稳态引射过程自维持临界截面研究

Self-Sustaining Critical Section in Steady Ejecting Process

关键词:  引射器  自维持  临界截面  流量控制机制  引射比

Key words:  Ejector  Self-sustaining  Critical section  Mass flow rate control mechanism  Entrainment ratio

摘要:

为了进一步完善引射理论，从引射系统性能受背压影响的规律出发，提出了引射过程自维持临界截面的概念，以之来定义一次流动量抵达壁面或者边界层的流场法向截面，并利用背压影响的数值模拟结果给予了证实。在此基础上，将控制引射流量的机制划分为第一临界机制、第三临界机制、背压影响机制和自维持临界截面控制机制，自维持临界截面控制机制下拥有最大的引射比。当扰动区域及其影响区域仅处于自维持截面的下游时，引射比不会发生变化；当扰动及其影响区域处于自维持截面的上游时，引射过程受到影响，引射比发生变化。

Abstract:

To improve and perfect the ejector theory， the concept of self-sustaining critical section is put forward in steady ejecting process based on the relationship between the ejector performance and back-pressure， and the concept is used to define the normal cross-section where the primary flow reaches the wall or the boundary layer. The theory was proved by using CFD results of back-pressure’s effect on ejecting process. On this basis， the mass flow rate control mechanism of ejector can be divided into four categories， including the first critical regime mechanism， the third critical regime mechanism， back-pressure dominating mechanism and self-sustaining critical section dominating mechanism. The entrainment ratio is the biggest in the four statuses while the ejector works at the self-sustaining critical section dominating mechanism. While the disturb zone and its infection zone are downstream of the self-sustaining critical section， the entrainment ratio will not change. While the disturb zone and its infection zone are upstream of the self-sustaining critical section， the ejecting process will be affected， and the entrainment ratio will change.