Investigations on High-Speed Flash Boiling Atomization of Fuel Based on Numerical Simulations

Flash boiling atomization(FBA)is a promising approach for enhancing spray atomization,which can generate a fine and more evenly distributed spray by increasing the fuel injection temperature or reducing the ambient pressure.However,when the outlet speed of the nozzle exceeds 400 m/s,investigating high-speed flash boiling atomization(HFBA)becomes quite challenging.This difficulty arises fromthe involvement ofmany complex physical processes and the requirement for a very fine mesh in numerical simulations.In this study,an HFBA model for gasoline direct injection(GDI)is established.This model incorporates primary and secondary atomization,as well as vaporization and boilingmodels,to describe the development process of the flash boiling spray.Compared to lowspeed FBA,these physical processes significantly impact HFBA.In this model,the Eulerian description is utilized for modeling the gas,and the Lagrangian description is applied to model the droplets,which effectively captures the movement of the droplets and avoids excessive mesh in the Eulerian coordinates.Under various conditions,numerical solutions of the Sauter mean diameter(SMD)for GDI show good agreement with experimental data,validating the proposed model’s performance.Simulations based on this HFBA model investigate the influences of fuel injection temperature and ambient pressure on the atomization process.Numerical analyses of the velocity field,temperature field,vapor mass fraction distribution,particle size distribution,and spray penetration length under different superheat degrees reveal that high injection temperature or low ambient pressure significantly affects the formation of small and dispersed droplet distribution.This effect is conducive to the refinement of spray particles and enhances atomization.

Rheological Properties and Structural Changes in Different Sections of Boiled Abalone Meat

Changes in tissue structures, rheological properties of cross- and vertical section boiled abalone meat were studied in relation to boiling time. The adductor muscle of abalone Haliotis discus which was removed from the shell, was boiled for 1, 2, and 3 h, respectively. Then it was cut up and separated into cross- and vertical section meat. When observed by a light microscope and a scanning electron microscope, structural changes in the myofibrils were greatest in the cross section meat compared with the vertical section meat. When boiling time was increased from 1 h to 3 h, the instantaneous modulus E 0 and rupture strength of both section meat decreased gradually with increased boiling time, and no significant differences were observed between these two section meat for the same boiling time. When boiled for 1 h, the relaxation time of cross section meat was much longer than that of vertical section meat. There were no significant changes in the relaxation time of vertical section for different boiling time, but the relaxation time of cross section meat was reduced gradually with increasing boiling time. These results confirmed that the difference in rheological properties between the cross- and vertical section meat was mainly due to the denaturation level of myofibrils when heated for 1 h, as well as due to the changes in the amount of denatured proteins, and the manner in which the inner denatured protein components weve exchanged after boiling time was increased from 1 h to 3 h.

Effect of Gd on neutron absorption properties and electrochemical corrosion behavior of Zr-Gd alloy in boiling concentrated HNO3

A Zr-Gd alloy with neutron poisoning properties and resistance to boiling concentrated HNO3 corrosion was developed based on a corrosion-resistant Zr-702 alloy to meet the demand for neutron shielding in the closed-loop treatment of spent fuel and the nuclear chemical industry.In this study,1 wt.%,3 wt.%,5 wt.%,7 wt.%,and 9 wt.%Zr-Gd alloys were designed and fabricated with Zr-702 as the control element.The electrochemical behavior of the Zr-Gd alloys in boiling concentrated HNO3 was investigated,and the neutron shielding effect on plate thickness and Gd content was simulated.The experimental results demonstrate that the corrosion resistance of the alloy decreased slightly before~7-9 wt.%with increasing Gd content;this is the inflection point of its corrosion resistance.The alloy uniformly dissolved the Gd content that could not be dissolved in the Zr lattice,resulting in numerous micropores on the passivation coating,which deteriorated and accelerated the corrosion rate.The MCNP simulation demonstrated that when the Gd content was increased to 5 wt.%,a 2-mm-thick plate can shield 99.9%neutrons;an alloy with a Gd content≥7 wt.%required only a 1-mm-thick plate,thereby showing that the addition of Gd provides an excellent neutron poisoning effect.Thus,the corrosion resistance and neutron shielding performance of the Zr-Gd alloy can meet the harsh service requirements of the nuclear industry.

