Foreword
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The function of the automotive engine cooling system is to allow the engine to be moderately cooled under all operating conditions to maintain operation at the right temperature. At present, the automotive engine cooling system not only protects the engine, but also has the effect of improving fuel economy and reducing emissions. In order to better understand the car engine cooling system, this article will detail the working principle of the car engine cooling system.
The main job of the automotive engine cooling system is to dissipate heat into the air to prevent the engine from overheating, but the cooling system has other important functions. The engine in the car is operating best at the appropriate high temperature. If the engine cools, it will accelerate component wear, which will reduce engine efficiency and emit more pollutants. Therefore, another important function of the cooling system is to warm the engine as quickly as possible and keep it at a constant temperature.
How does the car engine cooling system work?
There are two types of automotive cooling systems: liquid cooling and air cooling. The cooling system of a liquid-cooled liquid-cooled vehicle circulates liquid through pipes and passages in the engine. When the liquid flows through a high temperature engine, it absorbs heat, which lowers the temperature of the engine. After the liquid flows through the engine, it flows to the heat exchanger (or radiator), and the heat in the liquid is dissipated into the air through the heat exchanger. Air-cooled Some early cars used air-cooling technology, but modern cars barely use this method. This cooling method does not perform liquid circulation in the engine, but dissipates heat through the aluminum sheets attached to the surface of the engine block. A powerful fan blows the aluminum sheets to dissipate heat into the air to cool the engine. Because most cars use liquid cooling, there are a large number of pipes in the cooling system in the piping system.
After the pump delivers the liquid to the engine block, the liquid begins to flow in the engine passage around the cylinder. The liquid is then returned to the thermostat through the cylinder head of the engine where the liquid exits the engine. If the thermostat is turned off, the liquid will flow directly back to the pump through the tubing around the thermostat. If the thermostat is turned on, the liquid will first flow into the radiator and then back to the pump.
The heating system also has a separate cycle. This cycle begins with the cylinder head delivering liquid through the heater bellows and back to the pump. For vehicles equipped with automatic transmissions, there is usually a separate cycle to cool the transmission fluid built into the radiator. Transmission fluid is drawn from the transmission through another heat exchanger in the radiator. Liquid vehicles can operate over a wide temperature range well below zero degrees Celsius to well above 38 °C.
Therefore, no matter which liquid is used to cool the engine, it must have a very low freezing point, a high boiling point, and a large amount of heat. Water is one of the most effective liquids for absorbing heat, but the freezing point of water is too high for automotive engines. The liquid used in most cars is a mixture of water and acetylene glycol (c2h6o2), also known as antifreeze. By adding acetylene glycol to water, the boiling point can be significantly increased and the freezing point can be lowered.
The pump circulates the liquid whenever the engine is running. Similar to the centrifugal pump used in automobiles, the pump delivers liquid to the outside by centrifugal force while continuously pumping liquid from the center. The pump inlet is located closer to the center so that liquid returning from the radiator can contact the pump vanes. The pump blades deliver liquid to the outside of the pump from which the liquid enters the engine. The liquid from the pump first flows through the engine block and cylinder head, then into the radiator, and finally back to the pump. The engine block and cylinder head have a number of channels that are cast or machined to facilitate liquid flow.
If the flow of liquid in these pipes is smooth, only the liquid in contact with the pipe will be cooled directly. The amount of heat that is transferred from the pipe to the heat of the pipe depends on the temperature difference between the pipe and the liquid that contacts the pipe. Therefore, if the liquid in contact with the pipe is cooled rapidly, less heat will be transferred. By making turbulence in the pipe, mixing all the liquid, the liquid in contact with the pipe is kept at a high temperature to absorb more heat, so that all the liquid in the pipe is effectively utilized.
The transmission cooler is similar to the radiator in the radiator, except that the oil does not exchange heat with the air, but exchanges heat with the coolant in the radiator. The pressure tank lid pressure tank lid increases the boiling point of the coolant by 25 °C.
The main function of the thermostat is to warm the engine quickly and keep it at a constant temperature. It is achieved by adjusting the amount of water flowing through the radiator. At low temperatures, the outlet of the radiator will be completely blocked, ie all coolant will be circulated again via the engine. Once the temperature of the coolant rises to between 82-91 ° C, the thermostat opens, allowing liquid to flow through the radiator. When the temperature of the coolant reaches 93-103 ° C, the thermostat will remain open.
The cooling fan is similar to the thermostat, and the cooling fan must be controlled to keep the engine at a constant temperature. Front-wheel drive vehicles are equipped with fans because the engines are usually mounted laterally, ie the output of the engine is towards the side of the car.
The fans can be controlled by a thermostatic switch or an engine computer that will turn on when the temperature rises above the set point. These fans will turn off when the temperature drops below the set point. Rear-drive vehicles with cooling fans equipped with longitudinal engines are usually equipped with engine-driven cooling fans. These fans have a thermostatically controlled viscous clutch. The clutch is located in the center of the fan and is surrounded by the airflow from the radiator. This type of special viscous clutch is sometimes more like a viscous coupler for an all-wheel drive vehicle. When the car overheats, open all windows and run the heater while the fan is running at full speed. This is because the heating system is actually a secondary cooling system that reflects the condition of the main cooling system on the car.
Heater Piping The heating bellows on the dashboard of a car are actually a small heat sink. The heater fan allows air to flow through the heater bellows and then into the passenger compartment of the car. The heater bellows is similar to a small radiator. The heater bellows draws hot coolant from the cylinder head and then recirculates it back into the pump so that the heater can operate when the thermostat is turned on or off.
Conclusion
Modern automotive engine cooling system design (automobile engine maintenance) should consider the following factors: friction loss inside the engine; power of the cooling system pump; combustion boundary conditions, such as combustion chamber temperature, charge density, charge temperature, etc. Understand the working principle of the car engine cooling system, and consider each influencing factor to help design a car engine cooling system with better performance.
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