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Turbine Guy10/09/2020 20:26:32
228 forum posts
125 photos

Thanks Dave,

As I've previously stated, the propellers meet most of my needs. I threw in Werner's method because I feel it has a lot of merit and is probably the way I would go if I needed to find the power at specific speeds or a range of speeds. As you mentioned, any of the methods have their limitations and vary considerably in their complication and cost.

Stay well,

Byron

Mike Tilby10/09/2020 21:04:06
avatar
18 forum posts
8 photos

Byron, did I send you a copy of the article by Jim Bamford describing his syrup-tin dynamometer? If not I’ll do so. His device, made in the 1950’s, was a very simple water-brake dynamometer. It had a simple paddle that rotated in water inside the syrup-tin. The tin was pivoted and had an arm attached on which weights could be attached and adjusted in distance from the axis until the arm was balanced horizontal when the turbine was stationary. The shaft from his turbine entered the tin through the centre of one of the pivots and as the paddle turned it tended to rotate the tin. The load on the turbine was adjusted by bending the blades of the paddle (or the water level). Prof. Dennis Chaddock, who had used spinning bars equivalent to your propellers, later wrote that Jim Bamford’s syrup-tin dyno was a brilliant innovation.

Too many years ago I made one of these syrup-tin dynos and played around with it. Now I’m older and greyer I thought I’d make a proper one with discs as invented by Froude. That is part built. My initial intention was to use one of the cheap electronic scales one can buy to measure force on the arm instead of weights, but it would be much better to record torque continuously rather than writing down the reading from time to time while also controlling a boiler etc. Recently, a friend who is an electronics expert, built a dyno with a motor/generator to provide an adjustable load. In his device the motor is only the load and torque on the motor is measured directly with a load cell. I understand that analysing the signal from a load cell requires a very high gain accurate amplifier and,based on past experience, I foresee problems with interference etc. So combining a torsion bar with a water brake has some attraction for me. However, at current rate of progress the time when I’ll need the dyno is a long way off.

Regards, Mike

Turbine Guy11/09/2020 00:12:57
228 forum posts
125 photos
Posted by Mike Tilby on 10/09/2020 21:04:06:

Byron, did I send you a copy of the article by Jim Bamford describing his syrup-tin dynamometer? If not I’ll do so. His device, made in the 1950’s, was a very simple water-brake dynamometer. It had a simple paddle that rotated in water inside the syrup-tin. The tin was pivoted and had an arm attached on which weights could be attached and adjusted in distance from the axis until the arm was balanced horizontal when the turbine was stationary. The shaft from his turbine entered the tin through the centre of one of the pivots and as the paddle turned it tended to rotate the tin. The load on the turbine was adjusted by bending the blades of the paddle (or the water level). Prof. Dennis Chaddock, who had used spinning bars equivalent to your propellers, later wrote that Jim Bamford’s syrup-tin dyno was a brilliant innovation.

Too many years ago I made one of these syrup-tin dynos and played around with it. Now I’m older and greyer I thought I’d make a proper one with discs as invented by Froude. That is part built. My initial intention was to use one of the cheap electronic scales one can buy to measure force on the arm instead of weights, but it would be much better to record torque continuously rather than writing down the reading from time to time while also controlling a boiler etc. Recently, a friend who is an electronics expert, built a dyno with a motor/generator to provide an adjustable load. In his device the motor is only the load and torque on the motor is measured directly with a load cell. I understand that analysing the signal from a load cell requires a very high gain accurate amplifier and,based on past experience, I foresee problems with interference etc. So combining a torsion bar with a water brake has some attraction for me. However, at current rate of progress the time when I’ll need the dyno is a long way off.

Regards, Mike

Hi Mike,

You sent me both Jim Bamford's and Prof. Chaddock's articles. I have read them several times and gained a lot from both of them. Thanks again for sending these.

I'm not at a stage yet that I feel I need a more elaborate method for doing my turbine testing. Prof. Chaddock felt the data he had on his bars was adequate enough to use them. I feel the data for the propellers I use is at least as good. I agree with everyone that for low speeds the extra complexity might be needed.

Stay Well,

Byron

Turbine Guy17/09/2020 15:17:31
228 forum posts
125 photos

I have a few more things I would like to try with the tangential turbine. The following drawing shows a preliminary design of a new turbine that hopefully will allow me to test the merit of these concepts. The first thing I will try is to run at less than sonic velocity. My calculations indicate that there is a potential for higher performance running at below sonic velocity for the convergent only nozzles. My tests and Werner Jeggli’s tests have shown that there needs to be a free space for the gas exiting a sonic nozzle to expand to supersonic velocity before contacting the rotor. I discuss this in the post of 31/01/2020 in this thread. I can’t provide the free space with the open pockets, since a close clearance between the rotor OD and housing ID is needed to keep the gas from flowing over the rotor. I wasn’t able to make the flow subsonic by using multiple nozzles in my Turbine 3. I tried several times to add a nozzle and each time the tiny drill drifted far enough that the nozzle was useless. I decided I would try a larger nozzle and try getting the starter drill with the 60 degree taper closer to the inside diameter of the housing. You can see from the drawing below that the length of the nozzle diameter is very short with this design. The increased nozzle diameter and short length will help keep the nozzle from drifting and decrease the pressure drop in the nozzle. I will discuss the other things I want to try in later posts.

