基于CFX的新型豆粕单螺杆挤出机数值模拟分析

单螺杆挤出机是加工以豆粕为原料的膨化食品行业中使用的关键设备。普通单螺杆挤出机存在混合不充分、比能耗低的缺点,为了提高其性能,运用ANSYS/CFX软件对具有三角屏障混炼元件以及反向螺纹元件的新型单螺杆挤出机的流道进行流场分析。研究分析豆粕在其流道中的运动情况,包括速度矢量图、速度流线图、宏观压力图,并和具有普通单螺杆元件挤出机进行对比分析,结果表明:新型组合式单螺杆挤出机的建压能力较好,可切断重排豆粕的速度流线,有利于豆粕更好地混合。研究结果可为单螺杆挤出机设计提供参考。     

基于CFX的豆粕单螺杆挤出机的三维流场分析

运用CFX方法对具有转动螺纹机筒的单螺杆挤出机的流道进行流场分析,研究分析豆粕在其流道中的运动情况,包括速度矢量图、速度流线图、宏观压力图及挤出量,与具有普通机筒的单螺杆挤出机进行对比分析。结果表明:由于机筒具有反向螺纹及反向转动功能,使流场建压能力增强,挤出性能大幅度提高,速度流线产生涡运动,豆粕充分混合。研究结果可为单螺杆挤出机加工提供理论参考。     

生物柴油/矿物柴油混合燃料低温流动特性及流变特性研究

采用多功能低温测定仪和旋转粘度计测定了生物柴油/矿物柴油混合燃料的冷滤点、凝点和粘度,研究了混合燃料的低温流动性能及流变学性能.结果表明:0#柴油调入生物柴油后,混合柴油的冷滤点降低,粘温性提高,低温流动性改善;不同温度下,剪切速率对混合燃料表观粘度影响不同.当温度高于冷滤点时,剪切速率对混合燃料表观粘度影响较小;当温度低于冷滤点时,剪切速率增大,混合燃料表观粘度降低,且随温度降低,表观粘度随剪切速率增大而降低更为明显.     

不同嫁接方式下大豆对干旱胁迫的响应

为明确大豆地上和地下部分对干旱胁迫的响应及对产量的影响,以用于大豆抗旱改良,利用耐旱型品种 辽豆14与干旱敏感型品种辽豆21进行相互嫁接,采用盆栽试验,在结荚期进行水分胁迫处理（土壤含水量保持在 田间持水量的50%）13 d后,测定大豆叶片相关生理指标和各器官生物量。结果表明,水分胁迫使辽豆21自身嫁接 植株叶片的叶色值、叶面积、PSII 系统光化学量子产量Y（II）,调节性能量热耗散Y（NPQ）、最大电子传递速率 ETRmax、半饱和光强下最小饱和光强Ik显著降低,非调节性能量热耗散Y（NO）显著提高。无论以哪个品种为砧木, 与辽豆21相比,辽豆14作为接穗始终具有较高的叶色值、叶面积、Y（II）,Y（NPQ）、ETRmax和Ik,从而获得较高的植 株生物量。另外,干旱条件下,辽豆14作为砧木具有较高的根系活力,能使辽豆21接穗的叶面积、Y（II）,Y（NPQ）、 ETRmax和Ik显著提高,最终获得荚重的增加。由此说明,大豆PSII性能和物质生产能力主要由地上部叶片特性决 定,但干旱下大豆的生长也会受到根系生理活性的影响。     

转基因抗草甘膦大豆的光合及荧光特性

本文比较了转基因抗草甘膦大豆40-3-2与常规栽培大豆荷豆13在光合、叶绿素荧光以及繁殖适合度参数上的差异,以评价在我国农田生境中转基因大豆相对于本土栽培种是否具备更强的入侵性或杂草化特征。结果表明,40-3-2花期叶片净光合速率低于同期的荷豆13,但水分利用策略优良,即蒸腾速率低、水分利用效率高,环境适应能力强。叶绿素荧光测定显示40-3-2全天只有轻微的光抑制现象,其光系统Ⅱ能够在高温和强光照条件下维持较高的光化学效率,而荷豆13叶片在正午时有强烈的光抑制。尽管如此,在没有除草剂选择压条件下,在生长和繁殖适合度上40-3-2相对于荷豆13无竞争优势,入侵性风险较低。     

