What is the structure and working process of an internal combustion engine?

Four strokes: suction, compression, work, exhaust.

Upstairs, you can take a look at the internal combustion engine.

The working principle of a diesel engine (internal combustion engine).

The general implementation would be:

1. Mixed combustion of fuel and air;

2. Generate heat energy;

3. The gas expands when heated;

4. Convert mechanical energy into external work through mechanical devices.

The principle of energy conversion.

As a type of heat engine, the energy of the internal combustion engine** is the heat generated by fuel combustion, that is, the chemical energy contained in the substance is first converted into heat energy, and then becomes mechanical energy. Liquids can theoretically be used as working mediums because they increase pressure through phase changes (vaporization), and gases can increase pressure when heated and expanded.

The working medium of the internal combustion engine is mostly the gas produced by the mixed combustion of fuel and air, and after the heated expansion, the pressure increases, and the high-temperature and high-speed gas is then worked externally through a certain mechanical device. In the case of internal combustion engines, the working medium must be replaced (open cycle), i.e. the burned gases are discharged and fresh gases are introduced.

There are four processes of air intake, compression, work and exhaust. Introduce a combustible mixture (or fresh air) into the cylinder; The combustible mixture (or fresh air) entering the cylinder is then compressed, and the combustible mixture is ignited when the compression is near the end point (or the diesel fuel is injected into the cylinder at high pressure to form a combustible mixture and ignited); The combustible mixture is ignited and burned, and the expansion pushes the piston down to achieve external work; Finally, the exhaust gases after combustion are discharged. That is, the four processes of air intake, compression, work and exhaust.

Introduction to Internal Combustion Engines:The internal combustion engine is a kind of power machinery, which is a heat engine that burns fuel inside the machine and converts the heat energy released from it directly into power. In a broad sense, the internal combustion engine includes not only the reciprocating piston internal combustion engine, the rotary piston engine and the free piston engine, but also the rotary impeller jet engine, but the internal combustion engine is usually referred to as the piston internal combustion engine.

In the past, the resurrection piston type of piston internal combustion engine was the most common. A piston internal combustion engine mixes fuel and air and burns it in its cylinder, and the heat energy released causes the cylinder to produce high-temperature and high-pressure gas. The gas expansion pushes the piston to do work, and then outputs the mechanical work through the crank connecting rod mechanism or other mechanisms to drive the driven machinery to work.

The common ones are diesel engines and gasoline engines, which change the internal energy by doing work by converting the internal energy into mechanical energy.

For example, the old-fashioned tractor with Chinese characteristics has only one cylinder, and there is a big flywheel next to the head, which only needs to be cranked by hand when starting, because the energy generated by the work stroke is far greater than the energy required by the other three strokes, so the flywheel is driven to rotate when doing work, and then the flywheel only needs to provide a little kinetic energy to the other three strokes, so that it can run continuously, but the speed is not particularly stable. There are also old liberation cars, which all need to be hand-cranked to input an initial kinetic energy into the flywheel. Of course, batteries are now used as starting power.

The internal combustion engine is divided into four processes: air intake, compression, expansion and exhaust, to evaluate the working capacity of an internal combustion engine, it is necessary to look at the working capacity of each of its work projects, and then give some overall performance indicators.

Let's start with the air intake process. Looking at the air intake process of an internal combustion engine, there are three main indicators: air intake volume, air intake temperature, and air pressure at the end of intake.

The final pressure of the inlet air is generally less than the outside air pressure because of the inlet resistance and the fast gas flow rate. The final temperature of the intake air is higher than the external temperature because the air intake is in contact with the high-temperature parts, and the waste cannot be completely discharged when exhausting. Generally speaking, the more air intake, the more fully the working volume is utilized, which is good for improving power.

So, how to judge the amount of air intake, quantitative judgment, the introduction of the concept of charge coefficient, the so-called charge coefficient is the ratio of the actual air intake to the theoretical air intake. The charge factor reflects the actual air intake.

So where does the difference in the charge coefficient of different engines come from? There are two main factors: the construction factor and the use factor.

The structural factors are the size, number, and lift of the engine's valves, the size of the intake ducts, and the smoothness of the cross-section. The use factors include the speed of the engine, the load of the engine, the different speed charge coefficients, and the speed of a convex curve relationship. For gasoline engines, the opening of the intake valve under different loads should be changed, and the change of the intake valve will lead to the maximum air intake volume and the reduction of intake resistance.

For the diesel engine, the different loads change the amount of fuel injection, and the intake resistance of the diesel engine is not affected by the load, so the load has little impact on the charge coefficient of the diesel engine.

How to improve the charge factor of the air intake process? In two ways, it reduces the intake resistance and prolongs the intake time. Reducing intake resistance is a structural consideration.

