Pelton Wheel Bucket Design (Solidworks)

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@tofo2 3 жыл бұрын

Nice tricks A short note: =========== I think the design using an elliptical shape is favorable. The mechanics of the bucket first should reflect water has low friction to the surface and feels pressure forces perpendicular to the surface like air against a sail. In a stationary bucket it keeps constant speed as nothing slows it down in the direction it is heading. The forces are perpendicular to direction of motion and only pushes water to change direction. If a bucket would move in a straight line at constant speed half of the jet, once onboard, an observer sitting on the spoon knowing nothing about the outside world, would just notice water enters at jetspeed/2 and exits in reverse direction it came in and still at jetspeed/2 without any energy lost. On the spoon there are no moving parts so the acceleration forces does not do any work. In the outside world to where the bucket is fastened, the bolts transfer the force the onboard observer reported. But in the outside world the force moves linearly and exerts work. And look!, The water falls dead as the reverse motion in the bucket is canceled by its forward motion and it has lost all its energy. Indeed energy has been transferred from water to the mechanical motion. One thing to notice is at impact the when water is forced to follow a curve, the molecules only communicate with each other through pressure forces and internal friction of the liquid, so pressure in the liquid will start accelerating them sideways and on all further paths they travel this balance of dispersion and internal pressure and acceleration will be in balance. Therefore the crush the beam as little as possible a curved surface reduces the "tear" and chaos in the water. Use all available time in the bucket to keep acceleration constant to reduce stress and diversion. As the cup in reality moves in a circle the cup turns while water makes its way in its Newtonian stubbornness. It means to the observer at the spoon the nozzle flies across the sky. For a molecule at a rotating bucket if the bucket where discus -shaped it would look the same no matter at what angle water enters it would be reflected back opposite the direction it entered. It would just slide sideways in the cup as it rotates but follow the shape presented to water in the direction it is moving. So if the cup is a discus moving away from the nozzle it will reflect back water in reverse. Now the cup does not only rotate. It is pulled out of the jet as it rotates. So for the discus to reflect water back it has to be stretched and compensate for where the water molecule is currently at in its sliding path through the bucket. The surface where water lands should always reverse water backwards from where it came while the spoon rotates and retracts. And the water mass lives it life split up in two reverse flows on a plane in line with the nozzle centerline and parallel to the turbine axis. In real life as with few cups on a small wheel a water molecule travels through the cup at surfaces with variating distance from center of rotation. This means the frame of reference for the observer on the spoon is obscured. It is not in fact it steady pace, the molecule fells it accelerates both due to centrifugal forces and coriolis forces when radius changes. Fortunately centrifugal forces are small as water can just slide "sideways" and stay on it´s plane if the cup surface adjusts for it as it turns. As the water molecule makes it through the cup moving in a circle it should only feel forces along the plane it is split. Actually many shapes will do as long as water is treated with elegance and comes to a halt and drops dead. I think it impossible to treat all molecules fairly. In reality they will be all over the place, but an engineer must always have a concept even if it is wrong.

@samwebb9373 3 жыл бұрын

Hi Tore, Thank you for your response, very interesting. Perhaps it would be useful to play around with some CFD to find out what the optimum surface geometry of the bucket should be to produce the maximum power on the wheel. I think you are right that the solution would be much more complex than the rectangular shape of the bucket in my video, if that is what you are trying to say. Sam.