Analysis of the dimensionless torque in cone drum false twisting mechanism

An investigation of the dimensionless torque in the newly developed cone drum twister texturing mechanism is reported. The cone drum twister is one of the outer surface contacting friction-twisting devices in false-twist texturing. In this cone drum twister, a filament yarn passes over the surface of the cone drum that rotates by the passing yarn without a special driving device. This research is composed of the theoretical analysis of the false twisting mechanism and the experimental analysis at room temperature. The equations have been derived which shows interrelationship of the conical angle of cone drum, the wrapping angle, the drag angle, and the yarn helix angle. Theoretical values of dimensionless torque were calculated and were compared with the experimental results. It is shown that, as the conical angle and the projected wrapping angle increased, the dimensionless torque also increased. But the conical angle was reached to 30.75°, the dimensionless torque decreased.     

Demonstration that Feeds Containing <1% Fishmeal Can Support Grow‐out of Large Juvenile Red Drum,Sciaenops ocellatus,and Reduce Nutrient Waste

We conducted a 16‐wk feeding trial with large juvenile red drum, Sciaenops ocellatus. Four diets were randomly assigned to six replicate tanks per treatment. Three isonitrogenous (ca. 44.5% protein) and isolipidic (ca. 14.1% lipid) extruded diets were formulated to compare a fishmeal‐based diet with diets using alternative protein sources. Diet 1 contained 19.60% fishmeal and 21.42% poultry meals as primary protein sources. Two alternative diets were formulated reducing the fishmeal to 0.61% by substituting poultry meals (33.85%) and soybean protein concentrate (11.55% in Diet 2 and 11.70% in Diet 3). Diet 3 also included Allzyme Vegpro® and Allzyme® SSF at 0.04%. Diet 4, a natural diet consisting of chopped cigar minnows, squid, and shrimp, was used as a positive control to compare growth rates of formulated feeds to near maximum growth under these culture conditions. We found that reducing the amount of fishmeal to <1% by using alternative protein sources did not affect the growth rate, survival, or health of red drum but improved assimilation of phosphorus, reduced potential release of P to the environment, and significantly lowered the amount of feeder fish needed in feed. The control diet identified performance benchmarks for future feeds development work.     

胶乳分离机高速转鼓流体动力学特性

为研究胶乳分离机转鼓离心流场动力学特性,基于FLUENT二相流模型,模拟了胶乳的分离过程以及转速、橡胶粒径对分离效果的影响,以浓乳的干胶含量为综合特征参数进行模型验证试验,理论分析影响分离速度的因素、碟片内液流的流动状态及轨迹、浓缩极限等问题。模型中设置鲜胶乳体积分数初始值为0.330,浓乳黏度0.038 48 m Pa·s,表面张力系数0.034 N/m,橡胶粒径为5μm,胶清按水的属性设置,碟片间隙为0.5 mm。计算结果表明:转鼓转速为7 250 r/min时,胶乳进入转鼓10 s时橡胶粒子与胶清已呈现明显分离倾向;当转鼓分别为6 750、7 250和7 750 r/min时,浓乳中的干胶体积分数分别为0.588、0.613和0.636,转速越高,干胶体积分数越大,但转速超过7 250 r/min,干胶体积分数的增幅变缓,流体压力和结构应力也将明显增加;在7 250 r/min工作转速下,当胶乳粒径分别取1、2、3、4和5μm时,浓乳中干胶的体积分数分别为0.354、0.392、0.447、0.531和0.601,浓乳中干胶体积分数随粒径增大而增加,轻相出口处因流体涡漩体积分数有一定波动。浓乳干胶含量的仿真结果与实测值高度接近,相对误差为3.83%,由此验证了模型的可靠性。轻/重相分离速度与粒径、转速直接相关,因科氏力轻相/重相轨迹与碟片母线有偏离,胶乳浓缩存在上限,轻/重相出料路径合理,离心去除细微杂质的能力强。研究结果为揭示胶乳离心浓缩机理、优化分离工艺及结构提供了理论参考。     

