What is the small and large circle of blood circulation. Small and large engine cooling circle

Let us recall a little more about this cooling system.

IN liquid cooling system special coolants are used - antifreezes of various brands with a thickening temperature of 40 ° C and below. Antifreezes contain anti-corrosion and anti-foaming additives that eliminate the formation of scale. They are highly poisonous and require careful handling. Compared to water, antifreezes have a lower heat capacity and therefore remove heat from the cylinder walls of the engine less intensively.

So, when cooling with antifreeze, the temperature of the cylinder walls is 15 ... 20 ° C higher than when cooling with water. This speeds up engine warm-up and reduces cylinder wear, but may overheat the engine in summer.

The optimum temperature regime of the engine with a liquid cooling system is considered to be one at which the temperature of the coolant in the engine is 80 ... 100 ° C at all engine operating modes.

Used in car engines closed (sealed) liquid cooling system forced circulation coolant.

The internal cavity of a closed cooling system does not have a constant connection with the environment, and communication is carried out through special valves (at a certain pressure or vacuum) located in the plugs of the radiator or expansion tank of the system. The coolant in such a system boils at 110 ... 120 ° C. Forced circulation of coolant in the system is provided by a liquid pump.

Engine cooling system consists of:

cooling jacket for the head and cylinder block;
radiator;
pump;
thermostat;
fan;
expansion tank;
connecting pipelines and drain taps.

In addition, the cooling system includes a heater for the vehicle interior.

How the cooling system works

I propose to first consider the schematic diagram of the cooling system.

1 - heater; 2 - engine; 3 - thermostat; 4 - pump; 5 - radiator; 6 - cork; 7 - fan; 8 - expansion tank;
A - small circle of circulation (thermostat is closed);
A + B - large circle of circulation (thermostat is open)

The circulation of the liquid in the cooling system is carried out in two circles:

1. Small circle - the liquid circulates when starting a cold engine, ensuring its rapid warming up.

2.Large circle - the movement circulates when the engine is warm.

Simply put, the small circle is the circulation of the coolant WITHOUT the radiator, and the large circle is the circulation of the coolant THROUGH the radiator.

The design of the cooling system differs in its design depending on the car model, however, the principle of operation is the same.

The principle of operation of this system can be seen in the following videos:

I propose to disassemble the system device according to the sequence of work. So, the beginning of the operation of the cooling system occurs when the heart of this system - the liquid pump - starts up.

1. Liquid pump (water pump)

The liquid pump provides forced circulation of liquid in the engine cooling system. Vane pumps of the centrifugal type are used on car engines.

Look for our liquid pump or water pump on the front of the engine (the front is the one that is closer to the radiator and where the belt / chain is located).

The liquid pump is connected by a belt to the crankshaft and generator. Therefore, to find our pump, it is enough to find the crankshaft and find the generator. We'll talk about the generator later, but for now I'll just show you what to look for. The generator looks like a cylinder attached to the engine body:

1 - generator; 2 - liquid pump; 3 - crankshaft

So, we figured out the location. Now let's take a look at its structure. Let us recall that the structure of the entire system and its parts is different, but the principle of operation of this system is the same.

1 - pump cover;2 - The persistent sealing ring of the stuffing box.
3 - Oil seal; 4 - Pump shaft bearing.
5 - the hub of the fan pulley;6 - Locking screw.
7 - pump roller;8 - Pump casing;9 - Pump impeller.
10 - Suction branch pipe.

The work of the pump is as follows: the pump is driven from the crankshaft through a belt. The belt turns the pump pulley, rotating the pump pulley hub (5). This, in turn, drives the pump shaft (7), at the end of which there is an impeller (9). The coolant enters the pump casing (8) through the inlet (10), and the impeller moves it into the cooling jacket (through a window in the casing, as seen in the figure, the direction of movement from the pump is shown by an arrow).

Thus, the pump is driven by the crankshaft, the liquid enters it through the inlet pipe and goes into the cooling jacket.

The operation of the liquid pump can be seen in this video (1:48):

Let's now see, where does the liquid come from to the pump? And the liquid enters through a very important part - the thermostat. It is the thermostat that is responsible for the temperature regime.

2. Thermostat (thermostat)

The thermostat automatically adjusts the water temperature to speed up engine warm-up after starting. It is the operation of the thermostat that determines which circle (large or small) the coolant will go.

