Model Turbines

[Turbine GuyParticipant @turbineguy]

I glued Rotor 6 PLA shown in the last post to a shaft and ran it in Tangential Turbine 6 shown in the following drawing and spreadsheet. I made an error in guessing where to glue Rotor 6 PLA on the shaft which resulted in getting much higher compression on the spring than I wanted, but as you can see in the spreadsheet the performance wasn’t that bad for the first test. Normally I would run several tests to find the optimum position of the rotor in the housing and the best spring compression before adding the performance in the spreadsheet. When I disassembled the turbine to reposition the rotor on the shaft, I found that the extension of the rotor on its outer face had broken off. I mentioned in the last post that the rotor was designed to be cast in bronze and had several areas that were two thin for a material like PLA. I am in the process of trying to fix the rotor assembly but it will require enough changes that it will have to be called a new assembly.

[Michael GilliganParticipant @michaelgilligan61133]

I must confess that I only dip-in occasionally  … but I am always impressed by your dedication to this research.

Thanks for sharing it

MichaelG.

[Turbine GuyParticipant @turbineguy]

Hi Michael,

Thanks for your kind comment.  I try to show how well turbines have performed for several designs of varying complexity and requiring different equipment to make or parts to purchase.  I hope that this information will help people thinking about making a model turbine what they can expect in performance for models like the types tested.

Hope you are doing well,

Byron

[Turbine Guy]

On Turbine Guy Said:

I glued Rotor 6 PLA shown in the last post to a shaft and ran it in Tangential Turbine 6 shown in the following drawing and spreadsheet. I made an error in guessing where to glue Rotor 6 PLA on the shaft which resulted in getting much higher compression on the spring than I wanted, but as you can see in the spreadsheet the performance wasn’t that bad for the first test. Normally I would run several tests to find the optimum position of the rotor in the housing and the best spring compression before adding the performance in the spreadsheet. When I disassembled the turbine to reposition the rotor on the shaft, I found that the extension of the rotor on its outer face had broken off. I mentioned in the last post that the rotor was designed to be cast in bronze and had several areas that were two thin for a material like PLA. I am in the process of trying to fix the rotor assembly but it will require enough changes that it will have to be called a new assembly.

I fixed the rotor assembly mentioned in the quoted post by glueing Rotor 6 PLA to a set screw collar as shown in the following photo. I used the glue from my fly tying kit that was designed to bond plastics to metal and it was strong enough for me to finish the testing of Rotor 6 PLA. I was able to try various positions of the rotor in the housing and try various amounts of spring compression by changing the number of shim washers. My thinnest shim washers are only 0.001” thick so I can find the ideal location of items very close to their best positions. It took me several tests to find the ideal position of the rotor assembly shown in the following photo but the ideal position did not get any better performance than I got with the original rotor assembly as shown in the drawing of the quoted post. Reducing the spring force pressing the rotor against the inner ball bearing did not increase the performance so apparently the original assembly as shown in the quoted post gave the best performance for Rotor 6 PLA and the spreadsheet in the quoted post has the best performance for the Tangential Turbine 6.

[Turbine Guy]

On Turbine Guy Said:

I want to see how the model turbines I have built compare with ones that can be purchased. The Radial Turbine Link describes the Radial Turbine I just purchased shown in the photo below. The radial turbines seem to be the type most available and I have not tested this kind of turbine. I picked this particular model since it appeared to be a good design that seems to have ball bearings on each side of the rotor as shown in the drawing below. It also includes a speed reducer which is something I have also wanted to test. I created a Radial Turbine 1 folder and will update it as I get more information. This model is coming from China so It will be about a month before I receive it.

Edited By Turbine Guy on 09/01/2023 20:55:37
Edited By Turbine Guy on 09/01/2023 20:58:27

The quoted post describes my purchase of the turbine I call Radial Turbine 1. The posts following this post discuss my testing of this turbine and what others have done with this turbine. I believed that I could improve the performance by designing a radial turbine for the GWS EP 2508 propeller I use in my turbine performance spreadsheet. I thought that by reducing the blade height, covering the blade on both sides, increasing the amount the flow is turned, and adding a radius to turn the exhaust flow would improve the performance. I 3D printed the rotor I call Radial Rotor 2A shown in the following photo and used it in what I named Radial Turbine 2 shown in the following drawing. The following spreadsheet was updated to include the performance of this turbine.  This design did significantly improve the performance over Radial Turbine 1.

[Turbine Guy]

On Turbine Guy Said:

On Turbine Guy Said:

I want to see how the model turbines I have built compare with ones that can be purchased. The Radial Turbine Link describes the Radial Turbine I just purchased shown in the photo below. The radial turbines seem to be the type most available and I have not tested this kind of turbine. I picked this particular model since it appeared to be a good design that seems to have ball bearings on each side of the rotor as shown in the drawing below. It also includes a speed reducer which is something I have also wanted to test. I created a Radial Turbine 1 folder and will update it as I get more information. This model is coming from China so It will be about a month before I receive it.

