MECHANICAL ENGINEERING JOB INTERVIEW QUESTIONS

1.) What do you understand by acoustic velocity ?

Ans: Accoustic velocity is the speed of a small pressure (sound) wave in a fluid.

2.)Explain difference between cohesion, adhesion and capillarity ?

Ans: Cohesion is the attraction of like molecules.
Adhesion is the attraction of unlike molecules for each other.
Capillarity is the elevation or depression of a liquid surface in contact with a solid.

3.)What is bulk modulus of elasticity ?

Ans: It represents the compressibility of a fluid. It is the ratio of the change in unit pressure to the corresponding volume change per unit of volume.

4.)What is is entropic exponent ?
Ans: It is the ratio of the specific heat of a gas at constant pressure to the specific heat at constant volume.

MECHANICAL ENGINEERING JOB INTERVIEW QUESTIONS

1.What is critical temperature in metals ?

Ans: It is the temperature at which the phase change occurs in metals.

2.What is coaxing ?

Ans: It is the process of improving fatigue properties by first under-stressing and then increasing the stress in small increments.

3.What is the difference between basic hole and basic shaft ?

Ans: A basic hole is one whose lower deviation is zero and in case of basic shaft the upper deviation is zero

Factors Affecting Detonation In IC Engine

Factors Affecting Detonation In Internal Combustion Engine:

In an internal combustion engine cylinder sometime sudden and violent knocks are experienced, this is known as "Detonation". This knock is set up by a high pressure wave giving loud pulsating noise as it strikes against cylinder walls, cylinder head and piston.

Following are the main factors, which affects detonation:-

01) The fuel used in internal combustion engine will considerably effects on the chances of detonation. Alcohol and benzol do not cause detonation but it can not be use due its low calorific value and other objections to use as fuel. Again alcohol cannot blend with petrol in the presence of water.

02) The detonation is also promoted by increase in compression ratio. The compression ratio at which detonation just occurs is known as the Highest Useful Compression Ratio. Higher the compression ratio higher the chances of detonation and lower the output.

03) If the carbon deposits are in the cylinder and used excessive sparking temperature, the detonation will increased rapidly.

MECHANICAL ENGINEERING JOB INTERVIEW QUESTIONS

1.) What is the direction of tangential acceleration ?

Ans:The direction of tangential acceleration may be same or opposite to that of angular velocity.

2.)Why excess air is required to burn a fuel completely ?

Ans: Excess air is required to ensure adequate mixing of fuel and air, avoid smoke, minimize slagging in coal burning, and to ensure maximum steam output.

3.)Which type of plant will you recommend for remote location if power is required in six to twelve months time ?

Ans: Diesel engine power plant.

4.)What do you understand by forced convection ?

Ans: When convection heat transfer occurs between a solid body and a fluid and where circulation of fluid is caused and controlled by some mechanical.

Thermodynamic Processes

MECHANICAL ENGINEERING JOB INTERVIEW QUESTIONS

1.)What happens if gasoline is used in a Diesel engine?Diesel engine will work ?

Ans.:No, It will not work,as the Compression ratio of Petrol engine is 6 to 10 & that of Diesel engine is 15 to 22. Thus on such high compression, gasoline gets highly compressed & it may blast.

2.)Why different types of sound are produced in different bikes though they say run on SI engine?

Ans:Engine specifications are different in different manufactures like as Bore Diameter(CC), Ignition timing.Also the exhaust passage take more responsible for sound.

3.)1 hp how much watt?

Ans: 746.2Watt

4.)Explain Bicycle rear wheel Sprocket working?

Ans:Rear wheel sprocket works under the principle of ratchet and pawl.

Spark Plug

 

A spark plug (sometimes in British English a sparking plug, colloquially a plug) is a device for delivering electric current from an ignition system to the combustion chamber of a spark-ignition engine to ignite the compressed fuel/air mixture by an electric spark, while containing combustion pressure within the engine. A spark plug has a metal threaded shell, electrically isolated from a central electrode by a porcelain insulator. The central electrode, which may contain a resistor, is connected by a heavily insulated wire to the output terminal of an ignition coil or magneto. The spark plug's metal shell is screwed into the engine's cylinder head and thus electrically grounded. The central electrode protrudes through the porcelain insulator into the combustion chamber, forming one or more spark gaps between the inner end of the central electrode and usually one or more protuberances or structures attached to the inner end of the threaded shell and designated the "side", "earth", or "ground" electrode(s).
Spark plugs may also be used for other purposes; in Saab Direct Ignition when they are not firing, spark plugs are used to measure ionization in the cylinders - this ionic current measurement is used to replace the ordinary cam phase sensor, knock sensor and misfire measurement function.[citation needed] Spark plugs may also be used in other applications such as furnaces wherein a combustible fuel/air mixture must be ignited. In this case, they are sometimes referred to as flame igniters.