This unit looks like this in reality:

How the thermostat works very simple: the thermostat has a sensitive element, inside which there is a solid filler. At a certain temperature, it begins to melt and opens the main valve, and the additional valve, on the contrary, closes.

Thermostat device:

1, 6, 11 - branch pipes; 2, 8 - valves; 3, 7 - springs; 4 - balloon; 5 - diaphragm; 9 - stock; 10 - filler

The operation of the thermostat is simple, you can see it here:

The thermostat has two inlets 1 and 11, outlet 6, two valves (main 8, additional 2) and a sensitive element. The thermostat is installed in front of the inlet to the coolant pump and is connected to it through branch pipe 6.

Compound:

Throughbranch pipe 1 connects fromengine cooling jacket,

Through branch pipe 11 - with bottom diverting radiator reservoir.

The sensing element of the thermostat consists of a cylinder 4, a rubber diaphragm 5 and a stem 9. Inside the cylinder between its wall and the rubber diaphragm there is a solid filler 10 (fine crystalline wax), which has a high coefficient of volume expansion.

The main valve 8 of the thermostat with a spring 7 begins to open when the coolant temperature is more than 80 ° C. At temperatures below 80 ° C, the main valve closes the fluid outlet from the radiator, and it enters the pump from the engine, passing through the open additional valve 2 of the thermostat with a spring 3.

When the temperature of the coolant rises above 80 ° C, a solid filler melts in the sensitive element, and its volume increases. As a result, the rod 9 leaves the cylinder 4, and the cylinder moves upward. At the same time, additional valve 2 begins to close and, at a temperature of more than 94 ° C, blocks the passage of the coolant from the engine to the pump. In this case, the main valve 8 opens completely, and the coolant circulates through the radiator.

The operation of the valve is clearly and clearly shown in the figure below:

A - small circle, the main valve is closed, the bypass valve is closed. B - a large circle, the main valve is open, the bypass valve is closed.

1 - Inlet pipe (from the radiator); 2 - Main valve;
3 - Thermostat housing; 4 - Bypass valve.
5 - Branch pipe of the bypass hose.
6 - Branch pipe for supplying coolant to the pump.
7 - Thermostat cover; 8 - Piston.

So, we have dealt with the small circle. Disassembled the device of the pump and thermostat, connected to each other. Now let's move on to the large circle and the key element of the large circle - the radiator.

3. Radiator (radiator / cooler)

Radiator provides heat removal from the coolant to the environment. Tubular-plate radiators are used on passenger cars.

So, there are 2 types of radiators: collapsible and non-collapsible.

Below is their description:

I want to say it again about the expansion tank (expansion Tank)

A fan is installed next to the radiator or on it. Let's now move on to the design of this very fan.

4. Fan (fan)

The fan increases the speed and amount of air passing through the radiator. Four- and six-blade fans are installed on car engines.

If a mechanical fan is used,

The fan includes six or four blades (3) riveted to a crosspiece (2). The latter is screwed to the pulley of the liquid pump (1), which is driven by the crankshaft using a belt drive (5).

As we said earlier, the generator (4) also engages.

If an electric fan is used,

then the fan consists of an electric motor 6 and a fan 5. The fan is four-bladed, mounted on the shaft of the electric motor. The blades on the fan hub are located unevenly and at an angle to the plane of rotation. This increases the fan flow and reduces the fan noise. For more efficient operation, the electric fan is located in the casing 7, which is attached to the radiator. The electric fan is attached to the casing with three rubber bushings. The electric fan is switched on and off automatically by sensor 3 depending on the coolant temperature.

So let's summarize. Let's not be unfounded and summarize by some picture. You should not focus on a specific device, but you need to understand the principle of operation, because it is the same in all systems, no matter how different their device is.

When the engine is started, the crankshaft begins to rotate. Through a belt drive (let me remind you that the generator is also located on it), rotation is transmitted to the pulley of the liquid pump (13). It drives the shaft with the impeller in rotation inside the housing of the liquid pump (16). The coolant flows into the engine cooling jacket (7). Then, through the outlet (4), the coolant returns to the liquid pump through the thermostat (18). At this time, the bypass valve in the thermostat is open, but the main one is closed. Therefore, the liquid circulates through the engine jacket without the involvement of the radiator (9). This allows the engine to warm up quickly. After the coolant heats up, the thermostat main valve opens and the bypass valve closes. Now liquid cannot flow through the thermostat bypass pipe (3) and is forced to flow through the inlet pipe (5) into the radiator (9). There the liquid is cooled and flows back to the liquid pump (16) through the thermostat (18).

