MULTI-FUEL STORAGE SYSTEM AND METHOD OF STORING FUEL IN A MULTI-FUEL STORAGE SYSTEM

摘要

Advantages such as reduced emissions of NOx can be achieved if engines are fuelled with mixtures of gaseous fuels such as hydrogen and natural gas. It is also desirable to store the gaseous fuels separately so that the fuel mixture ratio can be changed responsive to engine operating conditions. However, compared to liquid fuels, a problem with storing gaseous fuels is that they generally require larger storage volumes to hold an equivalent amount of fuel on an energy basis. There are also obstacles to storing some gaseous fuels such as hydrogen in liquefied form because of the energy required to liquefy them and the extremely low temperatures needed to store such gaseous fuels in liquefied form. The invention relates to an apparatus for increasing the storage density of gaseous fuels such as hydrogen by storing them in gaseous form at high pressures and at sub-ambient temperatures. An apparatus is provided for separately storing a first gaseous fuel and a second gaseous fuel. A first vessel defines a first thermally insulated space for holding the first gaseous fuel in a liquefied form. A second thermally insulated space that can hold the second fuel is disposed within the first vessel. The second thermally insulated space is separated from the first thermally insulated space by a thermally conductive fluid barrier. The second gaseous fuel liquefies at a lower temperature than the first gaseous fuel, whereby the second gaseous fuel can be stored within the second thermally insulated space in a gaseous form at a sub-ambient temperature.