Gas Film Disturbance Characteristics Analysis of High-Speed and High-Pressure Dry Gas Seal

The dry gas seal（DGS） has been widely used in high parameters centrifugal compressor, but the intense vibrations of shafting, especially in high-speed condition, usually result in DGS＇s failure. So the DGS＇s ability of resisting outside interference has become a determining factor of the further development of centrifugal compressor. However, the systematic researches of which about gas film disturbance characteristics of high parameters DGS are very little. In order to study gas film disturbance characteristics of high-speed and high-pressure spiral groove dry gas seal（S-DGS） with a flexibly mounted stator, rotor axial runout and misalignment are taken into consideration, and the finite difference method and analytical method are used to analyze the influence of gas film thickness disturbance on sealing performance parameters, what＇s more, the effects of many key factors on gas film thickness disturbance are systematically investigated. The results show that, when sealed pressure is 10.1MPa and seal face average linear velocity is 107.3 m/s, gas film thickness disturbance has a significant effect on leakage rate, but has relatively litter effect on open force; Excessively large excitation amplitude or excessively high excitation frequency can lead to severe gas film thickness disturbance; And it is beneficial to assure a smaller gas film thickness disturbance when the stator material density is between 3.1 g/cm3 to 8.4 g/cm3; Ensuring sealing performance while minimizing support axial stiffness and support axial damping can help to improve dynamic tracking property of dry gas seal. The proposed research provides the instruction to optimize dynamic tracking property of the DGS.

Impact of Mid-and Upper-Level Dry Air on Tropical Cyclone Genesis and Intensification:A Modeling Study of Durian(2001)

The impact of mid-and upper-level dry air,represented by low relative humidity(RH)values,on the genesis of tropical cyclone(TC)Durian(2001)in the South China Sea was investigated by a series of numerical experiments using the Weather Research and Forecasting model.The mid-level RH was lowered in different regions relative to TC Durian(2001)’s genesis location.Results suggest that the location of dry air was important to Durian(2001)’s genesis and intensification.The rapid development of the TC was accompanied by sustained near-saturated mid-and upper-level air,whereas low humidity decelerated its development.Water vapor budget analysis showed that moisture at mid and upper levels was mainly supplied by the vertical convergence of moisture flux and the divergence terms,and consumed by the condensation process.The horizontal convergence of moisture flux term supplied moisture in the air moistening process but consumed moisture in the air drying process.With a dryer mid-and upper-level environment,convective and stratiform precipitation were both inhibited.The upward mass fluxes and the diabatic heating rates associated with these two precipitation types were also suppressed.Generally,convection played the dominant role,since the impact of the stratiform process on vertical mass transportation and diabatic heating was much weaker.The vorticity budget showed that the negative vorticity convergence term,which was closely related to the inhibited convection,caused the vorticity to decrease above the lower troposphere in a dryer environment.The negative vorticity tendency is suggested to slow down the vertical coherence and the development rate of TCs.

Analysis and Modeling of Wangqing Oil Shale Drying Characteristics in a Novel Fluidized Bed Dryer with Asynchronous Rotating Air Distributor

In order to replace the conventional distributor, a novel asynchronous rotating air distributor, which can optimize the drying ability of fluidized bed and strengthen the drying performance of oil shale particles, is creatively designed in this study. The rotating speed of the asynchronous rotating air distributor with an embedded center disk and an encircling disk is regulated to achieve the different air supply conditions. The impacts of different drying conditions on the drying characteristic of Wangqing oil shale particles are studied with the help of electronic scales. The dynamics of experimental data is analyzed with 9 common drying models. The results indicate that the particles distribution in fluidized bed can be improved and the drying time can be reduced by decreasing the rotating speed of the embedded center disk and increasing the rotating speed of the encircling disk. The drying process of oil shale particles involves a rising drying rate period, a constant drying rate period and a falling drying rate period. Regulating the air distributor rotating speed reasonably will accelerate the shift of particles from the rising drying rate period to the falling drying rate period directly. The two-term model fits properly the oil shale particles drying simulation among 9 drying models at different air supply conditions. Yet the air absorbed in the particles' pores is diffused along with the moisture evaporation, and a small amount of moisture remains on the wall of fluidized bed in each experiment, thus, the values of drying simulation are less than the experimental values.

