In the car, it is designed to protect the working unit from overheating and thereby controls the performance of all motor block. Cooling is essential function in the operation of an internal combustion engine.

Consequences of a malfunction internal combustion engine cooling can be fatal for the unit itself, up to the complete failure of the cylinder block. Damaged nodes may no longer be subject to restoration work, their maintainability will be equal to zero. It is necessary to treat the operation with all care and responsibility and carry out periodic flushing of the engine cooling system.

By controlling the cooling system, the car owner directly takes care of the "health of the heart" of his iron "horse".

Purpose of the cooling system

The temperature in the cylinder block when the unit is running can rise to 1900 ℃. Of this volume of heat, only a part is useful and is used in the required operating modes. The rest is taken out by the cooling system. engine compartment. Increase temperature regime beyond the norm is fraught negative consequences that lead to burning lubricants, violation of technical clearances between certain parts, especially in piston group which will reduce their service life. Overheating of the engine, as a result of a malfunction of the engine cooling system, is one of the reasons for the detonation of the combustible mixture supplied to the combustion chamber.

Engine overcooling is also undesirable. In a "cold" unit, there is a loss of power, the oil density increases, which increases the friction of non-lubricated components. working combustible mixture partially condenses, thereby depriving the cylinder walls of lubrication. However, the surface of the cylinder wall undergoes a corrosion process due to the formation of sulfur deposits.

The engine cooling system is designed to stabilize the thermal conditions necessary for the normal functioning of the motor vehicle.

Types of cooling system

The engine cooling system is classified according to the method of heat removal:

• cooling with liquids in a closed type;
• air cooling in open type;
• combined (hybrid) heat removal system.

Currently, air cooling in cars is extremely rare. Liquid can be open type. In such systems, heat is removed through a steam pipe in environment. A closed system is isolated from the outside atmosphere. Therefore, this type is much higher. At high pressure the boiling threshold of the cooling element increases. The refrigerant temperature in a closed system can reach 120℃.

Air cooling

Natural forced air cooling is the most simplest way heat dissipation. Engines with this type of cooling emit heat into the environment using radiator fins located on the surface of the unit. Such a system has a huge lack of functionality. The fact is that this method directly depends on the small specific heat of air. In addition, there are problems with the uniformity of heat removal from the motor.

Such nuances prevent the installation of an efficient and compact installation at the same time. In the engine cooling system, air is supplied unevenly to all parts, and then the possibility of local overheating must be avoided. Following the design features, the cooling fins are mounted in those places of the engine where the air masses are the least active, due to aerodynamic properties. Those parts of the motor that are most susceptible to heat are placed towards the air masses, while the "colder" sections are placed at the back.

Forced air cooling

Motors with this type of heat dissipation are equipped with a fan and cooling fins. Such a set of structural units makes it possible to artificially inject air into the engine cooling system to blow the cooling fins. A protective casing is installed above the fan and fins, which participates in the direction of air masses for cooling and prevents heat from entering from the outside.

The positive aspects in this type of cooling are simplicity design features, light weight, lack of refrigerant supply and circulation units. The disadvantages are the high noise level of the system and the bulkiness of the device. Also, in forced air cooling, the problem with local overheating of the unit and diffuse airflow has not been solved, despite the installed casings.

This type of engine overheating warning was actively used until the 70s. The operation of the forced air type engine cooling system has been popular on subcompact vehicles.

Cooling with liquids

The liquid cooling system is by far the most popular and widespread. The process of heat removal takes place with the help of a liquid refrigerant circulating through the main elements of the engine through special closed lines. The hybrid system combines the elements of air cooling at the same time as liquid. The liquid is cooled in a radiator with fins and a fan with a casing. Also, such a radiator is cooled by supply air masses when the vehicle is moving.

The liquid cooling system of the engine produces a minimum noise level during operation. This type collects heat everywhere and removes it from the engine with high efficiency.

