The characteristics of mixing impellers covering flow, solid suspension, gas dispersion, blending, circulators, and wastewater applications are shown.New impellers are described in terms of process gains, and the development is shown using lab studies, Laser Doppler Velocimeter, and computational fluid dynamics.
Discussion on the use and verification of CFD models for blending, solid suspension, and gas dispersion. Describe the development of an automated preprocessor for the Fluent code and the use with MRF and sliding mesh models
Discussion of the problems and characteristics of mixing in the pharmaceutical industry and solutions to maximize yields.
Analysis of scale-up and scale-down for the many similarity functions in mixing. An example is that it is easy to blend on a small scale but difficult to achieve homogeneous blending on a large scale.
The mechanical design of a mixer is analyzed with emphasis on the fluid forces that are imposed on the impellers by the fluid continuum in the mixing vessel. The importance of the mechanical interaction of the mixing process with the mixing vessel and impeller is stressed.
The evolution of draft tube circulators in mixing applications is shown. Applications include precipitators and other configurations showing required head-flow characteristics.
1. Determine what is required for the process.
2. Determine what is the optimum impeller type for the process is.
3. Use tools to analyze different impeller designs.
4. Determine fluid forces for impeller and shaft design.
5. Develop methods of manufacture.
This shows better solid suspension of A310 compared to pitch blade turbine at 60% of the power
Comparing the better blending of A410 versus a marine propeller.
Computational Fluid Dynamics
Used to obtain Flow and Turbulent characteristics.
The studies are used to define the Power Number (Np), Flow Number (Nq), and shear characteristics on the Impeller.
Power = Np * Density * (Speed)^3 * (Impeller Diameter)^5 Flow = Nq * (Speed) * (Impeller Diameter)^3 As a function of Reynolds Number, Froude Number, Gas Rate, Proximeter to Tank Walls, etc.
Measure Dynamic Blade and Shaft Loading as a function of Reynolds Number, Froude Number, proximeter of tank configuration, gas rate, etc., to correctly design mechanical stress loadings.
Specific manufacturing methods allow different functional designs for the process. Strive to obtain process gains with cost-effective manufacturing methods.
Fluid forces are reaction forces of the fluid on the mixing impeller as a result of transient fluid flow asymmetries. (See paper by Weetman and Gigas 2002)
These loads are dynamic and are transmitted from the impeller blades to the mixer shaft, gear reduce,r and mixer support structure.
Fluid forces are amplified in the presence of dynamic resonance conditions. This occurs if resonances are at the shaft speed or the blade passage frequency.
Weetman uses the state of the Art "Pimento" Portable Spectrum Analyzer.
Low-Frequency Accelerometers and Proximeter are used to measure vibrations and forces.
By applying a force at the impeller, the mixer system can be calibrated to measure the fluid forces. ( Weetman patent).
*Weetman Patents and Trademarks assigned to SPX Process Equipment, Lightnin Operation
Figures: Courtesy of SPX Process Equipment, Lightnin Operation
Copyright (2020) Ronald J. Weetman, Ph.D. Fluid Mixing Consultant