乙醇改性大豆蛋白制豆胶的研究

研究乙醇改性大豆蛋白对木材用豆胶的胶粘性能的影响.乙醇可使大豆蛋白发生部分变性,使蛋白分子中疏水性基团暴露出来,以提高豆胶的耐水性.通过正交试验优化出最佳条件:乙醇浓度30%,蛋白与水质量比1:9、改性时间45 min、改性温度75℃.将上述最佳条件下制得的豆胶施在胡桃木样品上,经三个循环的48 h水浸泡和48 h空气干燥后剪切强度由未浸泡前的81.6 MPa降至73.9 MPa,仅下降了9.4%.结果表明:乙醇改性后的豆胶的粘接强度和耐水性都有所提高.     

高水分蒸煮挤压小麦混合粉的研究

食品蒸煮挤压技术是多学科交叉所产生的一门高新技术,蒸煮挤压作为一种高温短时的加工方法,能够将输送、压缩、混合、蒸煮、杀菌、成型等多种操作单元同时完成。本实验优化了双螺杆机的加工工艺参数,DS56-Ⅲ型双螺杆挤压膨化机挤压腔内限流区的温度在125℃．含水率为40％、螺杆转速为215rpm,该条件下得到的最好产品膨化度为2．51,经过蒸煮挤压后的食品含水率为35％～37％。     

氮肥施用量对超高产玉米光合性能及产量的影响

在田间栽培条件下,研究不同施氮量对玉米植株光合性能及产量的影响。结果表明,增施氮肥能够增加玉米叶片的叶绿素含量、叶面积指数,提高光合速率、蒸腾速率和气孔导度。施用过量的氮肥会造成植株贪青徒长,使生育后期的光合速率、蒸腾速率和气孔导度下降,影响产量。施氮量300 kg/hm2为试验区最适施氮量。     

绿茶提取物的消除无氧性运动疲劳作用分析

本文对绿茶提取物的消除无氧性运动疲劳作用进行分析,对绿茶提取物功效进行调查,发现绿茶提取物能够提高运动员身体的运动强度,进一步增强运动员身体体质,缓解疲劳,提高抗压能力。通过摄入绿茶提取物可以促进运动员血清的活性的提高,能够缓解肌肉拉伤和修复无氧运动,避免身体骨骼的损伤和细胞膜的受损,同时能够减速身体蛋白质的分化,增强人体抗氧化酶的活动,从而促进身体的新陈代谢,提高运动员的氧自由基,从而增强运动员无氧运动的能力。     

渍前和渍后喷施外源调节物质对花期渍水小麦生长和产量减损效应的差异

为明确渍前和渍后施用外源物对长江中下游地区渍水小麦生长和产量减损效应的差异,以当地主栽品种扬辐麦4号为供试材料,对渍前和渍后喷施外源调节物质(DDTC、GA、肥料元素和复配外源物)后花期渍水胁迫下小麦光合与叶绿素荧光特性、干物质积累与转运及籽粒产量进行了比较分析。结果表明,花期渍水胁迫后小麦光合性能减弱,光能利用和电子传递受阻,花后光合同化物积累减少,籽粒灌浆速率降低,粒重和产量下降。渍前和渍后喷施外源调节物质均可提高花期渍水小麦的叶片光合性能,增强叶片光能利用和电子传递能力,促进籽粒中花后光合同化物积累,提升籽粒灌浆速率以及粒重,从而增加籽粒产量。与渍后喷施相比,渍前喷施外源物能够有效提高花期渍水小麦的叶片光合速率、光化学效率和叶绿素含量以及降低热耗散;渍前喷施外源物能够有效促进花期渍水小麦的花后光合同化物积累,降低花前营养器官贮藏物转运;渍前喷施外源物能够有效提升花期渍水小麦的籽粒灌浆速率,促进粒重和籽粒产量增加。综上所述,与渍后喷施相比,渍前喷施外源调节物质能够有效提升花期渍水小麦光合性能,促进干物质积累与转运以及降低籽粒产量损失,从而减少渍水胁迫对小麦生长和产量的不利影响,其中...     

