Structural, Pasting, and Thermal Properties of Ultra-high Pressure-treated Lotus Seed Starch

Lotus seed starch （15%, w/w） was subjected to ultra-high pressure （UHP） at 500 MPa for 10～60 min. The effects of UHP on the structural, pasting, and thermal properties of starch were investigated using solid-state 13C CP/MAS NMR, differential scanning calorimetry （DSC）, HPSEC-MALLS-RI, and a rapid visco analyzer. The 13C CP/MAS NMR results revealed a reduction in the relative crystallinity and peak intensity of the crystalline state with increasing the UHP time. The molecular weight of native starch was 1.433 × 107 Da, which was higher than that of the UHP-treated starch. Viscograms of UHP-treated starch revealed an increase in paste viscosity, peak time, and pasting temperature and a reduction in breakdown and setback viscosity compared to the native starch. Furthermore, the DSC results showed a reduction in gelatinization temperature and gelatinization enthalpy with increasing the UHP time.

Effects of ultra-high hydrostatic pressure on foaming and physical-chemistry properties of egg white

The influences of ultra-high hydrostatic pressure treatment on foaming and physical properties (solubility, hydrophobicity and sulfhydryl content) of egg white were investigated. A pressure range of 0-500 MPa, time range of 0-20 min and pH range of 7.5-8.5 were selected. The foaming property of egg white is improved by 350Mpa and 10min. The treatment resulted in in- crease of sulfhydryl content of egg white, while solubility and hydrophobicity were significantly decreased.

Enzymatic Hydrolysis of Hairtail Surimi in an Ultra-High Pressure Bioreactor

Amino acids have been extracted from Hairtail surimi using enzymes in an ultra-high pressure bioreactor. The extraction efficiency of different enzymes including papain, trypsin, and proteases (acid, neutral, alkaline) also has been evaluated, and it has been discovered that neutral protease behaved the best. The amino acids were analyzed using automatic amino acid analyzer, and the enzymatic digestion conditions were optimized. For neutral protease, the optimal condition was 50℃, 250 MPa, pH 7.0. Material to liquid ratio of enzyme is 6%. More than 29 amino acids were detected after 24 hours of hydrolysis;the enzymatic hydrolysis rate can reach 83.29%. The results show that enzymatic digestion under ultra-high-pressure provides a very promising approach to extract amino acids from Hairtail surimi.

THERMAL MODELLING OF COLLISIONAL OROGENY: IMPLICATIONS FOR THE ULTRA-HIGH PRESSURE METAMORPHISM

The petrological research on the ultra high pressure metamorphism (UHP) of collisional orogen indicates that the upper crustal rocks is subducted to depths exceeding 100 km, and returned to the surface rapidly. In this study, we investigate the thermal structure of collisional orogen as a slab of continental lithosphere being subducted beneath an overriding wedge of continental lithosphere by the 2 D finite element method. The advection heat transfer due to the accretion of orogenic wedge is considered. The wedge is composed of the upper crust materials through the accretion from the down going plate to the upper plate. For identifying the significance of the geometric and/or kinetic factors on the thermal structure of continental subduction, the different combinations of parameters, including dip angle of subduction zone, accretion or erosion rates, and the convergence velocity etc., are used in modelling. The time span of continental subduction in our calculation is less than 30 Ma, according to the short duration of ultra deep subduction of continental slab suggested by the preservation of metastable pre peak low pressure mineralogy assemblage in the garnet of UHP rocks. Therefore, the steep dip angle of down going plate and/or low rate of accretion favour the ultra deep subduction of upper crust materials, especially for the slower down going slab. Meanwhile, taking the erosion rate as the level of exhumation rate of UHP rocks in some orogens (i.e., 1-2 km/Ma or more) does not result in the anatexis melting of crust of the overriding plate, due to the cooling effect of the rapid down going slab. However, the temperature structures of all models are generally cooler than those recovered by thermobarometric studies of the UHP rocks. This implies the significant increase of temperature after the rapid subduction of continental slab. Following the method of Davies and von Blackenburg (1998), we show that the slab breakoff can occur at the depth exceeding 100 km. Thermal modelling on the post subduction stage shows the heating related to the plate breakoff can cause the higher temperature recorded by the exhumed UHP rocks. The higher geotherm during post subduction stage leads to the weak strength of the orogenic wedge, and favours the faster upward movement of the UHP rock slices as ductile agents. The lower temperature gradient of the subduction slab predicted by modelling suggests the cold subducting slab could have transported significant fluids to mantle depth, not released during subduction. Accordingly, the absence of coeval calc alkalic magmatism in UHP orogens might resulted from the lower temperature as well as the fluid free circumstance, both are related to the rapid subduction of cold plate. Therefore, shear heating is not needed for explanation the thermal evolution of UHP orogen. On the other hand, the post collisional or late stage granitic plutonism is closely related to the deep seated heat producing materials of the accretion wedge.

