PD-01 Jet Engine

[ripp]

Hi Patty

www.youtube.com/watch?v=nxr7ZLanheU&list=UUqn6psLJ5zHRdmyzdREb3iA

Cheers
Ralph

[madpatty]

ripp,
Thanks for the link.....awesome video....will surely consider some important building techniques from the video....but my engine will be using the same compressor scroll that comes with the turbo......
I want to use as much OEM parts as possible.....

Cheers,
Patty

[racket]

I hope the guy in the Link video didn't bore that turbine wheel , thats a big NO NO , it can explode , they are NOT designed to have a bore , it weakens them too much .

Hi Patty

A reverse flow combustor probably won't produce any better outcome that using a "sore thumb" combustor mounted onto the standard turbine scroll on a turbo .

If you try and use your BIG compressor wheel with the same small turbine wheel , you'll continue to have problems , you MUST use the smaller comp wheel with it .

As for recommendations , I won't be providing any as I consider you're only lurching from one disaster to another without learning why this current engine isn't performing , all you'll do is carry over the same problems to the new engine , ..............learn to fix this one before embarking on a new build .

Have you ever used a fully balanced rotative in your current engine ??

If you haven't , then theres no point making a new engine and still use unbalanced, worn out, parts .

Currently you have absolutely no way of knowing how your component parts are working as you have virtually no instrumentation on the engine , if you do the same with the new engine you be just as much "in the dark" as with this current one

Cheers
John

[madpatty]

Hi Racket,
I once used a brand new shaft and it got burnt in very first run....didn dare to spend money afterwards.....

The reason I didn't use small impeller is because it has never shown any better results than yellow coloured turbine blades.....why won't i want my engine to run in a proper way......but you have got the results infront of you....

Even last time when i used the smaller impeller with larger throat area, the test showed entirely different results than what was expected.......
Tell me what to do when the smaller impeller hasn't shown me any improvement or atleast nearby anything what it is expected to do......

Is it possible that the trimmed exducer of the smaller impeller had reduced its pressure producing ability.....??

Cheers,
Patty

[racket]

Hi Patty

What were the specifications of your last engine test run ??

Which comp wheel did you use ??

What was the throat area of your new NGV ??

What were the dimensions of those throats ??

How many throats ??

What P2 ??

At what RPM??

What TOT at that P2 ??

Was there surge when you tested for it ??

The reduced diameter of the comp exducer has NOT reduced its pressure producing capability , BUT it has increased the relative power producing capability of the turbine wheel .

You mention you used the small comp with the larger throat area( NGV??) , this will produce high temps as the comp will flow in the choke region , a T2 gauge would have alerted you to this ...........you cannot tune an engine without having extensive instrumentation on that engine ...............this would apply to any engine you construct .

Cheers
John

[madpatty]

Hi Racket,

Impeller- 54/83
Throat area- 1220sq.mm
12 throats, same height as turbine exducer.

P2 6psi, 850deg. C

I haven't made any other run after last test i reported....you said rpm measurement is unnecessary......so all my encouragement for anything new is gone.....

First of all i am not making any turboshaft arrangement with this engine so i can go with higher TOT's.....it will just be a bench test run always....i can't finetune anything here because i know its all useless with the kind of machining done with this engine.....

Yours TV94 rotative has turbine exducer 16.9% larger in area wise than your compressor inducer.....mine has 15.3% bigger turbine exducer than compressor inducer....

Do you think this is enough to increase TOT's from 550deg C to 900deg.C........
The only biggest difference is my compressor exducer which is 18.5% larger diametrically than turbine inducer whereas yours is only 9.3% larger....,..

What if i trim down the exducer of large impeller exducer from 83 mm to 75mm??that will bring my compressor exducer in <10% range......
As far as your recommendations are concerned, i consider them very important for any engine i build........

