Car engine cooling system: device and principle of operation. Cooling system Engine oil cooling system

The main malfunctions of the cooling system. Symptoms of a malfunction: hypothermia or overheating of the engine. For a healthy state, the optimum temperature of the coolant, good thermal conductivity of the walls of water jackets and radiator tubes are necessary.

Care of the cooling system 1. Check the system for leaks daily. Repair if necessary. Check the presence of fluid in the vehicle's cooling system daily. Add fluid if necessary. Its level should be lower

Lubrication system. Purpose and device The lubrication system of the engine is necessary for the continuous supply of oil to the rubbing surfaces of the parts and the removal of heat from them. The surfaces of the mating parts of the engines are characterized by high accuracy and cleanliness of processing. However

Purpose and general arrangement of the car body Most passenger cars have a so-called load-bearing body on which the engine, transmission units, chassis suspension, and additional equipment are installed. For trucks, buses,

Chapter 1. Arrangement, armament and supply of boats 1.1. Purpose Boats are small open deckless watercraft designed to meet the needs of the ship. With their help, a wide range of tasks is solved: - detonation of floating mines; - landing; - delivery

22. System with unlimited solubility in liquid and solid states; eutectic, peritectic and monotectic systems. Systems with component polymorphism and eutectoid transformation Complete mutual solubility in the solid state is possible

(ICE) and their components are exposed to intense heat during the operation of various vehicles. At the same time, both overheating and hypothermia of the motor can provoke its failure. In this regard, one of the most important tasks for the developers of power units is to ensure the optimal thermal regime of their operation. A well-organized engine cooling system contributes to obtaining the best operational parameters of the internal combustion engine, which include:

1. Maximum power.
2. Minimum fuel consumption.
3. Extended service life.

The influence of temperature parameters on the operation of the motor

In one working cycle, the temperature in the internal combustion engine cylinders changes from 80 ... 120 degrees Celsius during the intake of a combustible mixture to 2000 ... 2200 degrees Celsius during its combustion. In this case, the power unit heats up quite strongly.

If the motor is not sufficiently cooled during operation, then its parts become very hot and change in size. Significantly decreases (due to burnout) and the volume of engine oil poured into the crankcase. As a result, friction between the interacting parts increases, which leads to their rapid wear or even jamming.

However, supercooling of the internal combustion engine adversely affects its operation. On the walls of the cylinders of a cold engine, fuel vapor condenses, which, washing off the lubricant layer, dilute the engine oil in the crankcase.

To eliminate the negative consequences associated with violation of the thermal regime, cooling systems are designed in such a way as to exclude overheating and hypothermia of the motor during operation.

As a result, the chemical properties of the latter deteriorate, which contributes to:

• increased consumption of engine oil;
• intensive wear of rubbing surfaces;
• a drop in the power of the power unit;
• increase in fuel consumption.

Classification

When the motor is running, it is necessary to ensure the removal of 25 to 35% of the generated heat. For its effective absorption (removal), water, air or a special liquid (antifreeze, antifreeze) are most often used. The coolant material determines the way the power unit is cooled.

There are systems:

1. Forced air cooling.
2. Liquid cooling with a closed cycle.

Liquid cooling system

Currently, for efficient cooling of automobile engines, a closed liquid cooling system with a closed cycle is used.

Design

Without fail, the system contains an expansion tank, which serves to compensate for changes in the volume of liquid when its temperature changes. In addition, a coolant is poured through it.

The system also includes:

• water jacket of the power unit (the space between the double walls of the cylinder block and its head in places where excessive heat is removed);
• temperature sensor;
• a bimetallic or electronic thermostat that provides the optimum temperature in the system;
• a centrifugal-type pump that provides forced circulation of the coolant in the system;
• a fan that increases the flow of oncoming air to the main radiator of the system;
• a radiator that transfers heat to the environment;
• heater radiator designed to transfer heat directly to the car interior;
• control device built into the dashboard of the car.

