TV94 TurboFan Build

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Ash Powers
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TV94 TurboFan Build

Post by Ash Powers » Fri Jul 20, 2007 4:22 am

Well guys, moving right along...... :)

The T04 GT build has served its purpose quite well and wanted to start a new thread for the final part of the GT project - a TV94 rotating group used in a GT of ~identical construction as the T04 GT, obviously a LOT bigger. The title of this thread notes this as a TurboFan, but not in the conventional, commercial turbofan engine layout you see on passenger airliners. This TurboFan will use the TV94 gas producer to drive a free-power turbine, likely an Allison or RR axial turbine wheel of appropriate size, coupled through a gearbox to a ducted fan unit of appropriate size. The goal is to produce a turbofan engine capable of producing in the neighborhood of 350-500lbs thrust. This will be used to power a VTOL aircraft - a "personal aircraft" if you will. :)

I have been working with my Garrett distributor to obtain geometric information on the various TV94 turbines and compressor wheels to find a well-matched combination for use as a gas turbine. Once again, John Wallis (racketmotorman) has been very helpful in filling me in on the desired geometries. I placed the order yesterday for the turbine and compressor wheel and they arrived to me today.

Costs so far:
$85.05 TV94 Compressor Wheel, 48-trim, 5.300" exducer, 3.85" inducer, 0.383" exducer blade tip height.
$327.70 TV94 Turbine Wheel, 67-trim, 5.100" inducer, 4.180" exducer, 0.790" inducer blade tip height.

These pieces are incredible works of engineering art. Seeing components of this scale is just awesome. :) So, enough chatter, on to the pictures!

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The last image shows a side-by-side comparison of this rotating group (far left) compared to several others I have here. Starting from left to right:
TV94 Compressor Wheel
TV94 Turbine
ST50 Compressor Wheel
ST50 Turbine
T04 P-trim Turbine wheel (as used in the T04 GT)
T25 Compressor Wheel
T25 Turbine Wheel

I've got a preliminary drawing for what this engine will look like which was taken directly from the T04 build - this larger version is essentially just a "scaled up" version of the T04GT. This engine will be around 9-10" diameter, ~18" long, and probably around 20lbs in weight.

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Rendering:
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I will not be machining the compressor diffuser from the plate aluminum I purchased, rather, I will build a pattern for casting it. I want to use wedge-shaped vanes rathern than the sheet aluminum vanes as it will eliminate airflow and mounting issues.

The turbine NGV will also be constructed similarly but it will be machined from 316SS for the backplate and the wedges produced from 316SS barstock, machined to shape/size, and fastened to the backplate.

The turbine/shaft will also be modified just like was seen in the T04 build - the shaft will be precision ground down for ceramic hybrid bearings, shortened and threaded, and a shaft extension will be used. This engine may ultimately end up using three bearings for the rotating group with one positioned at the midpoint of the shaft to help handle any issues with rotational harmonics.

One thing I have realized about this engine build is the greater flexibility of construction techniques that can be used due to the scale of the parts. In the T04 engine, I pretty much had to build the NGV using the backplate/sheetmetal vane approach. Trying to construct that part of the T04 engine using wedge-shaped vanes that bolt to the NGV inner plate as well as provide the threaded holes for attaching the NGV backplate would be very difficult to do and would require a bunch of really tiny fasteners, likely resulting in tons of broken taps and siezed fasteners from thermal exposure. I get the feeling that the larger engine will be easier to build and work on as well, especially having already built an engine that this larger version will be modeled after.

The same electronic system I developed for the T04GT will be used on this engine as well - I had several of the GTControl boards produced and will assemble another one for this project. I'll use the same Palm Tungsten PDA for this project and purchase another Bluetooth-Serial adapter and Serial DAQ device to complete it.

I took me basically 2.5 months to construct the T04GT to the point of its initial startup, including the construction of the electronic control system components and program coding. There was obviously several months that were spent thereafter making improvements to the gas producer to get it running as best a possible. Having already built the smaller engine and already equipped with the electronics, the build of this GT will likely go quicker and then the project will move into "new" territory for me - free power turbine and ducted fan design/development. :)

This post is undoubtely a "teaser" for the most part though - I will be collecting the rest of the bits and having a few small things done over the next few months in preparation for diving into this build sometime in November/December. These parts were just way too pretty not to post about and I have a hard time containing my excitement. :)

...... looking forward to later this year. :)

racketmotorman
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Post by racketmotorman » Fri Jul 20, 2007 5:37 am

Hi Ash

Nice "numbers" :-))

Cheers
John

Johansson
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Post by Johansson » Fri Jul 20, 2007 9:19 am

Another thread that I must follow, nice! :-)

//Anders

craigclavin
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turbine wheels

Post by craigclavin » Fri Jul 20, 2007 3:04 pm

hey, im very curious about them wheels. Did you buy them directly from Garrett? Where they replacement parts? I had no idea they would cost so much - i presume they are honed/balanced already?

Great work on all projects 8)
<img>

Ash Powers
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Post by Ash Powers » Fri Jul 20, 2007 3:14 pm

Yep - they are garrett components.

