TV94 TurboFan Build

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Rossco
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Post by Rossco » Wed Jan 23, 2008 1:23 pm

Hey Ash, lookin good! Per usual.

In need of a rendering?
Still cant get over the accuracy you pull of with your method. Ha, what happens when you want to go full scale? Just hire out a movie theater.
Give me a yell on skype anytime, i dont have aim running on this new machine, it'd be good to have a chew on this new toy.

Ill do a rendering up of your scaled drawing here at some stage, although let me know if you want something more accurate.

Rossco
Big, fast, broke, fix it, bigger, better, faster...
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Ash Powers
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Post by Ash Powers » Wed Jan 23, 2008 4:22 pm

Hahaha! Or I could just get a digital projector - have it shot right here on the garage wall. ;-)

I'd love to have a rendering of the engine but we'll hold off for the moment until I finalize the drawings - right now the drawings are sized for the TV94 compressor wheel and with the GT60 wheel the allison turbine will be a little larger as it wont need to be clipped as much.

I dont have skype anymore, or your skype name. I got a new laptop and I formatted my old one.. Mind emailing that to me? agpowers@bellsouth.net

Thanks!

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Post by Ash Powers » Tue Feb 05, 2008 7:13 pm

Got a nice visit by my Garrett representative this morning and spent a few hours discussing several things - business related as well as gas turbine related. I've been trying to get my hands on the GT60 compressor wheel and John Wallis tracked down a part number for it. My turbo supplier brought one over with him today so I could take a look at it. This thing is pretty sweet - it has a 4.16" diameter inducer vs. the TV94's ~3.8" inducer and it also uses a boreless design.

I've snapped a few pictures of it for all to see:

TV94 on left, GT60 on right
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The GT60 compressor wheel offers another 25% or so more massflow and does it with greater efficiency over a broader range of operation. Not sure quite yet if I will end up using this wheel or not - need to do some thinking about it, but if it is used, it will offer a nice boost in performance for the axial freepower!

.... more to come soon! :)

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Post by Johansson » Wed Apr 09, 2008 5:21 pm

Any more progress on the engine? I am sitting on the edge of my chair while waiting for the project thread to continue! :D

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Post by Ash Powers » Thu Apr 10, 2008 4:43 pm

Heya!

My plans were to start building this engine at the beginning of this year but I released a couple of new products in my business which has had us slammed over the past four months or so now. Literally working like 10-12 hour days. Fortunately I've packed away a good bit of cash in my efforts which I am sure will come into play once I start building this project but at the moment I'm just inundated with my business work. I am hoping the dust will settle around here within the next month or two and then I can get to start working on this project. Although I haven't been doing hands-on construction of it yet, I have come up with several nifty ideas and changes to hte VTOL airframe design which I am sure will work better than my previous ideas. :)

So, sit tight my friend - I will be joining in on the fun once again in the near future. :)

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Post by Jason » Thu Apr 24, 2008 3:00 pm

Can i get a copy of this turbine calculator spreadsheet....

PLEASE

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Re: TV94 TurboFan Build

Post by Ash Powers » Tue Jul 15, 2008 5:27 am

I have obviously been out of the GT loop for many months now as business this year has taken off and I've been working very hard to keep up with all of the demand... not much time at all to entertain gas turbines. :-(

But I have recently done some drawing board work on this new engine and have come up with a new design that I will be pursuing hopefully within the next couple of months. The previous engine design used a centrally located, normal direction flow combustion chamber but I have been having second thoughts on doing it that way for the sole fact that the shaft extension on the T04GT project just proved to be far too unreliable of a means to construct the rotating group. So, I have taken on the "PAL" engine design with the reverse-flow combustion chamber and using the native turbine shaft. This will definately eliminate any issues with balance and also avoid potential problems with CRS.

There are also apparent advantages to this combustor layout - the way the inlet air passes around the chamber will inherently create a strong recirculation in the primary zone which should benefit combustion. It will also be far easier to work on since combustion chamber and fuel system modification are a large part of the development of these engines - with this new layout, the rotating assembly will not have to be disassembled each time you want to get into the engine to make changes to the fuel injection or the combustion chamber. All that needs to be done is the rear nozzle flange bolts removed and the entire casing will come off, exposing the combustion chamber which can be easily removed from there.

Also, with the longer path that the incoming air has to travel from the compressor wheel, it allows more duct length for diffusing the air, which should lead to better efficiency. This engine incorporates both radial diffuser wedges as well as axial diffuser wedges.

As for the NGV, it too will be far easier to replace/modify, etc than the previous design which required that the rotating group be removed, CC removed, and bearing tube removed from the NGV plate. This new engine layout will use a modular NGV section which can be easily removed/changed, etc.

