Experimental Research On The Drag Coefficient Of Non-Spherical Particles

Gas-solid flow system has been widely used in industry,and most of solid particles in these systems are non-spherical.Studies on the flow behaviors of irregular non-spherical particles have been performed worldwide,but the full knowledge on the complex flow characteristics is still lacking,the drag coefficient is the core parameterto reveal the interaction between particles and fluid.The present work is devoted to revealing drag characteristics of irregular non-spherical particles by experiments.Firstly,experimental system was established to measure the particle drag coefficient in this study.Three particle shape descriptors,including polygonality,aspect ratio and circularity were selected to describe the shape of irregular non-spherical particles.The shape parameters and motion parameters of the experimental particles were obtained by processing the acquired image using a developed MATLAB program.The experimental system was verified and checked by gravity acceleration.Secondly,the drag coefficient for both standard spherical particles and regular non-spherical particles was determined and compared with classical experimental results.It is found that the experimental results from this study are in good agreement with existing classical experimental results.Thus,the feasibility and accuracy of the experimental system and the calculation method have been verified.Finally,experiments on the drag of irregular non-spherical particles were carried out to study the characteristics of drag coefficient of a single irregular non-spherical particle in high particle Reynolds number.Based on the experimental dates,a new correlation was developed for predicting the drag coefficient of irregular particles,and the influence law of particle shape,density,particle Reynolds number to the drag coefficient of irregular particle was found.The results of the study show that drag coefficient will decrease with the increase of particle Reynolds number when the range of the value of particle Reynolds number is 2500 to 10000.When the particle Reynolds number is less than 4000,drag coefficient will decrease first and then increase with the increase of polytonality.When the particle Reynolds number is more than 4000,drag coefficient will increase with the increase of polytonality.Drag coefficient will increase monotonically with the increase of particle density,but it will decrease monotonically with the increase of aspect ratio.However,drag coefficient will increase first and then decrease with the increase of circularity.