Critical flow steam jets

Steam jets, especially the primary jets, are forced out of critical flow, most commonly because... 

Cavitation can also lead to local destruction of protective layers. In rapidly flowing liquid and on solid surfaces that oscillate in the liquids, gas or steam bubbles are produced at sites at which the pressure in the liquid is briefly lowered to vapor pressure due to flow in excess of the critical flow rate threshold. When the pressure is raised again, these bubbles collapse suddenly (implosion) and a jet of liquid hits the material surface at a high rate of speed. This sudden stress load pattern is continuously exposing or creating active surfaces on which increased corrosion (cavitation corrosion) takes place in an aggressive medium. 

A simple method to influence the operational behaviour of a jet compressor is to throttle the motive pressure by a control valve. With a control as shown in Figure 4.9, the motive steam pressure can be reduced and thereby the motive mass flow rate is similarly reduced. This means that for lower motive flows the critical discharge pressure is also reduced. But as previously explained, this has no direct influence on either the suction capacity or the suction pressure, as long as the actual discharge pressure is lower than the critical one. 

---