Aqueous extraction of residual oil from sunflower press cake using a twin-screw extruder: Feasibility study

The objective of this study was to evaluate the feasibility of an aqueous process to extract the residual oil from sunflower press cakes using a co-rotating twin-screw extruder. Two different configurations were tested: the expression from whole seeds followed by the aqueous extraction, in two successive apparatus or in the same one. For the aqueous extraction stage, the oil yield depended on the operating conditions including screw rotation speed, screw profile, and inlet flow rates of press cakes and water. Liquid/solid separation required the addition of a lignocellulosic residue (wheat straw), upstream from the filtration zone. However, even with maximum fiber inlet flow (around 20% of the inlet flow rate of the solid matters for the highest amount of wheat straw), drying of the cake meal did not improve. The lixiviation of the material was also incomplete. Oil yield was better when the expression and the aqueous extraction were conducted in the same extruder. For all the trials carried out using such a configuration, the corresponding cake meal contained less than 10% residual oil, and the total oil yield was 78% in the best operating conditions. Nevertheless, the contribution of the aqueous extraction stage was extremely limited, less than 5% in the best trial, partly due to a ratio of the water to the press cake too low. For the aqueous extraction stage, the oil was extracted in the form of an oil-in-water emulsion whose stability was minimized because of its low proteins content due to their thermo-mechanical denaturation during the expression stage.     

Effect of co-monomer ratio in ABS and wood content on processing and properties in wood/ABS composites

Acrylonitrile-Butadiene-Styrene copolymers (ABS) reinforced with wood flour were investigated for rheological, mechanical and thermal properties. Three grades of commercial ABS resin (high flow (HF-ABS), medium impact (MI-ABS) and super high impact (SI-ABS) grades) were characterized using H-NMR and elemental analysis for the determination of co-monomer content. Wood flour from Para rubber trees treated with N-2 (aminoethyl)-3-(aminopropyl) trimethoxy silane was blended with ABS in the melt blending process using a twin-screw extruder. Wood flour contents used in this work were 0.0 %, 9.1 %, and 33.3 % wt. The composites with higher acrylonitrile contents showed higher melt viscosity especially at the low shear rate. Carreau’s model was used for curve-fitting. The extrudate swell ratio of the composites tended to increase at the shear rate of 10–500 s⁻¹ and then decreased dramatically once the shear rate were further applied. Neat ABS and wood/ABS composites with higher butadiene content illustrated a higher swelling ratio. The neat MI-ABS and composites showed the highest ultimate tensile strength and modulus due to the butadiene content effect. As the wood flour loading was increased, the tensile modulus of all ABS composites increased with the sacrifice of the tensile strength of composites. The elongation at break and impact strength were noticeably the highest for wood/SI-ABS composites among all because of the effect of rubbery butadiene content. Thermal stability of plastic in 9.1 % wood in HF-ABS composites was improved compared with the neat HF-ABS due to the low acrylonitrile content.     

含水率对大豆秸秆流动力学性能的影响

通过直剪切试验,测定分析细碎化处理后大豆秸秆的内摩擦角、粘聚力和流动函数值,研究其流动力学特性,为大豆秸秆纤维制取机螺杆的优化设计提供理论依据.以细碎化处理后大豆秸秆含水率为试验因素,采用单因素对比试验方法,得出了细碎化处理后大豆秸秆的内摩擦、粘聚力和流动函数值随含水率变化的显著性程度及其变化趋势.结果表明:含水率对内...     

醇法连续提取大豆浓缩蛋白及其副产物综合利用的生产实践

以脱脂低温大豆粕为原料,采用乙醇复式萃取器,双螺杆高湿挤压机挤压脱溶的连续生产工艺制取大豆浓缩蛋白.确定了最佳生产工艺条件.在制取大豆浓缩蛋白的基础上,在乙醇提取液的浓缩物大豆糖蜜中,提取分离具有特殊生理活性的大豆异黄酮、皂甙和低聚糖,生产出具有较高附加值的产品.     

