基于遗传算法的LNG气化混合工质配比研究

混合工质合适的配比可以使其放热曲线与LNG气化曲线更好的匹配,减少冷能损失,从而提高循环效率.初选R23和R170为第一级循环的混合工质,R290、R143a、R1270和R125为第二级循环的混合工质.利用Hysys建立了利用LNG冷能发电的两级低温朗肯循环系统.以系统净输出功为目标函数,利用Design Exper...     

基于混合工质的LNG冷能分段利用研究

LNG冷能释放可分为液相区、气液两相潜热区和气相区,基于以上特点建立了与之相匹配分段的三级朗肯循环发电工艺,循环介质分别采用甲烷-乙烷-丙烷的混合物、乙烯和乙烷-丙烷-正戊烷的混合物。文章对此系统进行了模拟核算与热力学分析。结果表明,当气相区循环采用低温烟气余热时,LNG的冷能的效率可达到41.15%,比单级朗肯循环效率(21%)提高了20.15%。若三级循环均采用烟气余热作为热源时,LNG效率可达到54.33%,远远高于常规发电方式。当换热器1的出口温度为-98℃,换热器3的进口温度为-60℃时,该工艺的效率存在最大值58.45%。     

太阳能与LNG冷能耦合发电系统研究

基于能的梯级利用和品位提升原理,本文提出一种耦合太阳能和LNG冷能应用的新型燃气-氨水联合循环发电系统。该系统将中低温太阳热能间接转化为高品质电能,以氨水作为朗肯循环工质,并最大化地利用LNG冷能。从系统性能和节能潜力出发,该系统热力学第一定律效率达65%~75%,系统(火用)效率达56%~64%,均远高于常规天然气基联合循环,而引入中低温太阳热能、高温燃气新途径利用、氨水工质朗肯循环以及LNG冷能应用是系统性能提高的关键过程。本文为化石能源和可再生能源的综合互补应用提供了新思路。     

LNG冷能发电朗肯循环工质研究

选取了R290(丙烷)、R1270(丙烯)、R134a(四氟乙烷)和R717(氨)四种循环工质,分析四种不同工质在蒸发温度、冷凝温度下对发电系统热效率及火用效率的影响关系。从热物性方面综合考虑,证明了丙烷应用于LNG冷能海水朗肯循环发电系统的可行性。     

利用LNG冷能与工业余热的有机朗肯循环研究

本文提出用有机朗肯循环同时回收LNG冷能和工业余热,选择乙烷作为工质,对循环进行了详细的热力分析.分析结果表明,随着蒸发压力的升高,循环热效率及做功量都增大;当蒸发器出口温度低于240℃,蒸发压力取值较高时,冷凝器会出现不允许出现的负夹点温差,冷凝器换热不足,换热后不能使LNG达到汽化的最终温度;利用温度低于260℃的工业余热与LNG冷能时,为解决原循环高压力下冷凝器的换热不足问题,需在原循环的基础上增加一个换热器。     

利用天然气冷量的朗肯循环发电流程的工艺模拟

高压天然气集输过程中节流会使天然气温度有明显的下降,提出了分别采用丙烷和混合工质的朗肯循环回收天然气的冷量进行发电。采用HYSYS软件对两种工艺分别进行了工艺模拟,结果表明采用混合工质时由于冷热流体间换热温差明显减小,因而循环效率提高了约40%。在夏季当天然气输量为55×104Nm2/d时,可以产生48.42kW的功率,冷能有效能的利用效率约为23.06%。     

LNG冷能用于CO_2跨临界朗肯循环和CO_2液化回收

提出了一种利用LNG冷能的新方案。一方面,采用CO2作为工质,利用燃气轮机的排放废气作为高温热源和LNG作为低温冷源来实现CO2的跨临界朗肯循环。由于高低温热源温差较大,循环能够顺利进行;另一方面,从燃气轮机排放的CO2废气在朗肯循环中放出热量后经LNG进一步冷却成液态产品。这样,不但利用了LNG冷能,而且天然气燃烧生成的大部分CO2也得以回收。计算分析了相关参数对跨临界循环特性的影响,包括循环最高温度和压力对系统的比功和火用效率的影响,并分析了回收的液态CO2的质量流量的变化情况。结果表明,这种新的LNG冷能利用方案是一种环境友好的高效方案。     

