Ejector Ranges

Design ranges for single stage ejectors and use of multi stage ejectors.

 

Definitions: 

Compression Ratio (CR) - ratio of discharge to entrained gas pressure

Pressure Ratio (PR) - ratio between the motive gas and entrained gas pressure

  

The feasible design range for single stage ejectors is illustrated below.

​

​

​

​

​

​

​

​

​

​

​

​

​

​

​

​

​

​

​

​

​

 

 

 

The graph is indicative only as it does not consider extreme entrainment ratios or variations in gas properties or temperatures. As a rule of thumb,  CR ~ PR^0.5 at PR <15 and moderate entrainment ratios.

 

The thermodynamic efficiency of an ejector generally decreases with increasing PR and also with increasing CR  Two stages in series are therefore considerably more efficient then a single stage when both PR and CR are high i.e. refer to the graph below (PR ~20, CR >4):

​

​

​

​

​

​

​

​

​

​

​

​

​

​

​

​

​

​

​

​

​

​