切流-横轴流玉米脱粒系统改进设计及台架试验

对玉米脱粒过程的研究,理论分析与数学建模存在着理想假设的局限性,整机田间试验受制于系统结构、环境条件而不能深入测试分析。为便于室内研究玉米脱粒过程,以4YL-4/5型收获机脱粒系统为参照,设计了切流-横轴流脱粒试验系统,结构设计模块化,可根据需要更换脱粒滚筒等关键零部件或调整技术参数,以便兼顾开展多种谷物脱粒试验研究。工作参数标定表明,试验台架可满足最高37 k W的工作负载,满足滚筒线速度为0~29.06 m/s、喂入量为0~8.08kg/s的谷物脱粒试验。在入口脱粒间隙为36 mm,出口间隙为12 mm,喂入量为2.6 kg/s的条件下,切流滚筒采用螺旋柱齿结构、横轴流滚筒采用柱齿-板齿结构形式,以不同的横轴流滚筒线速度为测试速度,对含水率在22%~32%的玉米果穗进行脱粒试验,试验表明:切流滚筒的脱粒物质量占比随着含水率的增加而减弱,当含水率在28%以下,切流滚筒与横轴流滚筒脱粒筛分段的脱粒能力几乎相当,当含水率高于28%,切流滚筒的脱粒物质量占比下降明显。脱粒系统在线速度15.84~18.72 m/s和含水率为22%~26%的条件下,籽粒破碎率指标满足国标规定值≤5%。在滚筒线速度为17.28 m/s、含水率为24%~26%区间内,脱粒系统的籽粒破碎率最低,平均值为1.7%。通过脱粒试验台,将玉米脱粒过程的试验研究与田间测试有效结合,可为玉米籽粒收获机脱粒系统的设计提供科学依据。     

双滚筒式收后地表残膜回收机设计与试验

针对残膜回收机存在的拾净率低、含杂率高等问题,该研究设计了一种双滚筒式残膜回收机,适用于秋收后地表残膜回收,采用机械拾膜、气力与机械协同脱膜方式完成作业过程。对捡膜和脱膜过程进行动力学分析,确定捡膜装置和脱膜装置的关键结构参数以及工作参数范围,根据滚轮中心运动轨迹设计并优化正反向凸轮轨道,得到凸轮结构参数,获得捡膜装置不漏捡的条件。运用气流特性分析软件模拟脱膜装置内部流场,分析得出气流运动形成的“O”形旋流利于残膜与杂质的分离。以机具前进速度、捡膜滚筒转速和脱膜滚筒转速为试验因素,残膜拾净率及回收混合物含杂率为试验指标,进行单因素试验,得到响应面试验水平的较优区间,并进行响应面试验,得出较优工作参数为机具前进速度6.72 km/h,捡膜滚筒转速56.7 r/min,脱膜滚筒转速569.78 r/min。田间试验结果表明,机具前进速度6.7 km/h、捡膜滚筒转速57 r/min、脱膜滚筒转速570 r/min时,平均残膜拾净率为86.1%,平均回收混合物含杂率为39.2%;相较于已有回收机的残膜拾净率（85.03%）提高了1.07个百分点,各项指标满足收后地表残膜回收要求。     

9L-200型灌木收获机设计与试验

针对柠条、沙棘、沙柳、紫穗槐等灌木植物机械化收获需求，研发设计了9L-200型灌木收获机。采用适合于沙地、沙坡、丘陵地、泥泞地的履带底盘，驱动采用定量液压泵+比例阀+变量行走马达；采用锯切原理，设计双圆锯盘向内旋转对灌木实施无支撑切割的切割拨送割台；开发组合式切碎滚筒装置；通过增减动刀和动刀刀架数量，实现切段长度的有级调整技术；设置了反转齿箱装置,达到堵塞快速排除的效果；经国家农机具质量检验检测中心现场检测及田间试验检测，该机型生产率为6-10亩/小时，物料切割长度20-40mm可调，各项性能指标达到了设计要求，满足了大规模灌木平茬收获的和工业化资源利用的市场需要。