21. Why boiler is purged every-time before starting firing of fuel?
Purging ensure that any unburnt fuel in furnace is removed. otherwise it may lead to explosion.
22. What is the difference between pipe and tube?
PIPE: Pipe are measured and sold with inner diameter. Pipe are used to transport fluids like water,oil,gas,etc.
TUBE: Tube are measured and sold with outer diameter. Tubes are generally used for structural purposes.
23. What will happen if reciprocating compressor run in exactly opposite direction?
No change in working because motion of the piston is unaffected with direction of rotation.
24. What is the difference between safety valve and relief valve?
A safety valve is a control mechanism that release the pressure when it crosses a set threshold and then resets back to original position. e.g. the valve on a pressure cooker or autoclave where you want to keep the contents at/under a specified pressure.
A relief valve is a relief mechanism to instantly relieve the pressure, that is triggered in extreme circumstances when the pressure has suddenly exceeded or is approaching failure criteria for the system itself, when material approach their yield limit and parts can start breaking.
25. What is the difference between supercharger and turbocharger?
The key difference lies in its power supply, the supercharger will take its power from the crankshaft whereas the turbocharge will draw power from exhaust gases that result from combustion.
Mechanical Engineering important question for interview.
26. Under Lewis gear design, tooth is considered as what beam?
Cantilever beam.
27. The function of an alternator in an automobile is to?
Continually recharge the battery.
28. How many types of gear boxes are there? List them.
There are 4 types of gear box: 1) sliding mesh gear box 2) Constant mesh gear box 3) Synchromesh gear box 4) Planetarty gear box.
29. State Newton’s three law of motion.
: The law of inertia:- Every object in a state of uniform motion tends to remain in that state of motion unless an external force is applied to it.
OR Newton’s first law of motion state that if a body is in rest, it will remain in rest and if a body in a motion, it will remain in motion. Until some external force does not applied on it.
:Acceleration is produced when a force acts on a mass. The greater the mass the greater the amount of force needed (to accelerate the object). Or the rate of change of momentum is directly proportional to impressed force. direction of impressed force is same in which the momentum take place.
: For every action there is an equal an opposite reaction.
30. Who invented the four stroke engine? According to you which one is more efficient, four stroke engine or a two stroke engine and why?
Nikolaus otto invented the four stroke engine. Both two stroke and four stroke engine have their own advantages and disadvantages. 4 stroke engine is more fuel efficient However, 2 stroke engine produce more power.