Effects of total pressures and equivalence ratios on kerosene/air rotating detonation engines using a paralleling CE/SE method

In this paper,the kerosene/air rotating detonation engines(RDE)are numerically investigated,and the emphasis is laid on the effects of total pressures and equivalence ratios on the operation characteristics of RDE including the initiation,instabilities,and propulsive performance.A hybrid MPI t OpenMP parallel computing model is applied and it is proved to be able to obtain a more effective parallel performance on high performance computing(HPC)systems.A series of cases with the total pressure of 1 MPa,1.5 MPa,2 MPa,and the equivalence ratio of 0.9,1,1.4 are simulated.On one hand,the total pressure shows a significant impact on the instabilities of rotating detonation waves.The instability phenomenon is observed in cases with low total pressure(1 MPa)and weakened with the increase of the total pressure.The total pressure has a small impact on the detonation wave velocity and the specific impulse.On the other hand,the equivalence ratio shows a negligible influence on the instabilities,while it affects the ignition process and accounts for the detonation velocity deficit.It is more difficult to initiate rotating detonation waves directly in the lean fuel operation condition.Little difference was observed in the thrust with different equivalence ratios of 0.9,1,and 1.4.The highest specific impulse was obtained in the lean fuel cases,which is around 2700 s.The findings could provide insights into the understanding of the operation characteristics of kerosene/air RDE.

Design and application of an air-cooled probe for total pressure measurement at combustor outlet

An air-cooled probe was designed for measurement of total pressure at combustor outlet;its cooling scheme combined the film cooling and convection cooling.With the aid of CFD technique,cooling effectiveness of the coolant jets at various blow ratios was compared;suitable blow ratios and configuration of film holes were chosen accordingly.The overall cooling performance of the probe was evaluated via CFD technique,the design was improved according to the simulation result,and the cooling effect of the leading edge was obviously strengthened by increasing the local coolant mass flow rate.The results of wind tunnel test indicated that,between Mach numbers 0.2 and 0.4,the probe achieved a high accuracy at various attack angles.The probe was utilized in an annular combustor rig test,the highest temperature reached 1 760 Kand total pressure reaches 1 036 kPa.The result of rig test demonstrates that the coolant film distribution consistent appropriately with the CFD results.

Effects of Gamma-Ray Irradiation on Dielectric Surface Breakdown of Polybutylene Naphthalate and Polybutylene Terephthalate Under Reduced Pressure

With the increasing application of electric and electronic devices in space and nuclear power stations, the polymeric insulation materials are inevitably exposed to various kinds of environments. Accordingly, it becomes necessary to investigate the effects of the radiation and air pressure on insulation materials. This paper describes the effects of gamma-ray irradiation and reduced pressure on dielectric breakdown of polybutylene naphthalate (PBN) and polybutylene terephthalate (PBT) by applying a DC pulse voltage. Both PBN and PBT were irradiated in air up to 100 kGy and then up to 1 000 kGy with a dose rate of 10 kGy/h by using a60Co gamma-source. The effects of total dose and reduced pressure on the time to dielectric breakdown and discharge quantity were discussed. Obtained results show that, while increasing the total dose, the discharge quantity decreased with PBN, but increased with PBT. With decreasing the air pressure, the discharge quantity increased with PBN, but decreased with PBT. With increasing the total dose, the time to dielectric breakdown increased with PBN, but decreased with PBT. With decreasing the air pressure, the time to dielectric breakdown increased with both PBN and PBT. The experimental results suggest that the chemical structure of polybutylene polymers plays a main role in the result of radiation reaction, which is related to cross-linking and degradation reaction.

