锤片式饲料粉碎机内气固两相流场压强的测试方法

粉碎机在工作过程中,粉碎室内部是一个复杂的三维流场,针对这种流场的测试,现有的方法很难对多相流场压力分布进行长时间、全方位的准确测量。为此,该文提出一种基于虚拟仪器技术的流场测试方法,根据该方法构建了一套测试系统,涵盖了仪器选型、数据采集与分析的程序设计等环节。以锤片式粉碎机样机为试验对象,对粉碎室内的流场进行多点测量。对采集到的各个测量位置的压强信号做数字信号处理,并做比较分析。结合前期研究成果,通过单相流对比试验以及流场仿真分析,论证了该测试方法及测试系统的可靠性。此外,该方法的提出和测量系统的开发,为课题组今后研究粉碎室内流场的压强分布规律,寻找压强与粉碎机结构参数之间的关系提供了技术支持,可望为新型粉碎机的优化设计提供理论依据。

Pressure test method of gas-solid two-phase flow field in grinding chamber with hammer mill

In order to test the flow field of the mill, the project group proposed a new method based on virtual instrument technology, and constructed a set of test system according to the method, which coverd the design of the instrument selection, data acquisition, data analysis and processing. In the program design process, we designed an integrated virtual digital filter using the powerful data and signal analysis tools in LabVIEW, which covers 6 kinds of commonly used digital filters. Taking a new type of mill prototype as the experimental object, the project group carried out many test experiments on the single air flow field and the air and solid two-phase flow field in the chamber. Firstly, the pressure and velocity of the air flow field in A section were tested by 2 kinds of test methods and the single flow field of the whole chamber was simulated and analyzed. Through the comparison, the result showed that the error was in the 5% and the 3 ones were consistent with each other. Secondly, when the speed was constant, the pressure distribution of the flow field near the wall under the condition of no load and load was consistent with that of the flow field near the wall. Thirdly, the influence of material concentration on the flow field near the wall was not obvious at the 1000, 1500, 2000 and 2500 r/min rotating speed of the air flow field, the effective value of the pressure decreased with the increase of the speed, and the air-solid two-phase flow had the same law. The effective value of the pressure in the corresponding test point was reduced. In air flow field, the pressure value of less than or equal to 1500 r/min was positive. This showed that in the work, the low speed of the pressure field was small, and the negative pressure of the back was small. Besides, rotation speed of the mill had a great influence on negative pressure, when the speed changed from 1000 to 2500 r/min, and the maximum negative pressure of test was from -20.35 to -411.15 Pa. The negative pressure calculated by back propagation (BP) neural network algorithm was from -37.24 to -678.42 Pa. The effect of material on the flow field near the wall was not much, but it would weaken the negative pressure in the center area. The sealing performance of the mill had great influence on the internal flow field. Under the 2500 r/min work condition, so the theoretical maximum negative pressure was -2.5 KPa, and the test maximum negative pressure was only -411.15 Pa. Therefore, the method and the measuring system provide the technical support for the following study on the relationship between the pressure and the structural parameters of the mill, and provide the theoretical basis for the optimization design of the new type of mill.