It is worth noting that some of the coolant enters the heater from the engine cooling jacket through port 2 and returns from the heater through port 1. But we will talk about this in the next chapter.

Hopefully the system will now be clear to you. After reading this article, I hope that it will be possible to navigate in another cooling system, having understood the principle of this one.

I also suggest that you familiarize yourself with the following article:

Since we have touched on the heating system, my next article will be about this system.

Strictly speaking, the term "liquid cooling" is not entirely correct, since the liquid in the cooling system is just an intermediate coolant that penetrates into the thickness of the cylinder block walls. The role of the diverting agent in the system is played by the air blowing over the radiator; therefore, it is more correct to call the cooling of a modern car hybrid.

Liquid cooling system device

The liquid engine cooling system consists of several elements. The most difficult one is called “cooling jacket”. This is a branched network of channels in the thickness of the cylinder block and. In addition to the jacket, the system includes a radiator for the cooling system, an expansion tank, a water pump, a thermostat, metal and rubber connecting pipes, sensors and control devices.

Propylene Glycol is a coolant (antifreeze) base and veterinarian-approved dietary supplement for dogs

The system is based on the principle of forced circulation, which is provided by a water pump. Due to the constant outflow of the heated fluid, the engine is cooled evenly. This explains the application of the system in the vast majority of modern cars.

Having passed through the channels in the walls of the block, the liquid heats up and enters the radiator, where it is cooled by the air flow. When the car is moving, natural airflow is sufficient for cooling, and when the car is at a standstill, airflow occurs due to an electric fan that is activated by a signal from a temperature sensor.

Details on the key elements of water cooling

Cooling radiator

The radiator is a panel made of small diameter metal tubes covered with aluminum or copper "plumage" to increase the heat transfer area. In essence, the plumage is a repeatedly folded ribbon of metal. The total total area of \u200b\u200bthe tape is large enough, which means that it can release a lot of heat into the atmosphere per unit time.

The most vulnerable element of the engine design is the turbocharger (turbine) operating at extremely high rpm. When overheated, destruction of the impeller and shaft bearings is almost inevitable.

Thus, the heated liquid inside the radiator circulates through all the numerous thin tubes at once and is cooled quite intensively. A safety valve is provided in the radiator filler cap that removes vapors and excess liquid that expands when heated.

Depending on the operating mode of the internal combustion engine, the cycle of movement of the coolant in the system may vary. The volume of fluid circulating in each circle directly depends on the degree to which the main and additional thermostat valves are open. This circuit provides automatic maintenance of the optimal temperature regime of the engine.

Advantages and Disadvantages of a Liquid Cooling System

The main advantage of liquid cooling is that the engine is cooled more evenly than if the unit is blown with air. This is due to the higher heat capacity of the coolant compared to air.

The liquid cooling system can significantly reduce the noise from a running engine due to the thicker block walls.

The inertia of the system does not allow the engine to cool down quickly after shutdown. Heated vehicle fluid and for preheating the combustible mixture.

Along with this, the liquid cooling system has several disadvantages.

The main disadvantage is the complexity of the system and the fact that it operates under pressure after heating the fluid. A pressurized fluid places high demands on the tightness of all joints. The situation is complicated by the fact that the operation of the system implies a constant repetition of the "heating - cooling" cycle. It is harmful to joints and rubber pipes. When heated, the rubber expands and then contracts as it cools, causing leaks.

In addition, the complexity and large number of elements in itself serve as a potential cause of "man-made disasters" accompanied by "boiling" of the engine in the event of failure of one of the key components, for example, the thermostat.

A cooling system is required to maintain the engine's optimum temperature.

The average engine temperature is 800 - 900 ° C, with active operation it reaches 2000 ° C. But periodically it is necessary to remove heat from the engine. If this is not done, the engine may overheat.

But the cooling system not only cools the engine, but also participates in heating it when it is cold.

Most cars have a closed-type liquid cooling system with forced circulation of liquid and an expansion tank (Figure 7.1). Figure: 7.1. Diagram of the engine cooling system a) small circle of circulation b) large circle of circulation 1 - radiator; 2 - branch pipe for circulation of coolant; 3 - expansion tank; 4 - thermostat; 5 - water pump; 6 - cooling jacket of the cylinder block; 7 - cooling jacket of the block head; 8 - heater radiator with electric fan; 9 - heater radiator tap; 10 - plug for draining the coolant from the block; 11 - plug for draining the coolant from the radiator; 12 - fan

cooling jacket of the block and cylinder head,
centrifugal pump,
thermostat,
radiator with expansion tank,
fan,
connecting pipes and hoses.