According to the method of movement of the liquid refrigerant, the systems are classified:

Engine cooling system device

Design liquid cooling has the same structure and elements as for gasoline engine as well as for diesel. The system consists of:

• radiator block;
• oil cooler;
• fan, with shroud installed;
• pumps (pump with centrifugal force);
• a tank for expanding the heated liquid and level control;
• refrigerant circulation thermostat.

When flushing the engine cooling system, all these nodes (except for the fan) are affected for more efficient further work.

The coolant circulates through the lines inside the block. The totality of such passages is called the "cooling jacket". It covers the most heat-prone areas of the engine. The refrigerant, moving along it, absorbs heat and carries it to the radiator block. Cooling down, he repeats the circle.

System operation

One of the main elements in the device of the engine cooling system is the radiator. Its task is to cool the refrigerant. It consists of a radiator crate, inside which tubes are laid for the movement of fluid. The coolant enters the radiator through the lower pipe and exits through the upper one, which is mounted in the upper tank. On top of the tank there is a neck, closed with a lid with a special valve. When the pressure in the engine cooling system increases, the valve opens slightly and the liquid enters the expansion tank, attached separately in the engine compartment.

Also on the radiator is a temperature sensor that signals the driver about the maximum heating of the liquid through a device installed in the cabin on information panel. In most cases, a fan (sometimes two) with a casing is attached to the radiator. The fan is activated automatically when the critical temperature of the coolant is reached or it works forcibly from a drive with a pump.

The pump ensures constant circulation of coolant throughout the system. The pump receives rotational energy by means of a belt drive from the crankshaft pulley.

The thermostat controls the large and small circle of refrigerant circulation. When the engine is first started, the thermostat circulates fluid in a small circle in order to motor unit warmed up faster operating temperature. After that, the thermostat opens a large circle of the engine cooling system.

antifreeze or water

Water or antifreeze is used as a coolant. Modern car owners are increasingly using the latter. Water freezes at sub-zero temperatures and is a catalyst in corrosion processes, which adversely affects the system. The only plus is its high heat dissipation and, perhaps, availability.

Antifreeze does not freeze in cold weather, prevents corrosion, prevents sulfur deposits in the engine cooling system. But it has a lower heat transfer, which negatively affects the hot season.

Faults

The consequences of a cooling failure are overheating or hypothermia of the engine. Overheating can be caused by insufficient fluid in the system, unstable job pump or fan. Also wrong work thermostat when it should open a large cooling circle.

Can be caused by severe contamination of the radiator, slagging of lines, bad job radiator caps, expansion tank or poor quality antifreeze.

The car engine generates a significant amount of heat during operation, heating up to high temperatures. Without a cooling system, a car engine will fail very quickly.

The main task of the vehicle is, first of all, to remove excess heat (energy) from the main elements of the unit.

It performs a number of additional functions:

• maintaining the optimum temperature working fluid automatic box gear;
• maintaining the optimum temperature in;
• exhaust gas temperature cooling;
• maintaining the optimum temperature of the engine oil;
• providing air heating and maintaining the set temperature in the ventilation, air conditioning and heating system.

What are engine cooling systems?

Modern engine cooling systems can be divided into three groups:

• air cooling system - in its work, excess heat is removed using air flows. It can also be called open;
• liquid cooling system - for removal excess heat from the motor uses a special fluid;
• combined system - equally uses the above two types of cooling.

Most common in cars got a liquid engine cooling system.

Features of the design of the car cooling system

Structurally, systems for gasoline and do not differ from each other. They work with the same efficiency.

We can distinguish the main elements of the cooling system of a modern vehicle:

• radiator;
• heat exchanger;
• water pump;
• expansion tank;
• thermostat.

All of them are combined into a single system that provides efficient removal of excess heat from the motor.

The principle of operation of the car cooling system

The control of the cooling operation of the machine is carried out by the control unit of the vehicle. This is a complex mathematical process that takes into account a large number of internal and external factors. It is tracked in real time. The control unit sets the optimal operating conditions for the system to effectively remove excess heat.