真空预冷对采后娃娃菜流通及货架品质的影响

为优选娃娃菜真空预冷的处理条件,维持采后娃娃菜的新鲜品质,在分析不同真空预冷终温(0、2和4℃)和不同真空预冷终压(400、600、800和1000 Pa)对采后娃娃菜预冷效果的基础上,进行了二因素三水平的中心复合响应面试验。结果显示,与不经预冷处理的对照和终温0℃的预冷组相比,在终压600 Pa条件下,2~4℃的预冷终温处理可更好地维持采后娃娃菜的外观品质,抑制其呼吸速率和丙二醛(MDA)含量的升高。在终温2℃条件下,与不经预冷处理的对照和终压1000 Pa的预冷组相比,400~800 Pa的预冷终压处理可更好地维持采后娃娃菜的外观品质,抑制其呼吸速率及MDA含量的升高。进一步的中心复合响应面试验结果显示,采后娃娃菜的真空预冷最优条件为终温4.0℃、终压600 Pa,该真空预冷条件不仅可维持采后娃娃菜的较好品质,而且可使活性物质可溶性蛋白、总酚和抗坏血酸的含量分别提高18.78%、18.47%和33.23%。因此,适宜的真空预冷处理是一种极具潜力的商品化处理技术,能有效维持采后娃娃菜在流通及货架期间的良好品质。

总温总压组合式受感器设计

由于一般总温传感器体积大、功能单一,不能适应小型飞行器安装使用,因此设计了一种小型总温总压组合式受感器。其中,对受感器外形结构、屏蔽罩、密封结构等进行设计,并设计一种温度压力一体式敏感组件,采用玻璃烧结工艺解决敏感组件的耐高温、密封、绝缘等关键技术。通过Fluent流体仿真软件对受感器流场进行模拟仿真,分析引压管对受感器内部流场的影响,结合仿真结果对受感器进行优化设计。经风洞试验校准,在Ma=0.3至Ma=0.9范围内,受感器总温恢复系数≥0.970;Ma=0.3(高度H=0)条件下,受感器时间常数小于0.9 s。1 MPa压力条件下进行气密性测试,1 min内压力下降不超过300 Pa;在Ma=0.3至Ma=1.0范围内总压误差优于±0.02,达到较高的技术指标要求。

不同负荷工况下660 MW循环流化床锅炉脱硝特性研究

为揭示不同负荷下循环流化床的运行特性,以某660 MW循环流化床锅炉为研究对象,在满负荷、75%负荷下,具体研究床温波动、风量配比、烟气含氧量和风煤配比对选择性非催化还原(selective non-catalytic reduction,SNCR)技术喷氨量和脱硝效果的影响。结果表明:满负荷运行时,在欠氧区,SNCR投射喷氨量与循环流化床锅炉给煤量保持同向变化趋势,若持续提高喷氨量,会导致氨逃逸较大,降低SNCR脱硝能力;当炉内给煤量保持稳定,在欠氧还原区内,适当提高二次风量(含氧量),会促进挥发分N的还原反应。75%负荷运行时,床温波动范围超过110℃时,为了满足脱硝要求,应适当提高一次风量、降低二次风量和喷氨量;床温波动范围低于50℃时,应适当降低一次风量和喷氨量;床温波动范围在50~100℃时,应适当降低二次风量和喷氨量;欠氧区内,喷氨量随总给煤量增多而增大。研究结果可以指导循环流化床优化运行,减少氮氧化物排放。

双洞隧道单斜井多掌子面风仓气动性能优化设计

为解决传统管道式通风在长大隧道大角度弯折处有较大局部阻力与风力损失的弊端,以西十高铁西岭隧道3#斜井为工程背景,提出风仓式通风方案,确定风仓接力轴流风机工作流量。采用控制变量法,以风仓进出风口、全压和风仓内风流平顺度为设计目标,以风仓隔板长度、风仓进出口位置为设计变量,基于Box-Behnken试验设计,进行风仓气动性能数值计算,得到各参数对风仓气动性能的影响顺序,最终确定风仓最优尺寸参数组合。研究结果表明:优化后风仓2个出口全压值基本相等,风机协调性好,风流场较均匀稳定,可有效缓解风仓内涡团现象。

