基于粒子图像测速法的大米抛光机内米粒运动规律分析

Analysis of rice grain motion characteristics in a rice polisher based on particle image velocimetry

[目的]通过研究抛光机运行参数、米粒运动规律、产生碎米率之间的关系,寻求抛光机的较优参数调控依据。[方法]通过分析抛光室内米粒的运动过程、开展全因素试验以及应用粒子图像测速法(PIV)对米粒运动轨迹进行分析,明确米粒的运动状态、碎米率与抛光机转速及压力门开度之间的关系。[结果]当压力门开度20 mm时,在试验转速范围内均不能形成有规律的米粒运动形态,此时不能达到米粒抛光要求。当压力门开度4 mm、转速为600~1400 r/min时,米粒呈现出螺旋升角较小且高低速区域交替出现的运动形态。当压力门开度8 mm、转速1400 r/min时,米粒呈现出高低速(速度差>3 m/s)区域交替出现的运动形态。上述两种工况下,米粒因过度揉搓或压力过大导致碎米率较高(>4%)。在试验范围内的其余工况下,米粒均呈现出螺旋角大小适中的高低速(速度差为2~3 m/s)区域交替出现的运动形态,此时碎米率为2%~4%,能够达到较好的抛光效果。[结论]不同工况下米粒形成的运动形态与产生的碎米率不同,在合适的压力门开度和转速下,米粒呈现出适当的运动形态,能达到较好的抛光效果。

[Objective]By studying the relationship between the operating parameters of the polishing machine,the motion patterns of rice grains,and the generation of broken rice rates,to seek the basis for optimal parameter control of the polishing machine.[Methods]By analyzing the motion process of rice grains in the polishing chamber,conducting full-factorial experiments,and applying Particle Image Velocimetry(PIV)to analyze the trajectory of rice grain movement,clarifiied the relationship between the motion status of rice grains,the rate of broken rice,and the rotational speed of the polishing machine as well as the opening degree of the pressure gate.[Results]When the pressure gate aperture was set to 20 mm,no coherent motion pattern wwas observed within the experimental range of machine speeds,rendering the rice polishing ineffective.In contrast,with a pressure gate aperture of 4 mm and machine speeds ranging from 600 to 1400 revolutions per minute,the rice grains exhibited an alternating motion pattern characterized by a relatively small spiral angle and the occurrence of regions with varying velocities.Furthermore,under the condition of a pressure gate aperture of 8 mm and a machine speed of 1400 r/min,the rice grains demonstrated an alternating motion pattern in regions of high and low velocities(with a velocity difference exceeding 3 m/s).In both of these scenarios,excessive friction and pressure leaded to a high rate of broken rice(exceeding 4%).In the remaining experimental conditions,characterized by appropriate pressure gate apertures and machine speeds,the rice grains exhibited a moderately sized spiral angle in alternating regions of high and low velocities(with a velocity difference of 2~3 m/s).This configuration resulted in a broken rice rate ranging from 2%to 4%,indicative of favorable polishing effects.[Conclusion]The motion patterns formed by rice grains and the resulting broken rice rates vary under different operating conditions.Under suitable opening degree of the pressure gate and rotational speed,rice grains exhibit appropriate motion patterns and achieve better polishing effects.