Jet Engine Project

[racket]

Hi Luke

Be careful with "electrical" pressure senders , our P2 temperatures( T2) can easily exceed the units temperature rating at higher P2 levels , so please check all of the Specs .

If you exceed the temp rating and the unit provides an incorrect reading you may be pushing the engine too hard :-(

The pressure pickup point needs to be in an area where air flow speeds are low and static pressure represents the total pressure .

Cheers
John

[lukenz]

Aug 13, 2019 16:26:36 GMT -5 racket said:

Hi Luke

Be careful with "electrical" pressure senders , our P2 temperatures( T2) can easily exceed the units temperature rating at higher P2 levels , so please check all of the Specs .

If you exceed the temp rating and the unit provides an incorrect reading you may be pushing the engine too hard :-(

The pressure pickup point needs to be in an area where air flow speeds are low and static pressure represents the total pressure .

Cheers
John

Thanks John, so somewhere like the top end of the chamber between the flame tube and outer casing? I actually have placed my T2 thermocouple just before the turbine inlet (exhaust side) is this going to be an issue?

Luke

[turboron]

lukenz, I silver braze a brass 1/4" NPT pipe union to the bottom third of the outer combustion case(OCC). Next, I drill an approximately 0.040" hole through the OCC wall. Finally, I install a readily available 1/4" NPT round pressure gage. I have not used a sensor for OCC pressure to date.

Thanks, Ron

[BFTO]

Aug 13, 2019 19:25:07 GMT -5 lukenz said:

Aug 13, 2019 16:26:36 GMT -5 racket said:

Hi Luke

Be careful with "electrical" pressure senders , our P2 temperatures( T2) can easily exceed the units temperature rating at higher P2 levels , so please check all of the Specs .

If you exceed the temp rating and the unit provides an incorrect reading you may be pushing the engine too hard :-(

The pressure pickup point needs to be in an area where air flow speeds are low and static pressure represents the total pressure .

Cheers
John

Thanks John, so somewhere like the top end of the chamber between the flame tube and outer casing? I actually have placed my T2 thermocouple just before the turbine inlet (exhaust side) is this going to be an issue?

Luke

Yes, place it in the upper half off the combustor depending on where your discharge pipe is located.

Thats turbine inlet temperature (TIT), can be bad if something happens to the probe and goes through your turbine wheel. Place it after the turbine wheel instead, to be on the safe side.

T2 = Compressor discharge temperature.

[racket]

Hi Luke

T2 ( compressor discharge temperature) can be incorrect if theres radiant heat from a red hot flametube wall in close proximity , we either need it to be shielded or placed in a position where theres minimal radiant heat as can be the case when installed down in the combustor between Tertiary holes and outlet where the flametube material shouldn't be "coloured" by gas temps .

Cheers
John

[turboron]

Luke, I use a hand held laser type temperature gun to measure Compressor Discharge Temperature (CDT). I point it at the OCC in the bottom third.

Thanks, Ron

[lukenz]

So things got a little more exciting this afternoon at work!

[lukenz]

Man it’s been a while since I was last here!

So I have ran the engine a few more times attempting a self sustain condition and have had a few successful moments.

More prominent though are the 2 main issues I am having and I’ll try and keep this prompt:

1- When the engine does run on its own the RPM is rather disappointing and then slowly dies off until needing a boost from the 3x air guns I use to start it. My diagnosis is the small 12V motorcycle battery can not keep up with the current draw from fuel pump and 12gph oil pump using (stupidly over spec for the oil flow a turbo needs) there for voltage depletes and the fuel pump can not supply the demand of the engine?

2- When I have the throttle (needle valve) fully closed which gives full fuel pump pressure to fuel injector the RPM still seems low except a one of event where the RPM went crazy and my mate panicked and cut the fuel pump switch. There are two parts to my theory here; a) the above voltage issue alone, and b) voltage combined with using a spray nozzle and not an oil burner nozzle, where the spray nozzle is to small and fine for a low pressure EFI pump like the Walbro 255 I am using (spray nozzle likely needs a higher pressure hydraulic pump)

Can anyone please shed any light/experience they may have? I’m thinking of running a permanent magnet type 12v automotive alternator to maintain my voltages and changing the fine spray nozzle out for a oil burner nozzle.

Lastly, please take a look at my flame tube photos, after 3-4 test runs. What story do the heat marks on the outside/inside of the flame tube tell me about how she’s running (I have yet to connect TIT/TOT and press gauges)

[racket]

Hi Luke

Flametube looks OK for what you've been doing , it'll need checking once running to full power .

