Regulation effect of the grille spacing of a funnel-type grating water–sediment separation structure on the debris flow performance

The size of pores or the grille spacing of water–sediment separation structures directly affects their regulation effect on the debris flow performance.A suitable pore size or grille spacing can effectively improve the water–sediment separation ability of the structure.The new funnel-type grating water–sediment separation structure(FGWSS)combines vertical and horizontal structures and provides a satisfactory water–sediment separation effect.However,the regulation effect of the grille spacing of the structure on the debris flow performance has not been studied.The regulation effect of the structure grille spacing on the debris flow performance is studied through a flume test,and the optimal structure grille spacing is obtained.An empirical equation of the relationship between the relative grille spacing of the structure and the sediment separation rate is established.Finally,the influence of the water–sediment separation structure on the regulation effect of debris flows is examined from two aspects:external factors(properties of debris flows)and internal factors(structural factors).The experimental results show that the gradation characteristics of solid particles in debris flows constitute a key factor affecting the regulation effect of the structure on the debris flow performance.The optimum grille spacing of the FGWSS matches the particle size corresponding to the material distribution curves d85~d90 of the debris flow.The total separation rate of debris flow particles is related to the grille spacing of the structure and the content of coarse and fine particles in the debris flow.

Analysis of the Heat Transfer Efficiency of an Automobile Engine under Different Grille Opening and Closing Conditions

Computational Fluid Dynamics is used to assess the thermal(heat transfer)performances of an automobile engine considering different grille opening and closing degrees.For this purpose the entire vehicle is modelled and three fundamental aspects are examined,namely,the open area of the air intake grille,the position of the upper and lower grilles and their shape.The results show that the opening area and position of the grille have some influence also on the aerodynamic characteristics of the automobile.With an increase in the opening angle of the grille,the CD(Drag Coefficient)value of the whole vehicle becomes higher.When the air intake grille of the car is fully open or closed,the CD value is 0.35434 or 0.31777,respectively,that is,the flow resistance in the engine compartment accounts for 10.32%of the CD value for the whole automobile.

Water film area and dust removal efficiency of string grilles:a theoretical analysis

Based onmultiphase flowtheory and capillary mechanics,the dimensionless bond number expression of the influence of string grille wire spacing on droplet spreading is derived.Taking a liquid film formed by spreading droplets based on Kelvin correlation,the Young-Laplace equation,and the Hagen-Poiseuille law,an equation for calculating the thickness and height of the liquid film is established with temperature,relative humidity and molar volume of liquid phase as independent variables.According to the theory of string grille filtration and dust removal,a dust removal efficiency calculation model covering the wet string grille wire group is constructed based on the liquid film thickness,height,wire diameter,water film area,and vortex shedding frequency.Finally,a theoretical analysis of the influence of water film area on the efficiency of wet string grille dust removal is carried out based on the spray pressure and the ratio of string grille wire distance to wire diameter.It is found that the effect of spray pressure on water film area and dust removal efficiency is more significant than the string grille wire distance diameter ratio.Moreover,the optimized combination of wet string grille wire distance diameter ratio 0.84,wind speed 3m/s and spray pressure 0.8 MPa is found,which could provide an important reference for engineering applications.

Evaluation of Sensory and <i>in Vitro</i>Cardio Protective Properties of Sardine (<i>Sardina pilchardus</i>): The Effect of Grilling and Brining

The aim of this study was to investigate the effect of grilling and brining on the sensory properties, the fillet fatty acid composition and the cardio-protective activity of sardine (Sardina pilchardus), studying the in vitro activity against Platelet-Activating-Factor (PAF) induced platelet aggregation. Sensory evaluation of grilled and brined sardine showed that grilled sardine had higher scores for the attributes: grilled fish, marine and fresh fish whereas brined sardine had higher scores for the attributes: salty, iodine, oily and bitter. Grilled sardine exhibited significantly increased fillet fatty acid content while the brined fish sample significantly decreased fatty acid levels. Polar lipids of all specimens (raw, grilled and brined) showed strong inhibitory activity against PAF action indicating that grilling and brining have not diminished the cardio-protective properties of sardine.

