There have been attempts to make liquid propellants work - which sound, perhaps not surprisingly, a bit like the problems associated with rocket propellants: h

There have been attempts to make liquid propellants work - which sound, perhaps not surprisingly, a bit like the problems associated with rocket propellants: https://en.wikipedia.org/wiki/Bulk_loaded_liquid_propellants https://en.wikipedia.org/wiki/Bulk_loaded_liquid_propellants [Inset obligatory 'Ignition!' reference].