I am planning to submit the drawings to my CNC shop soon to have them go ahead and machine out the diffuser plate and the NGV plate. You can see that my NGV section uses aerofoil shaped vanes which will be pretty much impossible to fabricate with the equipment I have here. It will be machined from a plate of 316SS, which proved to be very willing to take the heat in the T04GT project. The diffuser plate could be produced from a casting, but I'm leaning more towards outsourcing a little bit of the labor for this engine - not to mention, trying to machine a 9" diameter piece on my lathe will be pushing the limits of what I can actually fit on it. Just about everything else will be built by myself though.

I have also integrated a sealed bearing housing configuration. The bearing tube will be sealed at both ends by the turbine shaft seal and at the compressor end with another shaft seal. There will be a seperate feed line for the fuel/oil mix to be injected into the bearing tube at the far ends of each bearing. There will also be air feed ports drilled into the tube to provide for cooling air. Between the two bearings there will be a port in the bearing tube which will be connected to a dump pipe that exits the front of the motor. On this dump tube I plan to use an adjustable valve to regulate the bypass feed - probably later to just simplify it with jet of sorts once I have established a comfortable bypass rate. There is a heat shield placed directly behind the turbine wheel, which will be made from 316SS. I will also be using a thermal resistant shim between the NGV backplate and the bearing tube to try and minimize heatsoak of the bearing assembly. From the T04GT project I have come to really appreciate the need for keeping the bearings nice and cool - they simply do not last if they are overheated. The bearings will also be preloaded with a spring, seen just behind the front bearing - I'll have to play around with the preload force to find a suitable load for the assembly.

The fuel nozzles will likely be the style available on McMater-Carr - full cone spray, available in a wide range of flowrates, with 1/8" NPT male threads, and with an integrated filter. The combustor will use "L"-tube evaporators as shown in the image below and the injectors will be fed by a common rail with banjo fittings for easy servicing.

The image also shows the free-power turbine assembly - same as before on that one: Rolls-Royce Allison 250 4th stage turbine wheel with a hand-built NGV. Expecting to see around 170SHP at ~33KRPM - plenty enough to drive a 28" ducted fan and produce around 600lbs of thrust for the VTOL project. :)

So, without further adeu, here's the new engine layout:

Main case diameter: 9.0", gas producer length (to rear of casing): 15.25", total engine length: 22"
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Re: TV94 TurboFan Build

Post by Ash Powers » Mon Aug 04, 2008 6:05 am

Finally making some progress!! :)

I've had some 6061 plate here for some time now for this build and over the weekend I printed out the drawing for the compressor diffuser onto some sticky-back paper. The part was turned first on the lathe for concentricity and the compressor seat was machined out. I used my rotary table and the sticky sheet paper as a template, scribed the lines, and started milling away.

16 hours later:

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At the moment I still need to radius the bottom wall of the diffuser ducts at the periphery as well as radius the front tips of the vanes but I need to order some 6" aluminum bar to make the bearing tube from so I can mount this piece into my lathe. The plate is max diameter of 9.0" and it just barely fits onto my chuck but with just enough tolerance to work it. :) I've made a small change to the layout of the engine - I will be using a 5.75" diameter bearing tube to provide better fixing of everything and prevent any of the forces on the pieces from warping them - heat and pressure can have its way! I'll be ordering the barstock tomorrow and I already have the plate to machine the diffuser cover from. While I'm ordering materials I will also purchase the barstock to make the compressor inlet duct as well as purchase the 316SS plate and barstock to make the NGV section from. I hope to have a completed "core" with diffuser, NGV, bearing tube, and the rotating assembly put together within two weeks.

I've been waiting to start on this build for some time now - I intended to start building it at the beginning of this year so I am sure you can all understand my anticipation and frustration for having all these beautiful parts sitting on the shelf collecting dust, LOL.. So, onward and upward!

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Re: TV94 TurboFan Build

Post by Johansson » Sun Aug 10, 2008 2:00 pm

Hooray! :D

I am glad to hear that you found some time for this project, work has a nasty ability to get in the way of the more interesting things in life.

It is probably a good idea to use the PAL design, hopefully you won´t have to deal with the same balancing problems when you use the original shaft and since you intend to strap the engine to your back a bearing failure at high rpm´s could be lethal even with shielding around the engine due to the high rotating mass of the core.

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Re: TV94 TurboFan Build

Post by Ash Powers » Tue Aug 12, 2008 2:39 pm

Hi Johannson!

Fortunately I wont be strapping this to my back. :) The VTOL airframe will have the engine mounted horizontally along the centerline and none of my body will be in the plane of rotation.