利用液化天然气冷能的低温动力循环

提出一种带吸收器的混合工质低温动力循环,LNG和海水分别为冷源和热源。以单位LNG输出功和可用能利用率为性能参数对循环进行计算,并对采用四氟甲烷（CF₄）/丙烷（C₃H₈）和乙烯（C₂H₄）/丙烷（C₃H₈）新型混合工质循环与常规丙烷朗肯循环（ORC）进行比较。结果表明,本循环明显优于常规丙烷朗肯循环,单位输出功和最大可用能利用率分别比朗肯循环提高了66.3%和79.6%,最佳LNG利用温度分别为-59.6℃和-54.6℃。     

基于LNG冷能利用的公交车空调制冷系统优化

公交车的LNG燃料蕴含大量冷量,目前尚未得到利用。文中就LNG冷能用于公交车空调系统低温送风和空调系统的过冷循环分别进行了优化分析。应用Cleland公式和VB编程计算,结果表明:LNG冷能用于12m公交车低温送风,空调制冷系统COP可提高6.8%～8.6%;将LNG冷能用于12m公交车空调系统的过冷循环,空调制冷系统COP可提高18.2%。     

液化天然气CCHP系统的乙烯-丙烷级联动力循环及工艺模拟

文中提出了一种适用于LNG冷热电联产系统的两级乙烯-丙烷级联朗肯动力循环,并采用HYSYS软件对这一级联动力循环进行了工艺模拟,LNG的流量为219kg/h时,共可以产生电力14.06W,并向空调供冷50.24kW.与不采用冷量回收的装置相比,总的能量利用率从83.22％提高到了85.17％.这说明级联式动力循环通过梯...     

Guided-Wave Two-Dimensional Acousto-Optic Scanner Using Proton-Exchanged Lithium Niobate Waveguide

Two-dimensional scanning of a 0.6328 mum guided-light beam has been realized using noncolinear acousto-optic (AO) coplanar Bragg diffraction together with colinear AO guided-mode to substrate radiation-mode conversion in a Z-cut Xpropagation LiNbO3 proton-exchanged (PE) waveguide. The two surface acoustic (SAW) waves utilized are at the center frequencies of 500 and 200 MHz, propagating in the Y and X axes, respectively. Two-dimensional scanning of approximately 720 resolvable light beam spots, namely, 18 40 (horizontal vertical) scanning, has been demonstrated using a light beam of 1.0 mm aperture. The total number of resolvable beam spots can be greatly increased from 720 by simply utilizing SAW transducers of larger bandwidth and a light beam of greater aperture. It should also be possible to significantly increase the diffraction efficiency from 3 % by optimizing the parameters of the PE waveguide and the SAWs.     

Hybrid Wavelength and Code Division Multiple Access in Optical Networks

A review of schemes for multiple access in fiber optic networks shows that a hybrid of wavelength and code division multiple access (WCDMA) combines the best features of both. In particular, the hybrid scheme retains the large information carrying capacity of wavelength division multiple access (WDMA) and flexibility of code division multiple access (CDMA). In this paper WDMA, optical CDMA (OCDMA), and WCDMA networks are discussed. In OCDMA networks, concept of incoherent and coherent coding including inverse decoding and matched filter is introduced. The delay performance of both WDMA and WCDMA networks, under the simple suboptimum access protocols based on cyclic search, is computed. It has been shown quantitatively that tuning delay significantly affects the delay performance of both WDMA and WCDMA networks. Futhermore, delay performance of WCDMA networks is always better than the WDMA networks for the same tuning delay, load, and number of users.     

Femtosecond Transform-Limited Pulse Generation by Compensating for the Linear Chirp of SPM Spectra in Dispersion Shifted Fibers

A simple technique of pulse compression, based on the linear chirp compensation of self-phase modulation (SPM) spectra in dispersion shifted fibers, is demonstrated. The optimization procedure is carried out, for a short span of a single-mode fiber, using a parabolic law, which describes the behavior of the squared output pulse width versus the pump peak power in the case of Gaussian pulses. The experimental results give a minimum pulse duration of 233 fs, which is in good agreement with the model. Shorter and coherent pulses, down to 90 fs, have been obtained by inserting an interference filter at the optical output.     

