公交汽车CNG/汽油两用燃料发动机油行车试验研究

选用CNG/汽油两用燃料公交汽车进行实车试验,考察了研制的公交汽车CNG/汽油两用燃料发动机油的实际使用性能。试验结果表明,该油品具有良好的高温清净性、低温分散性,良好的抗氧化以及抗磨性能,可以满足公交汽车CNG/汽油两用燃料发动机油的使用性能要求。     

气质加气机及站用设备

随着国民经济的发展，日益加剧的大气污染已经严重威胁到人类的健康，而汽车尾气排放是造成污染的主要原因。LPG和CNG作为新型汽车代用燃料，属于替代汽油、柴油的最好环保车用燃料。     

燃料电池氢气加气机用超高压科里奥利流量计

液化石油气（LPG）和压缩天然气（CNG）用汽车加气（油）机的传统贸易计量仪表是容积式流量计。随着CNG用作汽车燃料日益增多和压力提高，CNG加气机用计量仪表品种已拓展到临界流文丘利喷喷（简称音速喷嘴）和科里奥利质最流量计（CMF），以克服容积式仪表天然气组分及其压缩系数变化和压力／温度修正计算误差增大的缺点．CMF和音速喷嘴则有较高计量精度。     

新型燃料汽车

新型燃料汽车指使用传统柴油、汽油以外的燃料，以内燃机为动力的汽车。新型燃料主要包括燃气（天然气、汽化石油气）、醇醚类燃料（乙醇、二甲醚等）、合成油、生物柴油、氢能等。     

天然气汽车的开发

地球上天然气资源丰富,可用以代替石油燃料使用。目前世纪上已有一百多万台使用压缩天然气（CNG0燃料的汽车,由于它具有清洁燃烧的特点,美国、日本都相继进行GNG汽车的实际开发。章介绍了丰田研制的佳美（Camry)CNG汽车及其大容量燃料罐和电喷控制系统的特点。     

基于红外光谱技术的两用燃料发动机油抗劣化性研究

应用红外光谱技术,根据润滑油组分中各官能团的红外光谱吸收峰的出现和变化,研究了开发的CNG/汽油两用燃料发动机润滑油与参比油在运行期间,润滑油的氧化值、硝化值、硫化值的变化程度,发现CNG/汽油两用燃料发动机润滑油运行18 000 km后,其氧化值变化范围为2.45(ABS/0.1 mm)、硝化值变化范围为2.03(ABS/0.1 mm)、硫化值变化范围为3.85(ABS/0.1 mm)。结果表明CNG/汽油两用燃料发动机润滑油有着良好的抗劣化性能,红外光谱技术是研究润滑油抗劣化性的有效方法之一。     

国V标准下自主品牌燃气发动机伤不起

正天燃气汽车与柴油汽车最根本的区别就是发动机不同。其工作原理有着很大的不同,柴油机为压燃式,着火点为220℃;汽油机为点燃式,着火点为427℃;天然气为点燃式,着火点为650℃。其他方面的不同如下:1、燃料不同:天然气车是指以天然气为燃料的汽车(有压缩天然气CNG和液化天然气LNG),故其发动机为天然气专用发     

加氢机设计中相关问题的探讨

燃料电池汽车的推广需要地面加注系统的支持，研制加氢机势在必行。本文介绍了压缩天然气（CNG）加气机的功能、系统构成和工艺流程，根据氢气和天然气的性质参数对比，提出了加氢机设计在材料、电气设备、安全设施等方面需要注意的问题，这对于加氢机的研制有重要的参考价值。     

中国汽车发动机市场调查简报

行业发展概况 绝大多数汽车使用以汽油或轻质柴油为燃料的往复活塞式内燃机。汽车主要用于运输，要求有质小、轻巧、省燃料、适应性好且可靠耐用的动力装置。汽油机升功率（每升气缸排量的功率）高、比质量（每单位功率的质量）小、起动方便、振动和噪声小，用于绝大部分轿车和轻型货车、部分中型客车和货车。柴油机燃料消耗率低、大修里程长，用于重型汽车、大部分中型货车及客车。由于能源关系，柴油机的使用范围不断扩大。     

压缩天然气汽车技术研究概况

压缩天然气汽车技术包括CNG汽车及加气站两大部分。该技术的研究成功,为改善环境污染、节能、缓解燃油供需矛盾、降低汽车燃料费用、增强交通运输业的活力起到了积极作用。本文介绍了CNG汽车技术使用发展概况,并对主要研究内容及技术指标水平作了分析.     

Natural frequencies of vibration of a class of solids composed of layers of isotropic materials

In a recent paper, the Ritz method with simple algebraic polynomials as trial functions was used to obtain an eigenvalue equation for the free vibration of a class of homogeneous solids with cavities. The method presented is here extended to the study of a class of non-homogeneous solids, in which each solid is composed of a number of isotropic layers with different material properties. The Cartesian coordinate system is used to describe the geometry of the solid which is modelled by means of a segment bounded by the yz, zx and xy orthogonal coordinate planes and by two curved surfaces which are defined by fairly general polynomial expressions in the coordinates x, y and z. The surface representing the interface between two material layers in the solid is also described by a polynomial expression in the coordinates x, y and z. In order to demonstrate the accuracy of the approach, natural frequencies are given for both a two- and three-layered spherical shell and for a homogeneous hollow cylinder, as computed using the present approach, and are compared with those obtained using an exact solution. Results are then given for a number of two- and three-layered cylinders and, to demonstrate the versatility of the approach, natural frequencies are given for a five-layered cantilevered beam with a central circular hole as well as for a number of composite solids of more general shape.     

