HMT GATE Practice Questions

Q1)  For a given material, the thermal conductivity K is

  1. A constant
  2. Depends upon shape and size of material
  3. Can be different with different directions
  4. Not a Constant                                                                                                                 (3)

Q2) Out of the following which is a property of material

1. Thermal Conductivity

2. Convective heat Transfer Coeffcient

3. Overall Heat transfer coefficinet

4. Thermal resistance                                                                                                           ( 1)

 

Morse test in SI engine

Just after combustion of fuel inside the cylinder, the heat power developed promptly converts into mechanical energy/time over the piston top. This mechanical energy/time or mechanical power (Fresh conversion of heat energy into mechanical energy over the piston top) is called as  Indicative power .The indicative power further transfers to the crank shaft by the help of connecting rod. The power available over the crank shaft is called as Brake power. The Magnitude of brake power is always less than indicative power because of losses associated with various types of friction (e.g. the friction between the piston outer surface and inner surface of cylinder, The friction between the piston rings and cylinder inner surface etc) The Brake power of an engine can be found by the help of a device called as  dynamo meter.  But there is no as such device which can measure the amount of indicative power of engine. For finding the indicative power Morse test has to be performed and that too can be performed over multi cylinder engines. In the following lecture you will learn how Morse test is performed in an engine to find the indicative power of a multi cylinder Engine..

Volumetric efficiency of an engine

When the suction stroke executes that according to theory, the amount of volume the piston displaces is exactly equal to the volume of charge sucked. However in actual practice the amount of charge sucked is lower than the displaced volume of piston. The ratio of amount of charge sucked and the amount of piston displacement is called as volumetric efficiency. In this tutorial there are details of volumetric efficiency principle

Why dual spark plugs are used in SI engines?

Generally one spark plug is sufficient to ignite the charge inside the engine cylinder. But inside the engine the charge burns with a particular burning rate. In case the piston is moving too fast inside the cylinder (In high speeds) then chances are developed i.e. charge did not completely burn and the end of working stroke has come.In case combustion starts by the help of two spark plugs at two different locations then the aforesaid problem can be resolved.  This video tutorial clearly demonstrates by animations i.e. why dual spark plugs are used in SI engines.