柴油引燃直线氢内燃机稀薄燃烧特性研究

直线氢内燃机特殊的自由活塞运动导致了较低的燃烧反应速率和放热等容程度。为减少燃烧时间损失,提高能量利用效率,在一台直线氢内燃机中尝试应用了引燃稀薄燃烧技术。首先通过原理试验验证了引燃稀薄燃烧技术的可行性,然后采用一种耦合活塞运动的迭代计算方法对柴油引燃直线氢燃料内燃机燃烧性能和运行特点进行了模拟研究。结果表明:采用引燃燃烧技术,有助于提高直线氢内燃机的燃烧速度,减小放热时间损失,增加指示效率。相对于传统点燃燃烧,引燃技术能够提高直线氢内燃机活塞往复运动频率和压缩比,增加直线氢内燃机输出功率,但是引燃燃烧会轻微加重直线氢内燃机的NOx污染物排放。     

基于Matlab的微型发动机燃烧过程仿真建模

为研究微型HCCI自由活塞发动机的工作性能,应用Matlab软件对其单次冲击的燃烧过程进行仿真建模,分别建立考虑传热、漏气的零维总包化学动力学模型和理想气体模型,并将仿真计算结果与试验结果进行比较.运用传热漏气模型对微型HCCI自由活塞发动机不同初始速度下的燃烧特性进行模拟,得到自由活塞初始速度对工作压力、温度、活塞运行位置的变化规律的影响以及不同初始速度下自由活塞的运动特性.结果表明气体泄漏和传热对燃烧过程影响较大,考虑传热漏气模型的微燃烧模拟结果与试验数据吻合较好,为微动力装置的性能评价和设计提供理论依据.     

内燃机缸内过程的一种多维数学模型

利用任意拉格朗日－欧拉法，求解具有缸头中心无气阀气口进排气模拟功能的内燃机缸内三维流动，喷雾和燃烧过程控制方程，为对比不同湍流模型对模拟结果的影响，除采用Ｋ－ε模型外，还首次引入传统代数应力模型对缸内流动进行模拟，计算结果表明；本文的多维模型，对内燃机燃烧过程的模拟结果是合理的，对进气过程的计算结果与实测结果基本吻合，对平顶活塞及带坑活塞缩过程的模拟结果，显示了两种湍流模型的差异。     

闭式燃烧室中丁烷燃烧的热声耦合机理

结合燃烧理论和声学理论,针对实际中出现的燃烧室空腔压力振荡问题,将声学模型和燃烧计算模型相耦合,用数学模型描述内燃机燃烧过程中的热声耦合现象.通过建立的数学模型,编制闭式定容燃烧的二维热声耦合计算程序对预混合丁烷进行计算,得出热声耦合的特性并给出了描述声场的压力云图,可以看到加入波动方程前后的燃烧过程存在差异.同时结合汽油机缸内燃烧压力实验数据与计算结果对闭式燃烧热声耦合的机理进行了分析.计算和实验数据的对比结果表明,在闭室燃烧过程中,放热与燃烧室声场存在相互影响,因此对内燃机燃烧过程进行研究时,应考虑声学因素.     

纯甲醇压燃过程及其循环变动的模拟分析

建立了适合于多种燃料燃烧过程的零维数学模型，并利用优化算法 Ｐｏｗｅｌｌ法对 Ｖ２ｂ 函数中的各参数进行优化求解。应用此模型对实机燃用纯甲醇的压燃过程进行 了放热率的变工况拟合和循环变动率的数学统计分析。分析的参数包括零维燃烧模型 中各特性参数、平均指示压力、最高燃烧压力、着火延迟期及放热率与着火延迟期的 相关系数等。     

耦合详细化学动力学的HCCI发动机工作过程三维数值模拟

将详细化学动力学的HCCI单区模型嵌入三维流体力学程序中，取代传统内燃机三维数值模拟中简化燃烧模型，利用详细化学反应动力学计算三维燃烧过程，建立三维CFD耦合详细化学反应动力学模型.生成了带复杂进气道的实际燃烧系统的贴体计算网格，建立了缸内直喷HCCI燃烧系统进气-喷雾-混合气形成-压缩-燃烧工作过程的模型.为满足模拟整个HCCI发动机物理化学过程（包括进气，压缩，喷雾，燃烧和排放）执行时间的要求，提出了一套能使计算工作量大为减少的详细化学反应动力学与三维CFD耦合的模拟策略，利用试验方法确定计算边界条件，预测了进气-喷雾-燃烧-排放的HCCI发动机工作过程，通过发动机台架试验对比验证了模型的准确性.     

