Vertical Pump Cavitation Suppression via Submerged Impeller
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Solution Overview
Problem
In liquid pressurizing apparatuses, cavitation often occurs at the impeller on the inlet side due to low suction pressure, leading to increased installation space and facility costs when attempting to suppress cavitation through booster pumps or elevated water heads.
Innovation Solution
A multi-stage vertical pump configuration with the first stage impeller positioned below the installation surface, reducing the number of pump revolutions and eliminating the need for a booster pump, while maintaining high discharge pressure and minimizing installation space by incorporating a tank above the device surface and a recessed pump design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If suction pressure is increased by using a booster pump, then cavitation is suppressed, but the number of installation devices increases
Solution Approach 1:
Instead of increasing suction pressure by adding a booster pump upstream, the invention inverts the approach by positioning the first stage impeller below the installation surface. This allows the impeller to be submerged in the liquid, creating negative suction pressure conditions that prevent cavitation without requiring additional pressurizing equipment.
Solution Approach 2:
The invention changes the vertical dimension of impeller placement from above/below the installation surface to below the installation surface. By positioning the first stage impeller in the vertical dimension below the surface level, the system utilizes the liquid head available at that depth to prevent cavitation, eliminating the need for a booster pump.
2Reliability
If water head is increased by providing a tank above the liquid pressurizing apparatus, then cavitation is suppressed, but installation space increases
Solution Approach 1:
Rather than placing the tank high above the apparatus to increase water head, the invention inverts the approach by placing the first stage impeller below the installation surface. This creates the necessary suction pressure conditions without requiring excessive vertical space above the device.
Solution Approach 2:
The solution shifts from utilizing vertical space above the installation surface to utilizing vertical space below the installation surface. By positioning the impeller below the surface, the system achieves cavitation suppression while minimizing the height requirements for the tank and overall installation space.
3Stress or pressure
If the number of impeller stages is increased to secure high discharge pressure, then discharge pressure is improved, but the number of revolutions of the pump increases leading to cavitation
Solution Approach 1:
Instead of increasing pump speed to achieve high discharge pressure, the invention inverts the approach by positioning the first stage impeller below the installation surface. This allows the use of multiple impeller stages at reduced speeds, as the submerged position provides adequate suction pressure to prevent cavitation even at lower revolutions.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration effectively suppresses cavitation, reduces installation space, and lowers facility costs by eliminating the need for a booster pump and optimizing the pump's design to achieve high discharge pressures without increasing equipment size or complexity.
Implementation Method 1
a tank (2) provided on a device installation surface (GL) for storing liquid so that a fluid level (FL) is located above the device installation surface (GL)
Implementation Method 2
multi-stage impellers (7) arranged in a vertical direction... a first stage impeller (7A)... configured such that the liquid from the suction port (5) flows into the first stage impeller (7A)
Implementation Method 3
cavitation is likely to occur on an impeller on an inlet side if suction pressure is small... it is possible to suppress cavitation in the first stage impeller by reducing the number of revolutions of the pump
Data Source
AI summary
A liquid pressurizing apparatus, comprises a tank provided on a device installation surface for storing liquid so that a fluid level is located above the device installation surface; and a vertical pump including a suction port connected to the tank, multi-stage impellers arranged in a vertical direction, and a discharge port for discharging the liquid passing through the multi-stage impellers. The multi-stage impellers include a first stage impeller positioned at the lowest part of the multi-stage impellers and being configured such that the liquid from the suction port flows into the first stage impeller. The first stage impeller is disposed below the device installation surface.