (during long run & full condition) if due to some reasons engine gets heated up beyond certain level… it produces NOx emission.
In order to avoid this pollution , we have to control the temperature rise inside the cylinder.
This can be achieved by mixing some amount of exhaust gas with intake air. By doing this the temperature inside the combustion chamber is reduced. And NOx is controlled.
122. What do you mean by super critical above 500MW in Thermal power plant?
In super critical boiler means all the steam to converted in to superheated steam at outlet of boiler no need to sent to super heater once again.
123. What is the purpose of scrapper ring?
Scrap the excess lube oil from the cylinder walls. There by preventing oil from entering combustion zone.
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124. How catalyst converter works?
In Fuel Cell, a catalyst is a substance that causes or accelerates a chemical reaction without itself being affected.
Catalysts participate in the reactions, but are neither reactants nor products of the reaction they catalyze.
125. What will happen if relief valve in Hydraulic system fails?
The main function of pressure relief valve is to maintain the pressure in hydraulic system.
It is one mounting which is used for safety. W
hen pressure increases then safety valve comes into action & if the valve get fail the system get damage due to excessive pressure.
126. What does CC Stand for?
CC is the abbreviated form of cubic centimeter.
It is the unit by which the capacity of an engine is designated.
It is the volume between TDC and BDC.
It represents the quantity of fuel-air mix or exhaust gas that is pumped out in a single piston stroke.
Alternatively it can represent the volume of the cylinder itself.
We have read that when the piston goes up and down then the engine works i.e. the suction,compression etc etc. then what happens in the case
of big vehicles, which start at stable condition, i.e. how does their piston moves when they are at rest. how suction,compression etc
Smaller vehicles like bikes, cars are started with the help of motors. initially, motors turn the crank shaft till sufficient suction pressure is reached.
when sufficient suction pressure is reached, the engine starts to suck the fuel in and then the cycle begins when the fuel is taken in and ignited. similarly, for huge engines, instead of motors, we use starting air. air at a pressure of 10-30 bar is fed to the engine which is at rest. this air rotates the engine till it attains sufficient suction pressure. once the pressure is reached, the cycle starts and it starts firing.
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127. What is the difference between S.S to EN8
SS- Stainless steel
En- Medium carbon steel
SS is Non Magnetic material & EN8 is Magnetic material
SS is Corrosion resistant & EN8 is Magnetic material
128. The Compression ratio of Petrol engine is always less than Compression Ratio of Diesel engine why?
Petrol is not self igniting , it needs spark to flame up in chamber.
Where as diesel is self igniting in dieselengine , to attain that state it requires high temp &pressure.
This temperature & pressure is more than what’s required in Petrol Engines by property of that fluid.
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129. What is the temperature of space ?
The short answer is that the temperature in space is approximately 2.725 Kelvin.
That means the universe is generally just shy of three degrees above absolute zero – the temperature at which molecules themselves stop moving.
That’s almost -270 degrees Celsius, or -455 Fahrenheit.
130. How to calculate the speed of conveyer in Meter Per Minute
Measure the diameter of the rollers around which the conveyor belt is wrapped.
Multiply the diameter of the roller by pi (3.14159).
This calculation will yield the circumference of the rollers.
Every time the roller spins one revolution, the conveyor will be moved a linear distance equivalent to the circumference of the roller.
Pi is a dimensionless factor, meaning it does not matter whether inches, centimeters or any other units of measurement are used.
Measure the revolutions per minute (RPM) of the rollers. Count how many full revolutions (rotations) are made by the roller in one minute.
Multiply the RPM by the circumference of the roller.
This calculation will give the linear distance traversed by a point on the conveyor belt in one minute.