Systems and methods for injecting and mixing a liquid hydrocarbon fuel to provide a uniform, homogenous fuel vapor mixture for introduction into a fuel reformer for use with a fuel cell are disclosed. Preferably, the system includes a fuel injector that generates and aspirate a liquid fuel in the presence of an atomizing gas stream; a diverging-converging mixing chamber, into which the atomized fuel and a secondary fluid stream are introduced, to enhance the mixing of the fuel and the added heated gas or steam; and a mixer/swirler, which can be centrally located in the mixing chamber between the upper and lower chambers, to stabilize the fuel vapor mixture further for greater uniformity and homogeneity. More preferably, grooves and/or brazed wires can be provided on the surfaces of the mixing chamber and/or mixer/swirler to channel any accumulated fuel so as to provide sufficient time to evaporate the accumulated fuel.