Post by ashpowers on Jun 29, 2014 22:54:16 GMT -5
I'm back! 
So although I have a big thread of this on pulse-jets this forum seems to have a good bit more participation and also members with experience to go along with it. I've been working on this small turbine I built back in 2008 and bringing the old girl back to life with some new upgrades.
I'm going to post a few pics of this project's components:
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And now these are images I just took this evening after building a lot of new parts.
New bearing housing, bearing sleeve, feed line and sealing fitting.
The turbine has been fitted with a permanently mounted shaft rather than having a shaft extension that clamped the rear bearing when it was screwed together. Problem with this is that it always seemed to throw it out of balance each time it was put back together so now the shaft is also fitted with a pair of deep-groove hybrid ceramic radial bearings that are pressed onto the shaft.
There are actually two preload springs - the one seen loads against the rear bearings and there is another that loads against the front bearings. These springs aren't really stiff - probably only about a pound or two of preload just to sinch up the running tolerances. The front bearings are angular contact ceramic hybrids. Total in these bearings is a little over $200. This engine actually survived pretty well with very inexpensive bearings I used before so now having doubled up and with much higher quality bearings I expect these will last a good bit longer... not to mention all the other goodies for the rotorbearing system.
This is one of the two oring seals - I used Aflas material for these, good to 450F so we will see how they hold up.
This is the rear oring.
This is an image of the front of the bearing sleeve. The small hole is where the lube comes in from the annular space where the fuel/oil mix is being pumped into.
Here is a side shot of the bearing sleeve. You can see center section is machined down about 0.020" smaller diameter than the two ~1" wide dampening pads. The hole at the top end of the image is at 45-degrees for teh rear bearings and the front carries through to the axial port you saw in the previous image. The feed coming from the bearing tube lines up with that ~1/8" wide annular space that is cutout to allow the fluid to carry through.
This is probably the weakest machining I've done on this entire engine but it is simple and effective. This is the cutout from the feed ring to allow fluid to pass into the space between the dampening pads and also to the rear bearing feed hole.
Just to show how it comes together:
You can see here that I have sweat fit a steel seat for the shaft seal.
Business end:
Built a new fuel ring but you can see how the bearing housing feed is arranged. (I will be brazing the ends of the 1/8" fuel injector tubes and then side-drilling them with a 0.027" bit. I wanted to have the fuel spraying onto the side wall of the vaporizer tubes to try and take advantage of that surface area. The hypodermic like needles I was using previously shoot straight down into the vaporizer tubes and seems a bit of a waste.
At this point I am waiting for some mandrel bent 321SS tubes to arrive to me to make a new combustion chamber. The idea is rather than having a flat head on the CC, I'm going to bisect the tubing to built a flow splitter into the top face of the CC that will smoothly split the air coming out of the diffuser - half to the inner liner and the other half to the outer liner.
I've also brought out all of the electronics and replaced a few components on the GT Control board that weren't working for some reason. The old Palm Tungsten PDA still works like a champ so all is well there. I'm going to drop a new fuel pump into the scooter's tank and clean everything out while I'm at it.
On top of that, I pulled out my old balancer and have done some work to it to build it into a full dynamic balancer. I located a magnetic angle position sensor - non-contact, that has an analog output signal relative to the angle position. I'll be making a balancing compressor nut that has a small flat disc neodymium magnet mounted into it. I've also built new pedestals that the shaft mounts onto and have installed dual ball bearings onto the standoffs for the shaft to rotate on. Additionally I've also obtained more piezoelectric buzzers so I can integrate a second one into the rig. To top that setup off, I'm using a USB DAQ device which will tie into the two transducers (buzzers) and the angle position sensor. The software that comes with the DAQ has a running graph display that can be easily used to visially observe the relationship between the two transducers and the angle position of the rotating group. Should be able to balance the group very well with this new setup. I'll post pics of that soon once I have it all ready to roll.
What I am ultimately planning to do with this engine is to build it into a turboshaft engine. I'll be building a sheet metal scroll housing for one of the ST50 turbines I have and setting up a chain drive reduction setup for it using some of the smaller-scale chains and sprockets to help handle the kind of speeds it will be seeing... Should be interesting and quite powerful compared to the turbojet setup I was using before and probably be able to run the gas producer at lower duty to preserve more life. So for now I'm working on getting the gas producer up to snuff and going from there.