Intelligent Identification of Rotating Stall for Centrifugal Compressor Based on Pressure Pulsation Signals and SDKAE Network

Most accidents of centrifugal compressors are caused by fluid pulsation or unsteady fluid excitation.Rotating stall,as an unstable flow phenomenon in the compressor,is a difficult point in the field of fluid machinery research.In this paper,a stack denoising kernel autoencoder neural network method is proposed to study the early warning of rotating stall in a centrifugal compressor.By collecting the pressure pulsation signals of the centrifugal compressor under different flow rates in engineering practice,a double hidden layer sparse denoising autoencoder neural network is constructed.According to the output labels of the network,it can be judged whether the rotation stall occurs.At the same time,the Gaussian kernel is used to optimize the loss function of the whole neural network to improve the signal feature learning ability of the network.From the experimental results,it can be seen that the flow state of the centrifugal compressor is accurately judged,and the rotation stall early warning of the centrifugal compressor at different speeds is realized,which lays a foundation for the research of intelligent operation and maintenance of the centrifugal compressor.

Numerical analysis and optimization of the inlet stage of a multi-stage high pressure compressor

An opti mization process is used to redesign blades of a high-pressure compressor.An artificial neural network (ANN) method is coupled to Navier-Stokes solvers and is applied to three different redesigns.A newrotor blade of a transonic compressor is designed by modifying thick,stacking line andinlet angle using a 3Dapproach,with a significant efficiencyi mprovement at the design point.The off-design behavior of this new compressor is also checked afterwards,which shows that the whole performance of the inlet stage is improved over a wide range of mass flow.The losses are reduced,proving the good performance of the opti mum.The whole results indicate that the opti mization method can find i mproved design and can be integrated in a design procedure.

Cyclic Pulsating Pressure Enhanced Segregating Structuration of Ultra-High Molecular Weight Polyethylene/Graphene Composites as High-performance Light-Weight EMI Shields

Currently,the enhancement in electromagnetic interference(EMI)performance of polymeric composite generally relies on either improving electrical conductivity(σ)for stronger electromagnetic(EM)reflections or tailoring structure for higher EM resonances.Herein,we proposed a novel technique called cyclic pulsating pressure enhanced segregating structuration(CPP-SS),which can reinforce these two factors simultaneously.The structural information was supplied by optical microscopy(OM)and scanning electron microscopy(SEM),both of which confirmed the formation and evolution of segregate structured ultra-high molecular weight polyethylene(UHMWPE)/graphene composites.Then,the result showed that CPP-SS can significantly improve theσof samples.Ultimately,advanced specific EMI shielding efficiency of 31.1 d B/mm was achieved for UHMWPE/graphene composite at 1-mm thickness and a low graphene loading of 5 wt%.Meanwhile,it also confirmed that the intrinsic disadvantage of poor mechanical properties of conventional segregated structure composites can be surpassed.This work is believed to provide a fundamental understanding of the structural and performance evolutions of segregated structured composites prepared under CPPSS,and to bring us a simple and efficient approach for fabricating high-performance,strong and light-weight polymeric EMI shields.