Under the guidance of the thermostat, 2 circulation circles perform their functions (Figure 7.1). The small circle performs the function of heating the engine. After heating, the liquid begins to circulate in a large circle and is cooled in the radiator. Normal coolant temperature is 80-90 ° C.

The engine cooling jacket is the channels in the block and the cylinder head. Coolant circulates through these channels.

A centrifugal pump assists in moving fluid around the jacket and throughout the engine system. forces fluid to move through the engine cooling jacket and the entire system.

The thermostat is a mechanism that maintains optimal thermal conditions of the engine. When a cold engine is started, the thermostat is closed and the fluid flows in a small circle. When the temperature of the liquid exceeds 80-85 ° C, the thermostat opens, the liquid begins to circulate in a large circle, getting into the radiator and cooling.

The radiator consists of many tubes that form a large cooling surface. This is where the liquid is cooled.

Expansion tank. With its help, the volume of the liquid is compensated when it is heated and cooled. The fan increases the air flow to the radiator, with the help of which the

liquid is waiting.

The pipes and hoses are the connection mechanism of the cooling jacket with the thermostat, pump, radiator and expansion tank.

The main malfunctions of the cooling system.

Coolant leaks. Cause: Damage to the radiator, hoses, gaskets and oil seals. Remedies: tighten the hose and pipe clamps, replace damaged parts with new ones.

Engine overheating. Reason: insufficient coolant level, weak fan belt tension, clogged radiator pipes, thermostat malfunction. Remedies: restore the liquid level in the cooling system, adjust the fan belt tension, flush the radiator, replace the thermostat.

Often novice drivers wonder what a small and large engine cooling circle is. As a rule, this question is asked when there are any problems that have begun with the cooling system. In fact, everything here is both complicated and simple. To answer this question, it is necessary to understand the principle of operation of this motor element, to understand how engine cooling works, and why it is necessary. This knowledge will allow you to identify the causes of the malfunction much faster, as well as avoid mistakes during the repair process. Thus, the car enthusiast needs to know the theory.

Why do you need a system?

The small and large circle of engine cooling are part of the overall system. Let's see why it is needed. To begin with, it is worth remembering the features of the power unit. During ignition, gases can reach temperatures up to 200 ° C. And only part of the generated heat is converted into work. The rest comes out with the exhaust and also heats up the engine parts. To avoid the problem of overheating of spare parts and their deformation, a whole range of design features is used. Heat is removed through air, oil, which lubricates the parts. But, most of the heat is removed by the water cooling system.

Based on the above, we can say that the cooling system protects the motor from overheating. Please note that technology uses several types of cooling systems:

Thermosiphon - here the circulation is carried out due to the difference in density between the liquid with different temperatures. Having cooled down, the antifreeze drops down to the engine, pushing a portion of hot liquid into the radiator;
Forced- circulation is due to the pump, which is usually driven by the crankshaft;
Combined system... The main part of the motor is cooled forcibly, and only some parts are heat removed by the thermosyphon method.

Cooling system

Now let's take a closer look at the cooling system of a modern passenger car. It should be noted that on all machines it is almost identical. The differences concern mainly little things, as well as in the placement of elements. Now, the forced version is mainly used; for mass cars, it has shown itself to be more effective. It consists of the following elements:

Fan... This element serves as an auxiliary function. Its task is to create an additional flow of air, which, blowing over the radiator, cools it. Nowadays, the fan is usually equipped with an electric motor. But, on some models, a forced drive from the crankshaft is used;
The engine itself contains cooling jacket. It is a network of interconnected channels, which do the bulk of the work of removing heat from the motor. The shirt is often called the small circle;
Water pump (water pump). The purpose of this element is to pump antifreeze from the engine to the radiator. Actually, this is one of the main components of a forced cooling system; if the pump fails, further work becomes impossible;
... Provides the direction of flows in a small circle or throughout the system. The adjustment is made depending on the temperature of the coolant;
Heater (stove). Since the heat of antifreeze is used to heat the passenger compartment, the stove is part of the cooling system;
Sensors... Usually 2 sensors are installed. One is in the engine, and is connected to the dashboard, the other in the radiator,. If the fan drive is forced, then a plug is installed in the radiator;
Expansion tank... It includes 2 functions at once. The first is the presence of a supply of liquid that can evaporate during operation. In this case, the missing volume is fed into the system, which is connected to the tank according to the principle of communicating vessels. Another function is the ability to vent steam. Part of the coolant evaporates, so that an emergency depressurization does not occur, it is discharged into the expansion tank.