月均气温对三叶青林下容器栽培苗光合特性及其块根总黄酮含量的影响

文章比较了2015—2019年五府山月均气温对三叶青林下容器栽培苗光合生理及其块根总黄酮含量的影响。结果表明,2015—2019年,五府山1月的气温最低,2—6月气温逐渐提升,7—8月气温达到最高值,9—12月气温逐渐下降。随着1—6月气温逐渐提高,五府山三叶青林下容器栽培苗叶绿素含量SPAD值、净光合速率(P_(n))、气孔导度(G_(s))、蒸腾速率(T_(r))、气孔限制值(L_(s))、瞬时羧化速率(CUE)、初始荧光(F_(o))、最大荧光(F_(m))、光下最小荧光(F′_(o))、光下最大荧光(F′_(m))、稳态荧光(F_(s))、PSⅡ最大光能转化效率(F_(v)/F_(m))、PSⅡ潜在光化学效率(F_(v)/F_(o))、PSⅡ实际光化学效率(ΦPSⅡ)、开放的PSⅡ反应中心捕获激发能效率(F′_(v)/F′_(m))、光化学淬灭系数(q P)和块根总黄酮含量显著提高(P<0.05),胞间CO 2浓度(C_(i))、水分利用效率(WUE)和非光化学淬灭系数(NPQ)显著下降(P<0.05);气温在7—8月达到最高值,五府山三叶青林下容器栽培苗叶绿素含量SPAD值、P_(n)、G_(s)、T_(r)、L_(s)、CUE、F_(o)、F_(m)、F′_(o)、F′_(m)、F_(s)、F_(v)/F_(m)、F_(v)/F_(o)、ΦPSⅡ、F′_(v)/F′_(m)、q P和块根总黄酮含量达到最大值,C_(i)、WUE和NPQ达到最低值;9—12月气温逐渐下降,五府山三叶青林下容器栽培苗叶绿素含量SPAD值、P_(n)、G_(s)、T_(r)、L_(s)、CUE、F_(o)、F_(m)、F′_(o)、F′_(m)、F_(s)、F_(v)/F_(m)、F_(v)/F_(o)、ΦPSⅡ、F′_(v)/F′_(m)、q P和块根总黄酮含量显著下降(P<0.05),C_(i)、WUE和NPQ显著提高(P<0.05)。本试验结果可为三叶青林下容器生态栽培提供气象因子(气温)依据。

低速大迎角进气道流场测试风洞试验研究

为满足某型飞机低速大迎角飞行试验进气道测试需求,研制集稳态总压、动态总压、稳态静压于一体的复合式进气道流场测量耙,为了分析评估不同形式测量耙探针的参数测量准确性,进行全尺寸的测量耙风洞试验,对试验数据进行分析,研究测量耙不同探针总压损失的角度特性和速度特性,为后续测量耙探针选型提供支持。

外界因素对玻璃钢制品TVOC释放变化的影响研究

以家具行业中广泛使用的玻璃钢制品为研究对象,利用环境舱法探究了其TVOC(总挥发性有机化合物)释放速率随时间、温度、相对湿度和气体交换率变化的释放规律。结果表明,玻璃钢制品中TVOC释放速率随时间变化符合一阶衰减模型,相关性良好;同时,提高温度、相对湿度和气体交换率可加速玻璃钢制品中TVOC的释放,释放初期影响显著,后期影响减弱。此外,针对玻璃钢制品的经济实用处理措施为:短时间增温、增湿、增大气体交换率的烘烤通风后,室外继续通风凉放15 d时间,这为提升玻璃钢制品环保性能提供了可靠参考数据。

马钢1#高炉炉况波动处理生产实践

针对马钢1#高炉炉芯温度持续下降,高炉全压差水平偏高,对炉况进行调整过程中,炉况出现大幅波动,进行干湿焦转换后炉况下滑严重,气流周向分布不匀,炉缸活跃性持续下降。为解决炉墙周向气流分布不均匀,改善炉缸工作状态,采用锰矿及萤石进行洗炉等恢复炉况,炉况好转后,逐步捅开长堵风口恢复炉况,风量、氧量恢复至4 900 m^(3)/min、9 000 m^(3)/h,负荷4.3,产量6 200 t/d,此次炉况波动,因后续采取的措施及时果断,炉况恶化趋势得到有效遏制并恢复。