Operating principle

The coolant is poured into the system through the expansion tank. Constantly circulating inside the system, it removes heat from the components of the motor that heat up during operation, heats up, enters the radiator, is cooled in the radiator by the oncoming air flow and returns back.

If necessary, the fan turns on, increasing the cooling efficiency. For closed cooling systems, the coolant temperature should not exceed 126 degrees Celsius. Thus, the optimal thermal mode of operation of the power unit is ensured.

Additional functions

In addition to its main task - the removal of heat from heating elements, the liquid engine cooling system also provides:

• Warming up the power unit in the cold season

Modern liquid cooling systems have two circuits through which coolant can circulate. This is done so that at the time of starting a cold engine, when its parts and the liquid itself are at a low temperature, the coolant circulates in a small circle (past the radiator).

This is provided by a thermostat, which, at the moment when the temperature rises to a certain level (70-80 degrees Celsius), opens, allowing the coolant to circulate in a large circle (through the radiator). Thus, an accelerated process of warming up the engine is carried out.

• Heating the air in the car

In the cold season, with the help of a hot coolant, the air in the car is heated. For this, an additional radiator is installed in the cabin and equipped with its own fan. With their help, the heat taken from the hot liquid is distributed throughout the cabin.

• Reducing the temperature of the air injected into the cylinders

Especially for engines equipped with turbochargers, two-circuit systems are provided, in which one circuit provides liquid cooling, and the second - air cooling.

In addition, the coolant cooling circuit is also a two-circuit system, one circuit of which cools the cylinder head, and the other cools the block itself.

This is due to the fact that in a turbocharged engine the temperature of the cylinder head must be lower than the temperature of the block itself by 15 ... 20 degrees Celsius. A feature of such a cooling system is that each circuit is controlled by its own thermostat.

Advantages and disadvantages

A liquid engine cooling system is present in almost all modern cars. Fundamentally different from air-cooled systems, it guarantees:

• uniform and rapid heating of the power unit;
• efficient heat dissipation in any engine operating conditions;
• reduction of power costs;
• stable thermal mode of operation of the motor;
• the possibility of using the generated heat to heat the air in the cabin, etc.

Among the few disadvantages of a liquid cooling system are:

• the need for regular maintenance and the complexity of repairs;
• increased sensitivity to temperature changes.

Faults and solutions

All liquid cooling systems are characterized by characteristic malfunctions. Most often found:

1. jamming of the thermostat in the closed position (liquid circulation is carried out in a small circle);
2. pump failure;
3. damage to the exhaust valve built into the plug of the expansion tank;
4. coolant leakage due to depressurization of the system (damage to seals, corrosion, etc.).
5. In addition, quite often the thermostat jams in the “Open” position (the coolant circulates in a large circle), which increases the warm-up time of a cold engine and contributes to the instability of the thermal regime during its further operation.

All these malfunctions are characterized by a significant increase in the operating temperature of the power unit, which can lead to boiling of the coolant and overheating of the motor.

All defects are eliminated by replacing faulty and / or damaged parts or components.

Air cooling system

Air-cooled motors were equipped with vehicles in the 50-70s of the last century. Typical representatives of such cars are Zaporozhets or FIAT 500. Now air-cooled engines are practically never found in the automotive industry.

Design and principle of operation

Structurally, the forced air cooling system is mounted in the engine compartment of the vehicle and consists of:

• suction or blower fan;
• guide ribs of the engine cooling jacket;
• controls (throttle valves that control the air supply or a clutch that regulates the fan speed in automatic mode);
• temperature sensor installed in the power unit;
• control device displayed on the dashboard in the car.

The motor is cooled by oncoming cold air. To enhance its flow, a blower type fan is most often used. It enhances the flow of cold dense air and ensures its supply in large quantities at low energy costs.

The suction fan requires a lot of power, but provides a more uniform heat removal from the parts of the power unit.

Advantages and disadvantages

Forced air-cooled motors are distinguished by:

• simplicity of design;
• low requirements for changes in ambient temperature;
• light weight;
• simple maintenance.