车用柴油机高压比宽流量增压器研制

目的 对于单级高压比宽流量增压器,为适应发动机强化指标,进行一系列的改进设计。方法 利用仿真设计与试验相结合的方法,对高海拔环境应用增压器进行改进设计。通过理论推导,确定压气机及涡轮的气动性能优化设计方法,开展高稳定裕度转子轴承系统设计方法研究与验证。结果 匹配高压比宽流量增压器的发动机与原机相比,高原功率恢复了17%,发动机排气温度降低了7%,增压器转速降低了13%。结论 在原机的基础上设计了压比为4.6的宽流量高性能涡轮增压器,成功实现了高压比宽流量增压器的设计,满足了发动机平原、高原不同环境的运行需求。

叶片破损对压气机性能的影响

为了研究叶片破损对压气机内部流场的影响机理,本文针对带有破损的跨音速压气机叶片进行气动性能变化规律和机理研究。通过NASA rotor 37实验结果验证了计算方法的准确性,利用数值仿真研究了叶片破损对压气性能的影响规律,并对2种典型工况下叶片破损前后的流场结构进行对比分析,探讨引起性能变化的具体原因。研究表明:叶片破损会导致压气机的压比降低0.6631%、绝热效率降低0.7877%,且压气机的稳定裕度降低更为明显。叶尖破损主要对叶顶流场结构产生影响,使叶顶区域泄漏流增强,当其与激波相互作用时,通道内产生了流动堵塞和流动损失。本文研究成果可为实际服役中的航空发动机特性评定提供理论参考。

不同频率下缓冲罐体积对有阀线性压缩机管系压力脉动的实验研究

有阀线性压缩机是液氦温区Joule-Thomson(J-T)节流制冷机重要部件,而管系压力脉动会造成制冷机出现温度与制冷量波动,从而影响制冷机温度稳定性。针对有阀线性压缩机管系压力脉动问题,以有线性阻尼的平面波动理论为基础,采用传递矩阵法构造了有阀线性压缩机管路缓冲罐压力脉动传递模型,获得有阀线性压缩机脉动质量流量的量化表达。搭建了有阀线性压缩机管系压力脉动测试平台,讨论了压缩机运行频率与进排气缓冲罐体积对压力脉动的影响。研究结果表明:管系压力脉动与压缩机运行频率有关,随着压缩机运行频率增大,管系压力脉动增大。进排气缓冲罐均可有效抑制压力脉动,但两者的压力脉动抑制能力相互独立,且缓冲罐体积越大,压力脉动抑制效果越好。随着缓冲罐体积的增加,进气缓冲罐进口处压力不均匀度减小到164/423,排气缓冲罐出口处压力不均度减小到8/23。

小型双缸往复式压缩机噪声模拟与实验

针对制氧机用小型双缸往复式压缩机噪声过大的问题,通过Fluent气动仿真与LMS Virtual.Lab多体动力学仿真模块联合模拟仿真,求解出压缩机压力脉动和轴承激励。以结构自由模态为基础,添加压力脉动和轴承激励为边界条件,并结合声振耦合理论,得到双缸压缩机的离散噪声分布及声压级云图。研究结果表明:决定压缩机噪声值的波峰频率为800、2 500和3 100 Hz,与固体模态频率相近;通过改变结构刚度可降低压缩机波峰噪声。研究结果可为小型往复式压缩机的噪声控制提供参考。