广西农业社会化服务体系和模式研究

对2011～2015年连续4年开展的白背毛木耳栽培基质添加豆粕试验与示范结果进行调查，结果表明：在常规栽培料发酵结束后加入豆粕栽培白背毛木耳，会导致污染率急剧增加，添加6%豆粕的菌包废包率高达32.5%；在常规栽培料建堆时，将豆粕与麸皮、轻质碳酸钙等辅料一起加入到木屑中进行充分发酵，可以显著提高木耳产量和品质。需要特别指出的是，相对常规料栽培白背毛木耳，添加豆粕的栽培料发酵时间和翻堆次数需要适当增加，必须确保培养料发酵充分，否则容易出现培养料氨味过重，以致菌丝不吃料或吃料困难，影响栽培效果。     

Melt blowing of ionic liquid-based cellulose solutions

The melt-blowing technique is usually used for thermoplastic resins, not for non-thermoplastic materials. In this study, nonwoven fabric was successfully obtained by a cellulose solution through melt-blowing technique. The solution was prepared by a twin-screw extruder after mixing cellulose pulp with 1-Allyl-3-methylimidazolium Chloride ([AMIM]Cl). Nonwoven fabric exhibited typical characteristics of those from melt-blown thermoplastic resins. Some aspects of meltblowing process are discussed, such as cellulose concentration, temperature of extrusion die and hot air pressure. In experimental range, to obtain nonwoven web, cellulose concentration was below 15 wt%. Temperature of extrusion die and hot air pressure had great influence on the fabric. With the increasing of temperature of extrusion die and hot air pressure, the fiber changed thin and the fiber web became better, while the fiber diameter became thicker after increasing the cellulose concentration. Elevating the temperature of extrusion die, the degree of polymerization decreased, and the quality of the fiber webs declined.     

沼渣与化肥配合施用对大豆生长发育、产量和品质的影响

采用随机区组设计,研究了沼渣与化肥配合施用对大豆生长发育、产量和品质,以及耕层土壤理化性质的影响。结果表明:与常规施肥相比,沼渣与化肥配合施用后,茎粗、根容和根瘤数均有所增加,植株生长表现较好;常规施肥+沼渣30.0×103kg.hm-2产量显著高于其它处理,粗蛋白含量较常规施肥处理提高1.12%,含油量提高0.04%,是大豆较优的施肥配比组合。     

A comprehensive 3D analysis of polymer flow through a conical spiral extrusion die

Several restrictions which are related to extruder machinery and nature of process material exist in the design of plastic extrusion dies. To this respect, it is very important to consider design criteria and limitations in order to operate extrusion dies at desired production rate and temperature. In the current study, flow field characteristics through a conical spiral mandrel die are analysed in detail by 3D Computational Fluid Dynamics (CFD) simulations. The effects of operating conditions such as production rate and temperature on pressure drop through the spiral mandrel die and the occurence of melt fracture are investigated. The temperature dependent viscosity versus shear rate data for grade QB79P (CarmelTech) polypropylene (PP) melt under study are measured by use of rotational and capillary rheometers. Stress terms in the momentum equations are modeled by Generalized Newtonian Fluid (GNF) Model. For this, Bird-Carreau Model is employed as the viscosity model for the polymer melt. 3D CFD analyses provide comprehensive data and understanding with regard to flow behaviour through complex extrusion dies.     

Microstructure formation and rheological behaviour of dough under simple shear flow

In a z-blade mixer, both shear and extensional deformations contribute to the development of dough structure. I effect of simple shearing versus z-blade mixing at similar levels of work input, on the microstructure and uniaxial extensional properties of two doughs prepared from flours of different strengths. With respect to microstructure, mixing initially increased the formation of coarse protein patches, leading to a heterogeneous dough structure with a high fracture stress (σ_max) and significant strain hardening. These parameters decreased with prolonged mixing. This was accompanied by loss of glutenin macro polymer (GMP) wet weight and formation of a more homogenous microstructure. Prolonged mixing typically led to an over-mixed state. In contrast, prolonged simple shearing did not affect GMP content or strain hardening and gave enhanced shear banding. Confocal scanning laser microscopy revealed that short-term simple shearing induced structure formation in the direction of the shear flow for both flour types, followed by formation of shear-banded gluten structures both parallel and perpendicular to the direction of shear flow. Uniaxial extension of dough oriented parallel or perpendicular to the shear field did not reveal anisotropy. Apparently, the observed heterogeneity on a scale of ‘mm’ was not relevant for this type of rheology. Nevertheless, a relative weakening of dough strength (reduced fracture stress) was observed as a function of long-term shearing. This seems to be related to a local segregation effect caused by differences in visco-elasticity between the gluten phase and the starch granules. The results of this study reveal important features of the dough processing and underline the importance of not only work input, but also the type of deformation applied.