The disadvantages of the air cooling system include:

• a large loss of motor power, which is spent on ensuring the operation of the fan;
• high noise level during fan operation;
• insufficient cooling of individual engine elements due to uneven airflow;
• the impossibility of using excess heat to heat the cabin.

(hereinafter - ICE) is a strict sequence of microexplosions of the combustible mixture in the cylinders. Accordingly, the engine temperature also rises, which becomes critical. Such processes inevitably lead to the failure of the power unit of any vehicle. That is why a cooling system is necessarily used in all modern internal combustion engines.

Functions and types of system

The main purpose of the cooling system for both gasoline and diesel internal combustion engines is to force the removal of heat from engine parts that heat up during its operation, and to maintain its operating temperature.
In addition to this function, the car's cooling system performs a number of other related tasks:

1. acceleration engine warm-up up to operating temperature;
2. air heating for interior heating;
3. cooling engine lubrication systems ;
4. exhaust gas cooling (when using recirculation);
5. air cooling (with turbocharging);
6. lubricant cooling in the gearbox (with automatic transmission).

Depending on the principle of operation and method of operation, it is customary to distinguish between the following cooling systems:

• liquid (based on heat removal by a liquid flow);
• air (based on airflow cooling);
• combined (combining the principle of operation of liquid and air systems).

System Structure

The vast majority of internal combustion engines have a liquid cooling system (closed type), using the principle of forced circulation. It is she who, on the one hand, is able to provide the most efficient cooling, and on the other hand, is a more ergonomic and comfortable way to remove excess heat from the engine.


The device and schematic diagram of the engine cooling system (both diesel and gasoline) includes the operation of the following components:

1. radiator with fan (electric, mechanical or hydraulic);
2. heater radiator ("stove") with an electric fan;
3. cooling jackets for the cylinder block and block head;
4. circulation (water) pump ("pump");
5. expansion tank;
6. radiator tap "stove";
7. connecting pipes and hoses.

Water, antifreeze, antifreeze can be used as a coolant. The cooling system of the vast majority of cars uses antifreeze, as a better option, due to the good ratio of cost and functional characteristics.

How the system works

The principle of operation of the engine cooling system (both gasoline and diesel) is very simple and is based on targeted circulation of the coolant. The coolant, taking heat from engine parts (in cooling jackets), under the influence of pressure created by the water pump, begins to circulate through the system, exercising heat exchange.

Initially, the movement of the liquid is carried out with the thermostat closed in a small circle, that is, without the operation of the radiator. This is done in order to speed up the process of warming up the engine and bringing it to operating temperature. After the liquid returns to the cooling jackets, the circulation process continues.

In the event that the temperature reaches high levels (within 100 degrees), the thermostat opens, and the coolant begins to move in a large circle, entering the radiator. This immediately cools the engine, because a liquid that has not previously been used (which was in the radiator) enters the cooling system. The radiator itself is cooled by the flow of atmospheric air.


With further heating of the engine (for example, in summer), when the liquid does not have time to cool down to the required temperature level, a special device automatically turns on an electric fan (“sloth”), an additional cooling radiator and partially the engine. The fan runs until the required level of liquid temperature is reached, and a special device turns it off. The mechanical version of the fan, connected to the crankshaft by a belt drive, operates in a constantly operating mode.

If necessary (for example, in the cold season), the coolant enters the “stove” through the open heater valve, where, with the help of a radiator, on the one hand, it additionally cools down, giving off excess heat, and on the other hand, it heats the air in the car.

Main system malfunctions

If we turn to paragraph 2.3.1 of the SDA and the "List of malfunctions ...", with which the movement of vehicles is limited, then they can find a complete absence of references to problems associated with the engine cooling system. This means that system breakdowns are not positioned as malfunctions with which movement is prohibited. And, therefore, the cooling system and its repair is a personal matter for each driver, the degree of his comfort on the road.

What are the main "non-serious" problems that an internal combustion engine cooling system can experience?

