揉碎玉米秸秆螺旋输送理论模型分析与试验

Theoretical model analysis and test of screw conveyor for rubbing and breaking corn straw

针对农业纤维物料螺旋输送机理不明确、输送功耗大、生产率低等问题,该文对揉碎玉米秸秆的螺旋输送过程进行理论分析,建立了同时考虑物料的压缩特性、螺距的变化及螺旋轴离心力作用的物料所受压力、螺旋输送装置的生产率和功耗的数学模型,并通过轴向推力、生产率和功耗试验数据修正了上述模型。结果表明,当喂入量30 kg/min、转速58 r/min、螺距在160～300 mm的范围内变化时,压力、生产率和功耗的理论值与实测值的相对误差分别在11.7%、8.6%和5.9%以内;当螺距250 mm、喂入量30 kg/min、螺旋轴转速在58～148 r/min的范围内变化时,压力、生产率和功耗的理论值与实测值的相对误差分别在5.1%、6.9%和5.4%以内;当螺距250 mm、转速58 r/min、喂入量在10～70 kg/min的范围内变化时,压力及生产率和功耗的理论值与实测值的相对误差分别在5.9%、5.8%和5.2%以内。该研究为适合输送农业纤维物料的螺旋输送装置的设计及生产提供较为精确的理论依据。

Screw conveyor is widely used in the crop harvest and processing of agricultural fiber materials, for the screw conveyor has the advantages of simple structure, reliable work, low cost, easy operation management, good tightness, less pollution to the environment, and so on. However, there are some problems such as low productivity and high power consumption in the process of conveying the agricultural fiber materials, because the theoretical study about the screw conveying process of fiber material is not perfect enough and conveying mechanism is not clear. In order to solve these problems, the theoretical analysis of conveying process about screw conveyor was carried out. Firstly, corn straw was rubbed and broken, some hypotheses were made about its movement condition, and its screw conveying model was built. Based on the plug flow theory, non-plug solid conveying theory and Triaminic non-plug conveying theory, the motion and stress of corn straw micro-unit in the screw groove were analyzed. Continuity equation and kinematics equation were built and then solved. The model of the pressure on material under different working conditions was obtained. On this basis, the productivity model and power consumption model were built. The variation of the pressure on material, the productivity and the power consumption with the pitch, rotational speed and feeding quantity was analyzed. The experimental platform of screw conveyor that can accurately measure the axial thrust and power on line was developed by the research group through using loop force measuring sensor, torque speed sensor and computer. The parameter of the experimental platform was that the conveying gap length was 2 500 mm, the diameter of the screw blade was 250 mm, the diameter of the center axis was 60 mm, the pitch was 160, 200, 250 and 300 mm respectively, and the space between the screw blade and the casing was 5-8 mm. The samples were from the corn stalks crushed by the 9R-40 type crusher, which were less than 180 mm long and 2-8 mm wide, and had 52.87% moisture content. The impact of pitch, rotational speed and feeding quantity on axial thrust, productivity, and power consumption was studied in the experiment. The results showed that： 1） When the rotational speed was 58 r/min and the feeding quantity was 30 kg/min, the pressure decreased, the productivity increased and the power consumption decreased firstly and then increased with the pitch increasing. 2） When the pitch was 250 mm and the feeding quantity was 30 kg/min, the pressure and the power consumption increased, and the productivity increased firstly and then decreased with the rotational speed increasing. 3） When the pitch was 250 mm and the rotational speed was 58 r/min, the pressure, the productivity, and the power consumption increased with the increase of feeding quantity. Finally, the contrastive analysis was made between the theoretic and the experimental value. The results showed that when the pitch was 160-300 mm, the rotational speed was 58-148 r/min, and the feeding quantity was 10-70 kg/min, the relative error of theoretic and the experimental results of the pressure on material, the productivity and the power consumption was within 14%, 11% and 11%, respectively. The model of the pressure on material, productivity model and power consumption model were modified by the test data of axial thrust, productivity and power consumption, respectively, the results show that： when the pitch was 160-300 mm, the rotational speed was 58-148 r/min, and the feeding quantity was 10-70 kg/min, the relative error of the theoretic value and the experimental value of pressure on material was within 11.7%, 8.6% and 5.9%, respectively; the relative error of the theoretic value and the experimental value of productivity was within 5.1%, 6.9% and 5.4%, respectively; and the relative error of the theoretic value and the experimental value of power consumption was within 5.9%, 5.8% and 5.2%, respectively.