25-08-2017, 09:32 PM
I.C. ENGINE
1ENGINE.pptx (Size: 460.5 KB / Downloads: 48)
INTRODUCTION
Internal combustion engines transforms about 25 to 35% of the chemical energy in the fuel in to mechanical energy.
About 35 percentage of the heat generated is lost in to the surroundings of combustion space, remainder being dissipated through exhaust and radiation from the engine.
The temperature of the burning gases reaches inside the engine cylinder about 2000 to 2500° C.
The engine components like cylinder head, cylinder wall piston and the valve absorb this heat.
Such high temperatures are objectionable for engine life.
Requirements of a good Cooling System
It should remove only about 30% of the heat generated in the combustion chamber. Too much cooling reduces the thermal efficiency of the engine.
A good cooling system should remove heat at a faster rate when the engine is hot. During starting, the cooling should be very slow.
The components in the cylinder must be reasonably hot (250°C).
Over-cooling of the engine results in insufficient vaporization of fuel, loss of power, high fuel consumption, higher emissions, starting troubles, excessive formation of sludge, lower thermal efficiency and greater wear and tear of parts.
Necessity For Engine Cooling
Engine valves damage due to over heating.
Damage to the materials of cylinder body and piston.
Lubricating oil decomposes to form gummy and carbon particles.
Thermal stresses are set up in the engine parts and causes distortion and cracking of components.
Pre – ignition occurs (i.e. ignition occurs before it is required to igniter due to the overheating of spark plug).
Reduces the strength of the materials used for piston and piston rings.
Overheating reduces the efficiency of the engine.
CONSTRUCTION
CONVENTIONAL CONSTRUCTION used in heavy vehicles . A separate frame is used in this case.
UNITARY CONSTRUCTION used in cars and no separate frame is used in this case.
SEMI INTEGRAL FRAME
The rubber body mounts are replaced by stiff mounts so part of the frame load is transferred to the body structure .
This type of frame is popular in small european cars and american cars.
Frame is heavy
HEATING SYSTEM IN A CAR
A car heater is designed to warm the passenger cabin of our car.
This system makes use of excess heat from the engine's internal combustion process.
The engine's excess heat is absorbed by a circulating liquid coolant.
The heated liquid coolant is carried from the engine through the hoses to the radiator often called the heater core .
A fan is positioned in front of the heater core to blow cold outside air over the fins so that it heats up and becomes the hot air which blows out through heater vents.