Multistage Centrifugal Pump Recirculation Flow Control
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Solution Overview
Problem
Conventional multistage centrifugal pumps face challenges in accurately meeting required discharge flow and delivery head, especially at low specific speeds, due to manufacturing tolerances and geometric dependencies, making it difficult to adjust discharge flow without impacting delivery head.
Innovation Solution
A multistage centrifugal pump design incorporating a recirculation path with a flow control rod that adjusts the recirculation flow from downstream of the first stage impeller to the suction chamber, allowing for easy modification of discharge flow without altering the hydraulic unit's geometry, thereby enabling precise adjustment of discharge flow to match desired values at a given delivery head.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the geometry of the hydraulic unit (impellers and diffusers) is adapted to adjust discharge flow, then the discharge flow can be modified, but the delivery head is substantially impacted and manufacturing precision is compromised due to tolerances
Solution Approach 1:
The pump system is segmented into a fixed hydraulic unit (impellers and diffusers) that maintains delivery head, and a separate recirculation flow control mechanism that adjusts discharge flow. This segmentation allows independent optimization of each function without compromising the other.
Solution Approach 2:
A recirculation path acts as an intermediary mechanism between the pump outlet and inlet, allowing a portion of the discharged fluid to be redirected back to the suction chamber. This intermediary system enables discharge flow adjustment without modifying the hydraulic unit geometry, thereby preserving delivery head accuracy.
2Adaptability or versatility
If impeller trimming is used to adjust discharge flow, then discharge flow can be modified, but it is difficult to exactly meet required delivery head and discharge flow due to manufacturing tolerances
Solution Approach 1:
The recirculation flow control rod provides a dynamic adjustment mechanism that can be modified after manufacturing. Unlike static impeller trimming, the control rod allows continuous adjustment of the recirculation opening area, enabling precise matching of both delivery head and discharge flow requirements.
Solution Approach 2:
The system changes the parameter being adjusted from hydraulic unit geometry (which affects both head and flow) to recirculation flow rate (which primarily affects discharge flow). By controlling the recirculation opening area parameter, the system can independently tune discharge flow while maintaining delivery head.
3Adaptability or versatility
If a universal hydraulic unit is used to produce various pump curves, then adaptability is improved, but discharge flow adjustment is difficult without geometric modifications
Solution Approach 1:
The recirculation path with adjustable control rod serves as an intermediary mechanism that enables discharge flow adjustment without requiring geometric modifications to the universal hydraulic unit. This maintains ease of operation while achieving adaptability.
Solution Approach 2:
Instead of changing geometric parameters of the hydraulic unit, the system changes operational parameters by adjusting the recirculation flow rate. This allows a single universal hydraulic unit to produce various pump curves through parameter adjustment rather than geometric modification.
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 design allows for flexible adjustment of discharge flow to match specific application needs, using a universal hydraulic unit to produce various pump curves with the same set of impellers and diffusers, reducing the need for geometric modifications and enhancing efficiency, particularly in applications requiring low discharge flow and high delivery head.
Implementation Method 1
A recirculation path for the fluid is provided comprising at least one return opening and extending from the return opening to the suction chamber, wherein the return opening is located at or in the flow path downstream of the first stage impeller and upstream of the last stage impeller
Implementation Method 2
wherein a flow control rod is disposed in the recirculation path, and wherein the flow control rod is configured for adjusting a recirculation flow through the recirculation path into the suction chamber
Implementation Method 3
at least a first stage impeller and a last stage impeller for conveying the fluid from the inlet along a flow path to the outlet
Data Source
AI summary
A multistage centrifugal pump for conveying a fluid includes a pump housing with an inlet to receive the fluid and an outlet to discharge the fluid, a first stage impeller and a last stage impeller to convey the fluid from the inlet to the outlet, a shaft to rotate the first stage impeller and the last stage impeller about an axial direction, a suction chamber arranged upstream of the first stage impeller and in fluid communication with the inlet, a recirculation path for the fluid including a return opening and extending from the return opening to the suction chamber, the return opening located at or in the flow path downstream of the first stage impeller and upstream of the last stage impeller, and a flow control rod disposed in the recirculation path, the flow control rod to adjust a recirculation flow through the recirculation path into the suction chamber.