Therefore ejector curves at fixed ejector geometry are calculated at the design discharge pressure and an increased discharge pressure (see 3.2). These are more indicative of the response of a specific ejector to changes in inputs. The motive gas Mach No is provided for information.
Feb 25, 2018 helo there, first off kudos on simple crisp and to the point explanation. But could you help me with the design calculations for a simple ejector with air as the motive and suction fluid please. August 19, 2018 at 2:53 pm.
The term jet ejector describes a device in which a pumping effect is achieved using a motive fluid. A jet ejector requires no mechanical drive and has no moving parts. This basic principle applies to every jet ejector in different models and ranges of application. The application determines the design of the flow section.
A steam jet ejector is illustrated below as example (steam serves as motive fluid to create vacuum). The function depends, above all, on the design of the motive nozzle (2) and of the diffuser (4 + 5). The motive fluid passes successively through these two components.
Most ejectors have a fixed capacity curve as shown in Figure 1. In this type of ejector the capacity is a function of the absolute pres-sure at the suction inlet. Increasing the steam pressure above the design pressure will not increase the capacity of the ejector: as a matter of fact, it will actually decrease the capacity because of the.
The flow section will change along this path. The pressure in the motive nozzle (2) decreases and the velocity rises. Conversely, the flow is decelerated in the diffuser (4 + 5) while its pressure increases to the discharge pressure at the outlet of the jet ejector.
The section between motive nozzle (2) and diffuser (4 + 5) has the lowest static pressure, approximately equivalent to the suction pressure ps. At this point the suction flow enters into the ejector head (3) through the suction connection B and is mixed with the motive fluid flowing with high velocity. Part of the kinetic energy is transferred to the suction flow. Motive flow and suction flow pass together - as a mixture - through the diffuser, loosing velocity and gaining pressure. The increase from suction pressure ps to discharge pressure pd corresponds to the delivery head for the suction flow or to the pressure difference of the jet ejector. The ratio pd / ps is the compression ratio of a jet ejector.
Ejector Design Calculation Software 2016
ln a jet ejector the static pressure energy of the motive flow which cannot be directly transferred is thus converted into kinetic energy. Pvsyst software full version free. download full. This kinetic energy can be released to the suction flow by impulse transfer while both flows mingle. The diffuser converts the kinetic energy of the mixture consisting of motive flow and suction flow back into static pressure energy.
Ejectors Design
ln the steam jet vacuum ejector illustrated below, the critical pressure ratio is exceeded in the motive nozzle (2) (this can be recognized by the expansion of the nozzle cross-section downstream the minimum throat diameter.) The steam velocity exceeds the sonic velocity accordingly. Motive flow and suction flow are mixed at supersonic velocity and then decelerated to the sonic velocity upon reaching the diffuser throat. ln the diverging section of the diffuser, the pressure finally increases to the discharge pressure pd.
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