压燃式自由活塞直线发电机工作过程数值仿真

为研究压燃式自由活塞直线发电机的动力学特性,对其启动和稳态工作过程进行了数值仿真计算,并对自由活塞直线发电机的负荷特性和频率特性进行了分析.结果表明,与曲柄连杆式发动机相比,自由活塞发动机在其上止点附近有非常大的加速度,使得在上止点附近压缩行程较慢和膨胀行程较快.随着系统输出功率的提高,自由活塞发动机的缸内峰值压力、压缩比及指示效率不断下降;而直线电机载荷系数、峰值电磁力及循环加入能量不断增加.随着系统的运转频率不断提高,直线电机的载荷系数不断降低,最大峰值电磁力将在中间某一工作频率取得;而活塞平均速度、自由活塞发动机的指示效率和系统输出功率不断增加.     

传统缸内壁面传热模型在氢内燃机中的适用性

针对传统内燃机缸内传热模型在氢内燃机传热预测计算中的适用性问题,研究了LaunderSpalding模型、Huh模型、Poinsot模型、Han-Reitz模型和Rakopoulos模型在氢内燃机的压缩和膨胀冲程中的应用,为此编制程序将上述模型嵌入到开源计算流体动力学(CFD)工具包OpenFOAM的求解器中,并对一个氢内燃机缸内反应流动的算例进行了传热的预测计算和实验验证。研究表明:相对其他模型,Rakopoulos模型对氢内燃机传热热流的预测最为准确,优于AVL-Fire软件中推荐的Han-Reitz模型,可作为AVL-Fire软件二次开发进行氢内燃机的相关模拟计算;除Rakopoulos模型之外的模型适用性较差的原因是,不能准确描述氢内燃机缸内边界层中的工质物性及湍流黏性的分布规律,通过改进氢内燃机缸内边界层中的密度、黏度、湍流普朗特数分布有望提高氢内燃机传热模型的适用性;准确预测壁面热流峰值时刻需要对燃烧模型的火焰传播过程计算进行详细校核。     

对称与偏置曲柄滑块机构内燃机的动态特性比较

针对内燃机对称布置活塞与偏置布置活塞两种曲柄滑块机构建立了运动学与动力学数学模型,给出了用MATLAB数学软件进行计算和仿真的结果,分析对比了这两种曲柄滑块机构的动力学和运动学特性.计算和仿真结果表明,活塞偏置布置和增大活塞偏置距离有利于改善内燃机的动态性能.     

氢燃料内燃机NOx排放特性及机理

为深入研究氢燃料内燃机NO_x的生成机理,基于CONVERGE软件建立了三维网格耦合详细化学反应机理的氢燃料内燃机CFD仿真模型,进行了氢燃料内燃机在不同负荷下的燃烧及排放特性研究。模型的仿真结果和试验数据较为吻合。结果表明,氢气浓度增大有利于提高氢燃料内燃机的效率;NO的大量生成出现在不断升温的快速燃烧期,快速燃烧结束后NO总量不断减少,其缸内平均温度低于2 200K时NO总量趋于稳定;热NO,NNH和N_2O是NO生成最主要的路径,其中热NO路径产生的NO排放最多,其贡献率随着负荷增大而增大。NNH和N_2O路径在较低浓度时有接近25%的贡献率,而在燃空当量比为1.0时,这2种路径对NO生成的贡献率之和为负值。采用化学反应动力学方法得到了3种路径在不同负荷下对NO生成的贡献率,初步揭示了氢燃料内燃机NO_x生成的机理,为后续研究提供了理论参考。     

Markedness and its Interpretation in Language Use

Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.     

Features of Women's language

Language is a means of verbal communication. People use language to communicate with each other. In the society, no two speakers are exactly alike in the way of speaking. Some differences are due to age, gender, statue and personality. Above all, gender is one of the obvious reasons. The writer of this paper tries to describe the features of women＇s language from these perspectives： pronunciation, intonation, diction, subjects, grammar and discourse. From the discussion of the features of women＇s language, more attention should be paid to language use in social context. What＇s more, the linguistic phenomena in a speaking community can be understood more thoroughly.     