Microbiological Quality of Fresh and Grilled Mutton Sold in Ouagadougou, Burkina Faso

In Ouagadougou, grilled meats in the form of pieces and brochettes are very popular and well-known to consumers. The aim of this study was to assess the microbial quality of mutton meat sold in Ouagadougou, Burkina Faso. A total of 120 samples were collected from 20 meat grillers 60 samples of fresh meat and 60 samples of grilled meat. The sampling was done between the month of August 2018 and the month of February 2019. The samples were analyzed according to standard methods. The test performed were counts of Aerobic Mesophilic Bacteria (AMB), yeasts and molds, enterobacteria, Campylobacter spp, Staphylococcus aureus, Bacillus cereus, Brucella spp, Pseudomonas aeruginosa, the search for salmonella, and the detection of antibiotics residues. Results showed a high count of AMB (8.77 and 6.78 log UFC/g);enterobacteria (6.58 and 3.05 log UFC/g), Staphylococcus aureus (6.45 and 4.35 log UFC/g), Bacillus cereus (6.98 and 4.52 log UFC/g), Campylobacter (6.03 and 3.86 log UFC/g), yeasts and molds (4.80 and 3.26 log UFC/g) and Pseudomonas aeruginosa (0.45 and 0.15 log UFC/g), respectively in fresh meat and grilled meat. Presumptive Salmonella was found in 95% of fresh meat samples and in 75% of grilled meat samples. In the tested samples, no Brucella spp were detected. However, residues of antibiotics were found in 5% of fresh meat samples and 5% of grilled meat samples. Means of moisture and pH were respectively 74.91% and 6.05% for fresh meat and 53.21% and 6.06% for grilled meat. The average microbial counts recorded in fresh and grilled meat are significantly high and indicate poor hygiene in the raw material and ready-to-eat meat. Good practices of hygiene and processing guides should be developed for the meat grilling value chain actors to reduce contamination risks.

In Memoriam: Ray Grill(1966–2018)

Raymond John Grill, neuroscientist and champion for neurotrauma ＆ neurodegener- ation research, passed away on May 30, 2018 at the age of 52. Our research community has lost an excellent scientist and an exceptional mentor.

Eight Surprising Foods You’ve Never Tried to Grill Before

With summer in full swing,it’s time to fire up the grill.About 80%of American households own a grill,according to a 2013 study by the Hearth,Patio&Barbecue Association.The survey also found that those folks love grilling because cooking outdoors feels satisfactory,and the food'tastes so good.'But if you think grills are exclusively reserved for chicken wings and baby back ribs,you’re wrong.Add some of these foods to your next barbecue’s menu and get ready to become a bona fide grill master.

预制烤鱼水分分布及关键挥发性风味物质分析

以即热型预制烤鱼为研究对象,采用低场-核磁共振技术(Low field-nuclear magnetic resonance,LF-NMR)、顶空固相微萃取与气相色谱质谱联用技术(Headspace-solid phase microextraction-gas chromatography mass spectrometry,HS-SPME-GC-MS)对不同电烤条件下烤鱼水分分布及挥发性风味物质进行研究。结果表明:250℃烤制20 min的烤鱼加工损失率最低,持水力最高。烤鱼中水分主要形式为不易流动水,200℃烤鱼的弛豫时间T22、T23最低,其次是250℃烤鱼,T2反演谱整体向左移动,说明水的自由度降低。250℃烤制20 min的烤鱼不易流动水峰面积占比(A22)最高,达94.03%,自由水峰面积占比(A23)最低,为1.93%,说明肌肉组织持水较优。在5组烤鱼中共鉴定出70种挥发性物质,主要为醛类、酮类、醇类及烃类等。通过相对气味活度值(Relative odor activity value,ROAV)筛选出关键挥发性风味物质分别为12、9、11、8和8种。5组样品贡献较大的风味物质为己醛、1-辛烯-3-醇、壬醛等,其中愈创木酚和4-甲基苯酚是碳烤烤鱼特有的关键风味物质。通过主成分分析,不同条件烤制的烤鱼关键挥发性风味物质差异明显。相关性分析表明,A22与异戊醛、庚醛和2,3-辛二酮呈显著正相关(P<0.05),与壬醛和愈创木酚呈显著负相关(P<0.05)。该研究结果为预制烤鱼开发提供参考。

