5. Injection of gaseous fuels or liquefied gases

In principle, the injection of gases or liquefied gases is similar to that of liquids, and the previous systems could be applied. In practice, however, sealing problems when gas is injected, and the resulting safety issues, mean that systems other than common-rail cannot be used.

In a gas or liquefied gas application, it must be borne in mind that, during use, the pressure in the reservoir decreases, resulting in a change in the liquid/vapour constitution of the fuel taken from it. Vaporization also begins in the injector pipes themselves. For safety reasons relating to sealing, high pressure is only maintained in the injector during the injection phase; for the rest of the time, the injector is connected to the low-pressure circuit and must be isolated from the rail, thus transforming the injector into a three-way valve. In the event of an emergency, given the...