Abstract: Abstract: Fluent software was used and the Euler multiphase flow model was used to simulate the along-path resistance, flow velocity and dry powder concentration distribution characteristics of ultra-fine dry powder fire extinguishing agent with a particle size of 18 μm sprayed in a horizontal straight pipe with a diameter of 8 cm. The results show that in the range of flow velocity 25~150 m/s and ultrafine dry powder volume fraction 5%~15%, the resistance along the horizontal straight pipe has a quadratic function relationship with the flow velocity, and a linear function relationship with the dry powder volume fraction. The range of resistance value is 0.003 28~0.259 81 MPa/m. Affected by the friction of the pipe wall, the flow velocity of the two-phase flow on the cross section of the pipe presents a distribution characteristic of fast in the middle and slow in the surrounding area, and the effect of the volume fraction of solid particles on the flow velocity can be ignored. The gas-phase drag force generated by the different velocity distributions on the cross-section leads to the annular distribution of the ultrafine dry powder volume fraction. The gas-phase drag force is related to the initial velocity and has nothing to do with the dry powder volume fraction. When the flow rate is lower than 70 m/s, the ultra-fine dry powder is distributed in a crescent shape, and the volume fraction of the ultra-fine dry powder is the highest at the lower part of the pipeline close to the pipe wall. The volume fraction is the lowest near the pipe wall, and the flow velocity is greater than 70 m/s, which can effectively inhibit the sedimentation of ultra-fine dry powder.

Key words: Key words: gas-solid two-phase flow, ultra-fine dry powder, numerical simulation, resistance along the way