Circulation circles

Large and small are usually distinguished. Small is considered the main one. The liquid circulates through it immediately after starting the engine. The function of this circle is to maintain the optimum temperature for the operation of the power unit. The small circle includes a pump, a motor jacket and a stove. This allows the engine to warm up quickly. Also, at low air temperatures, antifreeze, moving only along a small radius, will not cool the power unit to a minimum temperature, on the contrary, retaining heat.

The outer radius (circle) of the cooling system includes a radiator and an expansion tank. Antifreeze circulation through it begins only after the engine reaches operating temperature. The opening of the supply occurs after the thermostat is triggered.

Conclusion... The cooling system is an essential element for engine performance. For a complete diagnosis of malfunctions, you need to know how the small and large engine cooling circle differ. Having understood this issue, it will be much easier for you to identify the cause of the malfunction of this system.

I propose to first consider the schematic diagram of the cooling system.

The circulation of the liquid in the cooling system is carried out in two circles:

1. Small circle - the liquid circulates when starting a cold engine, ensuring its rapid warming up.

2.Large circle - the movement circulates when the engine is warm.

Simply put, the small circle is the circulation of the coolant WITHOUT the radiator, and the large circle is the circulation of the coolant THROUGH the radiator.

The design of the cooling system differs in its design depending on the car model, however, the principle of operation is the same.

So, the beginning of the operation of the cooling system occurs when the heart of this system - the liquid pump - starts up.

Liquid pump (water pump)

The liquid pump provides forced circulation of liquid in the engine cooling system. Vane pumps of the centrifugal type are used on car engines.

Look for our liquid pump or water pump on the front of the engine (the front is the one that is closer to the radiator and where the belt / chain is located).

1 - generator; 2 - liquid pump; 3 - crankshaft

1 - pump cover; 2 - The persistent sealing ring of the stuffing box.
3 - Oil seal; 4 - Pump shaft bearing.
5 - the hub of the fan pulley; 6 - Locking screw.
7 - pump roller; 8 - Pump casing; 9 - Pump impeller.
10 - Suction branch pipe.

Thus, the pump is driven by the crankshaft, the liquid enters it through the inlet pipe and goes into the cooling jacket.

Let's now see, where does the liquid come from to the pump? And the liquid enters through a very important part - the thermostat. It is the thermostat that is responsible for the temperature regime.

Thermostat (thermostat)

This unit looks like this in reality:

Thermostat device:

1, 6, 11 - branch pipes; 2, 8 - valves; 3, 7 - springs; 4 - balloon; 5 - diaphragm; 9 - stock; 10 - filler

Compound:

Throughbranch pipe 1 connects fromengine cooling jacket,

Through branch pipe 11 - with bottom diverting radiator reservoir.

The operation of the valve is clearly and clearly shown in the figure below:

A - small circle, the main valve is closed, the bypass valve is closed. B - a large circle, the main valve is open, the bypass valve is closed.

So, we have dealt with the small circle. Disassembled the device of the pump and thermostat, interconnected. Now let's move on to the large circle and the key element of the large circle - the radiator.

Radiator (radiator / cooler)

Radiator provides heat removal from the coolant to the environment. Tubular-plate radiators are used on passenger cars.

So, there are 2 types of radiators: collapsible and non-collapsible.

Below is their description:

I want to say it again about the expansion tank (expansion Tank)

A fan is installed next to the radiator or on it. Let's now move on to the design of this very fan.

Fan (fan)

The fan increases the speed and amount of air passing through the radiator. Four- and six-blade fans are installed on car engines.

If a mechanical fan is used,

The fan includes six or four blades (3) riveted to a crosspiece (2). The latter is screwed to the pulley of the liquid pump (1), which is driven by the crankshaft using a belt drive (5).

As we said earlier, the generator (4) also engages.

If an electric fan is used,

So let's summarize.Let's not be unfounded and summarize by some picture. You should not focus on a specific device, but you need to understand the principle of operation, because it is the same in all systems, no matter how different their device is.

It is worth noting that some of the coolant flows from the engine cooling jacket to the heater through port 2 and returns from the heater through port 1.