Study of Varietal Influence Post Conservation on Biochemical and Sensory Qualities of Attiékéand Boiled Cassava (Manihot esculenta Crantz)

Cassava root is shortly preserved after harvesting due to its tanning and rapid physiological decomposition. Consequently, the commercial value is reduced and the craving of its finishes products. With an aim of improving physiological quality, post harvest food value “the effects of bleaching and conservation in silo-pits were evaluated. Four (04) varieties of cassava: Bocou1, Bocou2, Bocou3 and Yavo were collected fresh and healthy in 13 months of maturity. They were subjected to a bleaching (65°C /15 - 30 s) followed by a kinetic conservation (7 days of intervals) in silo-pit (1 × 0.6 × 0.5 m). Results show that Bocou2 variety has the high proteins content (2.64% ± 0.01%), followed by hydrocyanic acid (8.21 ± 0.01 mg/100 g) and total carotenoids (26.7 μg/100 g). The conservation influences positively the protein content, reducing sugars content, the dries matter content and the total phenolic compounds for all the varieties excluded Bocou2 variety whose protein content drops. As regard of the fat contents, a weak increase is observed. The sensory analysis reveals that the boiled cassava of the Yavo variety is more appreciated followed by Bocou1 variety. Concerning the Attiéké, Bocou3 variety gives the more appreciated dish followed by the Yavo variety. In conclusion, the silo-pit conservation after bleaching improves the physiological quality of the cassava and the sensory taste even during 14 days. This study has a huge impact of reducing the post harvests losses and increases the commercial value of cassava in the world.

Dietary Fibre and Fatty Acid Evaluation of Boiled, Roasted, Germinated and Fermented Breadnut (Ukwa bekee) Seed Flours

Evaluation of dietary fiber and fatty acid composition of boiled, roasted, fermented and germinated breadnut seed flour was investigated. The seeds were dehulled and washed. It was divided into four equal parts for different processing techniques: boiled, roasted, germinated and fermented. They were analyzed for dietary fibre and fatty acid composition using standard methods. Data were subjected to statistical analysis using Statistical Product for Service Solution (SPSS) version 23.0. Values were expressed as means and standard deviation, Duncan multiple range test was used in separating the means at 95% confidence interval. Dietary fibre composition showed that breadnut seed flours range from 4.94%(fermented breadnut seed flour) to 5.42%(roasted breadnut seed flour). Fatty acid profile showed that breadnut seed flours contain a greater amount of non-essential fatty acids which were highly significant (p < 0.05) in oleic acid (57.93%) for roasted breadnut seed flour followed by linoleic acid (25.76%) in fermented breadnut flour. Stearic acid was the only prominent non-essential fatty acid in the breadnut seed flour and ranged from 4.40%(fermented breadnut seed flour) to 6.27%(germinated breadnut seed flour). The study revealed that all the processed breadnut seed flours have appreciable quantities of dietary fibre and essential fatty acids than non-essential fatty acids. Breadnut seed should be recommended in wheat substitution in bakery industry and culinary uses. It is also recommended for weight loss program.

The Research on Sliced Boiled Chicken

Sliced boiled chicken is a kind of Chinese food which has a history of more than two hundred years.At the very beginning,it was offered to customers as a kind of fast food.After two centuries’development,it has become a cultural symbol of Guangdong region.In other words,the significance of sliced boiled chicken has transcended the food itself.It is an essential part of Cantonese life.Because it is a dish that is relatively easy to cook,we can see sliced boiled chicken everywhere in Guangdong Province,China.No matter in the city or in the countryside,in upscale restaurants or in fast food restaurants,if you want,you can easily find a place to enjoy the delicacy of sliced boiled chicken.However,most of the people just know to eat sliced boiled chicken.Only a small part of them will notice the history behind this dish.At the same time,though this dish is seen as a cultural symbol,most people just see it as a money making tool which greatly disturbs its development.