Extending the air intake time is based on the use factor. It is controlled by changing the time when the valve opens and closes. Introducing the concept of valve phase, the opening and closing time of the intake and exhaust valves is expressed by the angle of the engine.

Intake valve advance angle: The early opening of the intake valve can increase the opening of the valve when the intake process comes, increase the area and reduce the resistance. Intake valve extension angle:

The delayed closing of the intake valve allows the inertia of the high-velocity gas to enter some more gas. Exhaust valve advance angle: Take advantage of the pressure difference between the inside and outside to remove some exhaust gases first.

Exhaust valve delay angle: Takes advantage of the inertia of the high-speed flow of exhaust gases to take away more gas. Changing the gas distribution phase can improve the charge factor

An internal combustion engine is a mechanical device that converts the chemical energy of fuel into mechanical energy and runs continuously and continuously. The working process of the internal combustion engine is essentially a continuous and complex thermodynamic cycle process, which is roughly divided into three processes: combustion and heat release process, cylinder working fluid flow and heat exchange process, and thermodynamic and gas dynamics process of intake and exhaust system.

The purpose of studying the working process of the internal combustion engine is to improve the thermal efficiency of the internal combustion engine, produce the maximum power, and reduce the fuel consumption and low pollutant emissions of the internal combustion engine under the condition of ensuring the normal operation of the internal combustion engine. Therefore, the performance indicators of internal combustion engines are mainly proposed for power and economy, such as average indicated pressure, indicated thermal efficiency, and indicated fuel thermal efficiency. The above three processes will affect the performance indicators of the internal combustion engine, and the complexity of the working process of the internal combustion engine increases the difficulty of the research and makes the research methods diverse.

This article will mainly discuss the research methods of the working process of internal combustion engines, the test instruments used and the test principles, and the conditions for the use of the instruments.

1.Inspiratory stroke.

2.Compression stroke (conversion of mechanical energy into internal energy).

3.Work stroke (internal energy converted into mechanical energy).

4.Exhaust stroke.

Inhale, do work, stroke, exhaust.

1. The structure of the internal combustion engine and related terms.

In order to explain the working principle of the internal combustion engine, first introduce the structure of the internal combustion engine and related terms. The main body part of the diesel engine is a cylinder block 4 of cylindrical engine, and there is a cylindrical piston that moves up and down in the cylinder body, and in order to prevent the leakage of combustion gas, a piston ring of sealing gas is installed on the piston. The upper part of the cylinder block is the cylinder head, and the intake channel and the exhaust channel and the intake valve and the exhaust valve are on the cylinder head, and the injector is installed between the intake and exhaust valves.

The middle part of the piston is equipped with a piston pin, through which it is connected to the upper part of the connecting rod, and the lower part of the connecting rod is connected to the crankshaft, and the power is output through the flywheel at the end of the crankshaft.

Schematic diagram of the piston in the upper and lower extreme positions when the internal combustion engine is working.

1) Top dead center (also known as top dead center) - the position where the top surface of the piston is displaced to the farthest from the center line of the crankshaft.

2) Bottom dead center (also known as bottom dead center) - the position where the top surface of the piston is displaced closest to the center line of the crankshaft.

3) Piston stroke (also known as piston stroke) - the distance between the top dead center and the bottom dead center of the piston, in millimeters. When the piston moves one stroke, the crankshaft rotates half a turn (180 degrees). As a result, the piston stroke is equal to twice the radius of the crank.

4) Combustion chamber volume (also known as compression chamber volume) - when the piston is at the top dead center, the volume of the space above the top of the piston (including the pit at the top of the piston) and the bottom of the cylinder head (including the auxiliary combustion chamber inside the cylinder head) is the volume, and the unit is liters.

5) Cylinder working volume - the cylinder volume between the piston in the top and bottom dead center position, the unit is liters.

6) Engine displacement - the sum of the working volume of each cylinder of an internal combustion engine (for a single-cylinder internal combustion engine, its displacement is the working volume of the cylinder), the unit is liters.

7) Total cylinder volume - when the piston is in the bottom dead center position, all the sealing volume of the upper part of the piston, the unit is liters.

Total cylinder volume = combustion chamber volume + cylinder working volume.

8) Compression ratio - the ratio of the total volume of the cylinder to the volume of the combustion chamber.

Compression ratio = total cylinder volume.

The combustion chamber compression ratio indicates the degree to which the gas is compressed in the cylinder when the piston moves from bottom dead center to top dead center. The larger the compression ratio, the higher the gas is compressed in the cylinder during compression. The range of diesel engine compression ratio is generally 16 20.

The range of gasoline engine compression ratio is generally 6 8.

