"[EMAIL PROTECTED]" wrote: > > Hi, > > I am another newbie to the group, with a question. > I currently have a 12" (diameter) x 22" crossflow turbine set horizontally at > the end of a 11" (interior diameter) 13" (OD) pipe from a pond providing 10' > useable head. There is enough water to run the pipe full. The turbine is set > and works well, but I have not yet achieved a good nozzle design, in > particular: > what is the configuration and size of the rectangular opening, and how is the > shielding set up to allow water to reach the turbine blades without waste. > Diagrams, references, ideas welcome. Thanks. Chas Daloz
Chas, It is convenient to classify crossflow turbines according to their nozzle design and the method used to regulate part flow. As you may be aware crossflow turbines are able to operate over a wide range of head and flow conditions. The high part flow efficiency of this design makes it very suitable for these applications. The classification is: a simple valve or segment (Banki), hydraulic flap (Ossberger) profile shaped semicircular segment (Cink). A posting to this group dated 12 Feb 1999 from "Jerrytex Ltd." <[EMAIL PROTECTED]> contained an attachment named FRANJIC.DOC. It contains much of interest on this topic including detailed drawings of the Ossberger and Cink type of nozzles. If you are unable to locate this document from the group's archives, please let me know and I will email you a copy. The Banki type is the easiest to make, although perhaps it is a little less efficient than the others. Adjustment so that the stream strikes the blades correctly is essentially one dimensional. We have found that the stream has a tendency to fly over the top of the runner, however this can be greatly reduced by careful adjustment. Note that only a small number of blades are active in transferring power from the stream to the shaft at any one time. This generates vibration and much greater stresses on the blades than would otherwise be the case. For the Ossberger and Cink types this is much less of an issue. For the Banki type, the water exits the nozzle as a narrow stream having a rectangular cross section, with a width equal to the runner width and a thickness typically equal to 9.5% to 10% of the runner diameter, at full flow. This is the maximum thickness possible - increasing this value will allow more water through but will not increase output. Indeed it may even flood the turbine. The nozzle stream can however be thinner, and this is one of the nice things about the crossflow turbine - it performs well on part flow. A stream thickness of approx. 3.5% of runner diameter is considered the practical lower limit. We have built turbines with an adjustable flap that permits the depth of the stream to be adjusted according to the available flow. The software I use for doing the calculations you are now concerned with is at: http://www.planetarypower.com.au/info/microhydro/WalshHydro.xls It covers much more than you need, so just pick out the bits that interest you. The accompanying manual is at http://www.planetarypower.com.au/info/microhydro/crossflow_design.pdf Hope this helps and best of luck, Regards, Max Enfield Planetary Power ------------------------ Yahoo! Groups Sponsor --------------------~--> Get fast access to your favorite Yahoo! Groups. Make Yahoo! your home page http://us.click.yahoo.com/dpRU5A/wUILAA/yQLSAA/FGYolB/TM --------------------------------------------------------------------~-> Does your company feature in the microhydro business directory at http://microhydropower.net/directory ? If not, please register free of charge and be exposed to the microhydro community world wide! NOTE: The advertisements in this email are added by Yahoogroups who provides us with free email group services. The microhydro-group does not endorse products or support the advertisements in any way. More information on micro hydropower at http://microhydropower.net To unsubscribe: send empty message to [EMAIL PROTECTED] Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/microhydro/ <*> To unsubscribe from this group, send an email to: [EMAIL PROTECTED] <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
