| The cell-wall-breaking machine is a new type of house appliance which can produce a variety of drinks.Due to ultra-high rotating speed of its motor,the new cell-wall-breaking machine has some impressive features including higher juice production rate,higher nutrient retention rate and higher absorption rate after the cell walls of the fruits and the vegetables are crushed.Based on the experiences fed back by the users of the cell-wall-breaking machines,it has been noticed that the peel of fruit or vegetable will be left over in the machine due to not well-designed products produced by different brand.The unsatisfactory performance in crushing the raw materials causes unpleasant flavor and taste.Therefore,to study the function and characteristics of the high speed blender during crushing process in order to enhance the cell-wall-breaking rate in crushing fruit and vegetable is of considerable values in practical application.In the beginning of this thesis,the effective way for crushing fruit and vegetable was studied from movement and deformation point of view of the raw materials.Then,the mathematical model of the loop for cyclicly crushing the raw materials was established.Finally,an important index for evaluating performance of the machine in crushing the raw materials was set up to verify whether a loop for cyclicly crushing the raw materials can be formed.The CAD software,Solidworks,was used to build the simplified model of the cell-wall-breaking machine.The governing equations of the flow field were established based on the multiple reference system method.The standard k-εmodel of turbulence was selected for analysis.The FLUENT software was used for numerical simulation of the flow field during the process of shearing and crushing the raw materials.The distributions of the velocity of the flow in the cavity of the machine,the turbulent kinetic energy,and the velocity and surface pressure in the nearby of the cutting blade were analyzed.The motion law of the fluid in the cavity of the machine during breaking the raw materials was concluded.The corresponding numerical simulations were performed after the structural parameters such as the angle of the cutting blade,the number of the spoiler rib and the rotating speed of the motor were changed.It was found that,when the angle of the blade was 30~°,the number of the spoiler rib was sole and the rotating speed of the motor was 300 r/s,the cell-wall-breaking machine was under the optimal condition.Then,a cell-wall-breaking machine with plastic cup was selected to perform the experiments for shearing and crushing materials.The distributions of sizes of particles of the materials were analyzed and compared when the shearing and crushing process was carried out with different blade angles and rotational speeds.The experimental results verified the reliability of the results of numerical simulation.By analyzing the characteristics of a single-phase series motor,it can be seen that the load change has a greater influence on the motor speed,and the motor speed is an important factor that affects the material cell-wall breaking rate.Therefore,this paper designed a fuzzy self-adaptive PID controller based on the STM32 microcontroller to perform the hardware and software design of the series motor control system of the high speed blender,and carried out an experimental test,verifying that the fuzzy adaptive PID controller is the feasibility of series motor speed.Then three control modes with different rotation speeds were designed and tested.The experiment found that there was a good crushing effect under the variable speed control mode,which provided a certain basis for the optimization of the control mode.Finally,a recognition equation was established according to the effect of different fruit or vegetable on the start-up speed of a single-phase series motor,and the minimum mean error method was used to identify the material,which provided a new idea for realizing the intelligent control of house appliances. |
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