Simulation of single bubble dynamic process in pool boiling process under microgravity based on phase field method

We use the phase field method to track the gas-liquid interface based on the gas-liquid two-phase flow in the pool boiling process,and study the bubble nucleation,growth,deformation,departure and other dynamic behaviors on the heating surface under microgravity.By simulating the correlation between liquid undercooling and bubble dynamics,we find that the bubble growth time increases with the increase of liquid undercooling,but the effect of liquid undercooling on bubble height is not significant.Meanwhile,the gas-liquid-solid three-phase contact angle and the gravity level will also have an effect on the bubble growth time and bubble height.With the increase of the contact angle,the bubble growth time and bubble height when the bubble departs also increase.While the effect of gravity level is on the contrary,the smaller the gravity level is,the larger the bubble height and bubble growth time when the bubble separates.

Comparisons of Structured Surface Floors for Pool Boiling Enhancement at Low Heat Fluxes: Hands-On Learning Setup for Heat Transfer Classroom

Various enhanced surfaces have been proposed over the years to improve boiling heat transfer. This paper introduces an experimental setup designed for boiling demonstration in the graduate-level Heat Transfer course. The pool boiling performance of water under atmospheric pressure of 1.025 bar is investigated by using several structured surfaces at heat fluxes of 28 and 35 kW/m2. Surfaces with holes, rectangular grooves, and mushroom fins are manufactured by an NC-controlled vertical milling machine. The heat flux versus excess temperature graph is plotted by using thermocouple measurements of water and base temperatures of the boiling vessel. The separation, rise, and growth of individual vapor bubbles from the surface during boiling were recorded with a digital camera. The results for the plain surface are compared to the Rohsenow correlation. The enhancement of heat transfer coefficient (h) ranged between 15% - 44.5% for all structured surfaces. The highest heat transfer coefficient enhancement is observed between 41% - 56.5% for holed surface-3 (405 holes) compared to the plain surface. The excess temperature dropped around 29% - 34% for holed surface-3 (405 holes) compared to the plain surface. The heat transfer coefficient increases as the spacing between channels or holes decreases. While the bubbles on holed and mushroomed surfaces were spherical, the bubbles on the flat and grooved surfaces were observed as formless. The suggested economical test design could be appropriate to keep students focused and participating in the classroom.

Experimental and Numerical Analysis of the Influence ofMicrochannel Size and Structure on Boiling Heat Transfer

Computational fluid dynamics was used and a numerical simulation analysis of boiling heat transfer in microchannels with three depths and three cross-sectional profiles was conducted.The heat transfer coefficient and bubble generation process of three microchannel structures with a width of 80μm and a depth of 40,60,and 80μm were compared during the boiling process,and the factors influencing bubble generation were studied.A visual test bench was built,and test substrates of different sizes were prepared using a micro-nano laser.During the test,the behavior characteristics of the bubbles on the boiling surface and the temperature change of the heated wall were collected with a high-speed camera and a temperature sensor.It was found that the microchannel with a depth of 80μm had the largest heat transfer coefficient and shortest bubble growth period,the rectangular channel had a larger peak heat transfer coefficient and a lower frequency of bubble occurrence,while the V-shaped channel had the shortest growth period,i.e.,the highest frequency of bubble occurrence,but its heat transfer coefficient was smaller than that of the rectangular channel.

Lattice Boltzmann simulation of the effects of cavity structures and heater thermal conductivity on nucleate boiling heat transfer

The boiling heat transfer technology with cavity surfaces can provide higher heat flux under lower wall superheat,which is of great significance for the cooling of electronic chips and microelectromechanical devices.In this paper,the boiling characteristics of the cavity surfaces are investigated based on the lattice Boltzmann(LB)method,focusing on the effects of cavity shapes,sizes,and heater thermal conductivity on the heat transfer performance.The results show that the triangular cavity has the best boiling performance since it has less residual vapor and higher bubble departure frequency than those of the trapezoidal and rectangular cavities.As the cavity size increases,the enhancement of heat transfer by the cavity mouth is suppressed by the heat accumulation effect at the heater bottom.The liquid rewetting process during bubble departure is the reason for the fluctuation of the space-averaged heat flux,and the heater thermal conductivity determines the fluctuation amplitude.The evaporation of liquid in the cavity with high thermal conductivity walls is more intense,resulting in shorter waiting time and higher bubble departure frequency.

The‘New Normal’of Extreme Weather And the Urgency of Transformation“The era of global warming is over and the era of global boiling has arrived.”