The coolant moves in a large and small circle. If the engine is not warm enough, then the fluid moves in a small circle. The radiator is not involved in the process. This helps the engine warm up faster. As soon as the engine reaches operating temperature, the fluid begins to circulate in a large circle. Used where it is cooled by air flow.

A malfunction in the car's cooling system is fraught with overheating of the motor and its failure.

Thank you for your attention, good luck on the road.

When running, a car engine generates a lot of heat, so it must be constantly cooled to avoid damage.

As a rule, this is done with the help of a coolant (water) mixed with an antifreeze solution and circulating in special channels. Some engines are cooled by air currents that move over cylindrical cooling fins.

How coolant circulates

A typical liquid cooling system equipped with an engine driven fan. Please note that the bypass hose contains hot water for the heater. The sealed cover of the expansion chamber is equipped with a valve with a spring that opens at a certain pressure.

Water cooling system

The cylinder block and cylinder head, cooled by water, are interconnected by fluid channels. In the upper part of the head, all channels are reduced to a single drain.

Pump driven by pulley and belt drive from crankshaft, directs hot fluid from the engine to the radiator, which is a heat exchange device.

Unnecessary heat exits the radiator with the airflow, and the coolant returns through the inlet to the bottom of the block and passes through the channels again.

Typically, the pump sends the coolant up through the engine and down through the radiator, which is very advantageous given that as the fluid heats up, it expands, becomes lighter, and rises above the cold fluid. In other words, hot liquid always flows upwards, and the pump only helps to circulate it.

The radiator is connected to the engine by rubber hoses, and the honeycombs are connected to the upper and lower tanks by numerous thin tubes.

The tubes pass through holes in a bundle of thin sheet metal cooling fins, so the honeycomb has a large surface area and quickly loses heat when air passes through.

In older models, the tubes are arranged vertically, but in modern cars with a low front, cross-flow radiators with horizontal pipes are used.

In an engine that runs standard conditions, the coolant does not heat up above the boiling point.

The liquid never boils because the pressure in the system is increased, which means that the boiling temperature is higher than normal.

As a protection against overpressure, the radiator cap is equipped with a shut-off valve. When pressure rises excessively, the valve opens and coolant flows out through the overflow pipe.

In a cooling system of this type, with constant overheating of the engine, the liquid is gradually consumed, and the supply must be replenished.

In later models, the cooling system is sealed, and any excess fluid accumulates in the expansion chamber, where it cools and is then sucked back into the engine.

Why is a fan needed?

The radiator needs a constant supply of air to pass through the cells and cool them properly. When the car is moving, it happens by itself. When stopped, the airflow is controlled by the fan.

The fan can be powered by the engine, but if the vehicle is stationary or the engine is not overloaded, the running fan consumes excess fuel.

To avoid unnecessary costs, some vehicles use viscous couplings (fluid couplings), which are equipped with a temperature-sensitive valve that starts the fan until the fluid temperature drops to the desired value.

Some vehicles are equipped with electric fans that turn on and off according to the temperature sensor.

In order for the engine to heat up quickly, the radiator is separated from it by a thermostat, which is usually located above the pump. The thermostat is equipped with a valve, under which a wax cylinder is located.

As the engine warms up, the wax melts, expands and opens the valve, allowing coolant to flow through the radiator.

When the engine stops and cools down, the valve closes again.

Water expands when it freezes, so if it freezes in the engine, the block or radiator can burst. Therefore, antifreeze (usually ethylene glycol) is added to the water to lower the freezing point to a safe level.

Antifreeze does not need to be drained every summer. As a rule, it serves two or three years.

Air cooling system

In an air-cooled engine, deep cooling fins are provided on the outer surface of the cylinder block and cylinder head.

As a rule, the ribs expand towards the top, because. heat is concentrated there.

Horizontal air-cooled motors have air ducts on the fins.