Second, the working principle of the internal combustion engine.

The working principle of the internal combustion engine is to use the heat energy generated by the combustion of fuel in the cylinder, promote the piston to move through the heated expansion of the gas, and then transfer it to the crankshaft through the connecting rod to make it rotate to do work.

When the internal combustion engine is actually working, the transition from thermal energy to mechanical energy is countless successive transformations. And each energy transition, it must go through four processes: air intake, compression, work and exhaust. Each time the air is intake, compressed, worked and exhausted, it is called a duty cycle.

If the crankshaft makes two revolutions, the piston completes a working cycle through a four-person stroke is called a four-stroke internal combustion engine; If the piston completes a working cycle after only two strokes for each revolution of the crankshaft, it is called a two-stroke internal combustion engine.

The internal combustion engine works by allowing fuel to burn inside the machine to generate heat and transfer mechanical energy to the outside world.

The internal combustion engine is a power conversion system, which is a heat engine that causes a chemical reaction (combustion) between fuel and air inside the system, and converts the chemical energy (heat energy) released by the reaction into mechanical energy.

Internal combustion engine working process

1. Suction stroke, the piston goes down to form a difference between the pressure in the cylinder and the atmospheric pressure, which is commonly known as the vacuum degree, and the air outside the machine enters the cylinder due to the existence of the vacuum degree.

When the piston descends to the final position, the intake valve is closed, and the suction stroke is completed. In the operation of the machine, due to the relationship of speed, the air pressure in the cylinder is greater than the atmospheric pressure when the suction stroke is completed, and a delay time for the intake valve closure is set in the design to increase the air intake.

2. Compression stroke, after the completion of the suction stroke, the piston upward compressed air reaches a certain temperature to make the fuel burn, at this time there are two situations, one is the ignition given by the outside world, and the other is compressed to a certain time to make it spontaneously combusted.

3. Do the power stroke, compress the air burned after the piston goes down, so as to convert the heat energy into mechanical energy, which is realized through the connecting rod piston group and the crankshaft, under the action of high temperature and high pressure gas, the piston is pushed down through the connecting rod to make the circumference of the circular motion.

This circular motion is the mechanical energy that people need, and its energy is output to the equipment connected to the crankshaft, and part of it is converted into potential energy and stored in the flywheel connected to the crankshaft, and this potential energy is released in the form of flywheel inertia rotation to provide energy for the three strokes of the internal combustion engine: suction, compression, and exhaust.

4. Exhaust stroke, driven by the flywheel inertia, the piston will go up to discharge the combustion exhaust gas from the open exhaust valve, when the piston goes to the end position, the entire internal combustion engine work cycle is completed, and a new round of work cycle will start under the action of flywheel inertia.

The gasoline engine consists of two major mechanisms: a valve mechanism and a crank connecting rod mechanism. Five major systems: ignition system, starting system, fuel supply system, cooling system, lubrication system. The diesel engine is compression-ignition, so there is no ignition system.

The reciprocating piston engine of gasoline engine is composed of two major mechanisms and five major systems, namely: valve mechanism, crank connecting rod mechanism, air intake system, fuel system, ignition system, cooling system, lubrication system, diesel engine and gasoline engine have one less ignition system.

Hello, the internal combustion engine mainly includes five major systems and two major mechanisms. They are ignition, fuel feed, starting, lubrication, cooling, valve mechanism, crank linkage mechanism.

Two major mechanisms: gas distribution mechanism, crank connecting rod mechanism five systems: ignition system, starting system, fuel supply system, cooling system, lubrication system.

Find a professional school to ask for a clearer understanding, and you must find a professional to avoid being deceived.

Intake characteristics: piston down, intake valve open, exhaust valve closed.

Compression features: the piston goes up, and the intake and exhaust valves are fully closed.

Work characteristics: the intake and exhaust valves are fully closed. The gas is ignited, generating power, pushing the piston downward, and outputting power and wisdom to the outside world.

Exhaust characteristics: the door is closed before the intake, the exhaust valve is opened, the piston goes up, and the exhaust gas is pushed out of the gas source cylinder.

Inhale, compress, do work, exhaust.

The working principle of the internal combustion engine is: Mu rough let Chai Xunyuan oil or gas fuel burn in the cylinder, and use the gas with high temperature and high pressure generated during combustion to push the piston and drive the wheel forward. Electric locomotives, on the other hand, use electricity to turn the wheels electrically. Crack and.

The working process of an internal combustion engine

The working cycle of an internal combustion engine consists of processes such as air intake, compression, combustion and expansion, exhaust, etc. Among these processes, only the expansion process is the process of external work, and the other processes are all processes that are needed to better realize the work process.