MECHANICAL ENGINEERING JOB INTERVIEW QUESTIONS

1.)What is the name given to process of removing non condensables in steam and other vapor cycles ?

Ans: Deaeration process.

2.). We often come across use of jet pumps in process industry ? What is the reason for this ?

Ans: Jet pumps are easy to maintain and can be used to transport gases, liquids and mixtures of both.

3.)When it can be said that a fluid is Newtonian ?

Ans: When the shear stress is directly proportional to velocity gradient.

4.)Out of 2 stroke SI engine, 4 stroke SI engine, and 4 stroke CI engine, how the brake thermal efficiency behaves if these are to be used for road vehicles ?

Ans: 4 stroke CI engine has highest brake thermal efficiency followed by 4 stroke SI engine and the 2 stroke SI has lowest brake thermal efficiency

MECHANICAL ENGINEERING JOB INTERVIEW QUESTIONS

1.)What is operating pressure?

Ans.-Operating pressure is the standard level of pressure a system operates under, usually within a fairly narrow range of tolerances.

2.)Explain Otto cycle.

Ans.-An Otto cycle is an idealized thermodynamic cycle which describes the functioning of a typical spark ignition reciprocating piston engine,the thermodynamic cycle most commonly found in automobile engines.he Otto cycle consists of adiabatic compression, heat addition at constant volume, adiabatic expansion, and rejection of heat at constant volume.

3.)What is annealing?

Ans.-The steady heating of a metal at a certain temperature above the recrystallization phase followed by a gradual cooling process is called annealing.

4.)What is Carburizing?

Ans.-A surface hardening method that heats metal within a carbon-rich environment to increase carbon levels on the metal surface for added hardness is called Carburizing.

MECHANICAL ENGINEERING JOB INTERVIEW QUESTIONS

1.)Why excess air is required to burn a fuel completely ?

Ans: Excess air is required to ensure adequate mixing of fuel and air, avoid smoke, minimize slagging in coal burning, and to ensure maximum steam output.

2.)At what pressure and temperature the density of water and steam is same ?

Ans: At 225 kg/cm2 and 74.6° C.

3.)What is meant by quality of steam ?

Ans: It refers to amount of unevaporated moisture in steam. If steam is perfectly dry, it's quality is 100%.

4.) Why the efficiency of superheat Rankine cycle is higher than that of simple Rankine cycle?

Ans: Because the mean temperature of heat addition is higher for superheat cycle.

MECHANICAL ENGINEERING JOB INTERVIEW QUESTIONS

1.)What is the difference between Technology and Engineering?

Ans. Engineering is application of science. Technology shows various methods of Engineering. A bridge can be made by using beams to bear the load,by an arc or by hanging in a cable; all shows different technology but comes under civil engineering and science applied is laws of force/load distribution.

2.)What is the difference between Speed and Economic Speed?

Ans. The rated speed tells us about the maximum speed which can be achieved by a vehicle or some other machine but the economical speed means the speed limit at which the machine works efficiently with least consumption of fuel.eg-in normal bikes(not racing),the max.speed limit shown on speedometer is upto 120 kmph but companies always advice their customers to drive such bikes at around 60 kmph to have maximum mileage.

3.)Besides lubrication, what are two functions of lubricating oil in some turbines?

Ans.In larger units, lube oil cools the bearings by carrying off heat to the oil coolers. Lube oil in some turbines also acts as a hydraulic fluid to operate the governor speed-control system.

MECHANICAL ENGINEERING JOB INTERVIEW QUESTIONS

1.). What is factor of evaporation ?

Ans: It is the ratio of heat change from feed water to steam and the heat of vaporization of steam at atmospheric pressure.

2.)Which parameters influence the performance of gas turbines ?

Ans: Ambient conditions, inlet/exhaust pressure losses, fuels, and water/steam injection flow rates'influence the performance of gas turbines.

3.)Why steam is in open space and water inside tube in condensers used in power plants ?

Ans: Overall heat transfer coefficient can be increased by increasing velocity of water in tube. Further steam needs more space due to higher specific volume.

4.)What is radiosity ?

Ans: It is the rate at which radiation leaves a surface.