大温差水系统在高性能空调系统中的应用

常规空调水系统设计中,供回水温差通常为5℃。介绍一种大温差水系统,用于空调冷冻水和冷却水系统,通过大温差和常规5℃温差对比,阐述大温差可以减少空调系统总能耗及配套设备投资的优势,对比大温差对末端设备制冷的影响,旨在为打造高性能空调系统提供思路,降低空调系统的整体能耗。

关于变频多联机APF能效试验中针对低温制冷实测时准确性的检讨和建议

目前我国多联机变频空调机组均采用全年性能系数(APF)替代IPLV作为评价指标。基于现有多联变频空调器的调节范围广的特点,指出了现有APF中对于选择性试验即低温制冷工况实测时,会出现不符合实际的情况,利用实测数据和理论分析产生的原因,水平展开,并给出了针对实测的改进建议。

Probe design for measuring total temperature of combustor outlet based on water cooling

To obtain the outlet temperature of combustor,a kind of high-temperature and water cooling thermocouple was designed.The main factors affecting the results of thermocouple measurement were analyzed after numerical simulation.Results showed that the high-temperature water cooling thermocouple can achieve high temperature measurement under the condition of 2 400 K.With the increase of the distance between the water cooling structure and the stagnation cover,the temperature measurement result was more accurate,and the increase in the area ratio of the inlet and outlet of the stagnation cover within a reasonable range can make the measurement results more accurate.The surface emissivity of the measuring point had a great influence on the radiation error.The pressure and flow rate of cooling water can be effectively reduced after adding zirconia coating onto the surface of the rake body.

Relating Fish Hg to Variations in Sediment Hg, Climate and Atmospheric Deposition

This article addresses total fish Hg concentrations (THg) by variations in lake Sediment THg, atmospheric Hg deposition (atmHgdep), and climate, i.e., mean annual precipitation (ppt) and air temperature. The Fish THg data were taken from the 1967-to-2010 Fish Mercury Datalayer (FIMDAC). This compilation was standardized for 12-cm long Yellow Perch in accordance with the USGS National Descriptive Model for Mercury in Fish (NDMMF [1]), and documents Fish THg across 1936 non-contaminated lakes in Canada. About 40% of the standardized Fish THg variations related positively to increasing ppt and Sediment THg, but negatively to increasing mean annual July temperature (TJuly). Only 20% of the Fish THg variations related positively to atmHgdep alone. Increasing TJuly likely influences Fish Hg through increased lake and upslope Hg volatilization, in-fish growth dilution, and temperature-induced demethylization. FIMDAC Fish THg effectively did not change over time while atmHgdep decreased. Similarly, the above Fish Hg trends would likely not change much based on projecting the above observations into the future using current 2070 climate-change projections across Canada and the continental US. Regionally, the projected changes in Fish Hg would mostly increase with increasing ppt. Additional not-yet mapped increases are expected to occur in subarctic regions subject to increasing permafrost decline. Locally, Fish THg would continue to be affected by upwind and upslope pollution sources, and by lake-by-lake changes in water aeration and rates of lake-water inversions.

