膨化机小模孔模具物料挤出过程的流场数值模拟与分析

为了提高螺杆挤出小粒径膨化颗粒的效率与质量,利用POLYFLOW软件对直径为0.4 mm模孔的螺杆挤出过程进行了等温流场数值模拟,分析了模前压力、模孔过渡段锥孔角度等因素对模孔内熔体流场的影响。研究结果表明,随着物料进入模具前所受压力的增大,物料熔体在模孔中的流动速率、剪切速率增加,黏度降低,产量增大;不同过渡段锥孔角度下,熔体在模孔内的流动状态差异较小,各物理量的变化趋势随锥孔角度减小有所减缓,有利于物料均匀挤出。在实际生产中,提高模前压力、使用锥孔角度较小的挤出模板可以在一定程度上提高小粒径膨化颗粒的生产效率和颗粒质量。

不同工艺参数组合对肉鸡颗粒饲料加工质量、生长性能和养分表观消化率的影响

本试验旨在研究筛片孔径、调质温度、模孔直径的不同工艺参数组合对肉鸡颗粒饲料加工质量、生长性能和养分表观消化率的影响。以玉米-豆粕型全价配合饲料为肉鸡试验饲粮,在相同配方及模孔长径比一致的条件下,设计3因素2水平(筛片孔径:2.0和2.5 mm;调质温度:70和80℃;模孔直径:3和4 mm)的肉鸡颗粒饲料加工试验,选用864只1日龄爱拔益加(AA)肉仔鸡,随机分为8个处理,每个处理6个重复,每个重复18只鸡。饲养试验共42 d,分1~21日龄和22~42日龄2个阶段。结果表明:1)筛片孔径和模孔直径的交互作用以及调质温度和模孔直径的交互作用对颗粒硬度有极显著影响(P<0.01),调质温度和模孔直径的交互作用、筛片孔径和调质温度的交互作用以及筛片孔径、调质温度和模孔直径的交互作用对颗粒耐久性有极显著影响(P<0.01),筛片孔径和模孔直径的交互作用对颗粒耐久性有显著影响(P<0.05)。2)调质温度对1~21日龄肉鸡末重、平均日增重和平均日采食量有极显著影响(P<0.01),对22~42日龄肉鸡末重有极显著影响(P<0.01)。3)肉鸡1~21日龄,筛片孔径、调质温度以及2因素的交互作用对肉鸡养分表观消化率的影响不显著(P>0.05);肉鸡22~42日龄,筛片孔径、调质温度和模孔直径的交互作用对肉鸡干物质、能量和粗蛋白质表观消化率有极显著影响(P<0.01)。综合得出:相同筛片孔径和模孔直径下,颗粒硬度和耐久性随调质温度升高有增大趋势;相同筛片孔径和调质温度下,颗粒硬度和耐久性随模孔直径的增大有降低趋势;肉鸡1~21日龄,筛片孔径选择2.0和2.5 mm均可,调质温度为70℃时肉鸡的生长性能极显著高于80℃时,且料重比显著低于80℃时;肉鸡22~42日龄,当筛片孔径为2.0或2.5 mm、调质温度为70℃、模孔直径为4.0 mm时肉鸡生长性能较高、料重比较低;肉鸡1~42日龄,当筛片孔径为2.0或2.5 mm、调质温度为70℃、模孔直径为4.0 mm时肉鸡的生长性能较高、料重比较低;当筛片孔径为2.5 mm、调质温度为80℃时,1~21日龄肉鸡干物质、能量和粗蛋白质表观消化率较高;当筛片孔径为2.5 mm、调质温度为70℃、模孔直径为4.0 mm时,22~42日龄肉鸡干物质、能量和粗蛋白质表观消化率最高。

Trend analysis and comparison of basic parameters for tunnel blast design models

One of the most important factors influencing on a tunnel blast efficiency is the proper design of blasting pattern. Among blasting parameters, blasthole diameter and tunnel face area are more significant so that any change in these parameters could finally affect on specific charge and specific drilling. There are mainly two groups of methods for tunnel blast design categorized based on the parallel cuts and angular cuts. In this research, a software for tunnel blast design was developed to analyze the effect and sensitiveness of blasthole diameter and the tunnel face area on blasting results in different blast design models. Using the software, it is quickly possible to determine specific charge, specific drilling and number of blastholes for each blast design model. The relations between both of blasthole diameters and the tunnel face area with the above parameters in different blast design models were then investigated to yield a set of equations with the highest correlations to compare the methods. The results showed that angular method requires more blasthole numbers than parallel method in similar condition(blasthole diameter and tunnel face area). Moreover, the specific charge values yielded by the two methods are approximately the same and very close together.