Characterization of Ordovician carbonate reservoirs, southeastern Saskatchewan, Canada

The discovery of the prolific Ordovician Red River reservoirs in 1995 in southeastern Saskatchewan was the catalyst for extensive exploration activity which resulted in the discovery of more than 15 new Red River pools. The best yields of Red River production to date have been from dolomite reservoirs. Understanding the processes of dolomitization is, therefore, crucial for the prediction of the connectivity, spatial distribution and heterogeneity of dolomite reservoirs.The Red River reservoirs in the Midale area consist of 3～4 thin dolomitized zones, with a total thickness of about 20 m, which occur at the top of the Yeoman Formation. Two types of replacement dolomite were recognized in the Red River reservoir: dolomitized burrow infills and dolomitized host matrix. The spatial distribution of dolomite suggests that burrowing organisms played an important role in facilitating the fluid flow in the backfilled sediments. This resulted in penecontemporaneous dolomitization of burrow infills by normal seawater. The dolomite in the host matrix is interpreted as having occurred at shallow burial by evaporitic seawater during precipitation of Lake Almar anhydrite that immediately overlies the Yeoman Formation. However, the low δ18O values of dolomited burrow infills (-5.9‰～ -7.8‰, PDB) and matrix dolomites (-6.6‰～ -8.1‰, avg. -7.4‰ PDB) compared to the estimated values for the late Ordovician marine dolomite could be attributed to modification and alteration of dolomite at higher temperatures during deeper burial, which could also be responsible for its 87Sr/86Sr ratios (0.7084～0.7088) that are higher than suggested for the late Ordovician seawaters (0.7078～0.7080). The trace amounts of saddle dolomite cement in the Red River carbonates are probably related to "cannibalization" of earlier replacement dolomite during the chemical compaction.     

低渗透非均质砂岩油藏启动压力梯度研究

理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。     

On Tragic Consciousness In The Works By Ernest Hemingway

As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.     

A computer generator for randomly layered structures

AcomputergeneratorforrandomlylayeredstructuresYUJia shun1,2,HEZhen hua2(1.TheInstituteofGeologicalandNuclearSciences,NewZealand;2.StateKeyLaboratoryofOilandGasReservoirGeologyandExploitation,ChengduUniversityofTechnology,China)Abstract:Analgorithmisintrod…     

An Index mechanism for multi-scale view in spatial databases

There are numerous geometric objects stored in the spatial databases. An importance function in a spatial database is that users can browse the geometric objects as a map efficiently. Thus the spatial database should display the geometric objects users concern about swiftly onto the display window. This process includes two operations:retrieve data from database and then draw them onto screen. Accordingly, to improve the efficiency, we should try to reduce time of both retrieving object and displaying them. The former can be achieved with the aid of spatial index such as R-tree, the latter require to simplify the objects. Simplification means that objects are shown with sufficient but not with unnecessary detail which depend on the scale of browse. So the major problem is how to retrieve data at different detail level efficiently. This paper introduces the implementation of a multi-scale index in the spatial database SISP (Spatial Information Shared Platform) which is generalized from R-tree. The difference between the generalization and the R-tree lies on two facets: One is that every node and geometric object in the generalization is assigned with a importance value which denote the importance of them, and every vertex in the objects are assigned with a importance value,too. The importance value can be use to decide which data should be retrieve from disk in a query. The other difference is that geometric objects in the generalization are divided into one or more sub-blocks, and vertexes are total ordered by their importance value. With the help of the generalized R-tree, one can easily retrieve data at different detail levels.Some experiments are performed on real-life data to evaluate the performance of solutions that separately use normal spatial index and multi-scale spatial index. The results show that the solution using multi-scale index in SISP is satisfying.     

Jane Eyre——A Feminist In The 19th Century

In the 19th century the society was controlled by men, and women were just appendants of them, they had not any rights and freedom. But Jane was an exception, she showed some characteristics of early feminist. Jane showed her characteristics of feminism in three aspects: rebellion, equality, and independence. These characteristics were helpful to her success, and feminism is the only way out for women of that time.     

Achieving Unusual States of Matter Under High Pressure

正The periodicity of the elements and the non-reactivity of the inner-shell electrons are two related principles of chemistry,rooted in the atomic shell structure.Within compounds,Group I elements,for example,invariably assume the+1 oxidation state,and their chemical properties differ completely from those of the p-block elements.These general rules govern our understanding of chemical structures and reactions.Using first principles calcula-     

Exchange-Correlation and Electronic Excitation Energies from Pairing Matrix Fluctuations

We have developed an adiabatic connection to formulate the ground-state exchange-correlation energy in terms of pairing matrix linear fluctuations.This formulation of the exchange-correlation energy opens a new channel for density functional approximations based on the many-body perturbation theory.We illustrate the potential of such approaches with an approximation based on the particle-particle Random Phase Approximation(pp-RPA).This re-