喷油嘴喷孔加工工艺技术

基于日益严格的排放法规对喷油嘴的孔径,孔形,孔的位置度和喷孔的流量系数提出的越来越严格的要求,介绍了喷孔加工的最新工艺手段及相关设备的应用,加工基准的选择,各坐标轴系统的调整要求,K系数倒锥的加工成型,电脉冲电源的设计特点等技术手段,为喷孔加工工艺提供了设计经验。     

凹印机喷风嘴风速损失问题的流体动力学分析

现有凹印机干燥装置喷风嘴出风速度达不到要求,导致印品干燥不充分,同时降低了印刷速度.实际上,干燥效率低已经成为制约凹印机速度的主要因素.通过流体动力学的计算来模拟热风在风嘴内的流动状态,从结构设计上找出影响热风速度的主要因素,为干燥装置的优化改进提供理论依据,解决设计生产过程中的盲目性.通过对现有的喷风嘴结构的数值模拟...     

多排狭缝气体冲击射流换热的实验研究

气体冲击射流换热系数是喷气冷却装置设计时必需的参数。本文采用实验方法研究了多排狭缝喷嘴的冲击射流换热过程,主要考察了射流雷诺数ReS(43000相似文献   

纽马格公司三维卷曲变形装置的气流流动状态分析

从喷射机理方面对纽马格公司生产三维卷曲丝的变形装置的若干参数，如气流压力、温度、马赫数等进行了探讨，并阐述了控制气流临界截面上压力和温度参数的重要性。     

Impingement Drying of Paper

The complete drying history of paper dried under an array of multiple round jets of air was determined. The drying rate - paper moisture content relations, determined as a continuous function by on-line measurements for about 80 sheets, permitted examination of the following parameters: basis weight 20 to 50 g/m2, which covers the tissue to communication paper range; initial moisture content 1.5 to 3 kg water/kg fibre; nozzle to paper spacing of 5, 7.6 & 8.5 nozzle diameters: nozzle plate open area ratio from 1.4 to 3.1%; jet Reynolds number in the range of 450 to 11.100.

Three methods of quantifying the complete drying rate curves were tested. Use of the common assumption of drying rate linear with moisture content over the falling rate period gave inadequate representation. Secondly, the general method of Churchill for any transport process that has a transition between two asymptotic relations was applied for the fmt time to the drymg of paper. This approach gives     

不同湍流模型在射流推力矢量喷管数值模拟中的比较分析研究

利用数值模拟手段,分别求解以SA、SST k-ω、EASM k-ω或k-ζ湍流模型封闭的RANS方程,针对激波控制射流推力矢量喷管展开研究,在多个主喷流压比NPR(4.6,7.0,8.78,10.0)和次主流压比SPR(0.7,1.0)下,系统考察了四种不同湍流模型对射流推力矢量喷管性能参数及主喷管内壁面压力分布的预测能力,探讨了激波控制产生推力矢量随不同参数的变化规律。并基于数值分析,定量给出了二次射流所带来的主喷管性能损失。数值计算结果表明,四种湍流模型都能比较准确预测出射流推力矢量喷管的性能参数,在激波捕捉和压力预测方面,相对而言SST k-ω模型最为准确。     

实验研究喷嘴磨损规律的新方法

喷嘴属深长孔结构,传统方法难以得到喷嘴磨损随时间的变化关系。设计了拆分喷嘴,便于直观地观察喷嘴磨损情况。对总长35 mm的喷嘴进行磨损实验,得出喷嘴磨损随时间的变化关系,结果表明:喷嘴的磨损依次发生在收敛段与直线段过渡段、距直线段进口5～10 mm段、距直线段进口20～22 mm段;在上述3段中各选取1个典型断面进行分析,得到典型断面腔室直径随时间的变化关系,分析了各断面在不同时间磨损量不同的原因;分析了喷嘴磨损对切割能力的影响,结果表明:距直线段进口5～10 mm段磨损到一定程度后,磨料会发生严重的偏转,导致切割能力下降,喷嘴下游急速磨损,表明距直线段进口5～10 mm段为延长喷嘴使用寿命的关键部位。     

表面涂层改善柴油机喷油嘴抗磨性能的研究

提出在针阀的密封锥面上喷涂表面涂层来提高喷油嘴抗磨损性能的方案。根据喷油嘴的材料性能要求,选出Al2O3和DLC 2种代表性的表面涂层材料,利用ANSYS仿真分析喷涂2种涂层后喷油嘴的接触应力分布。结果表明,2种涂层材料显著提高了针阀密封锥面的强度、硬度和许用应力,针阀密封锥面承受冲击能力增强,其中DLC涂层对针阀偶件的保护作用更好;随着针阀密封锥面涂层厚度的增大,针阀偶件的最大接触应力减小,应力集中区域减小并向涂层上转移。通过发动机实验测试喷涂DLC涂层的针阀偶件的抗磨损性能。结果表明,DLC涂层针阀抗磨损性能明显好于无涂层针阀。     

Wear of ceramic nozzles by dry sand blasting

Monolithic B₄C, Al₂O₃/(W,Ti)C and Al₂O₃/TiC/Mo/Ni ceramic composites, which provided a reasonably wide range of mechanical properties and microstructure, were produced to be used as nozzles materials. The erosion wear of the nozzle caused by abrasive particle impact was compared with dry sand blasting by determining the cumulative mass loss of the nozzles made from these materials. Results showed that the hardness of the nozzle material plays an important role with respect to its erosion wear. On the nozzle entry bore section, the B₄C nozzle appears to be entirely brittle in nature with the evidence of large scale-chipping, and exhibited a brittle fracture induced removal process. While the erosion mechanism of Al₂O₃/TiC/Mo/Ni nozzle appeared to be a preferential removal of the metal binder followed by pluck out of the undermined Al₂O₃ and TiC grains under the same test conditions. On the nozzle center bore zone, the B₄C nozzle fails in a highly brittle manner, and there are lots of obvious micro-cracks and small pits located on this area. While the primary wear mechanisms of Al₂O₃/TiC/Mo/Ni nozzle is plowing and micro-cutting by the abrasive particles. Both types of material removal model seem to be occurred for the Al₂O₃/(W,Ti)C nozzle.     

Influence of divergent section on flow fields and discharge coefficient of ISO 9300 toroidal-throat sonic nozzle

The effect of divergent section of ISO 9300 toroidal-throat nozzle on discharge coefficient was analyzed based on the inviscid transonic flow model and laminar boundary layer theory. A series of numerical simulations were conducted to verify the results of theory, and investigate the effect of divergent section length L and diffuser angle θ operated at different Reynolds numbers. Combined with the numerical results in this study and the experimental data reported by Nakao, it showed the discharge coefficient increases with the rise of diffuser angle θ or the drop of divergent section length L. A lot of new results about the effect of divergent section were obtained. It indicated that the effect of divergent section on discharge coefficient of ISO 9300 toroidal-throat nozzle should be considered when Re<1.1×10⁴. At last, a concept of effective critical flow was proposed to discuss the effect of divergent section on discharge coefficient.