三缸内燃式水泵的动力性仿真

针对传统的活塞式内燃机-柱塞泵系统的缺点,研制了三缸内燃式水泵(ICWP).阐述了三缸ICWP的工作原理,建立了系统的运动学、动力学模型,并对其动力性进行了仿真.与活塞式内燃机-柱塞泵系统相比,三缸ICWP输出压力全工况改善20.67%～87.67%,输出流量在全工况基本没有变化,有效功率全工况改善20.67%～87.67%.     

PFI汽油机油气混合过程三维瞬态数值模拟

以KIVA程序作为三维瞬态模拟软件,对进气道喷油式汽油机(PFI汽油机)采用闭阀喷射模式在3 500 r/min全负荷工况以及800 r/min怠速工况下单个工作循环内的油气混合过程进行了计算研究.计算表明两工况有着相似的燃油蒸气浓度分布状况,并且点火前时刻两工况下缸内的混合气浓度分布都比较均匀,空燃比的变化范围不大.计算还表明,800 r/min怠速工况下的燃油蒸发状况明显劣于3 500 r/min全负荷工况,该工况下气道内不仅存在附壁油膜,而且部分油膜不能在本循环完全蒸发,致使点火时刻缸内的燃油蒸气浓度明显低于3 500 r/min工况下的燃油蒸气浓度.     

高压直喷天然气发动机外特性燃烧及NO_x排放

以六缸增压中冷发动机为研究对象,采集不同工况下示功图并对NOx排放进行了测试,分析了外特性燃烧特性及排放随转速的变化规律.试验结果表明:在外特性整个转速范围内,瞬时放热率呈先急后缓的趋势,转速越高,瞬时放热率峰值越低;由于低速时滞燃期较长,因此天然气预混燃烧比例较大,各燃烧阶段分界较明显,转速升高到1 100r/min时,滞燃期明显缩短,天然气预混燃烧比例减小,扩散燃烧成为天然气主导的燃烧模式;转速小于900r/min时,NOx排放随转速升高而增加;转速在900~1 600r/min之间时,随转速升高而降低;转速高于1 600r/min时,NOx排放没有明显变化.     

共轨压力对柴油机噪声及声品质的影响

以某493型柴油机为例研究共轨压力的提高对发动机噪声及声品质的影响机理。对发动机转速1 600 r/min和2 600 r/min全负荷工况下不同共轨压力的发动机噪声和缸内压力进行试验测量,对比不同轨压下的发动机噪声和声品质客观评价指标,并通过燃烧噪声的分析对其影响机理进行研究。最后,从发动机结构衰减和燃烧噪声方面对降噪提出方案。研究结果表明:提高轨压后,发动机整机噪声增大,高频范围更加明显;噪声响度、粗糙度和尖锐度升高;主要原因是轨压的提升使滞燃期内产生更多的可燃混合气,使得缸内压力、高频振荡幅值、压力升高率和放热率增大,燃烧更剧烈,导致燃烧噪声变大,主要体现在高频范围。     

汽油直喷发动机燃烧特性分析

通过试验研究了2.0 L汽油直喷(GDI)发动机在中、低转速和部分负荷下的燃烧特性,并与进气道喷射(PFI)发动机的燃烧特性进行了对比,同时分析了滚流比对GDI燃烧特性的影响.结果表明:在转速为2 000 r/min、平均有效压力为0.2 MPa的工况下,GDI发动机的燃烧速度要低于PFI发动机的;发动机在中、低转速工况下,提高气道滚流比可以增强缸内气流运动强度,提高混合气的燃烧速度;当发动机转速达到3 000 r/min时,高滚流比会引起燃烧过程恶化.进气道翻板的应用可以提高低转速发动机的气流运动速度,加快缸内混合气的燃烧,改善低转速发动机的热效率.在转速为2 000 r/min、平均有效压力为0.2 MPa工况下的计算流体力学分析结果显示,进气道翻板的关闭会增强缸内气流运动强度,提高可燃混合气分布的均匀性.     

均质二甲醚/乙醇喷雾压燃的燃烧和排放特性

在改装的2-135柴油发动机上对进气道喷射二甲醚(DME)引燃直喷乙醇的燃烧特性进行研究,分析了燃料预混合率和负荷对缸内压力、放热率、压力升高率和排放等的影响.结果表明:在发动机转速1000 r/min,平均有效压力pBME=0.27、0.41 MPa的工况下,缸内燃烧过程包括DME的均质充量压燃和乙醇喷雾燃烧2部分,随着预混合率增加,DME冷焰反应后的燃烧相位不断提前,燃烧过程由2个阶段发展到4个阶段,而后变为3个阶段;与此同时,缸内压力增大,循环变动减小;排放物中NOx的体积分数随预混合率的变化趋势与负荷有关,在pBME≤0.33 MPa时,NOx的体积分数随预混合率的降低而减小,但pBME=0.41 MPa时,情况则正好相反.     

