Tempo-Spatial Variations in Stomatal Conductance, Aperture and Density of Ligustrum sinense Acclimated to Different Light Environments

There was heterogeneous distribution in stomatal conductance (g-s) and stomatal aperture for both high- and low-light leaves of Ligustrum sinense Lour. in four designated positions within a leaf. Linear or exponential or polynomial relationships between g-s and stomatal aperture were found when regression of g-s and stomatal aperture was established. Statistical analysis revealed that the relationship between g-s and stomatal aperture for high-light leaves was more significant than that of low-light leaves. A linear relationship between g-s and stomatal aperture existed in both positions 1 and 3 for both high- and low-light leaves. The stomatal density of the low-light leaves was much lower than that of the high-light leaves. The sensitivity of stomata to changing environment for high-light leaves was higher than that for low-light leaves, which may also relate to the higher stomatal density for the high-light leaves.

双级压缩机前缘喷气改善喘振特性设计分析

针对某双级离心压缩机运行过程中小导叶开度下容易出现喘振导致压缩机运行范围小的问题,提出了一种在双级压缩机中间段进口前缘喷气的方案来改善压缩机小导叶开度下的喘振特性,提高其喘振裕度。并通过建模仿真分析的方法验证了此方案的可行性,通过分析发现,在小导叶开度/小流量工况下,双级压缩机中间段回转叶片通道发生了大面积的流动分离和低能流体堆积,使二级叶轮叶片进口攻角增大,导致二级叶轮极易容易进入喘振状态。通过在回转通道叶片前缘设定喷气口,给予一定量的喷气进入主流区,结果显示,喷气大大改善了回转通道内的叶片吸力面的流动,使原本因分离流动聚集的低能流体不在集聚,叶片出口的流动得到大大改善,进而使二级叶轮进口流动状态得到改善,减小了二级叶片前缘的攻角,推迟旋转失速的发生,使压缩机在小流量小导叶开度下喘振推迟,压缩机的喘振边界线提高,运行范围增大。