Cheers,
Patty

[racket]

Patty

I don't know how many times I've told you, but this is the last time, DO NOT USE THE LARGE COMPRESSOR WHEEL

As you're incapable of following my suggestions , there no point me offering anymore

Cheers
John

[madpatty]

Hi Racket,
What about the throat area for the smaller impeller??
Currently i am at 1220sq. mm.....

Cheers,
Patty

[madpatty]

So the stage is all set as Racket wanted since the very beginning......

Small impeller
BALANCED rotor
Throat area reduced to 836sq. mm(after blocking 4NGVs)
Fixed some air leaks......
Now a do or die test for this engine....

Cheers,
Patty

[madpatty]

Hi Racket,
As per your suggestions i today tested the engine with smaller impeller after balancing the shaft and fixing the air leakages.....

i must say this was the best run with the smaller impeller till now as the maximum pressure reached was about 7 psi.....engine had never behaved this good with the smaller impeller.....
But the temperatures were still around 850 deg.C and engine showed same oscillating behavior with lubricating oil.....

Attached below is the video showing the pressure gauge....the oscillations can be seen as the pressure rises and falls repeatedly:-



Below is the pic of the turbine wheel at 6 psi pressure:-



cheers,
Patty

[madpatty]

Hi Racket,
do i need to collect some additional information to start blaming the shaft tunnel as the main culprit except that i have tested the engine with the smaller impeller now...what about building and experimenting the engine around the standard shaft tunnel??
....the same design annular combustor that fits between the compressor and turbine and using the factory made bearing housing....

cheers,
Patty

[finiteparts]

Patty,

I watched your video showing the pressure gage and the sound of the engine suggests that you are running the compressor over near the surge line....it's hard to tell though, since that same sound can be made by air leaks from the engine, combustor duct resonance and basically anything that creates a oscillatory-type flow condition.

Do you have air leaks on the engine that might be making that noise? If so, try to use some high temp RTV to make a basic "seal" and see if your engine is still making that "howling" noise...or do as John suggested and tie some tufts near the inlet to see if you are getting a pulsing flow at the inlet to the compressor because the compressor is in a mild surge condition.

~ Chris

[finiteparts]

Also, if you are in a surge condition, you might need to remove one of the NGV plugs to move the engine mass flow up a bit and drop the P2 so that you move away from the surge line.

~ Chris

[madpatty]

Hi Chris,
Thanks for the reply...
Racket seems very annoyed....?

Actually i tried testing with a string tied near the compressor inlet but the test didn gave any satisfactory results not beause of surge but the oscillatory condition of the engine due to its inability to run on any oil pressure....

I will try to explain it a bit further....

"Say the engine was running at 7 psi.....and then it starts de accelerating as seen in the video(string moves a bit backwards) and pressure is about 3 psi now.......then again i have to switch ON the oil and again pressure starts to rise and it reaches 7psi again(string again moves towards impeller)......

This phenomenon keeps repeating itself.....for a proper test i need a stable running engine......for stable running engine i need consant pessure oil supply which my current shaft tunnel is not allowing......

Cheers,
Patty

[finiteparts]

Hi Patty,

I understand what you are saying about the engine speed issue, but you do not need a stable running engine to do this test. The time scale of the flow oscillations are much smaller than the rpm fluctuations that you are talking about. You should see the string stay fairly straight pointed towards the impeller inlet if you are getting good flow into the compressor, even if the engine speed is decreasing or increasing. If you are in a slight surge condition, the string will swing more wildly because the flow field entering the engine is less stable.

As for your oil pressure issues, I revert back to my comments given to you earlier on in your project. I feel that you are not getting good oil drainage out of the center housing, which leads to the housing filling with oil and increasing the viscous drag on the shaft. This absorbs more power from your turbine, slowing down the rpms, which reduces the capability of the compressor and thus restricting your engines operation to the lower efficiency performing zone.

If you want to redesign your engine bearing housing, I would say that is a good idea...remember, it's up to you...it's your engine...your design...your learning. Asking for help is great, but ultimately, it is up to you....so have fun and learn.

~ Chris