The Core Structure of the Ejector Valve
The vacuum pump ejector valve functions much like a precision-tuned air violin, with three key components playing in concert: The nozzle (which constricts the airflow channel), the mixing chamber (a zone for pressure conversion), and the diffuser (an energy recovery section). As compressed air rushes through the nozzle at speeds of 200–300 m/s, it creates a low-pressure zone within the mixing chamber; external gases are then entrained and swept away by this high-velocity stream, thereby achieving a vacuum effect. Interestingly, for every 1 mm reduction in nozzle diameter, the jet velocity increases by approximately 15%, though energy consumption rises correspondingly.
Aerodynamic Characteristics
During operation, the ejector valve exhibits two remarkable airflow phenomena: the *ejection effect* (where one volume of motive gas can entrain and carry away 3 to 5 volumes of the gas being evacuated) and *shock-wave pressurization* (a sudden surge in pressure as the airflow decelerates within the diffuser). Experimental data indicates that when the Mach number at the nozzle exit reaches 1.5, the vacuum level within the mixing chamber can attain 0.8 bar; furthermore, an optimized diffuser angle (typically between 8° and 12°) can boost kinetic energy recovery efficiency to over 70%.
The Art of Parameter Adjustment
In practical applications, it is essential to strike a balance across three key parameters: *motive gas pressure* (efficiency peaks between 0.4 and 0.6 MPa), *gas temperature* (efficiency declines by 1.2% for every 10°C rise), and *back-pressure tolerance* (entrainment capacity drops precipitously if the back pressure exceeds the design limit by more than 30%). Experience demonstrates that regularly cleaning carbon deposits from the nozzle (on a monthly basis) can maintain over 95% of the original performance, while adopting a stepped, multi-stage ejector design can further enhance the vacuum level by an additional 15–20%.
