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1、Chapter 2 Internal Combustion Engine,2.10 Cooling System 2.11 Lubrication System 2.12 Emission Control Systems,2.10 Cooling System,New Words,2.10 Cooling System,The purpose of the engines cooling system is to remove excess heat from the engine, to keep the engine operating at its most efficient temp
2、erature, and to get the engine up to the correct temperature as soon as possible after starting. Ideally, the cooling system keeps the engine running at its most efficient temperature no matter what the operating conditions are. Fuel burning engines produce enormous amounts of heat; temperatures can
3、 reach up to 4,000 F when the air-fuel mixture burns. However, normal operating temperature is about 2,000 F. The exhaust system takes away much of the heat, but parts of the engine, such as the cylinder walls, pistons, and cylinder head, absorb large amounts of the heat. If a part of the engine get
4、s too hot, the oil film fails to protect it. This lack of lubrication can ruin the engine.,On the other hand, if an engine runs at too low a temperature, it is inefficient, the oil gets dirty (adding wear and subtracting horsepower), deposits form, and fuel mileage is poor- not to mention exhaust em
5、issions! For these reasons, the cooling system is designed to stay out of the action until the engine is warmed up. There are two types of cooling systems: liquid cooling and air cooling. Most auto engines are cooled by the liquid type; air cooling is used more frequently for airplanes, motorcycles
6、and lawnmowers. The cooling system of a water-cooled engine consists of the engines water jacket, a thermostat, a water pump, a radiator and radiator cap, a cooling fan (electric or belt-driven), hoses, and usually an expansion (overflow) tank (Figure 2-23).,Fig.2-23 The cooling system of a water-co
7、oled engine,2.11 Lubrication System,New Words,2.11 Lubrication System,Fig.2-24 Engines lube oil circuit schematic,Reducing friction to minimize wear and loss of power is the primary job a lubrication system must perform. Residual oil on engine parts also provides lubrication for engine start-up. The
8、 engine oil forms a seal between the pistons, rings, and cylinders. It also helps to cool engine parts. Without the cleaning action of the lubricating system, carbon and varnish buildup would be excessive. The engine oil also absorbs the shock and dampens the noise of moving parts. How successful th
9、e lubrication system is in performing all these functions depends on a number of factors and conditions. There must be an adequate supply of good-quality lubricant delivered to all moving engine parts under sufficient pressure to provide hydrodynamic lubrication for rotating parts and oil adhesion t
10、o surface subject to sliding friction. Figure 2-24 shows a engines lube oil circuit schematic.,Fig.2-25 The parts of the lubrication system,2.12 Emission Control Systems,New Words,The purpose of the emission control system is just that it controls the emissions and exhaust from a vehicle. The idea i
11、s to turn the harmful gases a car manufactures into harmless ones that dont ruin the environment, or persons. Some of the problem gases are: 1) hydrocarbons (unburned) 2) carbon monoxide 3) nitrogen oxides There are five popular systems used to reduce emissions: the crankcase ventilation system,the
12、evaporative emission control system, the Exhaust Gas Recirculation (EGR) system, the air injection system and the catalytic converter system. In addition to these emission systems, modern vehicles incorporate an electronically controlled fuel injection system, which further reduces emissions. Note:
13、Not all vehicles are equipped with these emission systems.,The purpose of the positive crankcase ventilation (PCV) system is to take the vapors produced in the crankcase and piston blow-by, and redirect them into the air/fuel intake system to be burned during combustion. Exhaust gas recirculation (E
14、GR) systems reduce the amount of oxides of nitrogen produced during the combustion process.,The function of the fuel evaporative control system is to trap and store evaporative emissions from the gas tank and carburetor. A charcoal canister is used to trap the fuel vapors. The fuel vapors adhere to
15、the charcoal, until the engine is started, and engine vacuum can be used to draw the vapors into the engine, so that they can be burned along with the fuel/air mixture. The catalytic converter looks like a muffler. It is located in the exhaust system ahead of the muffler. As hydrocarbons or carbon m
16、onoxide in the exhaust are passed over the catalyst, it is chemically oxidized or converted to carbon dioxide and water.,Fig.2-26 Exhaust system,Fig.2-27 Positive crankcase ventilation (PCV) system,Fig.2-28 Evaporative emission control (EVAP) system,Fig.2-29 Exhaust gas recirculation (EGR) system,Fig.2-30 Air injection (AIR) system,Fig.2-31 Three-way catalytic converter (TWC) system with ceramic substrates,
