Optimization And Experimental Study Of Positive Pressure Pneumatic Walnut Shell And Kernel Separation Device

Walnut is known as one of the world’s four dried fruits,with high edible and medicinal value.With theincreasing production of walnuts in Xinjiang,labor costs are high,and mechanized processing is gradually replacing labor and becoming the main form of the walnut primary processing industry.Xinjiang walnut processing equipment requires small size,high efficiency,and low cost to be suitable for small-scale production methods.Based on this,our research team proposed a design concept for a Positive pressure pneumatic force type walnut shell and kernel separation device through preliminary research,which builds a Positive pressure pneumatic force test device.The device has the characteristics of a simple structure,high separation efficiency,and low manufacturing cost.In order to reveal the changes in the airflow field under Positive pressure pneumatic force conditions and improve the separation effect of the device,this article conducts two aspects of research,and test verification:On the one hand,conduct in-depth research from the walnut’s own attributes.Research is conducted to reveal the influence of moisture content on the terminal velocities of walnut shells and kernels,and the drying conditions with the largest difference in the terminal velocities of walnut shells and kernels are obtained.On the other hand,based on the CFD numerical simulation method,the influence of different structural parameters on the airflow field is explored,the distribution law of the internal airflow field is analyzed,and the structure of the walnut shell and kernel separation device is optimized.Conduct single factor experiments to explore the impact of various factors on the separation effect and secondary orthogonal rotation combination experiments to optimize the working parameters of the device and conduct experimental verification.It has important guiding significance for improving the separation effect of walnut shells and kernels and is conducive to promoting the development of full mechanization of walnut processing in China.The main research contents of this article are as follows:（1）Conduct research based on the inherent properties of walnuts.A batch of walnut shell kernels with different moisture contents was prepared by rehydration followed by drying.The terminal velocity of 1/2shell,1/4 shell,1/8 shell,1/2 kernel,1/4 kernel,and 1/8 kernel stored walnuts were 11.04–13.59 m/s,1/4.51–11.23 m/s,8.87–10.21 m/s,1.53–20.66 m/s,15.12–18.78 m/s,and 13.25–15.8 m/s,respectively.The terminal velocity of 1/2 shell and 1/8 kernel overlapped.As the moisture content increases,the terminal velocity of shells and kernels shows different patterns of change.The shells show a slow and then rapid trend,while the kernels show an exponential growth trend.When drying for 30 minutes,the overlap range of terminal velocity between 1/2 shells and 1/8 kernels is the smallest,at 0.71m/s.The separation performance was improved to a certain extent by the verification test.（2）Study on the walnut shell and kernel separation device.The airflow velocity was measured at multiple measuring points inside the Positive pressure pneumatic force walnut shell and kernel separation device,and it was found that there was uneven airflow inside the device,which causes walnut shell and kernel accumulation at the bottom of the device.A numerical simulation of the internal airflow field was conducted using Fluent software,and the effects of different angles of the air distribution plate and the curvature of the separation channel on the airflow field of the device were analyzed.Confirm that the air distribution plate can adjust the airflow,and the curvature of the separation channel was set to be 1.454–1.868 m^-1.Build a test bench and the Angle of air distribution plate and the curvature of separation channel can be adjusted.（3）The dip angle of the wind plate,the radian of the separation channel,and the frequency of the fan as the test factors.Using the cleaning rate and loss rate as indicators,conduct a quadratic orthogonal rotation center combination test to obtain the best working parameter combination:the inclination angle of the wind plate is 35°,the frequency of the fan is 31 Hz,and the curvature of the separation channel is 1.722 m^-1.