In a heater with water valves, air passes through the tube bundle. The temperature in the beam is determined by the amount of hot water passing through it.

A channel also passes through all the ribs, through which air is coming taking away excess heat.

The volume of air passing through the fan is determined by a temperature-sensitive sensor, so the temperature remains constant even on cold days.

Oil cooling

In engines with air-cooled and high-performance water-cooled engines, an additional small radiator in which the engine oil is cooled.

Cooling system

The cooling system is designed to maintain the normal thermal regime of the engine.

When the engine is running, the temperature in the engine cylinders periodically rises above 2000 degrees, and the average temperature is 800-900°C!

If you do not remove heat from the engine, then in a few tens of seconds after starting it will no longer be cold, but hopelessly hot. Next time you can run your cold engine only after it overhaul.

The cooling system is necessary to remove heat from the mechanisms and parts of the engine, but this is only half of its purpose, however, more than half.

To ensure a normal working process, it is also important to accelerate the warm-up of a cold engine. And this is the second part of the cooling system.

As a rule, liquid cooling systems are used on cars, closed type, With forced circulation liquid and expansion tank (Fig. 29).

The cooling system consists of:

cooling jackets for the block and cylinder head,

centrifugal pump,

thermostat,

radiator with expansion tank

fan,

connecting pipes and hoses.

On fig. 29 you can easily distinguish two circles of coolant circulation.

Rice. 29. Scheme of the engine cooling system: 1 - radiator; 2 - pipe for circulation of the coolant; 3 - expansion tank; 4 - thermostat; 5 - water pump; 6 - cooling jacket of the cylinder block; 7 - cooling jacket of the head of the block; 8 - heater radiator with electric fan; 9 - heater radiator valve; 10 – plug for draining the coolant from the block; 11 - plug for draining the coolant from the radiator; 12 - fan

The small circle of circulation (red arrows) serves to warm up a cold engine as soon as possible. And when blue arrows join the red arrows, the already heated liquid begins to circulate in a large circle, cooling in the radiator. Leading this process automatic device – thermostat.

To control the operation of the cooling system, there is a coolant temperature gauge on the instrument panel (see Fig. 67). normal temperature coolant during engine operation should be in the range of 80–90 ° С.

Engine cooling jacket consists of many channels in the block and cylinder head through which coolant circulates.

Centrifugal pump causes the liquid to move through the engine cooling jacket and the entire system. The pump is driven by a belt drive from the engine crankshaft pulley. The belt tension is regulated by the deviation of the generator housing (see Fig. 63 a) or tension roller drive camshaft engine (see Fig. 11 b).

Thermostat designed to maintain a constant optimum thermal regime of the engine. When starting a cold engine, the thermostat is closed, and all the liquid circulates only in a small circle (Fig. 29 a) to warm it up as soon as possible. When the temperature in the cooling system rises above 80–85°C, the thermostat opens automatically and part of the liquid enters the radiator for cooling. At high temperatures, the thermostat opens completely, and now all the hot liquid is directed in a large circle for its active cooling.

Radiator serves to cool the fluid passing through it due to the air flow that is created when the car is moving or with the help of a fan. The radiator has many tubes and baffles, forming a large cooling surface area.

Expansion tank necessary to compensate for changes in the volume and pressure of the coolant during its heating and cooling.

Fan It is designed to forcefully increase the air flow passing through the radiator of a moving car, as well as to create an air flow in the case when the car is stationary with the engine running.

Two types of fans are used: permanently on, with a belt drive from the crankshaft pulley and an electric fan that turns on automatically when the coolant temperature reaches approximately 100 ° C.

Branch pipes and hoses are used to connect the cooling jacket to the thermostat, pump, radiator and expansion tank.

Also included in the engine cooling system interior heater. Hot coolant flows through heater radiator and heats the air that enters the car.

The air temperature in the cabin is regulated by a special crane, with which the driver increases or decreases the flow of fluid passing through the heater core.

