Hi Thor, Very good advice on the dimensioning of the system, as well as very good links. You gave the formula regarding the diameter of the wheel vs the RPM. But I wonder what is the best RPM for the system. Obviously it should be given by the alternator we are using, but I am planning to make a homemade alternator (like they are doing it from scratch on several wind turbine projects). Therefore what would be the best RPM for such a system ? Concerning the alternator, do u have any advice for me ? I wanted first to use a simple induction motor, but many of them needs to have a gigantesque RPM (up to 10'000 for the little model I have !). For ur info, I have a head of 22m (~67 feet), with 22l/min (~5.8gpm). Hope to get ~50W at most, so nothing wilde, but I can have it 24h a day, 365days a year. Think worth the game !
Thanks for your help, Dominique --- Þórhallur Ragnarsson <[EMAIL PROTECTED]> wrote: > Hi Sergio. > > Some useful links: > > http://www.tev.ntnu.no/vk/publikasjoner/ > A textbook for students on hydro power machinery. > http://www.tev.ntnu.no/vk/publikasjoner/pdf/ArneKjolle/chapter2.pdf > http://www.tev.ntnu.no/vk/publikasjoner/pdf/ArneKjolle/chapter3.pdf > Detailed theory with formulas for many types of > turbines. > > http://www.microhydropower.net/ > Good general explanation of the Pelton turbine with > pictures. > http://www.microhydropower.net/turbines.html#Pelton > > http://en.wikipedia.org/ > Wikipedia, the free encyclopedia that anyone can > edit. > http://en.wikipedia.org/wiki/Pelton_wheel > > http://www.ecoinn.co.nz/ > Very well made runners with plastic spoons, > excellent pictures. > http://www.ecoinn.co.nz/product_detail.php?id=58 > > http://www.pressure-drop.com > Software to calculate pressuredrop for all kinds of > fluids, pipes, > fittings, nozzles, etc. > You can test it 4 weeks free. If you want use the > program after this time > you have to register by the author. > > Pressure-Drop can be used to find nozzle diameter > (by trial and error). > (I have not searched for a jet diameter formula > based on pressure and flow). > > http://www.du.edu/~jcalvert/tech/fluids/turbine.htm#Impu > Good explanation of Pelton turbine with formulas. > > Summing this up: > Bucket size approximately 2,5 - 4 times jet > diameter. > (Too small buckets do not use all the water > efficiently, > but too big buckets create more aerodynamic drag) > Water exit angle approx. 165deg (so the water does > not hit the back of next > bucket). > The edges where the jet hits the buckets should be > sharp to minimize losses. > The spacing between the buckets is made as big as > possible, > but not larger than to secure that all water > particles will hit a bucket. > > Theoretical velocity of jet: V = sqrt(2gh). (In > practice a bit less) > Peripheral velocity of the runner: u (u can take any > value from 0 to V) > Maximum power is obtained when u = V/2 (again in > practice a bit less) > Theoretical optimum RPM = 60*sqrt(2gh)/(2*pi*D) so > in theory D = > 42.3*sqrt(h)/RPM > A "practical" formula I found somewhere is: D = > 38.6*sqrt(h)/RPM > considering losses. > Rotor diameter (D) and jet diameter (d) are not > related in theory, > but there is a practical limit around D/d = 10, (a > large jet will partially > miss a small rotor). > > (A simple solution to find suitable jet diameter for > the pressure and flow > you are dealing with, could be to take a conical > nozzle from a sealant tube > and experiment with a knife........) > > Best Regards. > > Thor. > -------------------------------------------------------------------- > Thorhallur Ragnarsson Electronics > Technician/Instructor > Holtakoti > Verkmenntaskolinn Akureyri > IS-641 HUSAVIK > Eyrarlandsholti > Iceland IS-600 > AKUREYRI > [EMAIL PROTECTED] Iceland > [EMAIL PROTECTED] [EMAIL PROTECTED] > http://www.simnet.is/holtakot > http://thor.vma.is/not/thor > -------------------------------------------------------------------- > > > At 17:10 17.9.2005 +0000, kunoserg1703 wrote: > >Hi, it´s the Guatemalan student. I was wondering if > any of you can > >help me finding the formulas on pelton design. > > > >I specifically need to know the bucket dimensions, > and what is their > >relation with other pelton dimensions. I also need > to know the > >relationship between rotor and nozzle dimensions. I > have tried to find > >them over the internet, but I could only find the > velocity relations, > >and power formula. If anyone can point me to a web > page that contains > >the dimensions formulas, or email me them, I would > appreciate it. > >Thanx. > > > >Sergio Linares > > > > > > > > > > > > > > > >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. 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