So although I have a big thread of this on pulse-jets this forum seems to have a good bit more participation and also members with experience to go along with it. I've been working on this small turbine I built back in 2008 and bringing the old girl back to life with some new upgrades. I'm going to post a few pics of this project's components:
And now these are images I just took this evening after building a lot of new parts.
New bearing housing, bearing sleeve, feed line and sealing fitting.
The turbine has been fitted with a permanently mounted shaft rather than having a shaft extension that clamped the rear bearing when it was screwed together. Problem with this is that it always seemed to throw it out of balance each time it was put back together so now the shaft is also fitted with a pair of deep-groove hybrid ceramic radial bearings that are pressed onto the shaft.
There are actually two preload springs - the one seen loads against the rear bearings and there is another that loads against the front bearings. These springs aren't really stiff - probably only about a pound or two of preload just to sinch up the running tolerances. The front bearings are angular contact ceramic hybrids. Total in these bearings is a little over $200. This engine actually survived pretty well with very inexpensive bearings I used before so now having doubled up and with much higher quality bearings I expect these will last a good bit longer... not to mention all the other goodies for the rotorbearing system.
This is one of the two oring seals - I used Aflas material for these, good to 450F so we will see how they hold up.
This is the rear oring.
This is an image of the front of the bearing sleeve. The small hole is where the lube comes in from the annular space where the fuel/oil mix is being pumped into.
Here is a side shot of the bearing sleeve. You can see center section is machined down about 0.020" smaller diameter than the two ~1" wide dampening pads. The hole at the top end of the image is at 45-degrees for teh rear bearings and the front carries through to the axial port you saw in the previous image. The feed coming from the bearing tube lines up with that ~1/8" wide annular space that is cutout to allow the fluid to carry through.
This is probably the weakest machining I've done on this entire engine but it is simple and effective. This is the cutout from the feed ring to allow fluid to pass into the space between the dampening pads and also to the rear bearing feed hole.
Just to show how it comes together:
You can see here that I have sweat fit a steel seat for the shaft seal.
Business end:
Built a new fuel ring but you can see how the bearing housing feed is arranged. (I will be brazing the ends of the 1/8" fuel injector tubes and then side-drilling them with a 0.027" bit. I wanted to have the fuel spraying onto the side wall of the vaporizer tubes to try and take advantage of that surface area. The hypodermic like needles I was using previously shoot straight down into the vaporizer tubes and seems a bit of a waste.
At this point I am waiting for some mandrel bent 321SS tubes to arrive to me to make a new combustion chamber. The idea is rather than having a flat head on the CC, I'm going to bisect the tubing to built a flow splitter into the top face of the CC that will smoothly split the air coming out of the diffuser - half to the inner liner and the other half to the outer liner.
I've also brought out all of the electronics and replaced a few components on the GT Control board that weren't working for some reason. The old Palm Tungsten PDA still works like a champ so all is well there. I'm going to drop a new fuel pump into the scooter's tank and clean everything out while I'm at it.
On top of that, I pulled out my old balancer and have done some work to it to build it into a full dynamic balancer. I located a magnetic angle position sensor - non-contact, that has an analog output signal relative to the angle position. I'll be making a balancing compressor nut that has a small flat disc neodymium magnet mounted into it. I've also built new pedestals that the shaft mounts onto and have installed dual ball bearings onto the standoffs for the shaft to rotate on. Additionally I've also obtained more piezoelectric buzzers so I can integrate a second one into the rig. To top that setup off, I'm using a USB DAQ device which will tie into the two transducers (buzzers) and the angle position sensor. The software that comes with the DAQ has a running graph display that can be easily used to visially observe the relationship between the two transducers and the angle position of the rotating group. Should be able to balance the group very well with this new setup. I'll post pics of that soon once I have it all ready to roll.
What I am ultimately planning to do with this engine is to build it into a turboshaft engine. I'll be building a sheet metal scroll housing for one of the ST50 turbines I have and setting up a chain drive reduction setup for it using some of the smaller-scale chains and sprockets to help handle the kind of speeds it will be seeing... Should be interesting and quite powerful compared to the turbojet setup I was using before and probably be able to run the gas producer at lower duty to preserve more life. So for now I'm working on getting the gas producer up to snuff and going from there.
