Using the direct simulation Monte Carlo direct method, rarefied gas flow into a vacuum through linearly diverging and сonverging сhannels has been studied. The problem has been solved in the complete geometrical setup, namely with including certain pre- and post-channel regions in the geometry under consideration. In a wide range of gas rarefaction, a mass flow rate through the channel, the gas flow diodicity, and flow field both inside the channel and in the regions upstream and downstream have been computed. Computation results are compared to corresponding data for the channel with a constant cross-section. A strong effect of channel geometry and gas rarefaction has been stated. In particular, in the dependence of the mass flow rate on the gas rarefaction, a so-called Knudsen minimum has been revealed; while in the flow field, one-dimensional distribution of gas density in the channel has been found. © 2022