First, the most common leak or coolant leak. Moreover, its reasons may be a change in street temperature (more often - the onset of the frost season). Among the popular reasons are the coking of pipes and hoses, which, under the constant influence of high temperature, lose their elasticity. Coolant leakage is also caused by physical damage to the main radiator and the “stove” radiator, obtained either chemically (for example, by the reagents that make up the antifreeze) or through mechanical action (for example, by impact).


Secondly, an equally popular malfunction is the failure (or jamming) of the thermostat. The thermostat valve (a device that is in constant contact with the liquid) gradually corrodes. Ultimately, it jams, which eliminates the operation in the "open-closed" system. The results of this state of the thermostat are twofold:

1. when jammed in the “open” position, the coolant moves only in a large circle (with constant use of the radiator), which leads to weak and prolonged engine warm-up and, accordingly, poor heating of the car interior;
2. when jammed in the “closed” position, the coolant, on the contrary, moves only in a small circle (without using a radiator), which causes engine overheating and can lead to irreversible changes in the structure of the metal, a decrease in the resource of the power unit and even to its breakdown.

Thirdly, a breakdown of the circulation pump (or “pump”) seems to be a serious nuisance. Most often, this malfunction is associated with the failure of the "pump" bearing - its main part. The reasons are commonplace - wear or low-quality spare parts. It is difficult to predict a breakdown, but it is more than possible to catch the beginning of the non-standard operation of the “pump” - by the characteristic whistling sound of the bearing. It means that the circulation pump requires immediate replacement.


Fourth, under certain conditions, clogging of the engine cooling system is possible. The reasons for this condition is, as a rule, the deposition of salts in the channels of the cooling system (radiator, block, block head). This disrupts the circulation of the coolant and the removal of excess heat from the engine and its parts deteriorates. Ultimately, this leads to overheating of the engine with all the ensuing consequences.

System operation and maintenance basics

Monitoring the state of the cooling system is a necessary condition for comfortable movement on the vehicle. Despite the fact that malfunctions of this system do not prohibit the operation of the car, the driver must understand the danger of the prospect of its failure. Overheating of the engine, which is more than possible in the warm season, and insufficient heating of the car interior in the winter, leads to the need for repairs, sometimes very expensive.
Compliance with the elementary rules for operating the engine cooling system will allow you to avoid, prevent or minimize the impact of malfunctions on the normal operation of the car.

Continuous monitoring of the coolant level

The expansion tank is used for visual control of the liquid level in the cooling system. The fact is that the volume of the cooling system is constant, but the volume of liquid varies depending on the operating conditions. When the coolant level (indicated on the expansion tank) drops or rises, it is necessary to correct its amount in the system.

System Leak Diagnosis

A constant decrease in the level of coolant is most often associated with its leakage. Numerous connections of pipes with elements of the cooling system, corrosion of the main radiator or radiator of the “stove” lead to a constant decrease in the liquid level in the expansion tank. Diagnosis of the problem is associated with the detection of dark spots on the nodes and assemblies located in the engine compartment, wet marks on the roadway, as well as the characteristic sweetish-sugary smell of antifreeze. More serious is the detection of traces of antifreeze on the dipstick, which leads to expensive engine repairs.

Symptoms of engine overheating or insufficient heating

Overheating can be due to several reasons:

1. jamming of the thermostat in the "closed" position;
2. clogging of the channels of the system;
3. insufficient fluid level in the system.

But insufficient heating of the car engine indicates only a jammed thermostat, which only works in the “open” position.

Summarize. The engine cooling system performs the functions of removing excess heat from the power unit formed during operation and maintaining the normal (working) mode of its operation.

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 heat removed consists of a part of the heat released in the engine cylinders, which is not converted into work and is not carried away with the exhaust gases, and from the heat of the friction work that occurs during 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 the 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 of a liquid cooling system with forced circulation of the 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 to the rapid heating of the engine to the optimum thermal regime. 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, this type of thermostats is used very rarely.

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.

A steam valve is installed in the radiator filler cap 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.