Nandi, I've recently built a turbine and helped a fellow select a pump for direct drive from the turbine. I haven't heard yet how it worked. In principle there are a couple of issues to consider. First, a centrifugal pump, unlike most generators, has a specified direction of rotation. With a Pelton, there is no issue as it is symmetric and can be flipped over to change the direction of rotation. A turgo on the other hand can also be turned over, but it changes the jet entrance and exit faces. In the case of the turbine I just built for this application this meant that the jet exit needed to be on the pump side. Normally I would prefer the other way so that it is easier to keep water off the pump bearings. A Pelton will deflect water toward the pump bearings no mater which direction of rotation is required.
The other factor is matching the torque vs. rpm curves of the pump and turbine. With a pump, the torque increases with rpm. With a turbine, the torque is highest at 0 rpm and decreases to 0 torque at freewheel rpm. Somewhere in the middle the two curves intersect. That will be the operating point. You need to match the turbine to the pump so that that point of intersection is also at the peak power rpm of the turbine. This rpm should also be a point compatible with matching the pump's output head and flow to that required by your application. The torque/power vs. rpm for the turbine can be computed with a momentum balance. I have such a spreadsheet for any impulse turbine on my web site. Unfortunately, it is setup only for units of hp, ft-lb, etc. See http://h-hydro.com/turgo_drive.html near the bottom of the page Most pumps are designed to be driven by an electric motor at 3600 or 1800 rpm (assuming 60Hz, or 3000/1500 rpm at 50 Hz). You should be able to obtain a pump curve from the manufacturer. These pump curves will likely be at 3600 or 1800 rpm. To scale to a different rpm, what is knows as "turbomachinery affinity laws" are used. These laws help scale a geometrically similar design to a larger or smaller size, or scale the performance of a fixed unique device as head, flow, rpm, power, etc. need to be changed. In the recent case I helped with, he was eventually able to find a 1200 rpm pump that matched his needs, but it was a custom industrial pump. This link has some info, but you can google "turbomachinery affinity laws" and find dozens of referrences. http://caltechbook.library.caltech.edu/22/01/chap1.htm For the same pump run under different conditions "D" or the characteristic diameter (usually the impeller or runner diameter) is fixed, and flow varies with rpm (double rpm doubles flow capacity), Head varies with rpm^2 (double rpm = 4x head) and the same for torque. Power varies as rpm^3. So if you have a pump rated at 1800 rpm and run it at 1400 rpm, its flow is reduced to 78%, head & torque to 60% of the 1800 rpm value, and power is reduced to 47% of the rated power. Joe --- In [email protected], "S.N.Group of Companies" <[EMAIL PROTECTED]> wrote: > > hi all!!!! > > > has any bodythought of using turbines to drive centrifugal pumps > directly?? > we are currently working on a concept wherein the turbine shft will be > directly connected to the drive shaft of a centrifugal pump . providing > flow all year round . > any help in this matter is solicited. > > regards, > nandi > ------------------------ 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/
