Coolant Impeller Layout for Dry-Run Motor Cooling in Pumps
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Solution Overview
Problem
Existing pumps, particularly submersible-rated pumps, face issues with insufficient coolant flow to the motor during extended dry-run cycles, overheating due to clogged passages, and the inability to isolate the working impeller from the coolant impeller, especially in applications where the motor is not fully submerged.
Innovation Solution
A pump design featuring a secondary coolant impeller with an offset suction eye and a mechanical seal, coupled to a drive shaft, which circulates coolant through a dedicated chamber to cool the motor effectively, even in dry-run conditions, and includes a motor shroud to separate coolant from the fluid being pumped.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single impeller is used to pump fluid, then the pump structure is simple, but the motor cannot be effectively cooled during dry-run cycles
Solution Approach 1:
The pump is divided into two functional sections: a primary impeller for fluid pumping and a secondary coolant impeller for motor cooling. This segmentation allows independent optimization of each function, with the secondary impeller specifically designed to circulate coolant through the motor housing during dry-run cycles to prevent overheating.
Solution Approach 2:
The secondary coolant impeller serves multiple functions: it circulates coolant through the motor housing for cooling, creates a vacuum at its suction eye to draw coolant through the system, and works in conjunction with the primary impeller's discharge to establish continuous coolant flow. This multi-functionality addresses the cooling need without adding excessive complexity.
2Temperature
If axial impellers are used to increase coolant flow, then cooling performance improves, but the head provided by single-stage units is limited
Solution Approach 1:
Different impeller types are used for different functions: the primary impeller is designed for fluid pumping with appropriate head generation, while the secondary coolant impeller uses axial blades optimized for high-volume coolant circulation. This local quality differentiation allows each impeller to excel at its specific task without compromising the other function.
Solution Approach 2:
The coolant circulation operates in a separate dimensional space from the primary fluid pumping. The secondary impeller creates a dedicated coolant flow path through the motor housing, independent of the primary fluid discharge. This dimensional separation allows the coolant system to provide sufficient flow for cooling without being constrained by the head requirements of the primary pumping function.
3Volume of moving object
If both working impeller and coolant impeller are located along the same drive shaft, then space is saved, but isolation between the two impellers becomes difficult
Solution Approach 1:
The coolant impeller is extracted from the primary fluid handling path and positioned in a separate coolant chamber. The mechanical seal is strategically placed to separate the coolant chamber from the primary fluid chamber, ensuring that coolant and pumped fluid remain isolated despite both impellers sharing the same drive shaft. This extraction maintains compact positioning while ensuring functional isolation.
Solution Approach 2:
The mechanical seal acts as an intermediary barrier between the primary fluid chamber and the coolant chamber. It allows the drive shaft to pass through while maintaining separation between the two fluid systems, enabling both impellers to operate on the same shaft without contamination or interference between the working fluid and coolant streams.
4Volume of moving object
If narrow passages are provided around the motor for coolant circulation, then compact design is achieved, but passages become clogged in solid handling applications
Solution Approach 1:
The secondary coolant impeller creates a vacuum at its suction eye before coolant enters the motor housing passages. This preliminary vacuum action draws coolant through the system and helps prevent debris accumulation. Additionally, the mechanical seal positioning and coolant chamber design ensure that coolant flow paths are established before solids can interfere with the circulation.
Solution Approach 2:
The coolant flow parameters are optimized by adjusting the secondary impeller blade geometry and suction eye positioning to create sufficient velocity and pressure differential. This ensures coolant flows rapidly through the motor housing passages, preventing solids from settling or clogging the passages even in compact designs.
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
The design ensures efficient coolant circulation to the motor, preventing overheating and maintaining pump performance across various operational conditions, including dry-run cycles, while isolating coolant and fluid streams effectively.
Implementation Method 1
The secondary impeller is adapted for circulating a coolant in the cavity
Implementation Method 2
the liquid in which it is submerged can provide a sink for the heat generated by the motor
Data Source
AI summary
A circulation system is provided to move a coolant liquid in a coolant chamber (44) formed between a housing (40) and a motor shroud (42) of a pump (10) for a fluid being worked upon. The circulation system has a coolant impeller (54) in a coolant impeller chamber (56). The coolant impeller is driven by a drive shaft (20) that also drives a primary impeller (24) that moves the fluid being worked on. The coolant impeller is positioned along the drive shaft between the motor and the primary impeller. The coolant impeller has a wide inner portion (74) and a peripheral base disk (76) that define a radially-offset suction eye (72) and support a plurality of impeller blades (70). A seal spring (86) compressively acts on the inner portion, providing a mechanical seal.