船舶柴油机气缸套凸肩裂纹原因分析

分析柴油机故障中常见的机体裂纹故障原因,认为由于设计缺陷和管理及操作不当,易造成船舶柴油机缸体上的裂纹多发生在气缸套凸肩处。如不及时处理这些裂纹和故障,就会造成缸套的裂纹直至出现缸套漏水等严重后果,针对NANTAIQUEEN轮柴油机对该类型故障的检修提出具体措施。     

Phase change analysis of an underwater glider propelled by the ocean＇s thermal energy

The phase change characteristic of the power source of an underwater glider propelled by the ocean＇s thermal energy is the key factor in glider attitude control. A numerical model has been established based on the enthalpy method to analyze the phase change heat transfer process under convective boundary conditions. Phase change is not an isothermal process, but one that occurs at a range of temperature. The total melting time of the material is very sensitive to the surrounding temperature. When the temperature of the surroundings decreases 8 degrees, the total melting time increases 1.8 times. But variations in surrounding temperature have little effect on the initial temperature of phase change, and the slope of the temperature time history curve remains the same. However, the temperature at which phase change is completed decreases significantly. Our research shows that the phase change process is also affected by container size, boundary conditions, and the power source＇s cross sectional area. Materials stored in 3 cylindrical containers with a diameter of 38ram needed the shortest phase change time. Our conclusions should be helpful in effective design of underwater glider power systems.     

螺旋折流板列管式换热器在轮机工程中的应用

介绍了螺旋折流板列管式换热器的结构特点,对其流动换热的机理以及影响因素作了分析,并的对其在轮机工程中的适用问题提出了看法。     

抛物线拱桥拱圈荷载传递规律的数值积分分析

鉴于定值计算方法的机械性和有限元法的复杂性,依据力学原理,利用积分手段,提出了抛物线拱桥拱圈荷载传递的简化连续分析方法,总结出了抛物线拱桥拱圈支承力衰减的基本规律,为拱桥的优化合理设计提供了一个有效的理论依据。     

沥青运输船装卸系统优化设计

针对沥青的特性,本文对沥青装卸系统进行了分析,在沥青泵组、装卸管系、伴热管系等方面提出了几种可行的设计方案,并对这些方案作了比较,指出了设计中应注意的一些问题。     

液化蒸气爆炸——火球对人体的伤害评价

为了使操作及管理人员对液化蒸气爆炸所产生的火球对人体所造成的伤害有一个具体的评判标准,本文通过数学公式及计算,结合图表,将液化气体容量与伤害范围以及对人体的伤害程度联系起来。通过此评价方法,人们可以方便地了解到爆炸火球与人体伤害程度的关系,以求更好地避免人体伤亡。实验结果证明了该算法的有效性。     

Initial results from long-term measurements of atmospheric humidity and related parameters in the marine boundary layer at two locations in the Gulf of Mexico

Measurements of boundary layer moisture have been acquired from Rotronic MP-100 sensors deployed on two NDBC buoys in the northern Gulf of Mexico from June through November 1993. For one sensor, which was retrieved approximately 8 months after deployment, the post- and precalibrations agreed closely and fell well within WMO specifications for accuracy. The second sensor operated continuously from June 1993 to February 1997 (3.5 years). Buoy observations of relative humidity and supporting data were used to calculate specific humidity and the surface fluxes of latent and sensible heat. Specific humidities from the buoys were compared with observations of moisture obtained from nearby ship reports, and the correlations were generally high (0.7–0.9). Surface gravity wave spectra were also acquired. The time series of specific humidity and the other buoy parameters revealed three primary scales of variability, small (h), synoptic (days), and seasonal (months). The synoptic variability was clearly dominant and occurred primarily during September, October, and November. Most of the synoptic variability was due to frontal systems that dropped down into the Gulf of Mexico from the continental US followed by air masses which were cold and dry. Cross-correlation analyses of the buoy data indicated that: (1) the moisture field was highly coherent over distances of 800 km or more in the northern Gulf of Mexico; and (2) both specific humidity and air temperature served as tracers of the motion associated with propagating atmospheric disturbances. These correlation analyses also revealed that the prevailing weather systems generally entered the buoy domain from the South prior to September, but primarily from the North thereafter. Spectra of the various buoy parameters indicated strong diurnal and semidiurnal variability for barometric pressure and sea surface temperature (SST) and lesser variability for air temperature, wind speed and significant wave height. The surface fluxes of latent and sensible heat were dominated by the synoptic events which took place from September through November with the transfer of latent heat being primarily from the ocean to the atmosphere. Finally, an analysis of the surface wave observations from each buoy, which included calculations of wave age and estimates of surface roughness, indicate that major heat and moisture flux events coincide with periods of active wave growth, although the data were insufficient to identify any causal relationships.     

石板坡长江大桥复线桥工程专用水泥对混凝土性能影响研究

针对石板坡长江大桥复线桥结构和施工特点生产的专用水泥通过对水泥矿物组成及水化热的控制,对降低混凝土温升,提高混凝土体积稳定性和耐久性起到了直接、有效的作用。采用专用水泥配制的高性能混凝土具有良好的综合技术性能。     

确定焊接反变形的数值模拟及规律分析

焊接接头附近局部的加热及冷却使被焊结构产生残余应力及角变形.目前在船厂精度控制中,通常采用构件焊接后对某些部位进行火工校正的方法来控制残余角变形.文章提供了另外一种有效控制结构残余角变形的方法:对结构焊前施加弹性的反向变形.利用热弹塑性有限元法来模拟结构的焊接过程,并对不同板厚、不同热源的结构分别进行数值模拟,最终确定焊接结构的弹性反变形规律:焊接前施加弹性反变形的结构在焊接后角变形趋于零.     

声阻抗在管路柔性元件降噪效果评估中的应用

本文根据传递矩阵法,建立了管路柔性元件的固有特性声阻抗和声学性能参数插入损失之间的关系.根据已有的管路柔性元件声阻抗参数获得不受工作环境影响的插入损失,给出管路柔性元件降噪效果的评估方法.