The main malfunctions of the cooling system

Coolant leakage may appear as a result of damage to the radiator, hoses, gaskets and seals.

To eliminate the malfunction, it is necessary to tighten the hose and tube clamps, and replace the damaged parts with new ones. In case of damage to the radiator tubes, you can try to patch holes and cracks, but, as a rule, everything ends with the replacement of the radiator.

Engine overheating happens due to insufficient level coolant, loose fan belt tension, clogged radiator tubes, or a malfunctioning thermostat.

To eliminate engine overheating, restore the liquid level in the cooling system, adjust the fan belt tension, flush the radiator, and replace the thermostat.

Often, engine overheating also occurs with serviceable elements of the cooling system, when the car moves with low speed And heavy loads on the engine. This happens when driving in heavy road conditions, such as country roads and all the annoying city "traffic jams". In these cases, it is worth thinking about the engine of your car, and about yourself too, arranging periodic, at least short-term "breathes".

Be careful while driving and avoid emergency mode engine work! Remember that even a single overheating of the engine breaks the structure of the metal, while the life expectancy of the "heart" of the car is significantly reduced.

Operation of the cooling system

When operating the car, you should periodically look under the hood. A timely noticed malfunction in the cooling system will allow you to avoid engine overhaul.

If coolant level in expansion tank dropped or there is no liquid at all, then first you need to add it, and then you should figure out (on your own or with the help of a specialist) where it has gone.

During engine operation, the liquid heats up to a temperature close to the boiling point. This means that the water that is part of the coolant will gradually evaporate.

If in six months daily operation the level in the tank has dropped slightly, this is normal. But if yesterday there was a full tank, and today it is only at the bottom, then you need to look for a place where the coolant leaks.

Leakage of fluid from the system can be easily identified by dark spots on the asphalt or snow after a more or less long parking. Opening the hood, you can easily find the leak by comparing wet marks on the pavement with the location of the elements of the cooling system under the hood.

The fluid level in the tank must be checked at least once a week. If the level has dropped noticeably, then it is necessary to determine and eliminate the cause of its decrease. In other words, the cooling system must be put in order, otherwise the engine may become seriously "ill" and require "hospitalization".

Virtually all domestic cars as a coolant, a special low-freezing liquid with the name Tosol A-40. Number 40 indicates the negative temperature at which the liquid begins to freeze (crystallize). In the conditions of the Far North, it is used Tosol A-65, and, accordingly, it begins to freeze at a temperature of minus 65 ° C.

Antifreeze is a mixture of water with ethylene glycol and additives. Such a solution combines a lot of advantages. Firstly, it begins to freeze only after the driver himself has already frozen (just kidding), and secondly, Antifreeze has anti-corrosion, anti-foaming properties and practically does not form deposits in the form of ordinary scale, since it contains pure distilled water . That's why Only distilled water can be added to the cooling system.

When operating a vehicle, control not only the tension, but also the condition of the water pump drive belt, since its breakage on the road is always unpleasant. It is recommended to have a spare belt in the travel kit. If not yourself, then one of the good people will help you change it.

The coolant can boil and cause engine damage if the fan motor sensor. If the electric fan has not received a command to turn on, then the liquid continues to heat up, approaching the boiling point, without any cooling assistance.

But the driver has a device with an arrow and a red sector in front of his eyes! Moreover, almost always when the fan is turned on, a slight additional noise is felt. There would be a desire to control, but there will always be ways.

If on the way (and more often in a traffic jam) you notice that the temperature of the coolant is approaching the critical one, and the fan is running, then in this case there is a way out. It is necessary to include an additional radiator in the operation of the cooling system - the interior heater radiator. Fully open the heater tap, turn on the heater fan at full speed, lower the door windows and "sweat" to the house or to the nearest car service. But at the same time, continue to carefully monitor the arrow of the engine temperature gauge. If she still enters the red zone, stop immediately, open the hood and "cool down".

