Jump to content
Mechanical Engineering Community

Asim Mehmood

Members
  • Content Count

    13
  • Joined

  • Last visited

About Asim Mehmood

  • Rank
    Member

Recent Profile Visitors

The recent visitors block is disabled and is not being shown to other users.

  1. Asim Mehmood

    Why diesel Engine don't have spark plug?

    One thing we know. We can’t use fuel in liquid form during compression, because liquids are incompressible. Now we have option to use diesel in vapour form. At atmospheric pressure, boiling point of diesel is 250°c to 300°c. And diesel in fuel tank have temperature around 40°c to 50°c. So it is not possible to make vapors (as in carburetor of petrol engine).So, how can we convert diesel into vapour form?There are three options: 1. If we put liquid diesel into a medium having pressure less than vapour pressure of diesel, it means we create vacuum inside the cylinder. During suction stroke we have vacuum and we can convert the diesel into vapors, but during compression stroke we must avoid auto ignition due to high compression ratio. The one and the only way to avoid the auto ignition in such case is to reduce the compression ratio. Which is not possible (2nd law of thermodynamics, higher is the pressure more is the power) if we want to get power from engine. Another important reason for using higher compression ratio is to get higher expansion ratio (more piston displacement) thus more power with same fuel consumption.Work done = pressure (mean effective pressure) × piston cross-sectional area × piston displacement. But still if someone manages this miracle, how he overcomes condensation of diesel during compression stroke where the pressure goes up again. So drop this option. 2. Increase the temperature of liquid diesel before putting into engine cylinder which is possible but not reliable. We have to use pre-heaters, which cost energy consumption and makes vehicles bulky. 3. Put liquid diesel into high temperature air (greater than saturation temperature of diesel) and provide some time for heat exchanging between them. In practical air standard engines third option is perfect as we produce high temperatures by compression. But still we can't use spark plug for ignition, since mixture present in the cylinder is heterogeneous (somewhere mixture within ignition limits and somewhere not). Ignition by spark plug required homogenous air fuel mixture. Now we have only 1 option to ignite the diesel, that is; compresses the air and raised the temperature of air up to ignition temperature of diesel and inject the diesel in cylinder.
  2. Asim Mehmood

    IC ENGINES

    Engine Speed= 1500 RPM No. of Revolution per Power Stroke= 02 Therefore No. of Power Strokes/min by 1 Cylinder= 1500/2 = 750 (Answer of B No. of Power Strokes/min by 20 Cylinders= 750 * 20= 15000 (Answer of a) (Answer of C) At the same time only and only 1 cylinder at power stroke.
  3. Asim Mehmood

    What is the difference between machine and engine??

    An apparatus using mechanical power and having several parts, each with a definite function and together performing a particular task. And engine is also one of the machine that converts the heat energy of the fuel into mechanical energy.
  4. Asim Mehmood

    Petrol engine

    https://www.facebook.com/icengine319/videos/435079353230242/
  5. Asim Mehmood

    Flywheel

    Flywheel is a heavy wheel on rear end of the engine. it stores the inertia which produced during power stroke of the engine and allow the crankshaft to rotate smoothly during other strokes.
  6. Asim Mehmood

    Thermodynamic Condensate Trap

    Can a thermodynamic trap is used in compressed air sytem? If yes can we use it vertically?
  7. Asim Mehmood

    reason for three rings in a piston

    Each ring is an expansion-sprung ring, but with a gap. By using 2-3 rings, and then alternating the locations of the gap, a complete seal can be made for when the piston moves upwards on both the compression stroke and the exhaust stroke and during combustion.Higher compression engines will sometimes use 4 rings to further the sealing ability.
  8. Asim Mehmood

    What is back plate in centrifugal pumps and its purpose?

    Back plate is the part of the pump which fits with the bearing housing with the help of bolts.Back plate consist of gland ring towards bearing side where mechanical seal or gland packings are arranged in such a way that handled fluid by the pump can be protected from leaking in atmosphere.Other end of the back plate is towards impeller which becomes one of the wall in between the suction casing.Potential energy of Sucked liquid will be turned to kinetic energy by the high speed rotaion of impeller,during this operation sucked liquid will be filling the close clearance in between backplate and impeller which helps in incresing of pressure.Back plate has wear ring in its id which has nearly 0.1 mm clearance with the wear ring on impeller which helps in preventing the back flow of the discharge to suction and increases the efficiency.
  9. Asim Mehmood

    Mechanical Engineering

    Why a magnetic nut is used in some turbocharger's compressor wheel?
  10. Asim Mehmood

    IC Engine

    Can engine trend to overheating?
  11. Asim Mehmood

    IC Engine

    A 12 cylinder V type diesel engine has two turbochargers. What happened if I run this engine without turbochargers?
  12. Asim Mehmood

    IC Engine

    3000 power strokes of 4 cylinders means 750 (3000/4) complete cycles of engine. We know 1 complete engine cycle has 2 revolutions of crankshaft. Therefore the speed of engine was 1500 RPM (750*2).
  13. Asim Mehmood

    IC Engine

    A 4 cylinder 4 stroke diesel engine was running with 3000 power strokes per minute. What was the speed of engine?
×