PD-01 Jet Engine

[madpatty]

Hi Guys,

One thing that has been observed during the recent tests is that engine runs with much lesser TOTs on gaseous fuel than on diesel. Today's test was also done using gaseous fuel. 

Though there are no visible flames coming out of the engine at any point when running on diesel but one thing that has been observed is that much of the heat is concentrated near the NGVs....even melting a NGV or two twice when running on diesel. In one of the videos of the test run using diesel the camera was focusing on one of the NGV blades and it was in good yellowish colour which surely means lot of heat there.

The same NGVs remain intact and in good shape after running on gaseous fuel. I need some thoughts here.

cheers,
Patty

[Johansson]

No real mystery, if the flame tube is a bit badly designed it will show on liquid fuel since it is a much more demanding fuel.

Gasseous fuel is already ready for combustion while liquid fuel needs to be evaporated before it can be mixed with air and burned.

Cheers!
/Anders

[madpatty]

But the flametube annulus has cross section greater than required 3 x inducer area for liquid fuel.

Inducer diameter- 54mm

Flametube ID- 168.5 mm
Flametube OD-211.5 mm

Holes in 30:20:50.

16 evaps tubes.
6mm ID 
8mm OD.

cheers,
Patty

[Johansson]

The hole pattern can mess things up if not correctly done, flame tube design is a bit of black magic so a bit of trial-and-error is often needed.

[racket]

Hi Patty

Still some work to do .

Did you try the "tube" recommendations I made in my Reply to your PM to me about the "string test" .

I'll include your PM and my answers to your PM query below , ...........for the benefit of other Members .



Hi Racket,
here is the link to the video of string test at compressor inlet as you said to perform.....is it surging or is OK??




cheers,
Patty


Hi Patty

At the 0:11 point in the video the string between the point where it contacts the housing wall and the end close to the wheel's inducer is steady , so it doesn't appear to be surge .

But that last bit of string is at an angle indicating the airflow going into the wheel isn't doing so correctly .

Your inlet angle in the housing is the problem , you need to make it a curved bellmouth rather than a "chamfer" .

If the string end is giving an accurate indication of your airflow, then you are only "feeding" air into ~half your inducer's cross sectional area , the outer "ring" is receiving "turbulence" .

Bellmouthing required for a smooth entry into the wheel, currently you have something approaching a "vena contracta" at the inlet , this will cause high temperatures due to the reduced mass flow through the turbine stage whilst trying to power a compressor wheel subjected to poor inlet flow conditions .

Cheers
John


Hi Patty

Theres one simple thing you could try first .

With the engine running at a reasonably high power level , carefully slide a 200mm long section of tubing over the compressor housing , the tubing will preferably have an ID a sliding fit over the current comp housing snout which appears to be ~90-100mm dia .

This will then simulate the usual air connection plumbing between an air filter and turbo which normally provides an axial air approach to the turbo inlet , your current setup has both axial as well as radial airflows trying to enter the comp housing/wheel.

The outer end of this tubing will experience a vena contracta , but due to its larger diameter the "throat" of the vena contracta will still be large enough to supply full axial air flow to your compressor wheels inducer .

If the addition of this tubing improves your engines performance it would be advisable to consider removing the tube and fitting/constructing a normal bell mouth feeding directly into your inducer to further improve the situation .

Cheers
John

[madpatty]

Hi Racket,
Till that tubing is arranged i removd the chamfer from the compressor intake and gave it a smooth curved bell mouth profile.

Yesterdays test was with that bell mouth profile.

Cheers,
Patty

[madpatty]

Hi Guys,

Another quick successful spoolup of the engine on gaseous fuel.

Max P2 of 19 Psi due to a bit lower fuel pressure as it was the same cylinder that i used in yesterdays run.





One thing though good occurred to me, how the temperatures today were even lower than yesterdays run when nothing new was done to the engine.

Temperatures were a good deal low as you can see no glow on the turbine wheel in this run.


cheers,

Patty 

[racket]

Hi Patty

Looking a much healthier coloured turbine wheel , you're getting there :-)

How are your rpm vs P2 readings compared with previous tests , are your P2 pressures increasing for the rpm used ?

Cheers
John

[madpatty]

Hi Racket,
The readings are as follows:-

P2(Psi)      RPM
7              72500
8              74500
10            81600
12            88900
15            97900

16            A1000
19            A7000

cheers,
Patty

[racket]

Hi Patty

Yep , rpm is reduced for the new P2 readings , engine is working "easier"

Cheers
John

[gyoung]

To Patty,
John and all the other people involved get huge round of applause from me. I'm a newbee to this field and am as lost as any another previous newbee. But this project of Patty's certainly has taught me quite a deal about following BASIC design and build parameters. Not only for making it easier to get the project running with less need for trouble shooting but to end the way you designed it. Doing it without getting hurt or killed, truly was an eye opener. The second part really struck home after reading the referenced information provided by Racket.

Those two build items are the most important parts of any project. Again thanks so very much.
Gene

PS
Patty it doesn't seem like it will be too long before you can open the champagne and celebrate. And John you truly are a patient man who hopefully hasn't pulled out all of his hair.

[racket]

Hi Gene

Welcome , I hope we can smooth your "education" in this fascinating but at times frustrating hobby .

LOL, theres still a bit of hair left

Yes stick to basic design if you don't want a lot of headaches , it doesn't take a lot to end up with a design that simply won't work , or if it does, is on the ragged edge of self destruction and barely able to sustain itself and is useless for any sort of power/thrust production , its just a noise producer burning lotsa fuel .

Cheers
John

[madpatty]

Hi Gene

Thanks buddy.

Surely John had been one of a great mentor in this engine build, though getting irritated with me at times when i wasn't following his advice.

And the target for champagne opening ceremony is 30 Psi P2, less TOTs and on diesel.....LOL

Cheers,
Patty

[madpatty]

Hi Racket,

From the rpm vs P2 numbers above due you think it is possible to reach 30 Psi P2.
As keeping in mind the max tip speed of 1450 ft/s of the larger wheel(compressor wheel here) max. rpm should be 101696 and my engine is already running greater rpm than this.

cheers,
Patty

[racket]

Hi Patty

No , not without increasing rpm/tip speed

Cheers
John