基于非靶向代谢组学分析不同包装方式预制烤鱼代谢物的差异

为探究不同包装预制烤鱼的代谢物差异,采用液相色谱-串联质谱技术,基于非靶向代谢组学方法分析比较托盒包装、真空包装和气调包装预制烤鱼的代谢物组成。结果表明,在二级质谱信息下,3种包装的预制烤鱼共鉴定出318种代谢物。依据正交偏最小二乘法判别分析模型的变量重要性投影值(variable importance projection value,VIP,VIP>1)和P<0.05,共筛选出47种差异代谢物,包括脂肪酸类10种,核苷酸类10种,氨基酸类9种,有机酸及衍生物类7种,苯及衍生物类3种,醇胺类2种,其他类6种。通过对47种差异代谢物相对含量的聚类热图分析,发现3种不同包装方式预制烤鱼的代谢物相对含量存在差异。其中,气调包装烤鱼的多种呈味氨基酸和单磷酸腺苷相对含量明显高于常规的真空和托盒包装。研究结果初步表明,气调包装对保持烤鱼鲜味有积极作用,将为烤鱼包装多样化发展提供方向。

基于GC-IMS分析泡椒味万州烤鱼堂食过程的“三层次”风味变化

为分析泡椒味万州烤鱼堂食过程中风味的变化,采用气相色谱-离子迁移谱(GC-IMS)技术结合偏最小二乘判别分析(PLS-DA)探究其堂食过程中3个阶段的整体风味差异性及关键的风味标志物。结果显示:在3个阶段中共筛选出65种差异性风味成分,基于这些成分的PLS-DA模型能够有效区分各阶段的风味,呈现“三层次”风味分明的特点;变量投影重要性分析表明,乙酸异戊酯、乙酸芳樟酯、香茅醛(D)、2-乙基-5-甲基吡嗪、丁酸丁酯、己醇、2,6-二甲基吡啶、2-丁醇、1-辛烯-3-醇、2-庚醇、丁酸异丁酯、乙酸乙酯、2-甲基-2-戊烯醛、3-蒈烯、2,5-二甲基吡嗪共15种风味成分是区分泡椒味万州烤鱼堂食过程中“三层次”风味的潜在风味标志物。该研究深入挖掘万州烤鱼风味特征,为提升万州烤鱼品牌价值和制定万州烤鱼风味标准提供了有力的支持。

油炸预制鱼冷冻复热过程中的品质变化

为解决新零售预制烤鱼经冷冻复热后口感下降的问题,选取草鱼为研究对象,以水分含量、持水力、水分分布及组成和微观结构等为指标,探究鱼肉油炸、冷冻、复热不同阶段的品质变化规律。结果表明,随冻融循环次数增加,鱼肉肌纤维破坏程度增加,水分含量显著降低(P<0.05),持水性变差,脂肪氧化和蛋白降解程度显著增加(P<0.05),风味发生改变。复热后,冻融1次鱼肉仍能保持较好口感,但冻融2次后鱼肉感官评分较低,且肌原纤维小片化指数、TBARS和TCA-可溶性肽含量较冷冻前样品分别增加了24.44%、225.84%和52.85%。综上,当油炸预制鱼产品在贮运流通过程中发生冻融次数超过2次时明显降低产品食用品质和消费者接受度。

三文鱼燃气烤制过程单增李斯特菌失活数值模拟

旨在构建三文鱼扒燃气烤制过程的热量传递模型,并结合微生物热失活动力学评估不同烤制条件下单增李斯特菌的失活行为。通过构建一维非稳态传热模型,基于有限差分法和最小二乘优化算法求解模型参数,获得三文鱼扒烤制过程中的温度分布;再结合“一般法”计算单增李斯特菌的致死量。结果表明,三文鱼扒的热扩散系数、火焰侧对流换热系数、空气侧对流换热系数分别为1.83×10^(-7)m/s^(2),15.18 W/(m^(2)·℃)和16.36 W/(m^(2)·℃)。验证试验显示,模型可用于描述三文鱼扒燃气烤制过程中的热量传递,中心温度预测值与实测值之间的RMSE介于1.48~3.33℃。此外,场景模拟计算表明,如果三文鱼扒烤制过程中翻转不均匀,即使加热至中心温度为71℃,则单增李斯特菌仍可能存活。在三文鱼扒烤制过程中,以2,3,4 min或5 min间隔翻转,当中心温度达到71℃时,各位置的单增李斯特菌累积致死量均大于5.21 lg(CFU/g)。本研究结果可为三文鱼安全烹饪提供科学指导。

