FJK-1 & FJK-2 Gas Turbines

[nersut]

Hi John

I was hoping that I could reuse some of the existing metals.
But okay I can see it now, it will be messy.

I made some sketches again with flame holder in 4.5 in & about 11 in i length. Don't mind the square holes. ;D Just a sketch.

I am not sure if there should be a gab between the flame holder & the turbine inlet.

Which one is the correct one?

Without gab.



Or with a gab



If there should be a gab, how much should there be?


Cheers
Erik

[racket]

Hi Erik

No gap , all air through the flametube holes .

You will need some sort of slipjoint to allow for differential expansion between flametube and outer can

Cheers
John

[nersut]

Hi John

Super, no gab then.
I was looking at Don Giandomenico's GR-1 Combustor Formula at www.rcdon.com/html/gr-1_turbojet_project_3_8_04.html where he mentioned that there should be a bypass section for extra cooling.



I will try to gather some stainless steel tubing today.


Cheers
Erik

[racket]

Hi Erik

Gaps are old technology as its impossible to know what the gap will be at running conditions when expansion of the various parts has taken place , put all air thru the FT wall holes .

Don does beautiful construction work and his Site is a great source of information for making the bits , I'd recommend it to anyone , but some of the turbine theory is a bit suspect as its been sourced from unreliable sources .

I generally have my slip joint at the outlet end of the FT , there can be several millimetres of axial expansion with a stainless flametube .

Cheers
John

[nersut]

Hi John

Okay, I will make my new flame-tube without a gab but make some sort of expansion joint.
And I am considering to make the combustor without the elbow, just strait on the turbo flange.
I am not sure about the length required for the flame-tube. Any idea?
I will be using the same high pressure fuel nozzle I used before.
The reason is that it atomizes the fuel very well, even with the undersized flame-tube (7.5 in long 2,5 in diameter) I used and no evaporator-tubes, it burned all of the diesel before exiting (no flames at the turbine wheel except when starting up with too much fuel)

I found some stainless tubes (11.5 in diameter) yesterday that I am going to cut & roll to 4.5 in for the flame-tube.


Cheers
Erik

[nersut]

Update

Today I made some flanges for the new combustor.
The new dimensions are:

• Combustor length: 35.5 cm (14 in)
  
• Combustor diameter: 15.5 cm (6.1 in)
  
• Flame-holder diameter: 11.5 cm (4.5 in)
  
• Primary area: 36 holes x 6 mm
  
• Secondary area: 8 holes x 10 mm
  
• Tertiary area: 8 holes x 16 mm
  

The raw flanges



Turbo flange



Flame-tube hole markups



Combustor markup



Tomorrow I will cut & roll the stainless tube for the combustor & the flame-tube & drill the holes.

I have some glowplugs from a old toyota diesel engine.
Are automotive glowplugs good as ignition source for gas turbines? Pros/Cons?

I will call this turbocharger based gas turbine: FJK-2! ;D


Cheers
Erik

[nersut]

Update - Flame-holder build.

Hi, today I began to build the new flame-holder for the FJK-2.

Marking up for the holes



Data:

• Primary:
  
• 1. row: 11 x 5,0 mm
  
• 2. row: 13 x 6,0 mm
  
• 3. row: 11 x 6,0 mm
  
• 4. row: 22 x 1,5 mm (film cooling holes)
  
• Secondary:
  
• 5. row: 8 x 10,0 mm
  
• 6. row: 21 x 1,5 mm (film cooling holes)
  
• Tertiary:
  
• 7. row: 8 x 16,0 mm
  

Actual total hole area: 32,07cm2
JetSpecs recommended: 32,42cm2, pretty close only 1 % off.



The holes are flared for better flow



Inside view with fuel nozzle test fitted



Flame-holder test fitted to the turbocharger



The flame-holder still needs to be welded together & the end has not been tapered yet to fit the turbine inlet.


Cheers
Erik

[racket]

Hi Erik

May I suggest you open up 4 of the 6mm holes in the 3rd row to 10mm diameter so as to provide some deeper penetrating air jets that will hopefully get to the centre of the flametube/fuel spray, those 6mm holes won't penetrate far enough.

What spray pattern is your spray nozzle ??

A hollow cone pattern will/should promote more stable combustion due to recirculation of flame back into the "hollow" in the centre of the spray .

Cheers
John

[nersut]

Hi John

I will follow your suggestion with the larger holes on the 3rd row.

I am using a Monarch 7.5 gph 60° spray angle I think it is a PLP - which is Semi-Solid-Cone pattern or a PL - Hollow-Cone pattern.
I am not sure, but I will check it.

I used the 7.5 gph@100 psi for the FJK-1 and I am probably going to use a bigger nozzle for the FJK-2.
I have a Monarch 9.5 gph@100 psi laying on the shelf.
My fuel pump can be regulated from 0 to 200 psi.

The Garrett TA5051 Turbocharger's flow characteristics is similar or between a Garrett GT40 & GT42.

Do you have any suggestions for the nozzle flow size for the FJK-2?


Cheers
Erik

[racket]

Hi Eric

With a ~2.5" inducer you should be flowing ~1 lb/sec of air so ~1 lb/min -60 lbs/hour of fuel, thats ~9 US GPH of kero .

There are "variables", notably the turbine stage size , that will influence the air flow and consequently the fuel flow.

I'd start with the same 7.5 GPH nozzle you're currently using , this should provide a bit of a safety factor in case something goes wrong in those first few spoolups , once you've established that the 7.5 nozzle can't provide sufficient fuel for full bore power you can then "safely??" increase the nozzle size by an appropriate amount .

We need to remember that the nozzles are generally rated at 100 psi fuel pressure, but that assumes the spray is into ambiant air pressures not a P2 pressure which limits the actual pressure drop across the nozzle .

Assuming a P2 of 30 psi and a fuel pressure of 100 psi , the actual pressure drop is only 70 psi , and as flow is at the sq root of pressure you'd only be flowing ~ 84% of its rated flow , so a 10 GPH nozzle would only be flowing like an 8.4GPH .

If you used your 7.5 GPH nozzle at 200 psi delivery pressure (170 psi pressure drop at 30psi P2) it'd give you a 9.78 GPH flow rate ..................sounds just right to me :-)

Cheers
John

[nersut]

Small update

I finally got my new EGT-meter.

It has a Digital & Analog (LED-bars) read out, and a build-in voltmeter.
The thermocouple is a K-type and can measure up to 1250 degree celsius.







I ran out of Argon for the TIG-welder... I will get a new bottle so I can finish the FJK-2


Cheers
Erik

[Johansson]

Nice temp meter!

[racket]

Good solid thermocouple ..............nice stainless fittings :-)

[nersut]

Small Update

I got a new bottle of Argon & I welded the new combustor housing & the flanges.

Not too funny welding 1 mm stainless steel sheet...



Combustor test fitted



Turbo flange



Top cap flange



Top cap test fitted

Tomorrow I will weld the flame tube together.

I want to finish the FJK-2 as fast as possible but it is a little difficult with two jobs...

And I only have some very basic tools to play with.
I build the FJK-1 & FJK-2 just using:

• TIG welder
  
• Angle grinder
  
• Handheld drill
  
• And some handtools.
  

Not impossible it just takes more time.

Yes the new EGT-meter looks cool!


Cheers
Erik

[Johansson]

Welding 1mm stainless is a royal pain in the ass, I must have layed a kilometer of 1mm weld during the pulsejet years but I never made one single centimeter that actually looked good.....