Liquid Ring Pump Air Injection for Start-Up Cavitation Control
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Solution Overview
Problem
Liquid ring pumps experience start-up cavitation and noise due to the slow opening of non-return valves, which is particularly problematic in low-pressure/high-vacuum conditions, leading to wear and failure.
Innovation Solution
Introduce a flow of air into the inlet manifold of the liquid ring pump during start-up by controlling the opening and closing of a valve within predetermined time periods to prevent rapid pressure drops.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a non-return valve is used at the inlet of the liquid ring pump, then gas flow in the opposite direction is prevented, but the valve opens slowly causing start-up cavitation
Solution Approach 1:
A gas supply line introduces air into the inlet manifold before the pump starts pumping, preparing the system for smooth operation. This preliminary action ensures gas is available in the inlet manifold when the pump starts, preventing cavitation during the transition period when the non-return valve is closing or has closed.
Solution Approach 2:
The gas supply line acts as an intermediary system that provides a controlled source of gas to the inlet manifold. This intermediary mechanism decouples the direct dependency between the non-return valve opening speed and the gas availability in the inlet manifold, allowing the pump to operate smoothly regardless of the valve's opening characteristics.
2Object-generated harmful factors
If the non-return valve opens slowly, then reverse flow is blocked, but cavitation and noise occur during start-up
Solution Approach 1:
The gas supply line is activated before the pump starts operation, introducing air into the inlet manifold in advance. This preliminary gas introduction ensures that when the pump starts and the non-return valve begins to close, there is already gas present in the inlet manifold to prevent the pressure drop that causes cavitation and noise.
Solution Approach 2:
The slow closing of the non-return valve, which initially appears harmful by creating a transition period vulnerable to cavitation, is actually beneficial as it provides a natural timing signal. The gas supply line exploits this timing by introducing gas during the valve closing period, converting the potentially harmful slow closure into a beneficial timing mechanism for cavitation prevention.
3Object-affected harmful factors
If gas is introduced into the inlet manifold during start-up, then cavitation is prevented, but additional system complexity is required
Solution Approach 1:
The gas supply line with solenoid valve is controlled automatically by a controller that activates it at the appropriate time during pump start-up. This self-service approach eliminates the need for manual intervention or complex external control systems, as the system automatically manages the gas introduction timing based on pump operation status.
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
Reduces or eliminates start-up cavitation and noise, improving pump efficiency and reducing wear, while maintaining effective vacuum operation.
Implementation Method 1
the non-return valve can open only relatively slowly, e.g. over several seconds. The present inventors have further realised that this may lead to cavitation occurring within the liquid ring pump at start-up
Data Source
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AI summary
A system (2) comprises: a suction line (34); a liquid ring pump (10) coupled to the suction line (34), the liquid ring pump (10) comprises a chamber (102) and an impe-ller (106) mounted within the chamber (102); a non-return valve (6) arranged to per-mit fluid to flow into the chamber (102) via the suction line (34) and to prevent or o-ppose fluid flow out of the chamber (102) to the suction line (34); a gas line (36) co-upled to the liquid ring pump (10) such that gas may flow into the liquid ring pump (10) via the gas line (36), which is coupled to the liquid ring pump (10) between the non-return valve (6) and the chamber (102); a valve (8) disposed on the gas line (36); and a controller (20) configured to control the valve (8). The system tends to be desirable to prevent or oppose start-up cavitation in the liquid ring pump.