机头波纹度对全静压探头测孔压强的影响

准确掌握飞机机头波纹度对全静压探头周围绕流及测孔压强的影响规律,对于提高飞机高度测量系统自身精度及其误差分析具有重要意义。采用计算流体力学方法,开展了机头波纹度对全静压探头测孔压强的影响规律研究。针对单独探头构型,进行了数值模拟方法的验证。针对单独机头构型,研究了波纹度对探头预安装位置附近的空间区域压强的影响规律。针对探头与理论机头和波纹度机头的组合构型,研究了波纹度对全静压探头绕流及测孔处压强的影响规律。结果表明:数值模拟方法能够满足机头全静压探头流场的数值模拟要求;波纹度对探头测孔处压强系数的影响变化量随着马赫数增加而增加;当马赫数固定时,波纹度的影响在第一组测压孔处随迎角增大而减弱,而在第二组测压孔处随迎角增大先增加再减弱。

罐采样-加压进样-气相色谱法测定环境空气中非甲烷总烃研究

建立了罐采样-气相色谱法测定环境空气中非甲烷总烃的分析方法。用罐采集环境空气样品至微负压状态,经除烃空气加压后,用气相色谱仪进行分析。并对氮气空白、除烃空气、样品保存期限、不同压力进样、不同正压压力进样、不同湿度、不同种类物质对总烃的贡献等进行了研究,在最佳实验条件下,非甲烷总烃的方法检出限为0.04μmol/mol,标准曲线相关系数均大于0.999 5,低、中、高浓度水平测定结果相对标准偏差均小于2.0%,低、中、高浓度的质控样品相对误差均小于2.0%。利用该方法对环境空气样品进行了检测分析,该法完全满足国家标准质控的要求,适用于环境空气和污染源无组织废气中非甲烷总烃的准确测定。

空气膨化关键工艺对青稞藜麦姜米茶品质的影响

本试验以青稞、藜麦为主原料,研制出了青稞藜麦姜米茶。通过单因素试验,研究了空气膨化温度和时间对青稞藜麦姜米茶总酚含量、体外降血糖活性和感官品质的影响。结果表明:青稞藜麦姜米茶制备的最佳工艺条件为空气膨化温度180℃,空气膨化时间10 min。在最佳工艺条件下制备的青稞藜麦姜米茶,汤色清澈透亮,茶味清香,鲜醇甘爽,此时青稞藜麦姜米茶的品质最好。

Experimental study on pressure and temperature distributions for low mass flux steam jet in subcooled water

A low mass flux steam jet in subcooled water was experimentally investigated.The transition of flow pattern from stable jet to condensation oscillation was observed at relatively high water temperature.The axial total pressures,the axial and radial temperature distributions were measured in the jet region.The results indicated that the pressure and temperature distributions were mainly influenced by the water temperature.The correlations corrected with water temperature were given to predict the dimen-sionless axial pressure peak distance and axial temperature distributions in the jet region,the results showed a good agreement between the predictions and experiments.Moreover,the self-similarity property of the radial temperature was obtained,which agreed well with Gauss distribution.In present work,all the dimensionless properties were mainly dependent on the water temperature but weakly on the nozzle size under a certain steam mass flux.

空气压力波治疗仪在预防全膝关节置换患者深静脉血栓中的应用

目的探讨空气压力波治疗仪不同使用频率及时间对全膝关节置换术后患者深静脉血栓(deep vein thrombosis,DVT)的预防效果。方法选取2018年1月至2020年12月在海军军医大学第三附属医院骨科行全膝关节置换的患者96例,随机分为A、B、C 3组,每组32例,A为主动功能锻炼组,B、C组在A组干预基础上,从术后第1天开始进行空气压力波治疗,B组每天治疗2次,每次30 min,C组每天治疗2次,每次60 min。比较3组患者DVT的发生率、患侧肿胀程度及血浆D-二聚体水平。结果干预第3天、第7天,B、C组患肢肿胀程度小于A组,差异有统计学意义(P<0.05);干预后B、C组血浆D-二聚体降低幅度明显,与A组比较差异有统计学意义(P<0.05);C组与A组下肢DVT发生率比较差异有统计学意义(P<0.05)。结论空气压力波治疗仪可以减轻全膝关节置换患者的患肢肿胀程度,降低D-二聚体水平,有效预防全膝关节置换术后DVT的发生。在患者耐受范围内,相同治疗频率治疗时间长则效果更佳。