Performance Characteristics of Ejector Devices.

摘要

A comprehensive performance analysis of ejector devices, which accounts for compressibility, heterogeneous operating media, and incidental flow losses under the simplifying assumptions of one-dimensional flow conditions and complete mixing at the end of the mixing section, leads to quite lengthy relations, which in part can be solved only by iteration. This report aims at arranging these relations in a way that they can be readily handled on a programmable desk calculator. The purpose is to study ejector devices on a basis as general as possible without sacrifice in accuracy. Various mixing modes, at constant area, at constant pressure, and at a defined pressure distribution are studied. An investigation of the optimum ejector reveals that an essential factor for the lay-out is the choice of the inlet Mach number ratio of the operating media. For constant area mixing the optimum ratio falls within a range, where the mixing mode has little influence on the performance. Thus the performance of constant pressure mixing, which is in general superior to that of constant area mixing, can be approached by constant area mixing if the inlet Mach number ratio is optimized. This is very important for supersonic ejectors since they do not allow the realization of constant pressure mixing due to the inherent presence of supersonic shocks during mixing. (Author)