Compressor wheel: 441813-7
Turbine Wheel: 442208-0001

For the size of these parts, the money spent was *cheap*. :)

racketmotorman
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Post by racketmotorman » Sat Jul 21, 2007 4:10 am

Hi Ash

Make that, VERY cheap :-))

Cheers
John

Ash Powers
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Post by Ash Powers » Fri Aug 10, 2007 1:47 am

Been making more progress on the Gas Turbine analysis spreadsheet - now on version 2 of the sheet and refining the layout of the different sections, integrating additional formulas and some changes to the formulas already existing. Will be a bit more time before the new version is completed but I'm making good headway on it.

I've also been in contact with my Garrett distributor and have obtained flow map data for both the compressor and turbine wheel. Pretty impressive, at least to me - having dealt only with really small gas turbines such as the T25 and T04 components, the TV94 maps are just awesome. :)

Image

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Ash Powers
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Post by Ash Powers » Fri Dec 28, 2007 2:04 pm

It has been a little while since I've posted to this thread and wanted to give a little update on the project. :)

I have been working on a new turbine calculator spreadsheet off and on for several months in preparation for the build process of the engine. I've acquired several texts over the past few months and integrated a lot of the thermodynamic calculations provided by them into an easy to use spreadsheet for determining operating conditions as well as assisting in the acutal manufacture of the parts.

At the moment, I have the rotating assembly and quite a few bits of material to make the parts from. I am still sitting on the fence waiting to hear back from my turbocharger component provider to see if some other bits are available. I have been collaborating with John Wallis about this build and we think some "fine-tuning"" of the parts used may ultimately benefit in the end result. Right now things are in the air WRT particular compressor wheels. However, the spreadsheet can be easily manipulated later on if I can obtain the parts.

Here is a screenshot of the latest revision of the spreadsheet:

Image

I've also obtained a parts manual and a service manual for the Teledyne J69 turbojet engine which has offered a good deal of information WRT centrifugal compressors / engine design, etc....

With the ~5.5" diameter compressor wheel, it appears that I can likely get away with a very small footprint: the engine is going to be designed around an 8.5" diameter casing of about 18" length.

I've also been playing around with a 1/4 scale model of the airframe that this engine will be put into. I have refrained from taking pictures of the model as it is quite comical in many ways - but it has been helpful in refining the layout of the parts to provide the most amount of safety without sacrificing functionality. I'll have to take some pics and post them so everyone can get an idea of it, but I'll wait until I have the layout refined.

At this point I am mostly waiting to hear back from my turbo supplier to see if I can obtain some higher-flow compressor wheels that will better match the flowrate of the Rolls-Royce Allison 250 4th stage axial turbine wheel. There are plenty of options availabe for the parts to be used in the final design of this engine so I'm just trying to accumulate the most information I can WRT the available components before I committ to a design.

In the mean time, I've purchased a 22" widescreen lcd monitor for my comptuer which will allow me to compile the final drawings for the engine in actual scale on the screen. I used this technique in the build process of the T04 gas turbine engine and it was very helpful - it is like having "digital" blueprints of the parts. :) Far more functional than having acutal paper prints of the engine.

I've also procured a source for low density urethane foam which will be used to create the airframe pattern. It is a 2-part liquid polymer that you mix and it will foam out and cure in a matter of minutes. I intend to cast this material into a plywood form of ~8'X4.5'X4' and then final shape the foam block according to the scale model I've built. Once it has been shaped, it will be glassed with ~2oz fiberglass cloth for rigidity and then a mold will be made from the plug. Once I have the mold halves finished I will be able to laminate the final airframe from a few layers of carbon fiber cloth and vacuum bag it. :)

So, a LOOOOOOOONG ways to go from here but I have my plans. :)[/list][/code]

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Post by Johansson » Sat Jan 12, 2008 11:25 pm

Niiiiiiiiice... :D

Bruno Ogorelec
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Post by Bruno Ogorelec » Sun Jan 13, 2008 4:47 pm

Ash,

I've been talking to a group of people trying to build 'backpack' helicopters for some time now. All their projects involve various adapted 2-stroke engines. I've been telling them that a small turbojet with a free-power turbine driving the rotors is just about the only answer that will be small enough and light enough and simple enough for the purpose.

They are ready to agree, but argue that a machine of that kind will be (a) horribly expensive and (b) consume vast amounts of fuel.

Could you make an educated guess on the probable cost of the parts and the work that will have to be done by outside specialists? (All those guys are extremely capable and have adequate workshops, so I suppose most of the simpler work would be done by themselves.)

Also, we are talking about a 40HP or thereabouts shaft power. Any idea -- a ballpark figure -- of the likely fuel consumption?

We are wondering if a machine you can carry on your shoulders (more or less), which can fly for, say, half an hour, can be built this way.

The only alternative I have found is a 40 HP German Wankel engine used on top-end karts, which costs about $ 6,000 with ancillaries. Everything else is simply too heavy to be considered portable.

