CAJ | 학술논문

为解决现有谷物风选装置存在的流场不均匀、宽度受限等问题，该文设计了一种以贯流风机作为风源的贯流式谷物清选装置。基于气相K-ε湍流模型和颗粒离散相模型，对清选室内气固两相流特征进行数值模拟计算。通过建立气相数学模型和边界条件模拟气体流动，同时利用双向耦合拉格朗日法追踪颗粒，得到了气相速度分布和颗粒相的运动轨迹。计算结果表明清选室内的气流场存在一定的水平分层现象，具体表现为靠近清选室上下壁板附近流速低、中部流速高，但在层内流场分布平稳，没有明显涡流产生，而且谷物中不同组分颗粒在清选室内的运动轨迹有很大差异。最后，在自制的贯流式谷物清选试验台上采用高速摄像技术拍摄了谷物在清选室内的运动轨迹，验证了数值模拟结果，表明该贯流式清选装置可有效分离脱出谷物的不同成分。
위해결현유곡물풍선장치존재적류장불균균、관도수한등문제，해문설계료일충이관류풍궤작위풍원적관류식곡물청선장치。기우기상K-ε단류모형화과립리산상모형，대청선실내기고량상류특정진행수치모의계산。통과건립기상수학모형화변계조건모의기체류동，동시이용쌍향우합랍격랑일법추종과립，득도료기상속도분포화과립상적운동궤적。계산결과표명청선실내적기류장존재일정적수평분층현상，구체표현위고근청선실상하벽판부근류속저、중부류속고，단재층내류장분포평은，몰유명현와유산생，이차곡물중불동조분과립재청선실내적운동궤적유흔대차이。최후，재자제적관류식곡물청선시험태상채용고속섭상기술박섭료곡물재청선실내적운동궤적，험증료수치모의결과，표명해관류식청선장치가유효분리탈출곡물적불동성분。
The airflow pressure field in the cleaning chamber of the traditional grain winnowing device is irregular, and is not applicable on occasions where high cleaning efficiency is required. Meanwhile, the centrifugal blower is hard to use to obtain a wide and steady wind source. Therefore, a cross-flow grain cleaning device was designed by employing the cross flow blower that is theoretically distributed evenly in the direction parallel to the blower shaft no matter how wide the blower is. And a horn-shaped airflow expansion channel was designed to increase the height of the blowing area. A feeding hopper and two feeding rollers were installed above the cleaning chamber to extrude the materials into a thin layer and accelerate the material layer to a certain speed. Based on the standardK-ε turbulent model and particle dispersed phase model, the characteristics of a gas-solid two-phase flow in the developed cleaning chamber were numerically simulated. The airflow model was developed by setting the inlet of the airflow expansion channel as the velocity inlet boundary, the outlet of the cleaning chamber as the outflow boundary, and the others as wall boundaries. The unstructured tetrahedral grid was applied to mesh the cleaning chamber model in Gambit. And by making the assumptions on the grain components which mainly consisted of gravel, whole grain, immature grain, and short stems: 1) All particles were modeled as equivalent spheres; 2) There was no interaction between particles; 3) There was neither heat nor mass transmission between particles and the gas phase, and the bidirectional coupling Lagrangian scheme was utilized to trace the particles’ movement. Finaly, the distribution of airflow velocity and the particle trajectory was simulated after setting the airflow velocity at the blower outlet and the material parameters. The simulation results indicated that the airflow in the cleaning chamber presented a certain delamination where the airflow near the top and bottom walls had lower velocity than that passing through the mid-chamber and the airflow distribution in each layer was stable without an obvious vortex. Each grain component had respective particle trajectory and was distributed at the bottom of the cleaning chamber in different arc-shaped areas which should be due to the high airflow velocity near the front and back sides and low airflow velocity in the middle of the cleaning chamber caused by the inward-incline of the front and back side boards of the airflow expansion channel. A test rig of the cross-flow grain cleaning device was built to verify the numerical simulation results of the gas-solid two-phase flow in the cross-flow grain cleaning device. A high-speed photographing system was used to record the motion graphics of the whole grains, short stems, and immature grains at a rate of 250 fps respectively. Then the trajectory of each component was identified by the graphic processing. The experiment results showed that the distribution area of the whole grain in the cleaning chamber did not overlap with that of the impurities. The trajectories of the short stems and immature grain were found to partly overlap in the experiment that was different from the simulation. The main reason for this phenomenon was that the short stems were modeled as an equivalent sphere in the gas-solid two-phase flow model. However both simulation and experiment results demonstrate that the whole grain could be separated from the impurities effectively in the developed cross-flow grain-cleaning device.