Specific features of operation of electrostatic microgenerators of energy

Specific features of operation of one- and two-capacitor microelectromechanical converters (MEMC) of energy of mechanical microscopic vibrations into electric energy with a modulated electrode-gap magnitude and with allowance for the mutual influence of electrical and elastic forces are analyzed, and the characteristics of these two devices are compared. The main factors restricting the increase in MEMC power are demonstrated to be the effects of “collapsing” and the condition of conservation of positive rigidity of the system. Expressions for estimating the limiting MEMC parameters are derived. The possibility of electrical energy generation in the presence of “real“ sources of wide-spectrum microscopic vibrations is considered.     

双丝杠驱动机构同步分析

介绍了双丝杠驱动机构工作原理,论述了双丝杠运动产生不同步的原因以及如何判定与解决同步问题。     

两种螺栓的拧紧特性的分析

目前,在拧紧特性的分析中忽略了不同表面处理工艺的影响,造成了不同表面处理工艺有可能导致摩擦系数和扭矩系数散差较大的问题,影响了拧紧的可靠性。以理论分析为基础,以达克罗螺栓和镀锌螺栓为例,分别进行扭矩-夹紧力实验,测试其摩擦系数,对比分析了二者的摩擦系数和扭矩系数的稳定性,利于工程实际中更准确、有效地控制螺栓的预紧力。     

某卫星转播车方舱减重设计

对某型卫星转播车方舱的装载要求进行分析,结果证明,必须对方舱舱体的质量进行严格的控制,在不影响整舱强度的条件下,采取各种方法,尽量将方舱质量减到最轻。本文从方舱的舱板、舱门及孔口和舱体拼装等几个方面,对可能采取的减轻质量的方法进行了分析,对方舱所用型材、拼装结构和涂胶量进行优化、减重分析和处理,结果可满足对整车的功能性要求和质量限制。     

空调器铜翅片专用多工位级进模的设计

通过对热交换器工作环境的分析和对其性能的研究,以铜翅片替代铝翅片既可以提高空调器制冷效率、又可增加防腐蚀能力。在参考国内铝翅片加工级进模研究理论的基础上,设计了铜翅片加工专用模具。整套模具采用子模分立式的设计方案,各凸、凹模采用分开加工方法,使相同结构尺寸的模具具有结构互换性。通过加工试验验证了此模具结构的合理性和可行性。     

某型号飞机起落架支柱减振筒内壁腐蚀原因分析

飞机起落架减振支柱在飞机起落和滑跑时,吸收撞击能量,对飞机安全起降的意义重大.减振筒是减振支柱中的重要部件,本文从工艺流程、理化分析、外场使用和腐蚀机理分析等方面,对减振支柱减振筒内壁的腐蚀原因及危害进行了综合分析,并提出了相应措施.     

膨胀套导向机构的设计

通过分析膨胀套在实际使用产生滑移受阻现象、卡死现象原因的实质,并在分析产生问题原因的基础上提出了改进措施即：增加导向机构。     

挖掘机液压系统控制性能分析

介绍了挖掘机液压系统的功率参数与流量控制机理,从液压系统的功率角度分析了液压挖掘机的功率控制方式,从挖掘机负流量液压系统与正流量液压系统的工作原理方面分析了其控制性能及优缺点,并总结了挖掘机负流量液压系统与正流量液压系统的技术价值、应用场合及改善方向。     

Analysis of transmittance and degree of conversion of composite resins

The objective of this study was to evaluate and correlate light transmittance (T), initial degree of conversion (IDC), and degree of conversion after 24 hr (DC24) for 22 composite resins (CR) for enamel and dentin use. The transmittance (n = 10) was measured with a spectrometer at a wavelength of 468.14 nm. The degree of conversion (DC; n = 5) was measured with Fourier Transform Near‐Infrared Spectroscopy before polymerization, immediately after photoactivation, and 24 hr after photoactivation. Both sets of values are provided as percentages. ANOVA and Games‐Howell (α = 5%) tests showed that Filtek Supreme Ultra gave the highest T values of all enamel CRs, while Esthet‐X HD presented the lowest. Meanwhile, Venus diamond gave the highest values of all dentin CRs, while Esthet‐X HD gave the lowest. For IDC and DC24, ANOVA showed differences between individual CRs and the two CR types (p < .0001). Despite the limitations of this study, it can be concluded that there was no correlation between T and either IDC or DC24 (p > .05); however, IDC and DC24 were strongly correlated (p < .05) by Pearson's correlation. That being said, as a higher DC reflects better mechanical properties, certain conclusions can be drawn about overall performance. The best IDC values were observed for the Opallis enamel resin and the Opallis and Premise dentin resins. Meanwhile, the best DC24 values were observed for the Opallis, Charisma, and Premise enamel resins and the Opallis and Premise dentin resins. Degree of conversion and light transmittance showed differences between composite resin types (enamel and dentin) and brands. It is important to know at the moment of composite choice taking into account mechanical and optical properties.