MECHANISM AND APPLICATION OF COAL DRY BENEFICIATION WITH AIR-DENSE MEDIUM FLUIDIZED BED

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EFFECT OF DRY COLD AIR ACTIVITY ON THE OFFSHORE RAPID INTENSIFICATION OF SUPER TYPHOON SAOMAI(2006): A NUMERICAL SIMULATION RESEARCH

Employing the mesoscale WRF(Weather Research and Forecast) model, Super Typhoon Saomai(2006) is simulated. The variation of track and intensity and its offshore rapid intensification process are well demonstrated by the model, and the temperature and humidity patterns associated with the dry cold air activity and their impact on and mechanism of the offshore rapid intensification of Saomai are mainly studied in this paper. The results indicate that high-resolution water vapor imagery can visually reveal the development, evolution, interaction as well as the mutual complementation of the dry cold air activity accompanied with the development of Saomai. The offshore rapid intensification phenomenon of Saomai is closely related to the dry cold air which originates from the upper- and mid-troposphere. Besides, the dry cold air from the upper troposphere is stronger than that from the mid-troposphere.Saomai intensifies as the dry cold air from the northwest moves toward its circulation but weakens when the dry cold air from the southwest is drawn into the storm. Dry cold airflows and their cold advection effect caused by the downward motion across the isentropic surface are favorable to the development of Saomai. The dry cold air always moves along an isentropic surface from the upper troposphere to the mid-troposphere around the typhoon circulation and contributes to Saomai's abrupt intensity change.

Artificial neural network techniques to predict the moisture ratio content during hot air drying and vacuum drying of Radix isatidis extract

Background:To predict the moisture ratio of Radix isatidis extract during drying.Methods:Artificial neural networks were designed using the MATLAB neural network toolbox to produce a moisture ratio prediction model of Radix isatidis extract during hot air drying and vacuum drying,where regression values and mean squared error were used as evaluation indexes to optimize the number of hidden layer nodes and determine the topological structure of artificial neural networks model.In addition,the drying curves for the different drying parameters were analyzed.Results:The optimal topological structure of the moisture ratio prediction model for hot air drying and vacuum drying of Radix isatidis extract were“4-9-1”and“5-9-1”respectively,and the regression values between the predicted value and the experimental value is close to 1.This indicates that it has a high prediction accuracy.The moisture ratio gradually decreases with an increase in the drying time,reducing the loading,initial moisture content,increasing the temperature,and pressure can shorten the drying time and improve the drying efficiency.Conclusion:Artificial neural networks technology has the advantages of rapid and accurate prediction,and can provide a theoretical basis and technical support for online prediction during the drying process of the extract.

Hot Air Drying and Quality of Red and White Varieties of Onion (Allium cepa)

This study was undertaken to investigate the drying characteristics of red and white varieties of onion (Allium cepa) in a convective dryer. The drying characteristics of onion slices were examined at air temperatures of 50℃, 60℃ and 70℃ and sample thicknesses of 2 mm. During the drying experiments, air velocity was held stable at 0.9 m/s. The effects of air temperature on the drying characteristics and quality parameters such as vitamins C and D, macro minerals (Mg, Na, P, Ca and K), non-enzymatic browning and thiolsulphinate of the dried onion slices were determined. For each of the plots of the drying curves from the mechanical drying tests, there was an absence of or just a very brief appearance of a constant rate period because onions are hygroscopic and hygroscopic foods tending to quickly enter the falling rate period;drying time decreased considerably with increased temperature. The time required to reduce the moisture content to any given value was dependent on the drying conditions, being the longest at an air temperature of 50℃, 0.9 m/s and the shortest at an air temperature of 70℃ and air velocity of 0.9 m/s. The loss of vitamin C, which is a thermo-sensitive compound, was the least at an air temperature of 50℃.

Characteristics of Dry Cold Air Intrusion in a Typical Strong Storm

Taking a typical strong storm in Guizhou on April 5, 2017 for example, the diagnosis analysis used the water vapor cloud and the initial field of EC thin grid, including physical quantity, surface and upper air meteorological observation, as well as radar observation data. For the environment parameter analysis, small CAPE value tended to underestimate storm intensity on potential forecast stage, strong vertical wind shear revealed the strong dry cold air was the important intensity factors of the storm. The water vapor cloud map can be used to monitor the most important features, the dry zone, the wet zone and the boundary between them. When dry intrusion is found, it can be used as one of the bases for the development of heavy rain. Dry cold air intrusion on high-level was traced by water vapor images. And in this process, the analyses revealed the role of dry cold air’s influence on intensity of the storm.