Phong,a 42-year-old Vietnamese motorcyclist begins his busy day at 5 a.m.In Hanoi,light motorcycles are an important mode of transportation.Countless motorcycles shuttle through the streets and alleys of the city,transporting parcels,goods,and passengers to various destinations.Phong usually works for 12 hours straight with little rest.However,the unprecedented heat waves this summer had often pushed daytime temperatures to above 40 degrees Celsius,making it extremely difficult for Phong to complete his daily routine.Phong prepared a hat,a wet handkerchief,and more drinking water.He even installed a small umbrella above his mobile phone rack to prevent the phone from overheating in the sun because it is his only source of work.Despite all the equipment,he is still worried.“If I suffer heat stroke or anything else,I will be unable to work,”he said.“I can’t afford it.”

亚麻催化氧化与碱煮一浴脱胶工艺及其性能

使用棉纺系统进行亚麻纺纱前需经过脱胶处理,为解决传统碱脱胶工艺得到的亚麻纤维白度低和氧化脱胶时纤维易氧化受损、木质素残留造成纤维断裂伸长率低的问题,采用N-羟基-3,4,5,6-四苯基邻苯二甲酰亚胺(NHTPPI)催化氧化与碱煮一浴的方法对亚麻落麻进行脱胶,研究了pH值,反应温度以及催化剂NHTPPI、助催化剂9,10-蒽醌、双氧水、氢氧化钠质量浓度等因素对脱胶后亚麻纤维断裂强度以及白度的影响,得到了NHTPPI催化氧化与碱煮一浴亚麻脱胶的最佳工艺:pH值为10.5,反应温度为83.6℃,NHTPPI、9,10-蒽醌、双氧水、氢氧化钠质量浓度分别为0.6、0.5、10.35、5.67 g/L,此优化条件下得到的亚麻纤维断裂强度为4.39 cN/dtex,白度为70.53%。将催化氧化与碱煮一浴脱胶、高碘酸钠氧化脱胶以及传统碱脱胶与双氧水漂白3种工艺进行对比,发现3种工艺得到的纤维主体长度在28 mm左右,白度均在70%以上,但催化氧化与碱煮一浴脱胶得到的亚麻纤维断裂强度最高,处理时间最短。

大竹蛏营养组成、呈味特性和体外抗氧化活性研究

为实现大竹蛏资源的高效、综合开发利用,以大竹蛏鲜肉(fresh Solen grandis meat,FSGM)、煮肉(boiled Solen grandis meat,BSGM)和煮液(Solen grandis boiling liquid,SGBL)为研究对象,对其营养组成、呈味特性和抗氧化活性进行分析比较。结果表明,新鲜大竹蛏出肉率为79.33%,煮后质量损失率为49.89%;FSGM蛋白质含量为(11.55±0.34)%,总糖含量最低,为(0.46±0.00)%;煮后蛋白质和灰分损失最大,BSGM中蛋白质、脂肪和总糖相对含量分别为(19.33±0.33)%、(1.59±0.09)%、(0.83±0.01)%;SGBL中干物质仅占2.90%,其中41.72%为蛋白质;FSGM和BSGM中18种氨基酸总量分别为(52.15±0.50)g/100 g和(64.04±0.06)g/100 g,谷氨酸含量最高,呈味氨基酸占比分别为(47.44±0.35)%、(47.80±0.05)%,FSGM和BSGM的第一限制氨基酸均为蛋氨酸+半胱氨酸,SGBL的第一限制氨基酸为色氨酸;FSGM和BSGM中均检测出16种脂肪酸,PUFA占比分别为(36.98±0.33)%和(28.57±0.15)%,SGBL中6种脂肪酸均为饱和脂肪酸;SGBL中牛磺酸含量最高,为(2073.93±56.90)mg/kg;FSGM和BSGM中均检测到10种单糖,葡萄糖和半乳糖二者之和占比分别为51.16%、66.69%,SGBL中95.20%的单糖为葡萄糖;SGBL游离氨基酸含量最高,为(10.68±0.06)g/100 g,其中39.83%为甘氨酸。BSGM中核苷酸总量最高,为(2388.04±99.57)g/kg,其中AMP含量最高,为(380.28±10.48)mg/kg;3组样品均检测到3种有机酸,绝大部分为酒石酸;经复合蛋白酶酶解的FSGM和经风味蛋白酶酶解的BSGM抗氧化活性最强。上述结果可为大竹蛏资源的进一步开发利用提供一定的理论参考和依据。