Effect ofγ-radiation on the spectral luminescence characteristics of impure cadmium tungstate crystals

Results of a study of the effect of γ-radiation on the spectral luminescence properties of cadmium tungstate crystals doped with silver, bismuth, and molybdenum cations are presented. Spectral characteristics of the nondnnnoped crystals are briefly described. Absorption and photo and X-ray luminescence spectra of the crystals taken before and after exposure to γ-radiation (5.5·10⁴ Gy) are compared. It is found that the spectral characteristics of the crystals doped with silver, bismuth, and molybdenum cations do not change markedly after the exposure. The relation between the type of impurity-induced defects, individual characteristics of the impurity cations, and the character of the effect of γ-radiation on the spectral luminescence properties of impure crystals is analyzed (preliminarily). Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 1, pp. 55–60, January–February, 1997.     

Research on beamforming method for dual-line array with space mismatch between the two line arrays

The performance of port/starboard discrimination of dual-line array will be seriously degraded when the space between the two line arrays of the dual-line array is mismatched. The directivity function of the delay-sum and delay-subtract beamforming is deduced and the port/starboard discrimination of the delay-sum and delay-subtract beamforming is also studied both under the ideal status and the status under which the space between the two line arrays of the dual-line array is mismatched. Analysis results show the delay-subtract beamforming has better performance of port/starboard discrimination. At last, the sea trial results demonstrate the theoretical results.     

Sorting of bending magnets for the SSRF booster

The Shanghai Synchrotron Radiation Facility(SSRF)booster ring,a full energy injector for the storage ring,is deigned to accelerate the electron beam energy from 150MeV to 3.5GeV that demands high extraction efficiency at the extraction energy with low beam loss rate when electrons are ramping.Closed orbit distortion(COD)caused by bending magnet field uniformity errors which affects the machine performance harmfully could be effectively reduced by bending magnet location sorting.Considering the affections of random errors in measurement,both ideal sorting and realistic sorting are studied based on measured bending magnet field uniformity errors and one reasonable combination of bending magnets which can reduce the horizontal COD by a factor of 5is given as the final installation sequence of the booster bending magnets in this paper.     

Retrieval of ultraviolet skylight radiances and O3 slant column densities from balloon-borne limb spectrometer

With a novel light-weight and absolutely calibrated ultraviolet （UV） spectrometer, UV skylight radiances and O3 slant column densities are measured by balloon-borne limb measurements in Xinjiang area, China. UV skylight radiances measured at the height of 31 km are compared with the results from Modtran in the wavelength range from 290 to 420 nm. O3 slant column densities are derived from radiance spectra in the Huggins bands （320 - 335 nm） using differential optical absorption spectroscopy method. And the parameter exhibits a good correlation with the same value simulated by radiative transfer model （Tracy）. The O3 profile simultaneously measured by an O3 sonde is used as input in Tracy calculations. The O3 sonde is launched on the same balloon.     

Design optimization of highly sensitive LSPR enhanced surface plasmon resonance biosensors with nanoholes

For breaking through the sensitivity limitation of conventional surface plasmon resonance (SPR) biosensors, novel highly sensitive SPR biosensors with Au nanoparticles and nanogratings enhancement have been proposed recently.But in practice, these structures have obvious disadvantages.In this study, a nanohole based sensitivity enhancement SPR biosensor is proposed and the influence of different structural parameters on the performance is investigated by using rigorous coupled wave analysis (RCWA).Electromagnetic field distributions around the nanohole are also given out to directly explain the performance difference for various structural parameters.The results indicate that significant sensitivity increase is associated with localized surface plasmons (LSPs) excitation mediated by nanoholes.Except to outcome the weakness of other LSP based biosensors, larger resonance angle shift, reflectance amplitude, and sharper SPR curves' width are obtained simultaneously under optimized structural parameters.     

Polymer gratings based on photopolymerization for low-order distributed feedback polymer lasers

Novel polymer distributed feedback(DFB)gratings are fabricated based on photopolymerization to reduce lasing threshold of polymer lasers.A photopolymer formulation sensitive to 355-nm ultraviolet(UV)light is proposed for the fabrication of polymer gratings and it can be used to form polymer films by spin-coating process.A very low surface-relief depth ranging from 12.5 to about 1.0 nm has been demonstrated with a refractive-index modulation of about 0.012.The experimental results indicate that such polymer gratings have promising potentials for the fabrication of low-order DFB organic semiconductor lasers.