Indoor Environmental Quality of Air Conditioned Residential Buildings in Extreme Dry Desert Climate

In this study, the indoor environmental quality (IEQ) in air conditioned residential buildings in a dry desert climate is examined from the perspective of occupants via two aspects: thermal comfort and indoor air quality. The study presents statistical data about the domestic-occupant thermal comfort sensations together with data describing the indoor air quality in Kuwaiti residential buildings. With respect to the latter, the overall IEQ acceptance using two measurements namely: physical measurements and subjective information collected via questionnaires, was used to evaluate 111 occupants living in twenty five air-conditioned residential buildings in the state of Kuwait. The operative temperature based on Actual Mean Vote (AMV) and Predicted Mean Vote (PMV) was identified using linear regression analysis of responses on the ASHRAE seven-point thermal sensation scale and was found to be 25.2°C and 23.3°C, respectively, in the summer season. Indoor air quality (IAQ) with respect to carbon dioxide concentration level was compared with the acceptable limits of international standards, i.e. ASHRAE Standard 62.1 [1]. The proposed overall IEQ acceptance findings in residential buildings show CO2 concentration level between 909 and 1250 ppm. However, this may be considered a higher level of CO2 concentration, which may require increasing ventilation rate through window operation or mechanical ventilation.

Surface Roughness Evaluation in Dry-Cutting of Magnesium Alloy by Air Pressure Coolant

In this paper, a studying of surface roughness in dry milling with air pressure coolant of wrought magnesium alloy AZ31B will be carried out. The effects of air flow, feed-rate per tooth, cutting velocity and number of inserts in a cutting tool on surface roughness have been examined. Surface roughness increases with increasing feed-rate per tooth and increasing number of inserts in the cutting tool. However, it is nearly unchanged under a specific range of cutting velocity in the experiment and improved by the flow of air cooling.

Effect of different drying methods on the taste and volatile compounds,sensory characteristics of Takifugu obscurus

Pufferfish is prone to deterioration due to abundant nutrients and high moisture content.Drying technology can extend the shelf life and enhance the flavor quality of aquatic products.The study investigated the effect of hot air drying(HAD),microwave vacuum drying(MVD)and hot air assisted radio frequency drying(HARFD)on the taste and volatile profiles of Takifugu obscurus.Different drying methods had significant influence on the color,rehydration,5’-nucleotides,free amino acids and volatile components(P<0.05).The results showed that HAD and HARFD could promote the flavor of T.obscurus by producing higher equivalent umami concentration(EUC)values,which were about two times of MVD group,and more pronounced pleasant odor according to sensory analysis.HAD is more appropriate for industrial application than HARFD and MVD considering the economic benefits.This study could provide a reference for the industrial application of drying T.obscurus.

一步式QuEChERS-气相色谱-三重四极杆质谱法快速测定风干牦牛肉中15种N-亚硝胺

建立了一步式QuEChERS自动提取和净化技术结合气相色谱-串联质谱同时测定风干牦牛肉中15种N-亚硝胺的分析方法。样品水化后,经乙腈提取,加入4.0 g MgSO_(4)和1.0 g NaCl除水,经十八烷基硅烷(C_(18))和N-丙基乙二胺(PSA)填料净化,采用DB-HeavyWAX色谱柱(30 m×0.25 mm×0.25μm)分离15种N-亚硝胺,在多重反应监测(MRM)模式下进行测定,外标法定量。结果表明,15种N-亚硝胺分离性能良好,在0.1~200μg/L范围内线性关系良好,相关系数(r^(2))≥0.999 0;检出限(LOD)为0.05~0.20μg/kg,定量限(LOQ)为0.10~0.50μg/kg;在1倍、2倍和10倍LOQ 3个添加水平下的平均回收率分别为79.4%~102.1%、80.6%~109.5%、83.0%~110.6%,相对标准偏差(RSD)为0.8%~16.0%。应用建立的方法检测2种不同加工工艺的市售样品,其中7种N-亚硝胺类化合物(N-亚硝基二甲胺、N-亚硝基二异丁胺、N-亚硝基二正丁胺、N-亚硝基甲基苯胺、N-亚硝基乙基苯胺、N-亚硝基吡咯烷、N-亚硝基二苯胺)均有不同程度检出,平均含量为0.08~20.18μg/kg,且熟制风干牦牛肉中N-亚硝胺的检出率和平均含量均高于传统生制风干牦牛肉。该方法实现了前处理的自动化,相较于其他传统方法,操作简单,实验效率高,人为影响因素小,检测灵敏度高,适用于风干牦牛肉中15种N-亚硝胺的快速测定,为研究肉制品中N-亚硝胺的测定提供了方法支持。