柴油机燃用小桐子油喷油及性能分析

通过发动机台架试验,在一台ZH11l5直喷式柴油机上直接燃用小桐子油,进行了喷油、燃烧以及排放试验.主要测量在标定转速为2 200r·min-1和最大转矩转速为1 760 r·min-1下的不同负荷的缸内燃烧压力、油管泵端压力以及NOx排放和烟度排放,并与燃用柴油时进行了对比分析.结果表明:小桐子油与柴油相比,相同工况...     

醇类汽油混合燃料发动机燃烧特性试验研究

在不改变汽油机参数的情况下,对汽油机燃用纯汽油和不同比例醇类汽油混合燃料的动力性、经济性和燃烧特性进行了对比试验研究.结果表明:与纯汽油相比,E10、M10的外特性输出功率和扭矩下降2%,M25下降7%;1800 r/min负荷特性下,E10、M10和M25的能耗率分别平均降低了3%、2.5%和5%;同一负荷工况下,E10、M10和M25的着火延迟期和燃烧持续期延长;同一负荷工况下,E10、M10和M25的缸内压力及其峰值降低且峰值推迟,E10和M25的缸内压力升高率降低,但M10的在低负荷时降低、中负荷时升高;同一负荷工况下,E10、M10和M25的缸内放热量及其峰值、瞬时缸内放热率峰值降低;同一负荷工况下,E10、M10和M25的燃烧循环变动程度增加.     

重型矿用汽车多参数动力性换挡规律

基于矿用汽车载荷变化大、行驶环境多变、油门变化频繁的特点,依据重载爬坡和轻载下坡的典型工况,制定了重型矿用汽车多参数动力性换挡策略.利用函数叠加法建立康明斯QSL-FR91674型发动机全特性曲线,得到不同油门开度情况下发动机输出转速与输出转矩的表达式.根据发动机输出动力特性,计算得到3550型矿用汽车车速、油门开度和加速度三参数动力性换挡规律.再结合道路状况识别方法、车辆载荷、驾驶员操作意图,针对轻载下坡和重载爬坡工况,修正得到重型矿用汽车多参数动力性换挡规律.在Maplesim中建立换挡模型,通过仿真计算,得到修正前后车辆轻载下坡路况时挡位和车速变化曲线,后者避免了不必要的换挡,保证了车辆的动力性能.     

小型压燃式发动机缸内辐射热量的实验研究

在一台小型高速单缸压燃式发动机上,利用商用辐射传感器测量了缸内辐射传热量。实验包括在变转速和变负荷情况下,缸内缸盖火力面辐射热流量的测量。研究表明,在不同的运转工况下,发动机缸内的辐射热量是变化的。负荷增加时辐射热量增加,转速增加时辐射热量减少。     

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.     

An Analysis of Catherine＇s Character——Wuthering Heights

Wuthering Heights, Emily Bronte＇s only novel, was published in December of 1847 under the pseudonym Ellis Bell. The book did not gain immediate success, but it is now thought one of the finest novels in the English language. Catherine is the key character of this masterpiece, because everybody and everything center on her though she had a short life. We can understand this masterpiece better if we know Catherine well.     

Lower Paleozoic oil relationships within Williston Basin, Canada

The Williston Basin is a significant petroleum province, containing oil production zones that include the Middle Cambrian to Lower Ordovician, Upper Ordovician, Middle Devonian, Upper Devonian and Mississippian and within the Jurassic and Cretaceous. The oils of the Williston Basin exhibit a wide range of geochemical characteristics defined as "oil families", although the geochemical signature of the Cambrian Deadwood Formation and Lower Ordovician Winnipeg reservoired oils does not match any "oil family". Despite their close stratigraphic proximity, it is evident that the oils of the Lower Palaeozoic within the Williston Basin are distinct. This suggests the presence of a new "oil family" within the Williston Basin. Diagnostic geochemical signatures occur in the gasoline range chromatograms, within saturate fraction gas chromatograms and biomarker fingerprints. However, some of the established criteria and cross-plots that are currently used to segregate oils into distinct genetic families within the basin do not always meet with success, particularly when applied to the Lower Palaeozoic oils of the Deadwood and Winnipeg Formation.     

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.     

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-     

Density Functional Theory for the Response of Periodic Systems to Electric Fields Based on the Vector Potential Approach

正The electronic and nuclear(structural/vibrational)response of 1D-3D nanoscale systems to electric fields gives rise to a host of optical,mechanical,spectral,etc.properties that are of high theoretical and applied interest.Due to the computational difficulty of treating such large systems it is convenient to model them as infinite and periodic(at least,in first approximation).The fundamental theoretical/computational problem in doing so is that     

On the Thermodynamic Limit for Responses to Static Electromagnetic Fields

For molecular systems,the quantum-mechanical treatment of their responses to static electromagnetic fields usually employs a scalar-potential treatment of the electric field and a vector-potential treatment of the magnetic field.Although the potential for each field separately is associated with the choice of an(unphysical)origin,the precise choice of the origin for the electrostatic field has little consequences for the results.This is different for the