May cause trouble over time thermostat, if it ceases to let liquid through a large circle of circulation. Determining if the thermostat is working is not difficult. The radiator should not heat up (determined by hand) until the pointer of the coolant temperature gauge reaches the middle position (the thermostat is closed). Later, hot liquid will begin to flow into the radiator, quickly heating it up, which indicates the timely opening of the thermostat valve. If the radiator continues to be cold, then there are two ways. Knock on the thermostat housing, maybe it will still open, or immediately, mentally and financially, prepare to replace it.

"Surrender" to the mechanic immediately if oil dipstick you will see droplets of liquid that have entered the lubrication system from the cooling system. It means that damaged cylinder head gasket and coolant seeps into the engine sump. If you continue to operate the engine with oil half consisting of Tosol, then the wear of engine parts becomes catastrophic.

Water pump bearing does not break "suddenly". First, a specific whistling sound will appear from under the hood, and if the driver "thinks about the future", then he will replace the bearing in a timely manner. Otherwise, it will still have to be changed, but with the consequence of being late for the airport or for a business meeting, due to a “suddenly” broken car.

Every driver should know and remember that on a hot engine, the cooling system is in a state of overpressure!

If the engine of your car overheated and "boiled", then, of course, you need to stop and open the hood of the car, but you can not open the cap of the radiator or expansion tank. To speed up the process of cooling the engine, this will practically do nothing, and you can get severe burns.

Everyone knows what a clumsily opened bottle of champagne turns out to be for smartly dressed guests. In the car, everything is much more serious. If you quickly and thoughtlessly open the cork of a hot radiator, then a fountain will fly out from there, but not wine, but boiling Antifreeze! In this case, not only the driver, but also pedestrians who are nearby can suffer. Therefore, if you ever have to open the cap of a radiator or expansion tank, then you should first take precautions and do it slowly.

The engine cooling system serves to maintain the normal thermal operation of engines by intensively removing heat from hot engine parts and transferring this heat to the environment.

The removed heat consists of a part of the heat released in the engine cylinders, which is not converted into work and is not carried away with exhaust gases, and from the heat of friction work arising from the movement of engine parts.

Most of the heat is removed to the environment by the cooling system, a smaller part - by the lubrication system and directly from the outer surfaces of the engine.

Forced heat removal is necessary because at high temperatures of gases in the engine cylinders (during the combustion process 1800-2400 ° C, the average gas temperature for the operating cycle at full load is 600-1000 ° C) natural heat transfer to the environment is insufficient.

Violation of proper heat dissipation causes deterioration of lubrication of rubbing surfaces, oil burnout and overheating of engine parts. The latter leads to a sharp drop in the strength of the material of the parts and even their burning (for example, exhaust valves). When the engine is severely overheated, the normal clearances between its parts are violated, which usually leads to increased wear, seizing, and even breakdown. Overheating of the engine is also harmful because it causes a decrease in the filling factor, and in gasoline engines, in addition, detonation combustion and self-ignition of the working mixture.

Excessive cooling of the engine is also undesirable, since it entails the condensation of fuel particles on the cylinder walls, deterioration of mixture formation and flammability of the working mixture, a decrease in its combustion rate and, as a result, a decrease in engine power and efficiency.

Classification of cooling systems

In automobile and tractor engines, depending on the working fluid, systems are used liquid And air cooling. The most widely used liquid cooling.

With liquid cooling, the liquid circulating in the engine cooling system receives heat from the cylinder walls and combustion chambers and then transfers this heat to the environment using a radiator.

According to the principle of heat removal to the environment, cooling systems can be closed And open (flowing).

Liquid cooling systems of autotractor engines have a closed cooling system, i.e. a constant amount of liquid circulates in the system. In a flow-through cooling system, the heated liquid, after passing through it, is released into the environment, and a new one is taken in to be fed into the engine. The use of such systems is limited to marine and stationary engines.

Air cooling systems are open. The cooling air after passing through the cooling system is discharged into the environment.

