Liquid Hydrogen - Uses

Uses

It is a common liquid rocket fuel for rocket applications. In most rocket engines fueled by liquid hydrogen, it first cools the nozzle and other parts before being mixed with the oxidizer (usually liquid oxygen (LOX)) and burned to produce water with traces of ozone and hydrogen peroxide. Practical H2/O2 rocket engines run fuel-rich so that the exhaust contains some unburned hydrogen. This reduces combustion chamber and nozzle erosion. It also reduces the molecular weight of the exhaust that can actually increase specific impulse despite the incomplete combustion.

Liquid hydrogen can be used as the fuel storage in an internal combustion engine or fuel cell. Various submarines (Type 212 submarine, Type 214 submarine) and concept hydrogen vehicles have been built using this form of hydrogen (see DeepC, BMW H2R). Due to its similarity, builders can sometimes modify and share equipment with systems designed for LNG. However, because of the lower volumetric energy, the hydrogen volumes needed for combustion are large. Unless LH2 is injected instead of gas, hydrogen-fueled piston engines usually require larger fuel systems. Unless direct injection is used, a severe gas-displacement effect also hampers maximum breathing and increases pumping losses.

Liquid hydrogen is also used to cool neutrons to be used in neutron scattering. Since neutrons and hydrogen nuclei have similar masses, kinetic energy exchange per interaction is maximum (elastic collision). Finally, superheated liquid hydrogen was used in many bubble chamber experiments.