切片厚度和护色处理对热风干燥雪花梨干品质的影响

采用热风干燥法制备雪花梨干。以色泽、硬度、弹性、咀嚼性、总酚、总黄酮、可溶性糖和感官评分为评价指标,考察切片厚度(3、4、5、6、7、8 mm)和护色处理(CaCl_(2)、NaCl、D-异抗坏血酸钠、柠檬酸溶液浸泡、热烫)对梨干品质的影响,并以Z-score(Z值)综合模型进行评价,优选出适宜的切片厚度和护色处理。结果表明:随着切片厚度的增加,梨干的颜色变深,硬度、弹性和咀嚼性增大,总酚和总黄酮含量降低,可溶性糖含量增加;Z-score综合模型评价结果显示,切片厚度为4 mm时,Z值总和最高。护色处理均能改善梨干色泽,提高总酚和总黄酮含量,但可溶性糖含量降低。D-异抗坏血酸钠处理组梨干的亮度值(L^(*))最高,红绿值(a^(*))和蓝黄值(b^(*))最低,色差值(ΔE)最小;CaCl_(2)处理提高了梨干的硬度;热烫处理降低了梨干的弹性和咀嚼性。Z-score综合模型评价结果显示,以0.8 g/100 mL D-异抗坏血酸钠溶液浸泡护色的Z值总和最高。综上,热风干燥制备雪花梨干的厚度和护色条件为:切片厚度4 mm、0.8 g/100 mL D-异抗坏血酸钠溶液浸泡10 min。

风干肉不同条件贮藏品质研究

目的:探究风干肉的加工优化方案及不同条件贮藏对风干肉品质的影响。方法:以风干肉猪肉为研究对象,探究不同包装方式、不同贮藏温度对风干肉贮藏特性的影响。结果:随着贮藏时间的延长,不同包装方式下的风干肉的过氧化值(Peroxidation Value,POV)和菌落总数呈现上升趋势,pH值先降低后升高。与普通包装相比,气调包装和真空包装可以较好地保持风干肉的质量,其中真空包装的风干肉贮藏时间更长。4℃贮藏的风干肉品质变化较为缓慢,25℃和40℃贮藏的风干肉品质变化加快,其中40℃贮藏的风干肉保质期最短。结论:风干肉采用真空包装在4℃下贮藏有利于保障风干肉的品质。

复配香辛料精油对鲶鱼肉风干肠品质及安全性的影响

为了探究不同的香辛料精油复配组合对鲶鱼肉风干肠品质及安全性的影响,在腌制好的鲶鱼肉馅中分别添加丁香精油和八角精油(CA组)、丁香精油和紫苏精油(CP组)、八角精油和紫苏精油(AP组)、丁香精油和八角精油和紫苏精油(CAP组),各种精油以质量比1∶1复配,添加量为肉馅质量的0.03%,搅匀后经灌肠、风干制成鲶鱼肉风干肠,以不添加香辛料精油组为对照(CK组)。对风干肠的水分含量、水分活度(a_(w))、pH值、色差、硫代巴比妥酸反应物(thiobarbituric acid reactive substance,TBARS)值、生物胺含量、N-亚硝胺含量、微生物数量进行测定,并对样品进行16SrDNA高通量测序分析。结果表明,AP组鲶鱼肉风干肠的水分含量为27.13%,a_(w)值为0.765。CA组的L*值和a*值较高,具有风干肠典型的外观。4个处理组的pH值均高于对照组,由高至低依次为CAP>AP>CA>CP。不同的精油复配组合在抑制脂肪氧化方面总体无显著差异(P>0.05),但均能显著降低风干肠的TBARS值(P<0.05)。AP组中生物胺和N-亚硝胺的含量较低,菌落总数、肠杆菌科数、气单胞菌数显著低于CK组(P<0.05)。高通量测序结果显示AP组和CAP组物种丰富度较低,且AP组中致病菌的相对丰度较低。综合分析,八角精油和紫苏精油复配(AP组)在改善鲶鱼肉风干肠品质和提高安全性方面效果优于其他组。

