Within the semi-empirical model of detonation of monodisperse suspensions of micro and nano-sized aluminum particles, two-dimensional flows in channels are studied by numerical simulations. The problems of the propagation of detonation in a plane channel and a channel with a section of linear expansion are considered. The influence of the particle size on the detonation regimes is analyzed. Analysis of the formation of cellular detonation in a flat channel showed that the irregularity of cellular structures manifests itself in the nanometer range, which is due to an increase in the activation energy of the reduced reaction during the transition from diffusion to kinetic combustion of particles. In the expanding channel, the propagation of detonation is characterized by the formation of a system of transverse waves, the regularity of which is related both to the size of the particles and to the magnitude of the expansion angle. The maps of detonation modes are obtained depending on the parameters: the particle size, the expansion angle, and the width of the output channel.