裙板格栅方向对高速列车设备舱通风性能影响研究

为研究不同方向格栅对高速列车车下设备舱通风性能的影响,以一段某型高速列车实车所用设备舱为试验对象开展了风洞试验,同时基于Realizable k-ε湍流模型构建了风洞试验的数值计算模型.通过风洞试验结果验证了数值模型的准确性,并获得了一套适用于设备舱裙板格栅区域的网格划分参数.基于经风洞试验验证的数值模型和网格划分参数,建立了头车包含设备舱的三车编组数值计算模型.以不同方向格栅(竖向和横向)为研究对象,分析了300 km/h速度等级下设备舱格栅通风口的通风量及设备舱内部的速度分布情况.结果表明:装配两种格栅时,设备舱的总进风质量流率基本一致,其中,装配竖向格栅时,其两侧的进风质量流率基本一致,但装配横向格栅时,其两侧的进风质量流率有所差异,相较于前者,其y-侧的质量流率减少了6.59%,y+侧的增加了6.79%.装配竖向格栅时,气流均匀地从整个格栅区域进入,其进入方向与列车运行方向相同,且速度较小;装配横向格栅时,气流集中从格栅右侧区域进入,其进入方向与列车运行方向相反,且速度较大.通过综合对比质量流率及设备舱空间气流速度,发现装配横向格栅时的通风性能较优.

400 km/h高速列车车下带格栅裙板区域气动噪声机理及影响因素分析

位于高速列车车体下部区域的通风口格栅与设备舱壁面构成格栅–空腔结构,列车高速运行时,该结构的流声耦合问题较为突出,有必要深入分析其流声耦合机理。将位于车体下部区域的带格栅裙板简化为带格栅的二维空腔模型(格栅–空腔结构),采用延迟分离涡数值模型(Delayed Detached Eddy Simulation,DDES)研究其气动噪声产生机理、流场和声场特性等。研究结果表明:当列车以400 km/h速度运行时,格栅–空腔结构开口处的剪切振荡较为剧烈,特别是空腔冲击边缘附近区域;基于总声压级的空间、频域分布和湍流压力波数–频率谱,发现形格栅–空腔结构的流场始终处于自激振荡的过渡状态,且各位置的总声压级和波数域上的振荡幅值始终低于V形格栅–空腔结构和半圆环形格栅–空腔结构;对目前常用的半圆环形带格栅裙板考虑通风口的出风作用后,观察到空腔内部的涡团演化明显减缓,直接导致格栅附近的总声压级大幅下降约15 d B,表明出风作用能够显著降低带裙板格栅的近场噪声。

基于主动进气格栅的热泵空调系统能耗控制策略

为了降低热泵空调系统的能耗,针对车速、进气格栅开口面积等不同参数,以匹配主动进气格栅(AGS)电动汽车的热泵空调系统为研究对象,开发了一种热泵空调热管理系统及能耗控制策略,仿真计算高、低温环境和不同AGS开度条件下的系统能耗,并采用实车环境舱标定方法分析了-7℃低温和35℃高温环境不同AGS开度下空调系统及风阻能耗实测值差异。试验结果表明:高温和低温环境下,AGS开度越大,风阻能耗越高,但空调与风阻综合能耗越低;AGS开度增大相同数值时,高温条件下的能耗贡献量大于低温条件下的能耗贡献量。

开槽两侧格栅对分体双箱梁涡激振动控制研究

分体双箱梁断面涡激振动性能及优化是大跨桥梁抗风设计面临的关键问题之一。以某大跨度悬索桥为背景,针对分体双箱梁制作节段模型进行风洞试验,分析不同攻角时主梁涡激振动性能,提出在开槽两侧沿主梁纵向对称布置气动格栅的优化方案,研究主梁开槽两侧格栅的透风率对涡激振动性能影响规律。结果表明:当阻尼比为0.25%,攻角为-3°、0°和+3°时,主梁竖向涡激振动的无量纲最大振幅分别为0.032、0.033、0.023;当攻角为0°和-3°时,主梁扭转涡激振动最大振幅分别为0.18°、0.13°。开槽处布置透风率50%的两侧格栅后,主梁竖向涡激振动消失。这是由于气流在上游断面迎风侧前缘及栏杆处发生分离,产生较大尺寸的上部旋涡,随着旋涡不断运动,与下游断面发生碰撞,同时主梁尾流产生交替脱落的旋涡,诱导分体双箱梁断面发生涡激振动。开槽两侧布置两侧格栅后,气流的分离作用被弱化,在开槽位置处旋涡尺寸明显减小,减弱对下游断面的作用,优化主梁的涡激振动性能。研究可为分体双箱梁抗风设计提供参考。