西藏传统风干牦牛肉中微生物群落组成及安全评价

为了揭示西藏传统风干牦牛肉中细菌和真菌群落组成及安全性,采用高通量测序技术对西藏林芝(LZ)、拉萨(LS)、山南(SN)、日喀则(RKZ)和那曲(NQ)地区的传统风干牦牛中细菌和真菌群落组成进行分析并探讨细菌和真菌的安全性。结果表明,西藏传统风干牦牛肉中富含丰富的微生物菌群,且细菌多于真菌;不同地区风干牦牛肉中微生物丰富度和多样性存在差异;不同地区风干牦牛肉样品中的主要优势细菌门是厚壁菌门(Firmicutes)、变形菌门(Proteobacteria)和放线菌门(Actinobacteria),主要优势真菌门是毛霉菌门(Mucoromycota)、子囊菌门(Ascomycota)和担子菌门(Basidiomycota);不同地区风干牦牛肉中的优势细菌属是假单胞菌属(Pseudomonas)、乳杆菌属(Lactobacillus)和片球菌属(Pediococcus),主要优势真菌属是根霉属(Rhizopus)和毛霉属(Mucor);不同地区风干牦牛肉中细菌和真菌群落组成存在差异。西藏传统风干牦牛肉中即存在功能性益生微生物菌群,又存在大量条件致病菌,具有一定的安全隐患。

无氟防水剂X-702M在化纤面料上的洗后晾干应用

研究了一款无氟聚氨酯防水剂X-702M在化纤面料上的洗后晾干防水性能。织物经过X-702M处理后的手抓痕较浅,且具有较柔软的手感。探讨了不同交联剂对化纤面料洗后晾干防水性能的影响。结果发现,交联剂AX-101Z洗后晾干的防水性能较好。当X-702M用量为50 g/L、AX-101Z用量为10 g/L时,织物具有较好的防水性能、洗后晾干防水性能、手抓痕、手感,在化纤面料上可以做到初期防水性能为5级(100分),洗涤5次后室温晾干防水性能达到3~4级(80~90分)。

‘赤霞珠’风干葡萄酒酿造工艺优化研究

目前我国对风干葡萄酒的研究处于起步阶段,酿造工艺还不完善,产品较少。试验以‘赤霞珠’葡萄为试材,以风干程度、酵母添加量、初始pH为影响因素,通过单因素结合响应面试验优化了‘赤霞珠’风干葡萄酒的酿造工艺。结果表明,本研究中‘赤霞珠’风干葡萄酒最佳酿造工艺条件为风干程度26.0%、初始pH3.7、酵母添加量210 mg·L^(-1)。在此条件下,酿造的‘赤霞珠’风干葡萄酒酒精度为15.5%,酒体清澈透亮、丰满协调、口感柔和、香气特征突出、余味绵长,感官评分达到93.50分。

Experiment research on grain drying process in the heat pump assisted fluidized beds

A heat pump assisted fluidized bed grain drying experimental system wasdeveloped. Based on this system, a serial of experiments was performed under four kinds of air cycleconditions. According to the experimental analysis, an appropriate drying medium-air cycle for theheat pump assisted fluidized bed drying equipment was decided, which is different from the commonlyused heat pump assisted drying system. The experimental results concerning the drying operationperformance of the new system show that the averaged coefficient of performance (COP) can reach morethan 2.5. The economical evaluation was performed and the power consumption for removing a kilogramwater from grains was about 0.485 kW-h/kg (H_2O), which shows its reasonable commercial efficiencyand great application potentiality in future market.

Prevalence and risk factors of dry eye disease in young and middle-aged office employee:a Xi’an Study

AIM:To estimate the prevalence of and risk factors for dry eye disease(DED)in young and middle-aged office employee in Xi’an.METHODS:This cross-sectional study of the prevalence of and risk factors for DED investigated 486 young and middle-aged Chinese office employee in Xi’an.DED symptoms and potential risk factors were assessed using the ocular surface disease index combined with a risk factors questionnaire,and tear function was evaluated using the tear film break-up time and Schirmer’s test.Possible risk factors for DED were estimated by binary Logistic regression analysis.RESULTS:DED was diagnosed in 100 females and 96 males,giving a prevalence of 40.3%[95%confidence interval(CI)=36.0%-44.7%].The multivariate binary Logistic regression model indicated that the possible risk factors for DED were being female(OR=1.592,95%CI=1.034-2.451,P=0.035),being aged≥40 y(OR=1.593,95%CI=1.034-2.454,P=0.035),using a VDT daily for>6 h(OR=1.990,95%CI=1.334-2.971,P=0.001),the presence of central air conditioning(OR=1.548,95%CI=1.053-2.276,P=0.026),and self-reported dryness of the mouth and nose(OR=1.589,95%CI=1.071-2.357,P=0.021).CONCLUSION:There is a high prevalence of clinically diagnosed DED in young and middle-aged video displayterminal(VDT)users.Interventions against the modifiable risk factors should be taken to prevent the occurrence and development of DED in this population.