NEW DEVELOPMENTS IN HIGH VACUUM APPARATUS. 181 



scribed which have been in successful operation in marine condenser installations 

 over two years and thereby have proven their fitness for marine service. Only two 

 types in a variety of sizes have so far been used in a large fleet of merchant ma- 

 rine and navy vessels. 



These are known as the "Radojet" and the Le Blanc air ejector. Both are 

 of the two-stage type, the stages being connected in series. A cross-section through 

 the Radojet is shown in Plate 74. Plate 75 shows a photograph of half a Radojet 

 cut through its vertical center line. 



Live steam is delivered from a source not shown through opening L through 

 strainer screen i, pipe 2, auxiliary steam valve 3, strainer screen 4, expansion noz- 

 zles 5, across suction chamber 6, of the first stage ejector, which is in communica- 

 tion with the condenser through the suction opening S. 



The steam expands in the nozzles, leaving the same with a very high velocity 

 and, while passing across suction chamber 6, entrains the air and vapors to be 

 compressed. 



The mixture passes into the diffuser 7, from where it is discharged at higher 

 absolute pressure than that of the air entering at >S into a double passage 8 com- 

 municating with the suction chambers 9 of the second stage. These two suction 

 chambers 9 are annular, giving the co-mingled fluid a large entrainment surface. 



Steam is simultaneously delivered through the strainer screen i into passage 10, 

 which communicates with the annular expansion nozzle formed between nozzle 11 

 and nozzle point 12. Nozzle point 12 may be adjusted toward or away from disc 

 II by the adjusting screw 13 which forms part of it, to vary the cross-section of 

 the nozzle passage, thereby changing the expansion ratio of the steam. 



The steam delivered by the annular nozzle 1 1 expands between the same and 

 nozzle point 12, leaving it as a jet of high velocity in the form of an annular sheet. 

 In passing across the section chambers 9, it entrains the co-mingled air and steam 

 received from the first stage and carries the mixture into the annular dififuser 14, 

 thereby compressing it to slightly above atmospheric pressure and discharging it into 

 casing 15 which has the discharge opening D. 



The steam nozzles of the first stage are bronze, that of the second stage is of 

 monel metal, and the nozzle point of special steel. The dififusers are bronze. In 

 the smaller sizes, the dififusers form part of the casing, while in the larger sizes the 

 diff users are secured to a cast-iron casing by bolts, forming a metal ground joint 

 with the casing. 



The strainers ahead of the nozzles protect them from becoming clogged by for- 

 eign substance. They are easily removed and are made of perforated monel metal 

 or monel metal wire gauze. The openings in the strainers are smaller than the 

 throat of the nozzles. 



The particular features of this type of air ejector are: — 



I. The use of a radial jet (from which the Radojet has derived its name), 

 which has a greater penetrating force and larger entrainment surface than that of 

 a cylindrical jet of equal length. Consequently better efficiencies are obtained. 