竖直互连小通道内流动沸腾传热强化机理分析

为推动流动沸腾技术在燃料电池散热领域的应用,该文以R141b为工质,对不同流速下的并联直通道及互连小通道内流动沸腾情况进行三维瞬态数值模拟。利用换热系数、基底温度及综合换热因子等参数对比各结构的换热性能,并探究互连小通道的换热强化机理。研究表明:换热趋势随气泡行为呈周期性变化,气泡脱离时的换热效果最佳;由连通口引发的二次流促进热量传递与壁温升高,使通道可提前2 ms满足成核条件,且气泡在10^(-4) m/s以上的二次流速作用下率先脱离;五连通通道的换热系数较并联直通道可提升19.6%~23.3%,继续增加连通口数,换热系数的相对增长率均不足3.5%;涡结构使压降随连通口数增加而增大,且增势并不减弱,八连通通道的压降较并联直通道增加29.5%~42%。可见,二次流在影响气泡行为、强化换热的同时也带来压力损失,综合换热性能与连通口数目不成正相关。

熬煮条件对鸡汤中低聚肽含量和感官品质的影响

为探究熬煮条件对鸡汤品质的影响,文章使用微量双缩脲法测定鸡汤中低聚肽含量,并结合感官评分等指标探究低温煮、超声波低温煮和常压蒸煮对鸡汤品质的影响。结果表明,超声波低温煮的低聚肽含量远远高于低温煮和常压蒸煮,并且3种加工方式的低聚肽含量都呈现逐渐上升的趋势。超声波低温煮在90℃熬制3 h时低聚肽含量达到最高,为0.90 mg/mL;低温煮在90℃熬制9 h时低聚肽含量达到最高,为0.751 mg/mL;常压蒸煮在熬制3 h时低聚肽含量达到最高,为0.747 mg/mL。由感官评价结果可知,超声波低温煮在80℃熬制2 h时感官评分达到最高,为92.8分;低温煮在90℃熬制6 h时感官评分达到最高,为92.4分;常压蒸煮在熬制2 h时感官评分达到最高,为90.6分。

超低甲醛释放木质素基胶黏剂的制备及应用

针对脲醛树脂耐水、耐候性能差和潜在甲醛释放的问题,以工业碱木质素(L)为原料,通过与苯酚(P)、尿素(U)和甲醛(F)共缩聚反应制备了符合ENF级Ⅰ类胶合板要求的木质素基胶黏剂(LPUs)。考察了L、P和U质量比对LPUs凝胶时间、游离甲醛含量、储存稳定性、固化反应活性以及胶合板理化性能的影响。结果表明:mL/(mP+mU)为1∶1时制备的树脂LPU1~LPU4中,随着尿素用量的增加,LPUs树脂的凝胶时间逐渐缩短,m(P)∶m(U)=30∶70时制备的LPU4,其凝胶时间为(18±2)min,约为LPU1(m(P)∶m(U)=90∶10)的凝胶时间(30±2)min的40%,游离甲醛含量从0.05%(LPU1)升高至0.18%,储存期由127 d缩短至14 d,表现出脲醛树脂的理化特性。DSC监测固化过程焓变行为表明,LPUs树脂反应活化能仅为商业酚醛树脂和脲醛树脂的2%~7.8%。mL/(mP+mU)=1且苯酚用量不低于尿素时制备的LPU1~LPU3树脂胶合板耐沸水胶合强度和甲醛释放量满足ENF级Ⅰ类胶合板要求,其中LPU2树脂的施胶量可降低至工业生产工艺的66.7%,此时,依然可以确保胶合板的耐沸水胶合强度和甲醛释放量满足ENF级Ⅰ类要求,可有效降低胶合板生产成本。

