A study of incompressible material transport using an annular ejector

Two-phase ejector/eductor flow used to pump an incompressible material from atmospheric conditions into a higher pressure vessel. The process was studied experimentally to establish the ejector operating characteristics and to develop a computer model to predict operational parameters. Parametric experiments were performed in which motive air pressure, exhaust pressure and secondary flow rate were varied and the resulting ejector suction pressure was measured. The study was done to establish whether the ejector was capable of pumping micronized coal from an atmospheric hopper to a higher pressure chamber, having pressures up to 75 psia. Traditional methods of establishing the ejector characteristics were used to define the operating parameters of primary interest. A computer model was developed to predict the operation of the ejector under study and then to compare the predicted performance with experimental results. In order to establish a theoretical model, a simple control volume analysis was applied to the system. A value for the wall drag coefficient was determined that caused the control volume analysis to agree with the experimental results under conditions of no secondary flow. Secondary flow was not included in the model, so an empirical correction factor was developed to predict the operating parameters with secondary flow. It was not possible to pump material from atmospheric pressure into a chamber at 75 psia using the ejector design studied, but the results indicate that operation at higher back pressures may be possible using a modified design and further study is suggested.