Progress 06/15/09 to 05/14/10
Outputs
OUTPUTS: This research project collected data allowing MDM Inc. to design a single-stage, high-efficiency axial flow pump capable of delivering 600 gallons per minute (GPM) of water at 2.5 ft of total dynamic head (TDH) to benefit the aquaculture community. This pump will dramatically reduce operating costs associated with recirculating aquaculture, encouraging the use of closed recirculating aquaculture systems by making the culture species produced in these systems cost-competitive with culture species produced in open systems. Task 1 was to assemble a prototype to be used as a test/calibration fixture to collect the data necessary for CFD modeling. Before assembly of the test fixture, each of the actual dimensions was compared to the design drawings to verify accuracy. The CFD model needed to be as accurate as possible since inaccuracies in the calibration data could have lead to incorrect model predictions. Measurements included propeller size and balance, shaft length and balance, and vane alignment and curvature. Calibration testing indicated that the test pump design could achieve a peak efficiency of 21% - unacceptably low for a commercially viable product, but higher than the efficiencies found during the internet search for available pumps for the theoretical system described above. A total of three configurations were run, and duplicated, at motor rotational speeds ranging from 1,200 rpm to 3,600 rpm to provide sufficient data for the CFD modeling. No configuration approached the design goals for either flow rate or efficiency during the data collection phase of this experiment. CFD software tools, working interactively with a comprehensive test program, provided a robust design cycle that allowed us to optimize the stage design in a minimum number of prototype iterations. Actual test data was fed back into the design software, facilitating refinement of coefficients to produce designs with efficiencies far exceeding products that are now available. The feedback loop of putting actual test data back into the model assured that the coefficients used for the performance predictions were updated and refined to reflect the experience. While actual pump performance rarely matches completely the software performance predictions at off-design conditions, at the design point, head flow and efficiency are generally within 3-5% of the predicted values. A number of the proposed pump configurations failed to converge to a solution during the CFD analysis. To obtain a response surface analysis, design parameters were calculated using standard theory from authors such as A.J. Stepanoff and J.F. Gulich. Based on standard theory, a simulated annealing optimization approach was used to randomly search the design space within preset limits and let the software find the designs that passed the highest number of criteria. The most promising output from the annealing simulation was used to optimize design performance by systematically exercising one variable at a time. PARTICIPANTS: Gene Ashe functioned as the PI in this project. He provided all the administration and project management to keep the project on goal. He also managed all the project communication between the team members. Ted Struttmann, as the Co-PI, was responsible for the CFD model analysis and construction. For Task 1 he functioned as the primary test and data collection engineer throughout various points in the project work plan, Stan Spence was called upon to implement the test fixture modifications and construction requirements. That also necessitated his help in the equipment assembly and helping Ted as a test assistant. Mechtronix, as noted before, was the project's primary CFD consultant. He evaluated the CFD calibration data and used that for the actual CFD model construction and analysis. Baldor, our motor vendor/consultant, provided the production constraints to any design that came out of the CFD based on production parts close to the design parameters of the roteller. TARGET AUDIENCES: Commercial-scale marine aquaculture has the potential to close the gap between an increasing demand for high quality seafood products and the maximum sustainable yields from marine fisheries. (Some project that the world's finfish catch will vanish by 2050). Intensive recirculating aquaculture systems (RAS) are recognized as a critical component of a commercially viable marine aquaculture development program, whether supporting systems for offshore cage culture, as broodstock and nursery facilities serving pond production sites, or as autonomous growout facilities. Intensive recirculation systems can avoid many land use and environmental problems involving the development of marine aquaculture facilities in coastal wetlands and lowlands. . RAS and water re-use systems use three types of pumping devices: 1. Air-lift systems, using air bubbles to lift water like an aquarium filter, 2. Standard pumps like those used in the swimming pool industry and 3. Axial flow pumps used in the commercial irrigation market. All are installed to circulate high water volumes through intensive filtration and to do so reliably. All of the present designs fall short when it comes to providing energy efficient performance. Air-lift systems don't require a lot of energy, but are severely limited in the actual lift or pressure they can provide. Standard swimming pool pumps can provide the flow and pressure demands, but their energy efficiencies are poor, not well matched to most of the applications. Axial flow pumps, the most efficient design for moving large volumes of water at low pressures, are made in sizes too large for RAS and small-flow applications. SBIR-supported Qsys design innovation provides high flow with sufficient pressure at unprecedentedly low energy cost, the key requirement for filtration system sub-components. Order of magnitude better performance is obtained with simpler internal designs that minimize turbulence. Axial flow or propeller-like designs move more fluid per watt than conventional centrifugal pumps. The physics are literally straightforward; water movement in an axial-flow pump does not take a 90 deg. turn, as in centrifugal pumps. The Qsys design has virtually no footprint due to its unique "pump-in-a-pipe" configuration. It looks just like a 4-6 inch piece of pipe, but an axial-flow pump will be inside. One end is the intake and the other end is the discharge with standard pipe flanges on either end. Retrofitting is simplified in that a section of pipe can be removed in order to install the pump. Results of this research are very encouraging. The proposed pump configuration promises to provide significant energy-related cost savings in the targeted market. A SBIR Phase II project is planned, to construct and evaluate a prototype. PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
The 3 propellers that meet our design objectives are capable of delivering an average of 597 GPM at 10 ft of TDH with efficiencies in excess of 90%. These designs differ only in the discharge angles of the hub and shroud and the wrap angles of the hub and shroud. As such, the design that will be chosen for Phase II will be based on ease of manufacturing, and therefore lowest cost. . Based on the results of the CFD model analysis, our motor consultant Baldor Inc. performed analyses to determine if a motor design could be combined with the wet rotor recommendations received from Mechtronix. Baldor was to determine if the current design iteration could be married to existing standard stator and rotor designs constrained by current production methods. Baldor was to further determine if laminations in both the axial and radial directions could be fit within the design envelope. The implementation of the research to evaluate Task 3 was, by its nature, an iterative process. The results of the CFD were used to create a combined rotor/propeller (roteller) that could deliver the stated performance goals. The resulting roteller design was forwarded to Baldor for evaluation against standard production stators capable of operating in the proposed "squirrel cage" configuration---a common stator to rotor design in which the rotating electrical field generates a rotating magnetic field that produces the torque to drive the rotor. There is no physical contact between the rotor and the stator as the torque generation is transmitted via alternating electric fields through an air gap separating the two. Baldor advised that there was no reason that the rotating electric field would travel through water (a water gap) with any more difficulty than it would through an air gap. The problem encountered was the focus on "production" stators. Although a stator configuration was available that would provide the necessary performance characteristics, it required a redesign of the roteller. No technical obstacles were evident designing a stator that would power the optimized roteller, but there was not sufficient budget in the Phase I proposal for prototype development of the magnitude necessary to create a custom-designed stator and roteller. The results of this research and our investigations into the potential commercialization of the final product are very encouraging. The proposed pump configuration promises to provide significant energy cost savings as indicated by the projected flow, head, and efficiency targets being met. The research method deviated from that proposed due to a number of unforeseen difficulties; specifically the inability of the proposed response surface methodology and the stator configuration. However, the alternate methods used to circumvent those obstacles provided for an enhanced understanding of the pump mechanics and the design constraints that will drive the Phase II effort to construct and evaluate a prototype. MDM is currently seeking alternate stator manufacturers who will be better suited to developing a custom prototype stator that will fit the optimized roteller that resulted from this research.
Publications
- No publications reported this period
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