混流泵启动过程非稳态空化的试验研究

为了分析混流泵启动过程瞬态扬程理论模型的适用性及非稳态空化过程,通过高速摄影和压力测量试验,探讨不同空化数、不同流量工况下启动过程中叶顶区空化状态特性。试验研究结果表明,已有理论模型可应用于混流泵启动过程,同时验证试验结果准确性。在启动过程中,空化最先发生在叶顶区域头部。当启动完成时,叶顶空化区域可分为两部分,一部分为出现在叶顶区的三角形的空化云团;另一部分为刮起涡空化。在同一流量工况下,随着空化数降低,垂直空化涡会在启动过程中出现并且发展。在同一空化数下,随着流量减小,垂直空化涡延迟出现,并且空化区域减小。     

Active control of noise amplification in the flow over a square leading-edge flat plate utilizing DBD plasma actuator

Perturbation is generally considered as the flow noise,and its energy can gain transient growth in the separation bubble.The amplified perturbations may cause unstable Kelvin–Helmohltz vortices which induce the three-dimensional transition.Active control of noise amplification via dielectric barrier discharge plasma actuator in the flow over a square leading-edge flat plate is numerically studied.The actuator is installed near the plate leading-edge where the separation bubble is formed.The maximum energy amplification of perturbations is positively correlated with the separation bubble scale which decreases with the increasing control parameters.As the magnitude of noise amplification is reduced,the laminar-turbulent transition is successfully suppressed.     

林州天然硅线石-红柱石复合矿粉对高铝质浇注料性能的影响

以山西特级矾土熟料为主要原料制备高铝质低水泥浇注料,研究了分别用质量分数为0、3%、5%、7%的林州天然硅线石-红柱石复合矿粉等量替代矾土熟料粉对浇注料基质物相和浇注料性能的影响.结果表明:将硅线石-红柱石复合矿粉加入到高铝质低水泥浇注料中,明显改善了浇注料的物理性能,提高了材料的烧后冷态强度和高温强度,改善了浇注料的抗热震性能,而且适量加入还明显提高了材料的荷重软化温度.综合各项性能认为,加入硅线石-红柱石复合矿粉的质量分数以5%为佳.