脱出物喂入量对多风道清选装置内部气流场的影响

Effect of extractions feed-quantity on airflow field in multi-ducts cleaning device

为研究联合收获机脱粒装置脱出物喂入量对清选装置内部气流场的影响,研制了多风道清选试验台,在清选室内振动筛上、下方分别布置25个气流速度测点,并在风机转速1 350 r/min、鱼鳞筛开度22 mm、分风板Ⅰ倾角24°、分风板Ⅱ倾角20°的额定工作参数下,采用VS110型热线式风速仪对清选装置内部无脱出物和1~4 kg/s脱出物喂入量工况分别进行气流场测量试验。试验结果表明:各测点的气流速度随脱出物喂入量的增大而有着不同程度的减小;无脱出物时各测点的气流速度最大,喂入量每增大1 kg/s,振动筛上方测点的气流速度下降1.2%~16.4%,振动筛下方测点的气流速度下降1.4%~9.3%;特别是在最大4 kg/s喂入量时,振动筛上方气流速度衰减较多,比无脱出物时气流速度下降12.6%~30.7%;相同喂入量条件下,振动筛横向1/3、2/3处的气流速度比1/2处大,振动筛纵向筛面上方前部气流速度较小、中后部气流速度较大、筛尾处气流有所回升。研究结果为多风道清选装置的设计和田间试验时参数调整提供依据。

To study the effect of threshed mixture feed quantity of combine harvester threshing device on the cleaning device＇s airflow field, a multiple-duct cleaning test-bed was developed. This test-bed included variable feeding device, multiple-duct cleaning device, transmission device, frame and control cabinet. The test-bed could adjust threshed mixture＇s feed quantity, fan rotation speed, vibration sieve opening, wind-board dip angle and other parameters. Also, through controlling discharge outlet opening and electromagnetic feeder frequency, the feed quantity could change （1-4 kg/s）. Moreover, the test-bed could automatically save the data and display the data on the computer screen. The test-bed was used for further study on the internal airflow field under various working conditions. In this study, 25 airflow velocity measuring points were arranged above and below the vibration sieve in the cleaning room. The feed quantity of non-material and 1-4 kg/s was tested by VS110 type hot-wire anemometers under rated conditions in which the fan speed was 1350 r/min, the vibration sieve opening was 22 mm, the dip angle of Wind-board I was 24°, and the dip angle of Wind-board II was 20°. The traditional hot-wire anemometer was easy to be damaged by material impact, but the anemometer in this study could avoid the problem, and furthermore, its measuring accuracy was higher. In single test, 10 hot-wire anemometers were used to measure the airflow velocity and save the data. Test experiment showed that the airflow velocity of each measuring point decreased with the increasing of feed quantity of threshed mixture; in the non-material case, the airflow speed arrived maximum. With every 1 kg/s feed quantity that was increased, the airflow velocity decreased by 1.2%-16.4% at the top of the vibration sieve. The airflow velocity decreased by 1.4%-9.3% at measuring point under the vibration sieve. Especially in 4 kg/s feed quantity that was the maximum quantity, the airflow velocity above the tail of the vibration sieve was more attenuated, which decreased by 12.6%-30.7% compared with non-material. Under the same feed quantity, the airflow velocity at the transverse 1/3 and 2/3 position of the vibration sieve was larger than that at the 1/2 position, which was caused by the multiple-duct centrifugal fan structure. The airflow velocity of the front above the vibration sieve at longitudinal direction was smaller and the airflow velocity in the middle and posterior was larger and the airflow velocity picked up in the end of vibration sieve; for the front position above the vibration sieve was only affected by the upper air-duct, while the middle part was influenced by the lower air-duct of multiple-duct centrifugal fan, and the sieve surface tail was close to the exit of the machine and the cut area suddenly changed small to cause the airflow velocity rising. The research provides the basis for the design of multiple cleaning devices and the adjustment of parameters in the field experiment. In the actual harvest operation, when the crop feeding quantity increases, appropriately increasing the fan speed or reducing wind-board dip angle is necessary in order to enhance the air stripping and stratification ability, and it also can guarantee the cleaning quality and efficiency.