Light intensity and image visualization of GDI injector sprays according to nozzle hole arrangements

The light intensity measurement and image visualization of multi-hole injection spray due to different hole arrangements and hole numbers were investigated. The light intensities and behavior characteristics of the GDI spray were analyzed through the axial and diagonal spray penetration, cone angle, and spray area from the spray images by using the image visualization system and image analysis system. The atomization performance of GDI injectors was analyzed by the local and overall Sauter mean diameter (SMD) measurement.     

多孔活性自燃金属的光谱辐射特性研究

多孔活性金属材料因为内部存在大量的孔隙，大大地增加了与空气的接触面积，使得其在空气中的燃烧较为猛烈，燃烧温度迅速上升。其燃烧过程属于固体燃烧的范畴，较为复杂。以镁为例，通过建立燃烧模型，来研究多孔活性金属的光谱辐射特性。首先，建立氧气总消耗量与活性金属剩余质量的关系，研究氧气在活性金属孔隙内的扩散浓度关系，通过求解活性金属热平衡方程得到活性金属燃烧过程中温度与时间的关系式，进而得到活性金属的峰值光谱辐射强度表达式；然后，将模型计算的仿真结果与红外热像仪测得的实验结果对比，结果表明，模型的计算结果与实验结果相一致，误差在了10%以内；最后，通过建立的燃烧模型来研究活性金属燃烧规律以及其光谱辐射特性，解决了高空、高速下的活性金属光谱辐射强度难以实验获得的问题，大大减小了实验成本与时间。分别对比不同时间活性金属箔片在1～3，3～5以及8～12 μm波段下的辐射强度，得出活性金属燃烧时的辐射强度主要集中在3～5 μm波段的结论。研究结果表明：自燃金属最大燃烧温度随高度的增加逐渐下降，随气流速度的增加先增加后减小，在速度为30 m·s-1时，温度达到最大；自燃金属的光谱辐射强度在2～6 μm波段达到最大。该模型也可以用来研究其他活性金属的燃烧特性。     

圆波导-矩形波导小孔耦合定向耦合器设计

 设计了圆波导-矩形波导通过小孔耦合的定向耦合器装置,应用于高功率微波器件输出功率测量。利用弱耦合波理论分析了单孔耦合,对单孔耦合进行了理论分析和数值计算,并在HFSS中模拟了中心频率34 GHz、耦合度－40 dB的TE₀₁TE₁₀单孔耦合,将数值计算结果和模拟结果进行了对比,两者最大差值为0.4 dB, 相对误差近1%,从而证实理论分析和数值计算的正确性,证实了此种单孔耦合器不具备定向耦合的条件。在单孔耦合的基础上利用相位叠加原理详细分析了多孔定向耦合阵列原理,得出多孔耦合器且满足反向相位相消的条件才具备定向耦合;为设计此种定向耦合器提供了设计理论和参考依据。在实际加工中只要给出标定的耦合度和方向性系数就可以确定耦合孔尺寸。     

Cobra probe measurements of mean velocities, Reynolds stresses and higher-order velocity correlations in pipe flow

This paper is concerned with the validation of a four-hole pressure probe, known as a cobra probe, for turbulence measurement. For the first time in the literature, third- and fourth-order velocity correlations measured using a pressure probe are presented. The probe measurements are compared with established data for fully developed pipe flow, and good agreement is found. A new probe calibration methodology and improvements to the data acquisition and processing system are also presented.