Edited By Turbine Guy on 09/01/2023 20:55:37
Edited By Turbine Guy on 09/01/2023 20:58:27

The quoted post describes my purchase of the turbine I call Radial Turbine 1. The posts following this post discuss my testing of this turbine and what others have done with this turbine. I believed that I could improve the performance by designing a radial turbine for the GWS EP 2508 propeller I use in my turbine performance spreadsheet. I thought that by reducing the blade height, covering the blade on both sides, increasing the amount the flow is turned, and adding a radius to turn the exhaust flow would improve the performance. I 3D printed the rotor I call Radial Rotor 2A shown in the following photo and used it in what I named Radial Turbine 2 shown in the following drawing. The following spreadsheet was updated to include the performance of this turbine.  This design did significantly improve the performance over Radial Turbine 1.

I noticed in the spreadsheet that I added in the copied post that the available energy for Radial Turbine 2 was not correct and resulted in an efficiency lower than it should be. The rest of the data added for Radial Turbine 2 is correct. I deleted the spreadsheet in the copied post and added the corrected spreadsheet below. The improvement in efficiency of Radial Turbine 2 compared with Radial Turbine 1 was very substantial. 3D printing the rotor with PLA filament did not produce as good of a finish as the 3D printed nylon parts I was getting from Shapeways that I have shown in this thread. The nylon is stronger and easier to machine but is not recommended by Flashforge for my 3D printer. Even with these deficiencies rotors 3D printed from PLA are strong enough and the finish smooth enough to make rotor with pretty good efficiency as shown in the last few posts.

 

[Turbine Guy]

On Turbine Guy Said:

I am convinced that the concept of the 3 blade rotor given in the link that was shown in the 18/04/2023 post is good but the simplicity is very deceptive. To work correctly, the surfaces must be smooth, the clearances very small, and must have minimum deflection. I have tried to come up with a low cost method to accomplish these goals but as I explained in the last few posts I had problems for each thing I tried. The finish of printed aluminum was way too rough. The wiping over edges rather than cutting off cleanly was a problem machining the printed nylon. The cost of CNC machining was way too expensive. The rotor would have to be supported on both sides to keep the deflection low enough. My goal for any of the turbines is to have a design that can be made at a reasonable cost and only require relatively simple machining so this is getting too complicated. Since 3 Blade Turbine 3 was able to get as good performance as some of the turbines I have tested even with the problems my rotors had, it shows the potential of this concept.
Edited By Turbine Guy on 08/07/2023 16:08:35

I mentioned in the quoted post the trouble I have experienced trying to make a model of the 3 blade rotor concept described in the 18/04/2023 post. I 3D printed a rotor I call 3 Blade Rotor 4 out of PLA and added it to the assembly I call 3 Blade Turbine 4 shown in the following drawing. The finish and accuracy of the channel that turns the flow like a blade was better than I got on the rotor 3D printed out of nylon by Shapeways. All the critical surfaces were very smooth and the accuracy of the channel was good enough to keep the flow from the nozzle in the narrow channel with the very tight clearances. The accuracy of the outer surfaces was also good enough to allow the very close clearance between the rotor inner face and the housing. The PLA machined to a very smooth finish without wiping over the edges. 3 Blade Rotor 4 was still supported the same way as 3 Blade Rotor 3 so I was not able to reduce the deflection of the rotor and close the clearances any further. I updated the following spreadsheet to show the test of 3 Blade Turbine 4. Getting the flow passages more accurate and smooth increased the efficiency of 3 Blade Turbine 4 over 3 Blade Turbine 3 from 8.0% to 13.9% as shown in the following spreadsheet.

[Turbine Guy]

On Turbine Guy Said:

I glued Rotor 6 PLA shown in the last post to a shaft and ran it in Tangential Turbine 6 shown in the following drawing and spreadsheet. I made an error in guessing where to glue Rotor 6 PLA on the shaft which resulted in getting much higher compression on the spring than I wanted, but as you can see in the spreadsheet the performance wasn’t that bad for the first test. Normally I would run several tests to find the optimum position of the rotor in the housing and the best spring compression before adding the performance in the spreadsheet. When I disassembled the turbine to reposition the rotor on the shaft, I found that the extension of the rotor on its outer face had broken off. I mentioned in the last post that the rotor was designed to be cast in bronze and had several areas that were two thin for a material like PLA. I am in the process of trying to fix the rotor assembly but it will require enough changes that it will have to be called a new assembly.

The last few posts have been for turbines with rotors 3D printed by me from PLA. Now that I have learned some of the more important print settings and speeds to machine the PLA, I have been getting rotors that probably perform close to what I could obtain with rotors machined from metal. This allows me to try different ideas, small improvements, and combinations of improvements until I get the best performance I am able to obtain for the type of rotor 3D printed in PLA. I only show in this thread the best performance I have obtained for a given concept and often it takes many attempts. It took me a few attempts to make Rotor 6 PLA discussed in the quoted thread that explained the rotor needed to be designed for 3D printing in PLA. Rotor 6 PLA R1 shown in the following drawing and spreadsheet was redesigned to make it stronger and try some ideas to improve the performance. After trying a few different things Rotor 6 PLA R1 reached the maximum performance for all the ideas I could think of. You can see from the drawings and spreadsheets in the quoted post and this post the changes that were made and the resulting improvement in performance.

[Turbine GuyParticipant @turbineguy]

Photos of the two rotors discussed in the previous post are shown below.

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