In order to avoid overheating of the engine, parts around the combustion chamber (Cylinder Liner, cylinder head, Valve, etc)Proper cooling is required.
There are three types of cooling devices for internal combustion engines: water cooling, oil cooling and air cooling.
The car engine cooling device is mainly water cooling, which is cooled by circulating water in the cylinder waterway, and the heated water in the waterway is introduced into the radiator (Water tank)After cooling by the wind, return to the waterway.
In order to ensure the cooling effect, the car cooling system is generally composed of radiators (1)Thermostat (2), Pump (3), Cylinder waterway (4)Cylinder head waterway (5)Fan, etc.
Take the car as an example. The radiator is responsible for the cooling of circulating water. Its water pipes and heat sinks are made of aluminum. The aluminum water pipes are made of flat shape. The heat sinks are corrugated and pay attention to heat dissipation performance, the installation direction is perpendicular to the direction of air flow, so as to make the wind resistance as small as possible and the cooling efficiency as high as possible.
The cooling water inside the radiator is not pure water, but water (Meet the quality of drinking water)Antifreeze (Usually ethylene glycol)
And a mixture of preservatives for various special purposes, also known as coolant.
The antifreeze content in these coolant accounts for 30% ~ 50%, which increases the boiling point of the liquid. Under certain working pressure, the allowable working temperature of the car coolant can reach 120 degrees Celsius, which exceeds the boiling point of water and is not easy to evaporate.
The engine is realized by the circulation of the coolant. The part that forces the coolant circulation is the water pump, which is driven by the crankshaft belt, and the pump impeller pushes the coolant to circulate throughout the system.
The cooling of these coolant to the engine should be adjusted at any time according to the operation of the engine.
When the engine temperature is low, the coolant will make a small cycle inside the engine itself, and when the engine temperature is high, the coolant will be in the engine-Make a big cycle between radiators.
The control component that implements different cycles of coolant is the thermostat.
The thermostat is actually a valve. The principle is to use the material that can be scaled with temperature, such as paraffin or ether, to open and close the valve. When the water temperature is high, the material expands to open the valve and the coolant is subjected to large circulation, when the water temperature is low, the material shrinks and closes the valve, and the coolant circulates.
In order to improve the cooling capacity of the radiator, a fan is installed behind the radiator to force ventilation.
The previous car radiator fan was directly driven by the crankshaft belt. When the engine is started, it will turn. It cannot change depending on the engine temperature. In order to adjust the cooling force of the radiator, install a movable hundred-page window on the radiator to control the wind to enter.
Modern cars have been widely used with fan electromagnetic clutch or electronic fan. When the water temperature is relatively low, the clutch is separated from the rotating shaft and the fan does not move. When the water temperature is relatively high, the temperature sensor turns on the power supply, make the clutch join the rotating shaft and the fan rotate.
Similarly, the electronic fan is directly driven by the motor and controlled by the temperature sensor.
These two forms of radiator fans are actually controlled by temperature sensors.
The radiator also acts as water storage and heat dissipation. If it relies solely on the radiator, it has three disadvantages. First, the water absorption side of the water pump is easy to boil due to low pressure, and the impeller is easy to erode; Second, the separation of gas and water is not easy to resist; Third, the high temperature coolant is easy to boil away.
Therefore, the designer installed an expansion water tank, and its upper and lower water pipes were connected to the upper part of the radiator and the water inlet of the water pump to prevent the above problems.
At present, the cooling system of the car is more complicated than in the past, mainly by adding temperature control components. The radiator fan can 'adapt' to the change of engine temperature. Coolant is generally used in the cooling system.
Of course, the heat of the engine is also the energy generated by the fuel, and cooling it is actually a last resort.
Therefore, people are studying a thermal insulation engine made of ceramic materials that do not need to be cooled. Once implemented in the future, the engine will be small and simple.