How to withstand more than two thousand degrees? Don't think about it because it doesn't need to be taken. The average macro temperature of the engine is also more than 100 degrees, some parts can have two or three Baidu, the hottest exhaust valve is a few hundred degrees.

The maximum temperature you can burn is more than 2,000 degrees Celsius (about 2,500 kilograms of gasoline and about 2000 kilograms of diesel oil). This is no problem, but there are two things to do with the engine.

In simple terms, the engine can remain macroscopically at more than 100 degrees because the energy delivered to it by the high-temperature gas in this state and the energy that the engine can take away by the cooling system are balanced.

Specifically, it is because the engine has a cooling system, and this cooling system (for the heat transferred by the combustion to the engine) is effective enough.

Consider a combustion chamber surrounded by cylinder heads, cylinder walls, pistons, and intake and exhaust valves. The cylinder wall and cylinder head are attached to the combustion chamber on one side and cooling water on the other.

Because of the good thermal conductivity of the metal, the cylinder walls and the cylinder head against the combustion chamber start to transfer heat to the cooling water immediately after the temperature rises, and the rate of this transfer is large enough to make the cylinder wall and the cylinder head. The temperature only needs to be slightly higher, and the established temperature gradient is sufficient to derive the heat transferred to them by the hot gases. (When the cooling water circuit works normally)

The above is the heat dissipation end, that is, the heat dissipation is effective, and the heat source end is the reverse. The so-called heat source is actually not so hot.

Although the maximum combustion temperature of the engine is more than two thousand, the time is very short. Only the beginning of the work stroke, if the air intake of the entire intake stroke is considered to be low temperature, there will be no more than one neutralization, which leads to the entire cycle. The average gas temperature is not so exaggerated, it is also a few hundred degrees.

The combination of the above two is why the engine's overall average temperature only needs more than 100 degrees. It is enough. The figure below shows the temperature of a cylinder wall in a complete cycle under an operating condition of an eight-cylinder gasoline engine. Subtracting 273 is the Celsius degree. This is more than 100 degrees.

In summary, it is the engine's relatively strong heat-dissipating ability and the very transient high-temperature transient characteristics caused by its own working principle, which makes it possible to withstand (or allow) high temperatures to obtain a very high mass per unit of working fluid. Power density. (not the engine)

If you want to see a more comprehensive temperature distribution, you can refer to the following diagram, which shows the temperature of the cylinder wall (minus 273 degrees Celsius), looking upwards from the position of the crankshaft, at a temperature of 100-200 degrees Celsius.

The following also illustrates a similar situation where the temperature inside the cylinder wall is measured at 120 (bottom) - 200 (top) degrees Celsius.

Of course, there are still some relatively important components, such as the cylinder head temperature is higher than the cylinder wall, because the contact with the hottest place, but the overall high tens of degrees, the actual temperature of the lower part of the cylinder wall is not high.

The temperature of the piston is also relatively high, because the piston is similar to the cylinder head and does not directly dissipate heat.

This is also why modern engines have a nozzle for spraying oil under the crankcase so that when the piston moves to the bottom, it can be cooled by the oil. Although there is no cooling water, it is also easier to use than it is not. .

This time, someone has already thought of it. In fact, the most serious problem is not the piston but the exhaust valve. Because it is different from other components in the combustion chamber, the back of the exhaust valve must continuously face the high temperature exhaust in the exhaust manifold. This time is not a transient problem, but a steady-state problem. General exhaust valves are required to withstand high temperatures of 700-800 degrees Celsius, which is why the so-called hollow sodium injection valve is used to increase heat transfer performance and reduce the load due to temperature rise. Porsche's exhaust valve temperature test of Carrera's self-priming engine, which was 991.1 before, probably looks like this. The back of the valve is basically at 600-700 degrees Celsius.

As far as the engine's temperature is higher, there are also exhaust manifolds and turbines, because they are constantly accepting the high temperatures of exhaust gas and are a complete steady-state phenomenon. At the maximum power point, the temperature is in the range of 950-1000 degrees Celsius, but this is not internal to the engine you are asking, but is "strictly" external.

This is the reason why no one uses a variable turbine on a gasoline engine other than the 911 Turbo.

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