Tangential Turbine 4

Turbine Guy17/09/2020 16:17:11
228 forum posts
125 photos

To try different concepts in the same turbine, I needed to make some compromises. Some of these compromises are shown in the drawing of the previous post. The second thing I wanted to try was having the flow exit from the rotor face rather than from the OD into a countersunk opening. The flow exiting into a countersunk opening is what I have used so far for all the tangential turbines I have made. The flow exiting the face of the rotor is what Jim Bamford used in his tangential turbine as shown in the drawing below copied from Experimental Flash Steam by J.H. Benson and A.A Rayman. For flow exiting the face of the rotor, the counterbore is not needed and simplifies the turbine. I designed a turbine for a friend using this concept but have not tried it yet. The compromise I made in Turbine 4 to test this concept was so that I could also test with the counterbore. I want to see which of these methods is the most efficient with the overlapping pockets. The rotor shown in the drawing of the last post shows the setup for running with the counterbore. I need to test this first since the flange on the outer face of the rotor will need to be machined off to allow the flow to exit from the face. When I complete all the testing with the counter bore, I will machine the outer face of the rotor and reduce the length of the shims to where the OD of the rotor is entirely under the ID of the housing. This is why I used such a long shim length and pushed the rotor so far out. A second nozzle, not shown in the drawing of the previous post, will also be needed since the rotor is in a different position.  This nozzle will be exactly the same except for its position that will be moved in the same amount as the rotor moves in.  

Bamford Stumph Turbine

Edited By Turbine Guy on 17/09/2020 16:27:35

Blue Heeler20/09/2020 07:37:38
avatar
217 forum posts

Very interesting thread.

Turbine Guy27/09/2020 12:34:16
228 forum posts
125 photos

After posting the drawing of Jim Bamford’s turbine shown in my last post, I thought I would try adding a new nozzle to Turbine 3. I ruined the existing nozzle when I tried putting an insert into it. I thought when I added the insert, that if it didn’t work, I could push it out. I tried to add a new nozzle several times, but each time the tiny nozzle drill drifted too far to be useable. Thor suggested that I run the nozzle drill at a much higher speed than I had been using. All my drill speed charts also recommended the higher speeds. I tried drilling the nozzle shown in the following drawing using the maximum speed of my milling attachment (4,000 rpm). I was able to drill the hole without the drill wandering or breaking. I didn’t realize the importance of using the right drill speed. The new nozzle is positioned where the rotor OD is overlapped by the housing so I can try having the flow exit from the rotor face instead of into a counterbore. The drawing also shows how one row of the rotor pockets will be removed. This will make a better comparison of the two methods since it will be with the same rotor, same nozzle size, and same nozzle angle. This will also allow me to use rotor 3 again since I can only run the axial rotor now.

Tangential Turbine 3 SD

Turbine Guy27/09/2020 12:35:55
228 forum posts
125 photos

The view of my 3D solid model showing the area near the new nozzle might make it easier to see how the flow enters and exits the rotor. The opening in the housing next to the new nozzle was used to mount the reversing chamber. The face of this opening is approximately where the center line of the new nozzle is. The center of the flow exiting the nozzle enters the rotor where this surface lines up with the rotor. The flow exits the rotor through the openings on the rotor face. The more of the face of the rotor that is machined off the larger the openings become but the amount the flow is turned is reduced. There will be an optimum value of the amount of material removed from the rotor. I will try to find the optimum amount by removing a little at a time and then testing.

Tangential Turbine 3 SD 2

Turbine Guy29/09/2020 17:19:34
228 forum posts
125 photos

I machined the face of Rotor 3 removing one row of pockets and opening the remaining row of pockets for side discharge. Machining the pockets off resulted in breaking the Loctite bonding the shaft to the rotor. I had to make a fixture clamping the rotor to the shaft with nuts to finish the machining. I then glued the rotor to the original shaft with Loctite 290 as I have done for all my other rotors. The following picture shows the finished rotor. I’ll start the testing tomorrow after the Loctite reaches it’s full strength. Because the Loctite didn’t withstand the force of machining the pockets, I won’t try removing the metal a little at a time as I previously planned to do. If the initial testing indicates this is necessary, I will key the rotor to shaft before I try any machining.

Rotor 3 SD

Turbine Guy30/09/2020 19:22:00
228 forum posts
125 photos

I updated the following test results to include running Tangential Turbine 3 with the side discharge (SD) rotor on air. I found the optimum position of the rotor was with 7 shims and setting the collar clearance to 0.004 in. The maximum speed obtained with the SD rotor had similar performance to that of the original rotor. There didn’t appear to be any disadvantages eliminating the counterbore required by the original rotor. This eliminates one machining operation on an already simple turbine. This was probably why Jim Bamford used this method on his turbine. I was concerned that the clearance around the rotor OD added by overlapping the pockets would be a problem. Apparently, the momentum of the air keeps it pushed against the turning surface of the rotor pocket. The loss in performance due to not turning the flow 180 degrees appears to be offset by less surfaces in the path of the air discharging from the rotor. The rotational (windage) loss improvement by removing one row of pockets makes a direct comparison of the two methods slightly unfair.

Turbine Test Results 11

Turbine Guy10/10/2020 13:10:32
228 forum posts
125 photos

Since I was able to test the performance of my Turbine 3 with a side discharge (SD) rotor, the effect of running at a lower pressure was the next thing I wanted to check. I ran a test of Turbine 3 SD with the 0.029” diameter nozzle on 12 psig with my EP2508 propeller. The power obtained was considerably less than estimated with my spreadsheet with the rotor velocity coefficient (RVC) I have been using. I could not find any reason for the performance being less than estimated other than the RVC. I ran a stall torque test and found the RVC at 12 psig the same way I have shown several times and it’s value was only 0.059. When I used this value of the RVC in my spreadsheet, the power estimated was very close to the test result. I updated the following turbine test sheet to show the results of these tests. Turbine Test Results 12

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