目的 针对变距螺旋主要以经验设计为主，缺乏系统设计方法的问题，提出一种函数拟合法。方法 首先以二次函数y=Ax2+Bx对变距展开线进行初始拟合，考虑进料段螺旋变距的均匀变化，再以线性函数y=Ax+B进行二次拟合。根据线性拟合结果，采用粒径为1.5 mm的小米物料对等距和变距螺旋进行离散元仿真。结果 得到了进料段变距设计方案，S1=0.4D，S2=0.56D，S3=0.72D，S4=0.8D。相比等螺距，在相同转速及外径下，变距螺旋进料段下料均匀，输送稳定，质量流量与实际流量相对误差为1.8%。结论 验证了变距设计的合理性，可为变距螺旋研究提供参考。

This paper aims to propose a function fitting method to solve the problem that the variable pitch spiral structure is mainly based on empirical design and there is a lack of system design methods. First, the initial fitting of the variable-distance spiral expansion line was performed by the quadratic function y=Ax2+Bx. Considering the uniform variation of the pitch-changing spiral of the feed section, the second function was performed by the linear function y=Ax+B. Based on the result of leaner fitting, discrete element of equidistant and variable pitch spirals was simulated with millet material with a particle size of 1.5 mm. The variable pitch design of the feed section was obtained as follows: S1=0.4D，S2=0.56D，S3=0.72D, and S4=0.8D. Compared with the equal pitch, at the same speed and blade outer diameter, the feeding section of the variable pitch spiral structure was relatively uniform, the conveying was relatively stable, and the relative error between the mass flow and the actual flow was 1.8%. The simulation results verify the rationality of the design of the variable pitch spiral structure, and have certain reference value for the study of the variable pitch spiral structure.