There are several advantages to the PAL design of which address the issues I had with the T04GT and will likely also produce better efficiency. Interestingly enough, I am breaking out the T04GT engine once again and making a few small changes to it for testing a few ideas. I'm not going to the PAL design on it but will take a different approach with the shafting issue. I am also changing the bearing lube/cooling air layout to the sealed setup like in the TV94 layout, and may be building a new NGV for it to take a closer look at the turbine inflow angle along the axial plane. I've spent some time eyeballing these turbine wheels and the inducer blade tips are "cupped" rather than straight vertical tips - I think it will be worthwhile to at least test whether or not the NGV needs to compliment the turbine tip geometry. You can see what I am referring to in this image:

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The NGV guides the gases into the turbine wheel along a radial path perpendicular to the wheel axis and after inspecting a turbocharger turbine housing, the gases are actually coming into the top edge of the inducer at an angle around 40 degrees or so which may be the reason the tips are cupped rather than straight and parallel to the shaft. The same was done on the TV94 turbine as well:

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This image shows the turbine inducer profile much better: (obviously this pic is "showing" the compressor wheel, but you can see the turbine wheel in the top right and how the inducer tips are contoured)

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I'm going to order up some new shaft material for the T04GT and will be making a mod to it similar to how Garrett's boreless comp wheels are attached to the shaft. I just hate to see the T04GT engine sit on a shelf in a non-running condition after all the work I've put into it and the shafting and bearing life has been the #1 reason for that, not to mention my lack of time available to do anythign with it. I'm also going to make some changes in the hot section to try and gain some insight into this NGV axial entry angle. The T04GT project was primarily to gain experience and knowledge with these engines so that I would be better prepared for building a larger one, so, expect to see some updates on the T04GT once again. :)

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Re: TV94 TurboFan Build

Post by Johansson » Thu Aug 14, 2008 5:14 am

The sealed housing lubrication is interesting, perhaps it works better than just letting it blow out behind the turbine wheel. John (racketmotorman) use a similar design on his new engine but he seems to have problems with bearing failures, hopefully he can sort it out soon.

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Re: TV94 TurboFan Build

Post by Ash Powers » Fri Aug 15, 2008 3:44 pm

Hi Johansson,

John and I have been communicating for some time about the bearing problems he has been having with FatMumma and he switched over to the sealed bearing tube design not too long ago. He was noting some of the signs that I Was seeing with the T04GT engine where it appeared that the fuel/oil mix coming out of the bearing tube was actually igniting and burning right at the head of the turbine, causing the TOT's to run high and overheating the turbine. We also suspect that the actual flame front may have been backing further up into the bearing tube and torching the rear bearing as well. I can onl speak from conversations he and I have had about this but if I am not mistaken, the new bearing tube design has proved to be successful and he has run the engine up to full speed several times now with good results.

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Re: TV94 TurboFan Build

Post by stoffe64 » Sun Nov 02, 2008 9:11 pm

how is this project progressing?

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Re: TV94 TurboFan Build

Post by Johansson » Wed Nov 26, 2008 6:27 am

Ash Powers wrote:(...)I've spent some time eyeballing these turbine wheels and the inducer blade tips are "cupped" rather than straight vertical tips - I think it will be worthwhile to at least test whether or not the NGV needs to compliment the turbine tip geometry. (...)
Have you any idea how the exhaust gasses in the original turbo housing are directed before they hit the tip of the blade? Looking at the pictures it seems the wheel is designed to have the flow hitting the blade tip as far in as possible to get the longest way to travel through the wheel and therefore transmit most torque to the wheel, but if the NGV blade is pointing 90 degrees to the tip it feels like most of the exhaust flow will hit the tip at the outer edge since they just have passed the 90 degree bend between the combustor and the NGV on a "normal" mirco turbine.

On the PAL design though the combustor is faced the other way around, so there is perhaps a higher percentage of the exhaust flow that enters at the right spot?

Oww what a headache, my brain is not designed for flow dynamics... :lol:

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Re: TV94 TurboFan Build

Post by Ash Powers » Sun Nov 30, 2008 9:09 pm

Hi Johansson,

If you have a turbocharger turbine housing that you can look closely at, take a look at how the volute is shaped around the turbine wheel. You will see that at the base of the turbine wheel (closest to the shaft seal) the gases are coming in perpendicular to the shaft but at the top edge of the turbine blades, the volute is shaped such that the gases are coming into the tips at about a 45-degree angle or so. What you are asking here is exactly where my concerns have been as well since that is going to have an effect on how the energy is transferred to the turbine. If you look at the layout I put together of this new engine you will see that the NGV's top plate (the side furthest from the shaft seal) I have angled that plate to somewhat mimic the inflow of gases that the turbine will see if it were placed into a standard turbocharger turbine housing. Also, if you look at how the turbine tips are "cupped", you can see that they are shaped that way in order to provide better impulse since the gases aren't all flowing in completely perpendicular to the blade tips.

On a side note, I have had a little time over the past few days to make some headway on this engine, although the work is rather trivial. I have bored all of the holes in the bearing housing and machined the NGV baseplate which is now connected to the bearing housing as well. For the time being the bearing tube has a bore perfect for the turbine shaft to slip into so I have what appears to be a complete "core", although there aren't any bearings or shaft seals in place. Right now I am putting the finishing touches on the diffuser plate to radius the outer lip of the baseplate where the gases make that 90-degree turn. I'm having to do those completely by hand with some carbide burrs, small files, and sandpaper. Kindof tedious work actually - I'll post up some pictures of the parts later once I have them finished up. :)

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