The classification of cooling systems is shown in fig. 3.1.

According to the method of circulating the liquid of the cooling system, there can be:

forced in which circulation is provided by a special pump located on the engine (or in the power plant), or pressure, under which the liquid is supplied to power plant from the external environment;

thermosiphon, in which the circulation of the liquid occurs due to the difference in gravitational forces resulting from the different density of the liquid heated near the surfaces of engine parts and cooled in the cooler;

combined, in which the most heated parts (cylinder heads, pistons) are forced to cool, and cylinder blocks - according to the thermosyphon principle .

Rice. 3.1. Classification of cooling systems

Liquid cooling systems can be open or closed.

open systems- systems that communicate with the environment using a vapor tube.

Most automotive and tractor engines currently use closed systems cooling, i.e., systems separated from the environment by a steam-air valve installed in the radiator cap.

The pressure and, accordingly, the permissible temperature of the coolant (100–105 °С) in these systems is higher than in open systems (90–95 °С), as a result of which the difference between the temperatures of the liquid and the air sucked through the radiator and the heat transfer of the radiator increase. This allows you to reduce the size of the radiator and the power consumption for driving the fan and water pump. In closed systems, there is almost no evaporation of water through the steam outlet pipe and its boiling when the engine is running in high mountain conditions.

Liquid cooling system

On fig. 3.2 shows a diagram fluid system cooling with forced circulation of coolant.

Cylinder Block Cooling Jacket 2 and block heads 3, the radiator and pipes are filled with coolant through the filler neck. The liquid washes the walls of the cylinders and combustion chambers of a running engine and, heating up, cools them. Centrifugal pump 1 pumps liquid into the cylinder block jacket, from which the heated liquid enters the block head jacket and then is forced out into the radiator through the upper pipe. The liquid cooled in the radiator returns to the pump through the lower pipe.

Rice. 3.2. Liquid cooling system diagram

Fluid circulation depending on the thermal state of the engine is changed using a thermostat 4. When the coolant temperature is below 70–75 °C, the main thermostat valve is closed. In this case, the liquid does not enter the radiator 5 , but circulates along a small circuit through a branch pipe 6, which contributes quick warm-up engine to optimum thermal conditions. When the temperature-sensitive element of the thermostat is heated to 70-75 ° C, the main valve of the thermostat begins to open and let water into the radiator, where it is cooled. The thermostat opens completely at 83–90 °C. From this point on, water circulates through the radiator, i.e., large circuit. The temperature regime of the engine is also regulated with the help of rotary shutters, by changing the air flow created by the fan 7 and passing through the radiator.

In recent years, the most effective and rational way to automatically control the temperature regime of the engine is to change the performance of the fan itself.

Elements of the fluid system

Thermostat designed to provide automatic control of the coolant temperature during engine operation.

To quickly warm up the engine when it is started, a thermostat is installed in the outlet pipe of the cylinder head jacket. It maintains the desired temperature of the coolant by changing the intensity of its circulation through the radiator.

On fig. 3.3 shows a bellows-type thermostat. It consists of a body 2, corrugated cylinder (bellows), valve 1 and a stem connecting the bellows to the valve . The bellows is made of thin brass and is filled with a volatile liquid (eg ether or a mixture of ethyl alcohol and water). Windows located in the thermostat housing 3 depending on the temperature of the coolant, they can either remain open or be closed valves .

When the temperature of the coolant washing the bellows is below 70 ° C, the valve 1 closed and windows 3 open. As a result, the coolant does not enter the radiator, but circulates inside the engine jacket. When the temperature of the coolant rises above 70 ° C, the bellows, under the vapor pressure of the liquid evaporating in it, lengthens and begins to open the valve 1 and gradually cover the windows with valves 3. At a coolant temperature above 80-85 ° C, the valve 1 fully opens, the windows are completely closed, as a result of which all the coolant circulates through the radiator. Currently given type thermostats are rarely used.

