Flexible Impeller for Liquid-Ring Vacuum Pump Cavitation
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Solution Overview
Problem
Liquid ring vacuum pumps face high stress and cavitation issues due to their rigid impellers, leading to efficiency losses and potential damage, as they must operate far from the cavitation limit to avoid damage, which reduces efficiency.
Innovation Solution
The impeller is made of a non-fiber-reinforced plastic material with a modulus of elasticity less than 4000 N/mm2, allowing for significant deformation and absorption of alternating loads, thereby reducing stress and cushioning sudden loads during cavitation, allowing operation closer to the cavitation limit without reducing service life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the impeller is designed with high stiffness to ensure reliable and low-vibration operation, then the impeller can withstand alternating loads, but deformation is prevented which necessitates larger tolerances between the impeller and pump housing, increasing leakage and reducing pump efficiency
Solution Approach 1:
The patent changes the material parameter (modulus of elasticity) from conventional high-stiffness materials (>100,000 N/mm²) to flexible materials (200-4000 N/mm²). This parameter change allows the impeller to deform elastically under load, maintaining tight tolerances and reducing leakage while still withstanding alternating loads through elastic recovery, thereby resolving the contradiction between strength and efficiency
Solution Approach 2:
The patent employs composite material structures, particularly fiber-reinforced plastics, which combine the flexibility of the polymer matrix with the strength of embedded fibers. This composite approach provides both the necessary elasticity to accommodate deformation and the structural integrity to resist loads, simultaneously achieving both high strength and high efficiency
2Reliability
If the impeller is made with high stiffness to prevent deformation under alternating loads, then reliability is improved, but sudden loads from cavitation are transmitted unfiltered to other pump components, causing potential damage
Solution Approach 1:
The flexible impeller material acts as a built-in cushion that absorbs and dampens sudden cavitation loads before they can be transmitted to other pump components. The elastic deformation of the impeller material during cavitation events dissipates impact energy, protecting the pump housing and other components from damage while maintaining operational reliability
Solution Approach 2:
Changing the material's modulus of elasticity to a lower range (200-4000 N/mm²) provides inherent damping characteristics that filter out high-frequency cavitation shocks. This parameter change transforms the impeller from a rigid load transmitter to a flexible load absorber, reducing harmful factor transmission while preserving reliability
3Duration of action of stationary object
If the pump operates far from the cavitation limit to avoid damage, then the impeller service life is extended, but pump efficiency is reduced due to the clearance required
Solution Approach 1:
The patent changes the operational parameter by allowing the pump to operate much closer to the cavitation limit (within 10-20% margin) compared to conventional pumps. The flexible impeller material's ability to withstand cavitation loads through elastic deformation enables this closer operation, simultaneously maintaining impeller service life and maximizing pump efficiency through reduced clearances
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 flexibility reduces the risk of damage from cavitation, increases pump efficiency by allowing operation closer to the cavitation limit, and minimizes noise emissions due to the material's damping properties.
Implementation Method 1
the impeller consists of a material whose modulus of elasticity is less than 4000 N/mm2... the impeller deforms significantly more under the influence of forces than comparable impellers made of conventional materials... the material is suitable for yielding to alternating loads and cavitation forces, thereby reducing stress
Implementation Method 2
Unreinforced plastic materials also offer the advantage of low noise emissions during cavitation operation, as they possess good damping properties
Data Source
Figure 1~2
Figure 3
AI summary
A liquid-ring vacuum pump comprises a pump casing (20) and an impeller (14) that is eccentrically mounted in the pump casing (20). According to the invention, the impeller (14) is made of a material having a modulus of elasticity of less than 4000 N/mm2. The invention further relates to an impeller (14) for such a pump.