El mar, 02 de 11 de 2004 a las 05:38, Michael Lawley escribi�: > Hi, > > To answer your questions. Below is data relayed to me by the client, I'm not > convinced about the accuracy of the data but here it is. > > Original unit was running at 131m on the gauge, 24- volt battery system. > The client has opened up the jet measuring the exhaust water and current flow to the > batteries. It seems a bit erratic to me so there is probably some experimental error > here. Our agent called in recently and advise that his measurements were at best > approximate, but is gives a general picture. > > Results below are for a worn bronze Pelton rotor > 2.5mm jet, 0.25 L/s, 1.5 amps, 36 Watts, 11% > 2.77mm jet, 0.3 L/s, 4 amps, 96 Watts, 25% > 3.0mm jet, 0.35 L/s, 7 amps, 210 Watts, 47% > 3.17mm jet, 0.40 L/s, 11 amps, 264 Watts, 52%
looks quite good (way too good?) performance for a car alternator. why did he use so small nozzles? it seems he has at least 1 l/s available in his stream > > The only result we got back for our turbine was with 5.1mm jet on the same > installation > delivering 30 amps at 24 volts. > > 5.1mm jet, 1 L/s, 30 amps, 720 Watts, 56% not bad... some efficiency gain. > > > We find that running a large rotor keeps the rpm down, the losses to air friction > and bearings are less at a lower rpm. We still run the Pelton rotor at its optimum > rpm and the Smart Drive magnetic rotor can be moved in and out to alter the running > speed until you achieve maximum output. > My understanding is that (at least for Pelton runners) that there are optimum nozzle-to-bucket and nozzle-to-p.c.d. (10-11%) relationships that one should not stray too far. Is it the case too for Turgo runners? or is this arrangement more tolerant? > I cannot agree that there is any rotor efficiency loss, if you run it at its optimum > speed (a little under half the theoretical jet velocity) the rotor will maintain > efficiency. > with 130 m head you have a Vjet around 50 m/s, and if you go with a 1000 RPM generator you'd need a runner with about 40 cm p.c.d. to match vjet/2. What is the pcd of your turgo runner? Best regards, Max > Regards > > > > Michael Lawley > Renewable Energy Engineer > EcoInnovation > 671 Kent Road > R.D.1 > New Plymouth > New Zealand > > Phone: (NZ) 06 752 2765 > Web site: www.ecoinn.co.nz > email: [EMAIL PROTECTED] > > > ----- Original Message ----- > From: Max Klohn > To: [EMAIL PROTECTED] > Sent: Tuesday, November 02, 2004 2:32 AM > Subject: Re: [microhydro] Abrasion and surface hardness > > > > Hi Michael, > > a "large", low RPM rotor at such high head and low flow? what is the % > efficiency penality you get from that choice? > > I agree from my own experience that car alternators are quite > inefficient, so the smartdrive efficiency gain should compensate for the > rotor efficiency loss. Just for curiosity, how much power was your > client getting before and now? > . > Max > > El vie, 29 de 10 de 2004 a las 17:33, Michael Lawley escribi�: > > By way of example, we recently supplied a turbine on a site with a 135m of head, > flow 0.5-1 L/s. > > > > The turbine the clients been using for the last 2 years had a bronze Pelton > rotor made in the USA using a car alternator. The bronze rotor has been all but worn > away after 2 years of continuous use. Also the car alternator needed the brushes > replacing every 6 months and overhauling every 12 months. With a small PCD rotor it > was running at about 2500 rpm. After 2 years of running the bronze rotor is very > badly worn and unusable. > > > > We supplied this client a plastic Pelton rotor turbine on a trial basis to see > what would happen. The rotor PCD is much larger as it is only running at 1000 rpm on > a smart drive PMG. > > > > After 50 days on test the client has decided to purchase the turbine, he has > indicated that some wear has occurred but is happy with the unit. After talking to > the client most of the wear occurred when he was doing high flow tests. We has a > 100mm line (way to large for the low flow he has most of the time). When he opened > up the line with a larger jet accumulated grit/slit in the line started to move and > sand blasted the rotor for may hours (the line is long and it took time to clean > out). His view is that most of the wear occurred at this time as up to this point > there was no noticeable wear on the spoons. > > > > We normally only approve them up to 100m of head. You can see from this example > that 135m might be pushing it. Even if the spoons only last 6 months, 4 sets are > still only a fraction of the price of the bronze unit. In fact he could buy over 10 > sets of replacement spoons for the price of one bronze rotor. If you always have a > spare set on hand then it is not a problem. It will not be long before we see > Chinese injection moulded Pelton spoons that will make even our ones look expensive. > > > > Metal spoons have advantages but the labour component required to polish and > balance them means that there are expensive to make in developed countries with high > labour rates. Injection moulding on the other hand takes about 10 seconds a shot. > > > > For most clients in the 20-70m range (that we commonly supply) we have not had > any reports of wear problem and we have enough of them out there to have heard of a > problem if it existed. We wouldn't give a 2 year warrantee if we thought they > wouldn't do the job. > > > > > > > > Regards > > > > > > > > Michael Lawley > > Renewable Energy Engineer > > EcoInnovation > > 671 Kent Road > > R.D.1 > > New Plymouth > > New Zealand > > > > Phone: (NZ) 06 752 2765 > > Web site: www.ecoinn.co.nz > > email: [EMAIL PROTECTED] > > > > > > ----- Original Message ----- > > From: Marc de Piolenc > > To: [EMAIL PROTECTED] > > Sent: Friday, October 29, 2004 1:52 PM > > Subject: [microhydro] Abrasion and surface hardness > > > > > > > > I'm a little disturbed at the assumption, evident in > > many recent messages, that a hard surface is > > necessarily more resistant to abrasion than a soft > > one. This is not correct, and people on this list in > > particular need to be aware of that. > > > > When a hard abrasive particle hits a hard surface, it > > loses nearly none of its kinetic energy, and in a > > turbulent stream may strike the surface again and > > again, each time spalling or scraping off a small > > amount of material. > > > > When it hits a soft surface, it tends to lose energy - > > essentially embedding itself temporarily. This can > > often result in LESS wear on a soft surface than on a > > hard one. The ultimate useful application of this > > property is in an industrial process called lapping, > > in which a soft tool (the lap) charged with an > > abrasive, is used to remove material from a much > > harder workpiece. > > > > It is therefore incorrect to assume that a plastic > > turbine bucket will necessarily have less wear in it > > than a metal bucket of the same profile. It MAY be so > > - not all soft surfaces have the property of resisting > > wear - but that must be substantiated by test. Surface > > hardness is only one of the relevant parameters. > > > > Best, > > Marc de Piolenc > > Iligan City, Philippines > > > > > > > > __________________________________ > > Do you Yahoo!? > > Yahoo! Mail Address AutoComplete - You start. We finish. > > http://promotions.yahoo.com/new_mail > > > > > > > > > > > > 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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