Hydro Posted December 31, 2023 Report Posted December 31, 2023 I wanted to discuss one design of a free-flow hydroelectric power station. To start, here's a video I came across online. https://www.youtube.com/watch?v=C1jyFKnUzps If anyone is interested, I will try to explain the principle of operation as I understand it
OceanBreeze Posted December 31, 2023 Report Posted December 31, 2023 Please proceed with your explanation and hopefully include the supporting math and physics. This forum can benefit from such a discussion. I personally would appreciate it if you can make your presentation here, without too much reliance on a youtube video. Thanks
Hydro Posted December 31, 2023 Author Report Posted December 31, 2023 This is not our video. Some kind of development from Romania. As the developers say (automatic translation into English): The design is a system (two rows) of rectangular blades (flat plate), the axes of which divide them into two unequal parts, the larger of which is always (due to the action of the flow) located behind the axis further downstream. The axes of the blades, with their upper and lower parts, are, in turn, fixed to the upper and lower chains closed in rings (or to any other flexible element). The chains transmit force through sprockets (impellers) to two vertical shafts, from which the mechanical energy of the moving medium (water, air, etc.) is transmitted through a flexible coupling and intermediate shaft to the shafts of electric generators. The designers state that: 1. Behind the turbine, the water has a speed 2-3 times greater than the flow entering the turbine. 2. Behind the turbine, the water level drops (exactly how much is not specified). 3. A few meters down from the turbine, a certain stable water vortex appears. 4. The power that such a hydraulic station produces is 2-3 times higher than a conventional free-flow turbine of the same size. I would like to start by discussing how real this is and is it possible?
OceanBreeze Posted January 1 Report Posted January 1 Without any data provided, the best I can do, speaking as a marine engineer, is point out some of the more obvious problems with this design. 1) Far too many moving parts. This will have a negative effect on both efficiency and reliability. 2) The application of hydrodynamic force is not smooth and continuous, as it is applied to basically two sets of flat plates moving in opposite directions, resulting in low torque and low efficiency. A much more efficient design which overcomes both of the above problems would be a modern version of an Archimedes screw; an Archimedes Hydrodynamic Screw turbine. You should instinctively note the smooth hydrodynamic profile. In fact, the entire body of the screw can be printed out using composite materials by a 3D printer. With experience, one can actually make a judgement on how well a hydro-power machine will work just by looking at it. Does your device even look like it belongs in the water? It doesn’t look very hydrodynamic to me. How about that screw; does it look as if it naturally belongs in a water environment? I’ll let you answer that! This design has achieved an efficiency of 70% (ratio of available hydraulic power to mechanical power extracted). Why build something with so many moving parts when a much simpler design will perform even better? https://www.researchgate.net/publication/326057381_Experimental_Evaluation_of_Advanced_Archimedes_Hydrodynamic_Screw_Geometries
Hydro Posted January 1 Author Report Posted January 1 It seems counterintuitive that a turbine not only produces energy, but also accelerates the flow. It seems that if a turbine takes energy from the flow, then it should slow down the flow. Doesn't anyone find this strange? Here's another video, more visual, I think. Now I’ll try to put a scientific article on this topic here
Hydro Posted January 1 Author Report Posted January 1 (edited) 1 hour ago, OceanBreeze said: Without any data provided, the best I can do, speaking as a marine engineer, is point out some of the more obvious problems with this design. 1) Far too many moving parts. This will have a negative effect on both efficiency and reliability. 2) The application of hydrodynamic force is not smooth and continuous, as it is applied to basically two sets of flat plates moving in opposite directions, resulting in low torque and low efficiency. A much more efficient design which overcomes both of the above problems would be a modern version of an Archimedes screw; an Archimedes Hydrodynamic Screw turbine. You should instinctively note the smooth hydrodynamic profile. In fact, the entire body of the screw can be printed out using composite materials by a 3D printer. With experience, one can actually make a judgement on how well a hydro-power machine will work just by looking at it. Does your device even look like it belongs in the water? It doesn’t look very hydrodynamic to me. How about that screw; does it look as if it naturally belongs in a water environment? I’ll let you answer that! This design has achieved an efficiency of 70% (ratio of available hydraulic power to mechanical power extracted). Why build something with so many moving parts when a much simpler design will perform even better? https://www.researchgate.net/publication/326057381_Experimental_Evaluation_of_Advanced_Archimedes_Hydrodynamic_Screw_Geometries I looked at the article. This Archimedes Hydrodynamic Screw turbine is a potential water head turbine. And it works on differences in water levels - water head. In fact, this can be seen in the picture. I have shown a free-flow hydraulic power station without using a water head. Like this one I think this is a fundamental difference. Edited January 1 by Hydro
OceanBreeze Posted January 1 Report Posted January 1 Of course, the Archimedes Hydrodynamic Screw turbine works best on differences in water levels - water head. However, it also works very well with a level flow of water passing through the screw. The new picture you posted is not anything like the design you originally posted. The picture shows a very workable Hydrodynamic turbine. I suggest you stay with a design like that, and forget about the original design you posted . .it will not work well.
Hydro Posted January 1 Author Report Posted January 1 You are absolutely right. We have already discussed among ourselves and decided that the design shown at the beginning is not very optimal kinematically. But I wanted to discuss not the actual design of this machine, but its operating principle. And it is different from the one shown below. As a result, it is significantly more energy efficient. It’s not for nothing that at the beginning I cited 4 points that distinguish the functionality of such a turbine from a standard one 1. Behind the turbine, the water has a speed 2-3 times greater than the flow entering the turbine. 2. Behind the turbine, the water level drops (exactly how much is not specified). 3. A few meters down from the turbine, a certain stable water vortex appears. 4. The power that such a hydraulic station produces is 2-3 times higher than a conventional free-flow turbine of the same size. I provide an article that describes the principle of its operation If everything is clear here, then I will continue
Hydro Posted January 5 Author Report Posted January 5 It seems to me that in this article the author draws attention precisely to the principle of operation, focusing not on the design of this device, but on the fact that various designs of such devices can be developed on this principle. Probably this design was taken as an example in which it was easiest to explain the principle. IMO
Hydro Posted January 9 Author Report Posted January 9 I found several more articles on this topic. Some are not in English. In my system this language is defined as Serbian. The automatic translation seems to be clear. For now I’m posting only the most interesting from my point of view
Hydro Posted January 10 Author Report Posted January 10 There, the text mentions the Froude number. As far as I know, in hydraulics and shipbuilding the Froude number is written slightly differently.
Hydro Posted January 11 Author Report Posted January 11 On 1/4/2024 at 4:52 PM, OceanBreeze said: I will need some time to review this. OceanBreeze, do you have an opinion on this article? Do you think that these calculations are not applicable to the design shown at the beginning of the topic?
Hydro Posted January 19 Author Report Posted January 19 I found another article on this topic. If no one has any opinions or objections to the previous ones, then I’ll post the next one. No objections?
OceanBreeze Posted January 19 Report Posted January 19 7 hours ago, Hydro said: I found another article on this topic. If no one has any opinions or objections to the previous ones, then I’ll post the next one. No objections? No objections. The articles are interesting. Unfortunately I still have not found the time to fully read/understand them. If I am able to get up to speed enough to make a meaningful comment, you will see it here.
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