| China is a big country with the crop straw resources.It has about 1/4 of the total amount of crop straw resources in the world,however,the utilization rate of straw resources is very low,a lot of straw is burned as waste in situ,it is not only a serious environmental pollution,but also a waste of resources.In view of the above problems,the technology of straw forming is an effective way.At present,the straw briquetting machine is mainly fixed,and the movable straw briquetting machine is just starting.Because of the less research on the application of straw shredding and throwing integrated device on the movable straw briquetting machine,the structural parameters and operating parameters are still lack of scientific research.Presently,straw shredding and throwing integrated device has some problems in actual production,such as uneven straw shredding,low efficiency of straw throwing,mismatching of operating parameters and so on.Considering the above problems,based on9SM-YJ-2000 type movable straw briquetting machine,the main structure of the straw shredding and throwing integrated device was improved.CFD was used to simulate the flow process of straw pellets in the device,and the influence factors were analyzed.What's more,The high speed camera test and matching test of feeding roller speed,impeller speed and main spindle speed was done.The research work done in this thesis are as follows:(1)The working principle of the movable straw briquetting machine was analyzed,and the three-dimensional model,structural scheme and drive system of the whole machine were established.what's more,the drive ratio and the main motion parameters of the drive system were determined(The main spindle speed was145~185 r/min,impeller speed was 450~810 r/min,feeding roller speed is 85~145r/min).In addition,through the suspension velocity of straw material,the minimum airflow velocity of rice straw pallets was determined that was 16.28 m/s.Theoretical analysis and improvement design of the main structure of straw shredding and throwing integrated device were carried out,and the related parameters were initially determined.(2)Solidworks was used to establish the flow channel model of straw shredding and throwing integrated device which consisting of impeller blades,volute and pipes.The mesh was divided by ICEM,and the flow channel model boundary was defined in Fluent.what's more,numerical simulation of gas-solid two-phase flow was done.Through numerical simulation,the results of the pressure field and velocity field distribution of straw pellet phase in the device were obtained,and the movement law of the straw pellets flowing in the device was analyzed.numerical simulation of gas-solid two-phase flow in straw shredding and throwing integrated device with different parameters under different working conditions was carried out.The influence of various parameters on the efficiency of straw throwing was discussed.The results showed that when the impeller speed was 630 r/min,the number of impeller blades was 3,the impeller blade inclination angle was 15°,and the radius of curvature of pipe was 700 mm,that the velocity distribution of straw pellets was even in straw shredding and throwing integrated device,the highest throwing speed could be 4.5~4.8 m/s,it help improve the efficiency of straw throwing.(3)The high speed camera test was carried to provide data for validation of the simulation model.The results showed that the experimental value was basically consistent with the simulation value and the simulation model established by Eulerian model in this study was reasonable.a central composite rotatable orthogonal experimental design of response surface methodology was employed to find the optimum technical parameters of movable straw briquetting machine.Straw compact density and productivity were selected as responses,and the feeding roller speed,impeller speed,and main spindle speed were selected as input variables.Variance analysis and response surface analysis were applied to analyze the test result by Design-Expert 8.0.6.The experiments showed that the contributing rate of every factor on density of straw briquetting was as follows:main spindle speed>impeller speed>feeding roller speed.And the contributing rate of every factor on productivity was as follows:feeding roller speed>main spindle speed>impeller speed.The results indicated that when the feeding roller speed was 125.84 r/min,impeller speed was 776.05 r/min,and the main spindle speed was 169.16 r/min,the straw compact density mean was 1.153 g/cm~3,and the productivity was 1135.87 kg/h,the feed rate of straw matches well with the requirement of straw,meet the requirement of briquetting of straw compression block. |
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