Rice. 3.3. Bellows thermostat

Now engines are equipped with thermostats in which the damper 1 opens with the expansion of a solid filler - ceresin (Fig. 3.4). This substance expands when the temperature rises and opens the damper 1 , ensuring the flow of coolant to the radiator.

Rice. 3.4. Solid fill thermostat

Radiator is a heat dissipating device designed to transfer the heat of the coolant to the surrounding air.

The radiators of automobile and tractor engines consist of upper and lower tanks connected to each other by a large number of thin tubes.

To enhance the transfer of heat from the coolant to the air, the fluid flow in the radiator is directed through a series of narrow tubes or channels blown by air. Radiators are made of materials that conduct and give off heat well (brass and aluminum).

Depending on the design of the cooling grille, radiators are divided into tubular, plate and honeycomb.

At present, the most widespread tubular radiators. The cooling grid of such radiators (Fig. 3.5a) consists of vertical tubes of oval or round cross section, passing through a series of thin horizontal plates and soldered to the upper and lower radiator reservoirs. The presence of plates improves heat transfer and increases the rigidity of the radiator. Tubes of oval (flat) section are preferable, since with the same jet cross section their cooling surface is larger than the cooling surface of round tubes; in addition, when water freezes in the radiator, flat tubes do not break, but only change the shape of the cross section.

Rice. 3.5. Radiators

IN plate radiators the cooling grid (Fig. 3.5b) is designed so that the coolant circulates in space , formed by each pair of plates soldered together at the edges. The upper and lower ends of the plates are also soldered into the holes of the upper and lower radiator reservoirs. The air cooling the radiator is sucked by the fan through the passages between the soldered plates. To increase the cooling surface, the plates are usually made wavy. Lamellar radiators have a larger cooling surface than tubular ones, but due to a number of disadvantages (rapid contamination, a large number of soldered seams, the need for more thorough maintenance), they are used relatively rarely.

Cellular radiator refers to radiators with air tubes (Fig. 3.5c). In the honeycomb radiator grill, air passes through horizontal, circular tubes, which are washed from the outside with water or coolant. To make it possible to solder the ends of the tubes, their edges are flared so that in cross section they have the shape of a regular hexagon.

The advantage of honeycomb radiators is a larger cooling surface than in other types of radiators. Due to a number of disadvantages, most of which are the same as those of plate radiators, honeycomb radiators are extremely rare today.

In a traffic jam filler neck radiator installed steam valve 2 and air valve 1 , which serve to maintain the pressure within the specified limits (Fig. 3.6).

Rice. 3.6. Radiator cap

Water pump circulates the coolant in the system. As a rule, small-sized single-stage low-pressure centrifugal pumps with a capacity of up to 13 m 3 /h, which create a pressure of 0.05–0.2 MPa, are installed in cooling systems. Such pumps are structurally simple, reliable and provide high performance (Fig. 3.7).

The casing and the impeller of the pumps are cast from magnesium and aluminum alloys, the impeller, in addition, from plastics. In water pumps of automobile engines, semi-closed impellers are usually used, that is, impellers with one disk.

The impellers of centrifugal water pumps are often mounted on the same shaft as the fan. In this case, the pump is installed in the upper front of the engine, it is driven from the crankshaft using a V-belt drive.

Rice. 3.7. Water pump

Belt drive can also be used when installing a centrifugal pump separately from the fan. In some engines of trucks and tractors, the water pump is driven from the crankshaft by a gear transmission. The shaft of a centrifugal water pump is usually mounted on rolling bearings and is equipped with simple or self-adjusting seals to seal the working surface.

Fan in liquid cooling systems, they are installed to create an artificial air flow passing through the radiator. Fans of automobile and tractor engines are divided into two types: a) with blades stamped from sheet steel attached to the hub; b) with blades that are cast in one piece with the hub.

The number of fan blades varies between four and six. Increasing the number of blades above six is ​​impractical, since the performance of the fan increases very slightly. Fan blades can be made flat and convex.