碳纤维格栅网-UHPC 增强RC 连续梁 负弯矩区裂缝性能研究

为研究碳纤维格栅网-UHPC(Ultra-High Performance Concrete)增强RC(Reinforced Concrete)连续梁负弯矩处的抗裂性能,设计7根配置不同的UHPC及碳纤维格栅网的试验梁,进行五点弯曲加载试验,分析碳纤维格栅网和UHPC的掺入、碳纤维格栅的网格尺寸、格栅的层数以及UHPC的铺设厚度等参数对负弯矩区开裂荷载和裂缝性能的影响,提出了适合碳纤维格栅网-UHPC增强的钢筋混凝土梁平均裂缝间距、裂缝宽度计算公式。试验结果表明:对照组试验梁的裂缝呈细且密的特点,有别于普通RC梁的裂缝少,宽度大;与普通RC梁相比,单独设置碳纤维格栅网、UHPC增强的试验梁负弯矩区段的开裂荷载分别提升了28.6%、85.7%,同时设置碳纤维格栅网和UHPC增强的4个试验梁分别提升了114.3%、128.6%、142.9%、171.4%;碳纤维格栅网格尺寸的减小、碳纤维格栅层数的增加、UHPC铺设厚度的增加均可以提高抗裂性能,并且使裂缝数量显著增加,裂缝间距和裂缝宽度明显减小。本文基于现有的国内外规范提出的适合碳纤维格栅网-UHPC联合加固的钢筋混凝土梁的平均裂缝间距、裂缝宽度计算值与试验值吻合较好,验证了计算公式的准确性。

PEMFC阴极流道结构的优化数值模拟

阴极流道结构的优化,可提升质子交换膜燃料电池(PEMFC)的性能。提出一种在正方体上加工通孔使截面呈格栅状挡块的设计。创建将格栅挡块加入到PEMFC阴极流道中的三维(3D)模型,研究对PEMFC性能的影响。在固定开孔率为0.36的前提下,开孔数量越多,PEMFC性能越好。当开孔数量为25时(GB-25),PEMFC的功率密度与未添加格栅挡块(GB-0)的相比可提高17.0%。研究多个格栅挡块在阴极流道中的排列方式对PEMFC性能的影响,发现当多个开孔数量为16的格栅挡块等距分布在阴极流道末端时(GB-16-3BE),PEMFC的性能最好,功率密度与GB-0的相比,提升了19.8%。

催化裂化装置再生器尾燃现象分析

自2021年3月,某炼油厂800 kt/a催化裂化装置再生器持续出现尾燃现象。根据烧焦罐烧焦理论,对比多套同类型装置的运行参数,从烧焦温度、催化剂停留时间、氧分压等多个方面进行了探讨。分析发现:烧焦罐内催化剂停留时间过短影响了烧焦效果,造成催化剂燃烧不完全,产生的大量CO遇到稀相过剩氧,导致再生器出现尾燃现象。当烧焦罐藏量增至45 t/h时,停留时间延长至81~90 s,再生器稀相温度降至721℃,稀密相温差降至20℃,再生器尾燃现象得到有效控制。

主动进气格栅在混动车型应用的关键技术研究

【目的】主动进气格栅(active grille shutter,AGS)技术是优化整车热管理性能、风阻和油耗的重要手段之一,但AGS在混动车型的应用价值尚未得到明确的多方位评估,这导致主机厂对该技术的应用仍有疑虑。【方法】该文首次进行AGS在混动车型应用的多方位研究,提出一种混动车AGS开度控制策略。基于某混动车型,采用UltraFluidX、Amesim和Star CCM+等科学工具进行仿真,并开展整车油耗试验,多方位地评估AGS对整车风阻、热管理性能和油耗的影响。【结果】该混动车型在高速行驶时关闭AGS可有效降低整车风阻7.85%,主要原因是气流无法进入机舱,从而降低了机舱阻力;在该混动车型上应用AGS可满足热管理系统的性能需求,优化空调箱内循环比例,进一步提升热管理系统性能;安装AGS密封导流装置是改善机舱内热回流和防止冷空气逃逸的关键措施,可提高格栅进气效率和热管理系统性能;配备AGS并采用该文提出的AGS开度控制策略的该混动车型油耗比未配备AGS的对应车型的降低5.20%,效果显著。【结论】AGS对混动车型的整车风阻、热管理性能和油耗等均有较大提升,良好的AGS匹配设计和关联控制策略实施是促使未来混动车型能耗下降的关键之一。