跨声速压气机叶栅流动状态的试验和数值研究

针对跨声速压气机叶栅风洞试验过程中存在的唯一冲角问题,通过开展不同来流马赫数以及不同背压条件下的平面叶栅风洞试验测量和数值模拟研究,阐明了高亚声和超声来流条件下跨声速压气机叶栅栅前流场唯一性不同的形成机制,分析了静压比对叶栅流动状态和激波结构的影响机制。研究结果表明:跨声速叶栅在低背压条件下叶栅内激波结构为双激波模式,表现为前缘脱体激波和通道正激波,随着背压的增加,通道激波位置逐渐前移并最终与脱体激波合并,形成单激波模式。超声速来流条件下,栅前流场参数受激波-膨胀波波系的影响呈现出波浪分布,其测量位置至少应距离叶栅前额线50%弦长。理论分析结果表明:跨声速叶栅的唯一冲角现象可扩展到高亚声速状态,但其物理机制有所不同,超声速状态下进口气流角取决于来流马赫数和叶栅入口几何形状,而亚声速状态下进口气流角取决于来流马赫数和叶栅喉部面积。随着静压比的提高,跨声速叶栅运行状态经历堵塞状态-溢出状态-设计状态的转变,在来流马赫数为1.10时总压损失系数由0.175递减为0.082,降幅超过50%。叶栅变背压试验结果表明,静压比超过1.379时流场三维效应增强,影响到叶栅流动的周期性,并且栅后节流板会干扰到尾迹参数的测量。该研究结果有助于理解跨声速叶栅运行状态、激波结构以及栅前流场唯一性机制,同时可对跨声速叶栅试验起到指导作用。

往复压缩机管系脉动分析与抑制方法研究

针对压缩机传统缓冲器对管路脉动抑制效率低的问题,基于ANSYS有限元分析软件对压缩机管路系统进行流体压力脉动分析与模态分析,对管路系统结构进行优化。压力脉动分析结果表明,缓冲器进口添加侧支吸纳器后,管路系统的压力脉动得到抑制。模态分析结果表明,由于管路的机械固有频率落在压缩机固有频率共振区内,增加防振管夹后可以提高管路的机械固有频率,从而避开压缩机激发态共振区,有效地控制了压缩机管路系统的振动。

R134a制冷机组中压缩机和回热器性能的试验研究

为研究R134a制冷机组中压缩机和回热器运转性能,以制冷机组运行压比为调节变量,使用压缩机排气温度、功耗、等熵效率、机组制冷量及系统能效比COP为评价指标,采用单一变量法对两元件运转性能进行测试。试验运行中,主要通过控制制冷机组蒸发温度、冷凝温度实现压缩机压比的调节。结果表明:压缩机排气温度、功耗随压缩机压比的增加而增大,机组制冷量、COP及压缩机等熵效率随压缩机压比的增加而减小;压缩机功耗与蒸发温度呈负相关,而其他性能指标与蒸发温度呈正相关。根据试验数据揭示压缩机等熵效率与压缩机压比之间的内在联系,所获取模型可实现压缩机等熵效率的高精度预测,预测平均误差约为0.45%。基于试验数据对比分析了回热器应用前后压缩机功耗、机组性能的变化趋势,除回热器在低压比工况下可明显提升机组制冷量外,在大部分工况下回热器可通过降低压缩机功耗提升机组整体性能。

双螺杆制冷压缩机排气压力脉动特性的实验研究

为研究一台冷水机组用双螺杆制冷压缩机的压力脉动特性,本文测录了压缩机压缩及排气过程的瞬态压力变化,解析其压力脉动频域特性,研究了运行转速和冷凝温度对压力脉动特性的影响,对比了压缩机采用变频与变滑阀两种容量调节方式在相同制冷量下的压力脉动、噪声和热力性能。研究结果表明:压缩腔压力脉动来源于转子工作容积内压力周期性升高,并受齿间多通道泄漏过程的影响;排气腔压力脉动来源于工作容积与排气腔的周期性连通与脱开,受排气压力及气体质量流量等因素影响。随着转速的升高,排气腔压力脉动从转速为1380 r/min时的58.6 kPa升至4200 r/min时的141.0 kPa。随着冷凝温度的升高,压力脉动幅值从34℃时的132.0 kPa升至57℃时的314.0 kPa。在相同制冷量下与容调滑阀相比,双螺杆制冷压缩机采用变频的容量调节方式在压力脉动、噪声和热力性能方面均具有显著优势,压力脉动降低54.6%以上,噪声值下降2.9 dB(A)以上,COP提升5.5%以上。

