An ejector is intended to move high gas-cut fluids and has a convergent section for an entry to the straight throat which is again followed by a divergent section. The throat has a very short entry transition and a straight section followed by a divergent section. Then admixture of working and suctioned substance with the steady pressure and velocity profile leaves the ejector. An eductor is a device intended to move high liquid-cut fluids. reduced velocity) as well as increase in liquid pressure was caused. At the inlet of the divergent section (expanding channel) there must be subcritical flow according to Huguenot theorem, so that compression (i.e. In case of subcritical flow, the mixing chamber has a shape of a cylinder and in case of supercritical flow it is tapered to slow down the flow. At the outlet of the suction chamber of the nozzle the admixture of substances has the same pressure but different velocity profile, that is to be conditioned in the mixing chamber.

Thanks to that there is a negative pressure formed in the suction chamber and it begins to suck-in the secondary (driven) liquid. Due to expansion in the nozzle the pressure is dropped and the velocity of the primary liquid is increased. This is partcularly relevant to vacuum systems - refer to the graph of a typical case below.The ejector works on the principle that the working substance enters the suction nozzle, that can be either classical tapering or Laval’s one, downstream which there can be supercritical flow. At above this back pressure, reverse flow of entrained gas will occur. The breakpoint occurs when the back pressures exceeds the maximum discharge pressure that the ejector can maintain even for zero entrainment. Additional aspects such a breakpoint analysis could be included. If there is an interest in this program, it could be made available. This is particularly relevant for vacuum ejectors.Ī computer program has been developed that determines the performance curve for a specific ejector geometry. The motive gas pressure and flow rate are kept relatively constant - the control systems maintain the balance between entrained gas pressure and flow and the discharge pressure. As the operating point moves away from the design point, performance will deviate increasingly from the ideal curves above. The particular ejector selected will have the correct geometry for optimal performance at one particular design point.

Each point on the curves above represents performance for an ejector that has been sized for the specific conditions.

Ejector design calculation software