Let’s talk in detail: How does a nuclear reactor drive an aircraft carrier?

Let’s talk in detail: How does a nuclear reactor drive an aircraft carrier?

From the perspective of technological development, most of human power sources still come from heat engines. There are fuel heat engines that directly burn fuel, and there are various medium heat engines (external combustion engines) that convert the temperature and pressure of heat-absorbing and exothermic media. When we get to the nuclear-powered aircraft carrier, the nuclear reactor we hear is just the heat source of a dielectric heat engine. Its essence is actually not much different from the train that has been used for more than 200 years.

The train generates heat by burning coal, and this heat heats the water in the superheat tube (30) in the train boiler, causing it to evaporate and boil to form water vapor. High-temperature and high-pressure water vapor enters the air chamber of the locomotive (26). Then the high-temperature and high-pressure water vapor enters the Vals Schertz valve, and driven by the wheel mechanism, the steam makes the piston reciprocate. In this process, water is heated into steam to complete the conversion process of thermal energy of coal fire into kinetic energy.

Early steamships were actually the same as steam trains, except that the steam engine did not drive wheels but webbed wheels to move the water. When steam outputs power, it still relies on the reciprocating motion of the cylinder. When power was realized on ships, an ancient design was soon used on ships. This design comes from Archimedes and was first used by the ancient Greeks to lift water for irrigation.

This is a mechanical device that uses a screw to lift water to a high place. On October 18, 1838, the steam schooner Archimedes was launched. Its propeller is exactly an Archimedes spiral. When "high-speed rotation" can be used as a form of propulsion for ships, the power design of large ships becomes a topic of "how to directly rotate the heat engine."

During World War II, large warships had widely adopted steam turbines as the conversion mechanism from steam internal energy to kinetic energy. This is actually very simple. When high-temperature and high-pressure steam enters the steam turbine, it will push the turbine of the steam turbine to rotate, and then the steam turbine will output power through the main shaft.

When the energy output of one steam turbine is not enough, multiple steam turbines can even be used in parallel to obtain greater power output. The main shaft of most steam turbines is directly connected to the propeller through the shaft. There is no electrical energy, gear box and a series of energy conversion processes at all. Through the engineering drawings of the battleship, you can find the four turbines and the long main shaft extending out. This is currently the most efficient form of power output for steam turbines. To adjust the speed, you only need to adjust the steam flow to the steam turbine without the need for excessive mechanical speed adjustment.

As for how much speed needs to be adjusted, it is really not like putting a car into gear. What is used in large ships is a device called a "car clock". This is a command transmission device. When setting It will make a sound when it reaches a new gear, so it is called a "bell". One is installed on the bridge, and the corresponding other one is installed in the engine room. When the clock on the bridge is turned, the clock in the engine room will sound, and the internal pointer will point to the corresponding gear. After the people in the engine room set the steam flow rate and boiler temperature according to the rules, they then turned the clock in the engine room, and the clock on the bridge also responded. This is a very fast command transmission system. But the instructions are not conveyed to the machine but to the people on either side of the clock.

The steam turbine solves the power output part of the ship, and the source of steam depends on the boiler. The structure of a typical marine boiler is similar to the structure of the steam train mentioned at the beginning. They are both a large number of water pipes burning in the fire.

The high temperature of the fuel heats the moisture in the water pipes to generate steam, which is sent to the steam turbine to drive the turbine to rotate. Of course, there is another option for large ships, which is "nuclear power", which uses the heat from nuclear reactors instead of boilers to produce water vapor. In the entire power system of a nuclear-powered ship, the role of the nuclear reactor is only equivalent to the fuel in the boiler, and the core temperature of the nuclear reactor will be maintained at about 900°C. Since nuclear power reactors are closed, we need to derive the temperature of the core. This is when you need to use the circulation system.

The same idea as water-cooled computers, still using water to dissipate heat. It's just that the water in the nuclear reactor is maintained at 150 atmospheres. Under this pressure, the water can still not boil below 340 degrees. The large amounts of flowing water remove heat generated from the reactor core.

This ultra-high temperature water absorbs heat from the reactor and is introduced into the heat transfer tube of the secondary evaporation device.

The pressure in the secondary evaporation device is 70 standard atmospheres. Water will begin to boil at about 260 degrees, producing high-temperature and high-pressure steam. There is steam now. This steam can be introduced into the turbine through pipes to drive the turbine to rotate.

The steam driven by the turbine will enter a cooling device to continue to be cooled into water, and then flow into the steam generator again, and the cycle repeats. The nuclear reaction is actually a boiler. The way to drive an aircraft carrier today is not much different from that of 200 years ago. It still boils water.