Automobile Engineering interview questions and answers - part 3

Part 1   Part 2   Part 3   Part 4   Part 5   Part 6 What are three methods of heat transfer? Three methods of heat transfer are conduction, convection and radiation. Conduction: The transfer of energy by collisions between the atoms and molecules in a material. Convection: Transfers heat when particles move between objects or areas that differ in temperature. Radiation: The transfer of energy by waves. Why the plastic materials used in the screwdriver's handles? Due to non-conducting nature of plastic, it is widely used for the electricity purposes. Moreover, plastic is cheap and strong so it is less prone to damage. Furthermore, plastic does not bend and does not slips from the users hands. Does diesel engine powered automobile use unit pump and unit injector? In the case of the engines powered by diesel fuel supply systems, unit pump & unit injector are operated by camshaft & thus pressure of injected fuel depends on engine speed. Whereas,in common rail systems it is independent of engine speed. If we use gasoline in diesel engine, what will happen? Adding gasoline to the diesel engine may blast off the engine. Compression ratio of the petrol engine is 6 to 10 and diesel engine is 15 to 22. Thus gasoline will get very highly compressed and might result in blast off engine. What is octane number and cetane number? Octane number can be defined as the percentage, by volume, of iso-octane in the mixture of iso-octane and h-heptane. It is the measure of rating of SI engine. While cetane number can be defined as the percentage,by volume, of n-cetane in the mixture of n-cetane and alpha methyl naphthalene. It is the measure of rating of CI engine. Explain the significance of governor in automobiles? Governor is an important component of automobile engine. It is used to regulate the main speed of engine during the variations in loads. With the variations in the load, fuel supply has to be maintained. This task is performed by the governor. In the case of high load on the engine, speed decreases, hence fuel supply has to be increased and similarly when load decreases then the fuel supply has to be decreased. What is the reason for emitting the white exhaust smoke during start of the vehicle? How will you prevent this? The main cause of white smoke is water or anti-freeze entering the cylinder, so the engine starts to burn it with the fuel. That white smoke is nothing but steam. Prevention measures: There are special gaskets i.e. head gaskets and primary gaskets that prevent the anti-freeze from entering into the cylinder area. This anti-freeze will produce a white steam which will accumulate at the tailpipe area. Part 1   Part 2   Part 3   Part 4   Part 5   Part 6 Write your comment - Share Knowledge and Experience Discussion Board governor function governor doesn't control speed,it controls amount of fuel quantity to be delivered. vivek 03-20-2015 11:13 AM AutoMobile Conductive heat flow involves the transfer of heat from one location to another in the absence of any material flow due to temp. Difference. Convection is the process of heat transfer from one location to the next by the movement of fluids. The moving fluid carries energy with it. The fluid flows from a high temperature location to a low temperature location. Heat transfer by radiation occurs when microwaves, infrared radiation, visible light, or another form of electromagnetic radiation is emitted or absorbed. An obvious example is the warming of the Earth by the Sun. A less obvious example is thermal radiation from the human body. Harsh Chovatiya 03-18-2015 03:07 PM First QA The answer for conduction you have given is for convection and convection for conduction.. Pls. Check it Rajagopalan 08-5-2014 06:39 AM