Abstract: Abstract: In order to optimize and expand the measure range of the swirl meter with 150 mm diameter, the incident angle of swirler is investigated to improve the performance of swirl meter. The internal flow fields of the swirl meter with different swirler incident angles are numerically simulated using RNG k-ε turbulence model based on CFD (computational fluid dynamics) technique. The pressure loss, instrument coefficient and the distribution of flow field are comparatively analyzed for the swirl meters. First, under the flow rates of 120, 300, 750, 1 200 and 2 100 m3/h, the numerical simulations and experiments are carried out to study the pressure loss characteristics and instrument coefficient of the swirl meter with 150 mm diameter when the incident angle of swirler is 57.5°. The commercial software Gambit is used to obtain the numerical mesh, and the structured and unstructured grids are used for different regions which take both calculation speed and accuracy into consideration. In the process of calculation, FLUENT software is used for the numerical simulation, and the RNG k-ε turbulence model is adopted considering its better prediction ability in complex unsteady flow condition; besides, the inlet boundary condition is set as velocity inlet, and the outlet boundary condition is set as outflow, which assumes the flow is fully developed. The medium of simulation is air and the density is 1.225 kg/m3; moreover, for the maximum velocity of air in this study is about 33 m/h (when flow rate is 2 100 m3/h) which is much less than Mach 0.3, therefore, the air is considered as incompressible fluid during the simulation. The experiment research is completed by sonic nozzle calibration device under a standard atmospheric pressure and the temperature of 24℃. The numerical results are in good agreement with the experimental ones, and therefore, the numerical method adopted in this paper is proved to be feasible for the research of swirl meter and can save lots of time in the future study. It is appropriate to use computational fluid dynamics method to investigate the influence of different incident angles (57.5°, 55° and 60°) on the pressure loss and instrument coefficient for swirl meter, and the design of swirl meter could be more efficient than ever by using CFD technique. As a result, two more swirlers at the incident angle of 55°and 60° are calculated with the same numerical method and geometrical model except for the incident angle. By comparing the pressure loss, instrument coefficient and pressure distribution of three swirl meters, it is found that the larger incident angle is, the bigger pressure loss of swirl meter will be. It is also found that the change of incident angle has some influence on the instrument coefficient, and the larger incident angle is, the larger instrument coefficient will be. As larger incident angle brings stronger vortex, the smaller minimum flow value can therefore be measured by swirl meter. By analyzing the pressure contour distribution of three models, it is found that the pressure drops quickly at the swirler region and leads to part of pressure loss, the lowest pressure is at the center of vortex and the distribution is nonuniform at throat and diffuser region, while the pressure becomes steady at the end of deswirler. As a whole, the swirl meter with swirler incident angle of 55° comes with the best performance.