During operation under varying conditions, the variation in the vibration frequency of the liquid ring vacuum pump (unit) is closely related to the dynamic balance of the internal liquid ring, gas-liquid interaction, and mechanical structural characteristics. As the core device relying on the liquid ring to create a vacuum, its vibration frequency fluctuations directly reflect the impact of changes in operating conditions on the stability of the liquid ring. This impact persists throughout the entire cycle of intake, compression, and exhaust.
When the intake pressure of the liquid ring vacuum pump (unit) decreases, the liquid ring needs to withstand a higher vacuum, leading to a decrease in liquid ring thickness and changes in surface tension. At this time, the contact state between the liquid ring and the impeller blades changes, and the liquid ring is prone to periodic fluctuations under the combined effects of centrifugal force and vacuum negative pressure. This fluctuation causes the liquid ring vibration frequency to rise, especially near the ultimate vacuum level, where the stability of the liquid ring decreases significantly, and the vibration frequency may exhibit a non-linear growth trend. Conversely, when the intake pressure increases, the liquid ring thickness increases, the interaction between the liquid ring and the impeller tends to stabilize, and the vibration frequency decreases accordingly.
Changes in exhaust pressure also have a significant impact on the liquid ring vibration frequency. Under high-pressure exhaust conditions, the liquid ring must overcome greater back pressure to complete the exhaust process, resulting in violent compression fluctuations in the exhaust zone. This intensifies the elastic deformation of the liquid ring, and the vibration frequency tends to rise due to increased energy dissipation. Under low-pressure exhaust conditions, however, the compression process is relatively gradual, and the vibration frequency remains low. It is worth noting that sudden changes in exhaust pressure can trigger transient instability in the liquid ring, resulting in short-term peaks in the vibration frequency.
Changes in the working fluid temperature are a key factor influencing the vibration frequency of the liquid ring. As the working fluid temperature increases, its saturated vapor pressure increases, accelerating the evaporation rate of the liquid ring, resulting in a decrease in thickness and density. This change in physical state weakens the liquid ring's damping effect, making it more sensitive to impeller rotation and subsequently increasing the vibration frequency. Furthermore, high-temperature working fluid reduces the liquid ring's surface tension, further exacerbating its fluctuation characteristics. Conversely, low-temperature working fluid enhances the liquid ring's stability and suppresses increases in vibration frequency.
Changes in impeller speed have a dual impact on the liquid ring's vibration frequency. At low speeds, the interaction between the impeller and the liquid ring is weak, resulting in low vibration energy and a low vibration frequency. However, as the speed increases, the centrifugal force exerted by the impeller on the liquid ring intensifies, causing both the vibration amplitude and frequency to increase. However, when the speed exceeds a critical value, the liquid ring may rupture due to excessive centrifugation, leading to drastic fluctuations in the vibration frequency and even equipment shutdown. Therefore, proper control of the impeller speed is key to maintaining a stable vibration frequency of the liquid ring.
The variation in the vibration frequency of the liquid ring of a liquid ring vacuum pump (unit) under variable operating conditions is essentially a reflection of the dynamic equilibrium of the gas-liquid two-phase flow. Changes in operating parameters such as suction pressure, discharge pressure, working fluid temperature, and impeller speed all affect the vibration characteristics of the liquid ring by altering its physical state and energy distribution. In practical applications, optimizing the equipment structure, controlling operating parameters, and strengthening condition monitoring are necessary to ensure that the liquid ring vibration frequency remains within a safe range, thereby ensuring stable operation and a long life of the liquid ring vacuum pump (unit).