高钙镁钛精矿沸腾氯化制备TiCl_(4)的热力学及动力学

针对高钙镁钛精矿难以满足沸腾氯化制备四氯化钛工艺问题,从热力学和动力学角度对高钙镁钛原料碳热还原—沸腾氯化制备TiCl_(4)工艺进行了深入研究。结果表明:钛精矿高温碳热还原历程为:FeTiO_(3)→TiO_(2)+Fe→Ti_(n)O_(2) n-1(n=4~9)+Fe→Ti_(3)O_(5)+Fe→Ti_(2)O_(3)+Fe→TiC_(x)O_(1-x)+Fe,碳氧钛生成的温度必须高于1400℃,此时钛精矿中的Ca、Mg、Al、Si、Mn等杂质元素在1800℃以内都不会被还原为对应的碳化物;高钙镁钛铁矿精矿碳热还原制备碳氧钛过程中,失重率随温度升高呈现4阶段上升,其中阶段1和3分别为受扩散控制生成金属Fe和碳氧钛的快速失重段,而阶段2和4分别为金属Fe和碳氧钛形核长大的缓慢失重阶段,4个阶段的表观活化能分别为49.84、-2.24、12.82、-2.53 kJ mol。沸腾氯化过程还原产物中的Fe、MgO和CaO均会优先被氯气氯化,但当存在TiO_(2)时,SiO_(2)和Al_(2)O_(3)则不易被氯化,碳氧钛较适宜沸腾氯化的温度为300~650℃,沸腾氯化前5分钟为还原产物中碳氧钛的快速氯化阶段,主要受表面化学反应的控制,而后5~20分钟为Ti_(2)O_(3)的缓慢氯化阶段,主要受颗粒内部扩散控制的影响。

不同压力蒸煮对中国菰米淀粉结构及理化特性的影响

以中国菰米淀粉为原料,利用扫描电镜、X射线衍射仪、傅里叶红外光谱仪检测在常压蒸煮、高压蒸煮条件下菰米淀粉的晶体结构,并分析其热稳定性、凝沉特性及消化特性,探究其在不同条件处理下晶体结构和理化性质的变化。结果表明:蒸制处理后,淀粉的表观形貌、晶体结构、短程有序性、粒径大小无显著变化,蒸制提高了淀粉的糊化峰值温度、老化程度,降低了相对结晶度和热焓值。高压处理可促进淀粉老化,利于提高淀粉抗消化性。煮制处理后,淀粉结构破损严重,晶体结构由有序向无序转变,糊化后无明显的凝沉特性,粒径显著降低。经蒸煮处理后,淀粉慢消化淀粉含量显著提升,利于维持血糖平衡。

二元堤基结构堤防管涌机理模型试验

为了科学解释二元堤基结构堤防管涌致灾机制并揭示其形成、演化过程和致溃规律,在考虑堤基强、弱透水层之间壤土过渡层作用的基础上,通过室内模型试验完整地模拟了二元堤基管涌从单个泡泉发展至管涌群并最终造成堤基塌陷溃决的全过程。试验结果表明:上部黏土及壤土层在渗流的顶托作用下向上隆起并在堤基内部产生层间水平渗漏通道,导致发生潜层砂沸,最终向上发展为表面砂沸的渗透破坏;二元堤基结构管涌发展可分为裂缝发展、潜层破坏、上覆层破坏、管涌通道上溯、堤基破坏和堤基溃决6个发展阶段;表面砂沸由潜层砂沸发展而来,潜层砂沸是由于土层内竖向坡降所引起的渗流力大于上部土体浮容重时造成的土层结构破坏所致,临界竖向坡降处于0.9~1之间;壤土层的存在会加快堤后自由边界区域管涌群的发展速度,但可以延缓管涌通道的上溯,对堤基具有保护作用。

硇砂传统炮制工艺与京帮炮制经验探讨

探讨了硇砂的传统炮制工艺以及京帮炮制的经验。硇砂临床效果显著,但由于不良反应大限制了其应用。古人对硇砂的炮制解毒进行了深入研究,包括对硇砂毒性的认识、净制法、炖法、煮法、煅制法等。京帮炮制硇砂的经验遵从古法,分为炖法与煮法两种,均属现代中药炮制的提净法。京帮醋制硇砂过程中需要注意制作的季节、所用器具、火候的控制、醋的选择等工艺细节。通过对硇砂的传统炮制工艺以及京帮炮制的经验的探讨,对硇砂的现代研究有借鉴意义。