I'd suggest you do some static testing of the fuel and oil pump to see how their pressures decay with extended use on the battery you have , but I'd think you'll be needing a decent sized car battery , I ran into similar problems with my 12/118 engine and needed more battery power .

What size is your fuel spray nozzle rating ??

[lukenz]

Mar 12, 2020 18:25:44 GMT -5 racket said:

Hi Luke

Flametube looks OK for what you've been doing , it'll need checking once running to full power .

I'd suggest you do some static testing of the fuel and oil pump to see how their pressures decay with extended use on the battery you have , but I'd think you'll be needing a decent sized car battery , I ran into similar problems with my 12/118 engine and needed more battery power .

What size is your fuel spray nozzle rating ??

John good idea on the static testing, I am fairly positive the oil pump flow rate is far to high and draws to much current. When you say the fuel nozzle rating, do you mean how much it can flow? All I can find on the nozzle is the information below from eBay:

“Description:
Low pressure fine atomization humidifier cool mist nozzle 304 stainless steel nozzle.
Coverage area: no wind or breeze under the condition of a nozzle 1-3 meters height cover about 1-2 square feet.
Filter: nozzle inlet is equipped with high quality stainless steel filter.
shape: solid cone / conical (60 degrees below the solid , more than 60 degrees will be slightly a little hollow )
When the liquid in the 2-10bar pressure is medium, the pressure reaches 10-20bar, the atomization particle is about 50um, 20bar can reach the suspended fog.The greater the pressure, the better atomization effect, the maximum pressure 50-70bar.
angle: the normal angle is about 60 degrees.
Widely used in humidification cooling, dust cooling, fog test, artificial fog, atomized fuel, evaporation, cleaning and , and landscape fog and so on.”

[racket]

12 gph isn't a very big oil pump , thats only ~1 litre per minute ..............what oil pressure does it maintain when measured at the turbo oil inlet ??

That spray nozzle sounds a tad small if it'll produce a "fog" at only 20 bar , again , you probably need to do a flow test , just suspend it in a bucket , cover/seal the bucket to prevent fuel from being ejected , then turn on the pump full throttle , its rated to 87 psi which would mean only ~50 psi pressure drop across the nozzle when the engine is running , do a rough "stop watch" run of a minute and check whats in the bucket , with a 68 mm comp inducer you need to find a pound of fuel in the bucket , at least 500 cc of fuel , your fuel pump is a bit overkill

One other thing ..............whats that thin tube projecting across the Primary Zone ??

[lukenz]

Mar 14, 2020 1:07:58 GMT -5 racket said:

12 gph isn't a very big oil pump , thats only ~1 litre per minute ..............what oil pressure does it maintain when measured at the turbo oil inlet ??

That spray nozzle sounds a tad small if it'll produce a "fog" at only 20 bar , again , you probably need to do a flow test , just suspend it in a bucket , cover/seal the bucket to prevent fuel from being ejected , then turn on the pump full throttle , its rated to 87 psi which would mean only ~50 psi pressure drop across the nozzle when the engine is running , do a rough "stop watch" run of a minute and check whats in the bucket , with a 68 mm comp inducer you need to find a pound of fuel in the bucket , at least 500 cc of fuel , your fuel pump is a bit overkill

One other thing ..............whats that thin tube projecting across the Primary Zone ??

Apologies, oil pump (it’s a scavenger pump) is 14L per minute 😬 still within appropriate flow rate for turbo lubrication?

Will do a flow test on nozzle this week when back at work.

John that’s a 5mm price of steel bar that completes the arc from the ignitor coming from the adjacent side of the FT, temporary setup to achieve ignition.

[racket]

Yep , oil pump probably a bit big for your turbo , but not excessively so , how are you regulating its flow/pressure ??

5mm bar ........best if its not in there.

Let us know how the fuel flow test goes

[lukenz]

Mar 14, 2020 4:27:14 GMT -5 racket said:

Yep , oil pump probably a bit big for your turbo , but not excessively so , how are you regulating its flow/pressure ??

5mm bar ........best if its not in there.

Let us know how the fuel flow test goes

I just have a correct sized bypass line returning to tank, the pump still has to much pressure though when oil is cold and auto shuts off so will look at using a shureflo as has been recommended on other posts here on this forum.

Does the 5 bar cause undesirable turbulence, or potential to break off and damage downstream components i.e turbine? This is only temporary so will experiment with another way to arc.

[racket]

Bar might impact the turbine wheel if it breaks.

You need a spring loaded pressure relief valve on the oil supply as flow through a coldturbo with cold oil is minimal whereas with hot components theres vastly more flow , a fixed oriface bypass won't work no matter what pump you use .