专用树脂安全生产自动化改造总结

为提升专用树脂生产的安全性,采取了一系列自动化提升措施:①对氯乙烯回收压缩系统进行了改造,在压缩机进口管线和回流管线上增加切断阀,并优化了DCS程序,由人工启停压缩系统升级为DCS一键启停;②对压力容器放空管线进行了安全升级,在爆破片和安全阀之间增设压力表;③在氯乙烯输送管线上增加了远程控制点并优化了输送程序;④在氯乙烯球罐及储槽注水管线上增加远传切断阀门,由人工现场操作升级为自动注水系统远程操作。

基于多模式加速及反步滑模的航空发动机压气机压力模拟方法

在航空发动机硬件在环仿真试验中,压气机出口压力模拟是一个重要的环节。为模拟压气机失稳过程中的气流突变现象,需要设计一种高精度的压力模拟系统,通过该模拟系统生成真实压力信号为全权限数字发动机控制器提供准确的压力激励。根据开关阀特性提出多模式加速切换策略,设计加速驱动波形及生成方法,结合现场可编程门阵列模块精确输出加速波形,提高开关阀启闭速度;在传统三模式与五模式切换的基础上设计七模式切换方法,结合反步滑模控制方法提高控制精度并证明了控制系统的稳定性。研究结果表明:在稳态压力测试中最大平均超调量为1.25%,最大平均稳态误差为0.016 MPa;在随机阶跃响应试验与正弦跟踪试验中仅有低于0.02 MPa的平均误差;压力模拟方法可满足航空发动机硬件在环仿真试验的高精度压力模拟需求,低成本的实现精准模拟压力。

电动汽车涡旋压缩机补气特性的数值研究

为研究短型线的汽车空调涡旋压缩机的补气特性,以一款排量为38 cm^(3)/r的电动汽车补气式涡旋压缩机为例,建立了三维非稳态数值计算模型,并通过实验数据验证了模型的准确性,误差在9.5%以内。通过模型分别研究补气压力和补气温度对涡旋压缩机性能的影响,结果表明:在补气过热度不变的情况下,随着补气压力的升高,压缩机排气温度先减小后逐渐增加,制热量呈增加趋势,当转速为5000 r/min和6000 r/min时,制热量最大增幅分别为20.5%和17.1%,制热COP先上升后下降,2种转速下有补气时制热COP的最大值较无补气时分别增加3.9%和2.3%,压缩机效率均先增大后减小,容积效率逐渐降低;在补气压力不变的情况下,随着补气温度的增加,排气温度略有增加,压缩机功耗、制热量及制热COP几乎保持不变;相较于补气温度,补气压力对压缩机性能的影响更大。

船舶进气畸变模拟板结构设计与参数分析

Significant aerodynamic engine instability can occur during the operation of marine gas turbines as airflow enters the compressor through a 90°turning and causes inlet distortion.This study adopts the method of simulating board equivalence to provide the target distortion flow field for ship compressors.The characteristics of the flow field behind the simulated board are obtained through experiments and numerical simulations,through which the relationship between the height of the simulated board and the total pressure distortion is elucidated.Subsequently,the study summarizes the prediction formula to achieve a distortion prediction of 0.8%–7.8%.In addition,this work analyzes the effects of drilling methods and diameters on flow nonuniformity by drilling holes into the simulation board.The results indicate that drilling holes on the board can weaken the nonuniformity of the flow field within a certain range and change the distribution pattern of total pressure in the cross-section.Furthermore,the total pressure distortion no longer changes significantly when the number of holes is too large.The proposed double simulation board structure is capable of obtaining the following two types of distorted flow fields:symmetrical dual lowpressure zones and low-pressure zones with high distortion intensity at the compressor inlet.The distortion equivalent simulation method proposed in this work can obtain various types of distortion spectra,thereby meeting the distortion parameter requirements for the antidistortion testing of marine engines.