Circular Rake Impeller for High-Distance Particle Suspension
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Solution Overview
Problem
Existing impellers in mixing applications, such as oil refinery and anaerobic digester tanks, face challenges in generating sufficient fluid velocity to suspend particles at large distances without excessive power draw or mechanical thrust, often requiring draft tubes that increase energy input and hinder efficient mixing.
Innovation Solution
An impeller design with blades featuring a circular raked helical geometry, variable pitch, and camber lines following an exponential curve, inducing primarily axial flow at the root and radial flow at the tip, minimizing power consumption while maintaining effective particle suspension across large distances without the need for draft tubes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a typical marine-style helical blade design is used, then mechanical thrust force is optimized, but fluid flow for mixing applications is not optimized
Solution Approach 1:
The blade geometry parameters are changed from traditional marine propeller designs to specific mixing-optimized parameters including circular rake angle, helical angle, and blade pitch distribution, transforming the impeller from thrust-optimized to flow-optimized configuration
Solution Approach 2:
The design approach is inverted by starting with fluid flow optimization requirements rather than mechanical thrust requirements, reversing the traditional marine propeller design philosophy to suit mixing applications
2Speed
If impeller diameter or blade tip velocity is increased to generate sufficient mixing velocity at distance, then particle suspension capability improves, but power draw increases
Solution Approach 1:
The blade pitch distribution is optimized to create a more efficient velocity profile, and the circular rake geometry is tuned to maximize flow collimation, achieving better mixing velocity at distance without proportional increases in power consumption
Solution Approach 2:
The circular rake geometry with curved blade surfaces creates more efficient fluid acceleration compared to straight or flat blade designs, improving power efficiency for generating mixing velocity at distance
3Productivity
If draft tubes are added to generate mixing flow at the bottom of the tank, then particle suspension at distance is achieved, but energy input and device complexity increase
Solution Approach 1:
The draft tube component is extracted/removed from the system by designing an impeller that generates sufficient mixing flow and velocity at distance without requiring the draft tube, simplifying the overall structure
Solution Approach 2:
The impeller is designed to self-generate the necessary mixing flow and velocity distribution throughout the tank without requiring additional components like draft tubes, making the system self-sufficient
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 impeller effectively suspends particles at significant distances with reduced power draw, enhancing mixing efficiency and eliminating the requirement for draft tubes, thus optimizing fluid flow and energy usage in large tanks.
Implementation Method 1
Each blade may define a leading edge having an approximately circular raked helical geometry
Implementation Method 2
capable of accelerating a near-zero intake velocity fluid, to generate a mixing zone that is collimated enough to have sufficient velocity vectors to suspend particles at a large distance away from the impeller
Data Source
AI summary
An impeller, a system for mixing a fluid, and a method of mixing a fluid in a tank are disclosed. For a sufficiently small impeller diameter and maximum blade tip velocity, the disclosed impeller, system, and method are capable of accelerating a near-zero intake velocity fluid, to generate a mixing zone that is collimated enough to have sufficient velocity vectors to suspend particles at a large distance away from the impeller, while minimizing the required power draw. An impeller may include a hub defining a longitudinal axis and plural blades spaced circumferentially about the hub. Each blade may include a root portion and a tip portion. Each blade may define a leading edge having an approximately circular raked helical geometry. A system for mixing a fluid may include a tank for containing the fluid, a drive shaft for extending into the tank, and the impeller.