What Is Hydrogen Combustion?

Hydrogen combustion is an effective way to utilize hydrogen. When hydrogen is burned in oxygen, it produces a light blue flame and generates water (gaseous). When pure hydrogen is ignited, hydrogen molecules and oxygen molecules are in contact with oxygen at the ignited position, that is, at the mouth of the catheter, and there is only hydrogen molecules in the catheter without oxygen molecules, and no chemical reaction occurs in the catheter; when the hydrogen is not pure, The hydrogen and oxygen molecules in the tube have been fully contacted. When the explosion limit is reached, the hydrogen and oxygen molecules in the tube and the container have ignited a severe chemical reaction. Because the chemical reaction at this time occurs in a limited space, and this reaction To release a lot of heat, the generated gas will rapidly expand and explode. When the proportion of hydrogen is higher than the upper limit of the explosion limit or lower than the lower limit, there is a shortage of hydrogen or oxygen, so it is a peaceful combustion. If the ratio of the two is within the explosion limit, the ratio is appropriate, the reaction speed is fast, and a large amount of heat is rapidly accumulated to cause the explosion .

In the French novel "Shen Qiu · Island" there is a saying: "I believe that one day hydrogen and oxygen will cause an endless source of light and heat." Oxygen supports combustion, and hydrogen can burn. 66% of the material on Earth is made up of hydrogen. The most convenient way is to produce hydrogen with water. After hydrogen burns work or generates electricity, it is reduced to water. This cycle is endless, inexhaustible, and inexhaustible. Therefore, hydrogen is also a new energy source that can be conveniently used by people ^[1]

Although the calorific value of hydrogen is lower than that of nuclear fuel, it is the highest among all fossil fuels, chemical fuels and biofuels, about 1.4x10 ⁵ kJ / kg, which is three times the calorific value of gasoline: hydrogen has good flammability and fast ignition , Has a wide flammable range when mixed with air, and has a high flash point

(1) Rich and lean combustion technology

The rich and thin combustion technology is in

There are two main ways to convert hydrogen into vehicle kinetic energy:

(1) Hydrogen as a vehicle

Hydrogen fuel storage technology is one of the key technologies for the promotion and application of hydrogen vehicles. At present, the storage methods of hydrogen fuel can be roughly divided into two categories, namely physical methods and chemical methods ^[4] .

Physical method of hydrogen combustion

(1) Gaseous hydrogen storage

Gaseous hydrogen storage is the compression storage of hydrogen in metal containers at a pressure of up to 20-25 MPa. This storage method takes up a lot of space,

Gaseous hydrogen storage

Not very practical. Even if the storage pressure reaches 40 MPa, the volume of 1 kg of hydrogen will occupy 30 L. The volume of 2.88kg gasoline with the same energy accounts for only 4.1L. In addition, the safety of gaseous hydrogen storage is poor, and the container must have sufficient strength and good tightness, and attention must be paid to the corrosive effect of hydrogen on the material and the possibility of brittle cracking ^[4] .

(2) Liquid hydrogen storage

Liquid hydrogen storage is to liquefy high-purity hydrogen through a cryogenic device and store it in a liquid hydrogen tank. The energy consumed by the liquefaction process is about 30% of the hydrogen calorific value, so the cost is high. Due to the low boiling point of liquid hydrogen, which is 20.4K (-252.6 ° C), it must be stored in a double-layer vacuum structure metal container with good insulation properties. The material of the container is to prevent cold and brittleness, and it is generally made of stainless steel or aluminum. The caloric value of each kilogram is about 3 times the calorific value of gasoline of the same quality, but the density of liquid hydrogen is only 1/10 of that of gasoline. Therefore, the volume of liquid hydrogen equivalent to 10L gasoline is about 30L. It is 4-5 times that of the gasoline tank ^[4] .

Hydrogen combustion chemical method for hydrogen storage

Chemical method of hydrogen storage mainly uses metal hydride (MH) as the hydrogen storage source.

First, hydrogen is supplied to the MH under pressure, and the stored gas is cooled and radiated to promote hydrogen absorption and storage. When hydrogen fuel is used, the metal hydride (MH) can release hydrogen under the condition of lower than the suction pressure or higher than the intake temperature, and it can be supplied to the engine through the air supply device. During the release of hydrogen, the metal hydride (MH) Need to absorb heat.

Metal hydrides do not ignite spontaneously and are relatively safe. Some cars use both low-temperature and high-temperature metal hydrides in order to take full advantage of their respective advantages ^[4] .