Viv
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Backpacks

Post by Viv » Sun Jan 13, 2008 7:42 pm

Thats real funny Bruno! you bugging my office again like you did in the old days? talk to me privately some time, on another note there is a company in Zagreb that has caught my interest so your local knowledge would be interesting to me.

Viv
"Sometimes the lies you tell are less frightening than the loneliness you might feel if you stopped telling them" Brock Clarke

Viv's blog

Monsieur le commentaire

Bruno Ogorelec
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Re: Backpacks

Post by Bruno Ogorelec » Sun Jan 13, 2008 8:14 pm

Viv wrote:Thats real funny Bruno! you bugging my office again like you did in the old days? talk to me privately some time, on another note there is a company in Zagreb that has caught my interest so your local knowledge would be interesting to me.

Viv
Ha-ha-ha... no, no, it's just threadbare minds thinking alike. :o)

Ask me about the company you're thinking about. My mail address is Bruno.Ogorelec@gmail.com. I may even know something. Or know somebody who knows.

Ash Powers
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Post by Ash Powers » Sun Jan 13, 2008 10:27 pm

Hi Bruno,

I'm budgeting about $1.5K for the turbofan build, plus or minus - shouldn't be a problem to keep it within that either..

The designed shaft power from this unit will be in the neighborhood of around 140HP - considerably more than what you are going to get from even a moderately sized two stroke or wankel and weigh considerably less.

I dont see any problems constructing the engine right here in my garage. I have aluminum casting equipment, mill/lathe, welding equipment, and all of the other various metal working tools. Once I finish up with the drawings I expect to have the engine together and running in just a couple of months.

As I proceed with the build I will be posting it here on the forum. You might want to take a look at my T04 GT build post - it has tons of pictures and descriptions of the engine for each part as I built them - some videos of it in operation as well. The TV94 engine will be built just the same with only a few variations and with the addition of an axial freepower turbine for shaft power.

Bruno Ogorelec
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Post by Bruno Ogorelec » Sun Jan 13, 2008 10:43 pm

Ash Powers wrote:Hi Bruno,

I'm budgeting about $1.5K for the turbofan build, plus or minus - shouldn't be a problem to keep it within that either..

The designed shaft power from this unit will be in the neighborhood of around 140HP - considerably more than what you are going to get from even a moderately sized two stroke or wankel and weigh considerably less.

I dont see any problems constructing the engine right here in my garage. I have aluminum casting equipment, mill/lathe, welding equipment, and all of the other various metal working tools. Once I finish up with the drawings I expect to have the engine together and running in just a couple of months.

As I proceed with the build I will be posting it here on the forum. You might want to take a look at my T04 GT build post - it has tons of pictures and descriptions of the engine for each part as I built them - some videos of it in operation as well. The TV94 engine will be built just the same with only a few variations and with the addition of an axial freepower turbine for shaft power.
Thanks, Ash; I'll look at the T04GT thread.

Ash Powers
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Post by Ash Powers » Wed Jan 23, 2008 12:03 am

So I got the 22" LCD monitor up and going with a new Dell D600 laptop I picked up and got to work on the TV94 TurboShaft engine drawings. This engine is going to be huge, LOL! It is 8.5" diameter and drawn to scale on my 22" monitor! I've pretty much got the design nailed down at this point. Here are two images of where things stand: one so you can see the pieces clearly and another with everything labeled.

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There are a few things I'm doing differently with this engine as compared to the T04GT project.

1) This engine will use a totally sealed bearing tube assembly. I will be using the turbine and compressor shaft seals and at each end of the bearing tube there will be cooling air slots machined as well as the fuel/oil mix being metered into both bearings. The center of the bearing housing will have a return tube that will exit the front of the engine and will have a needle valve on it to allow some adjutability of the flow. With a larger pressure differential to work with, I know the bearing tube will have positive flow all the time. It also wont be dumping raw fuel/oil mix into the turbine anymore which should be good for a little lower TOTs.

2) The compressor diffuser will use radial wedge vanes to eliminate any aerodynamic losses from the fixing bolts, fuel/oil line, starting gas line, and bearing tube return line.

3) This engine will also use an axial diffuser section to further aid in efficient compressor function.

4) There is proportionally greater combustion chamber volume. The T04GT suffered from a few design problems but one that I'm sure was a big detriment was the small combustor volume. I'm giving myself plenty of volume for the combustion process to occur in this engine.

5) For bearing preload, I will be using a disc spring specifically designed for use with the 6204 bearings. It has a maximum load of 26lbs but I wont be using much more than about 6lbs or so.

I have also found that the Garrett GT60 Compressor wheel is now available as a seperate part. This will make for a nice upgrade from the TV94 compressor wheel - going up from ~2.2lbs/sec to ~2.7lbs/sec will definately be good for more power producing potential in that RR Allison FPT wheel.

Here is a copy of the GT60 compressor map:

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Soooooo - things are coming along nicely at this point. I will be getting my hands on the GT60 compressor wheel in the next few weeks and in the mean time I will start producing some of the casting patterns for the compression stage components. Exciting times!!

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