竹质包装材料成型设备阻隔时间控制系统设计

目的目前材料成型设备未曾指定设备阻隔时间控制过程,导致系统运行时,受系统启动电压和负载变化影响较大,产生时滞现象,为此提出竹质包装材料成型设备阻隔时间控制系统设计。方法硬件设计方面,考虑系统运行环境和控制性能,设计系统硬件架构和通讯管理主机硬件结构,完成系统硬件设计。软件设计方面,建立系统设备阻隔时间控制模型,确定控制过程,进而控制设备阻隔时间。结果实验结果表明,设计的控制系统输出电压的收敛时间为0.08 s,控制时滞为7.5 s,控制时滞波动较小。结论设计的系统可以快速响应系统控制指令,受到电阻和电压变化影响较小,具有较快的收敛速度,较高的控制效率和精确率。

Study on conveyor natural frequency and time intervalfor switching off resistances

A conveyor belt driven by wound rotor motors produces dynamic tension, velocity and accelerationduring starting. The terrible situation (such as resonance) in dynamic analysis and design is that system naturalfrequencies are equal to those for switching off electric resistances. This paper analyzes and determines systemnatural frequencies based on a modeling method of receptances with the analysis of sub-systems model and of theprinciple of their addition and conveyor loop closure. It also puts forward to calculate the time interval for switching off electric resistances. The starting of one conveyor is simulated by lumped-mass-spring-model software tofurther illustrate the influence of time interval for switching off electric resistances on conveyor dynamic behavior. Two methods are also compared. The receptance model is proved to be an excellent alternative.

不同狭缝尺寸对正丁醇火焰传播及表面流动影响规律研究

本文根据实际火灾场景设计并进行了不同尺寸的大理石狭缝正丁醇火蔓延阻隔实验,测量了火蔓延在狭缝内蔓延时间和温度分布,并定量计算了狭缝内的表面流总热量和狭缝侧壁面热损失。研究发现,火焰在狭缝中表现为“跳跃–回缩–跳跃”脉动方式蔓延;在狭缝的冷壁效应和黏性力的耦合作用下,狭缝抑制甚至阻隔了火焰蔓延;狭缝火蔓延时间与狭缝长度成正比,与狭缝宽度成反比;当狭缝侧壁热损失占表面热流总热流的比例超过43.3%时,火蔓延被完全抑制,火焰无法穿过狭缝。