Turbo Jet not self sustaining (t04e turbo)

[sebsracing86]

Hi I am in need of some guidance with my T04e based propane TurboJet engine.

Here is a video of myself trying to get it running. It does not seem to self sustain. If anybody can tell me what I have done wrong I would greatly appreciate it. Link below.

youtu.be/-xFngHl4hG4

Here are the specifications of my engine:

Inducer - 40mm
Combustion chamber - 113mm x 250mm
Flame tube - 63mm x 247mm
^Primary 30 off 4mm holes
^Secondary 6 off 7mm holes
^Tertary 10 off 9mm holes

I used 30/20/50% ratio
I also left out drilling 1 hole from each section. Incase I had done too many.

For gas supply.
I have a 15mm copper pipe running in with 9 off 3mm holes drilled into an end cap on the pipe. It sits just below the end plate
I am not sure if this is correct but it seemed to work better with bigger holes and in the position I had it.

To ignite the chamber I have used a boiler ignition probe connected to a BBQ igniter to supply the voltage.

As displayed briefly in my video. The engine seems to start to get going and as the boost builds up it cuts out. It cannot self sustain.

Can anybody tell me what I have done incorrectly here. Or not done at all.

Thanks
Sebastian

[racket]

Hi

Sounds like not enough fuel getting into the engine .

Firstly ..............does your gas cylinder come equiped with a "safety" cutout if flow gets too great ??

Secondly ...............is there a fuel pressure regulator ??

If there is , throw it away and simply use the cylinder valve for regulating flow .

Thirdly .............all propane must exit the "injector" radially , no injection down the flametube .

Cheers
John

[racket]

OOPs , just noticed some pics have arrived :-(

Your fuel injection is wrong , refer earlier email

[sebsracing86]

Apr 11, 2021 16:57:40 GMT -5 racket said:

Hi

Sounds like not enough fuel getting into the engine .

Firstly ..............does your gas cylinder come equiped with a "safety" cutout if flow gets too great ??

Secondly ...............is there a fuel pressure regulator ??

If there is , throw it away and simply use the cylinder valve for regulating flow .

Thirdly .............all propane must exit the "injector" radially , no injection down the flametube .

Cheers
John

Hi thanks for your reply. Yes I forgot to mention that the gas bottle has a 0-4bar regulator on also the regulator says Pi max 16 bar and Q: 8kg p/h .
I will remove that on my next attempt.

I will make a new fuel injector. Do you have any suggestions what sizes of holes and how many?

Thanks

[sebsracing86]

These were some previous designs that I did not have much success with.

[racket]

Hi

Your copper pipe injector was a better design , its end was crimped over and only radial injection .

For a 40 mm inducer you probably only 6 to 8 X 1/16" diameter holes , the smallish holes keeps gas pressure higher making the jets of fuel spread further

With the regulator removed , most don't have sufficient flow capacity for a turbine engine , your flow rate should be up to the job , also the fuel pressure needs to overcome your P2 pressure before the fuel can enter the combustor , so at full power we need both pressure and flow from the cylinder , as long as the vapour pressure in the cylinder stays high enough the engine will maintain power , if power starts to drop off over time its generally because the cylinder starts to "freeze up" .

All the best with the next test run :-)

Cheers
John

[sebsracing86]

Apr 11, 2021 18:29:05 GMT -5 racket said:

Hi

Your copper pipe injector was a better design , its end was crimped over and only radial injection .

For a 40 mm inducer you probably only 6 to 8 X 1/16" diameter holes , the smallish holes keeps gas pressure higher making the jets of fuel spread further

With the regulator removed , most don't have sufficient flow capacity for a turbine engine , your flow rate should be up to the job , also the fuel pressure needs to overcome your P2 pressure before the fuel can enter the combustor , so at full power we need both pressure and flow from the cylinder , as long as the vapour pressure in the cylinder stays high enough the engine will maintain power , if power starts to drop off over time its generally because the cylinder starts to "freeze up" .

All the best with the next test run :-)

Cheers
John

Hi John. Thanks for your reply. At first I did try similar to 6 x 1/6 (actually 1.5mm) holes with the injector design mentioned. I had no success igniting it. Maybe the pressure was blowing the spark out? I will try again today with the regulator on the bottle removed too.

[racket]

Hi

With your current fuel injector you'll be producing a virtually core of pure propane within the flametube because with a multitude of small flametube wall holes their penetration would be limited and fuel/air mixing would be limited , the result is rather poor combustion until further down the flametube where the larger holes produce jets which penetrate the propane core .

You may need to light your propane before feeding the blower air into the comp to spool it up , I always light my start gas before applying the starter , its a common way to do things

Cheers
John

[sebsracing86]

Thank you very much John. I will give that a try today.
Regards
Sebastian

[sebsracing86]

Apr 12, 2021 3:03:57 GMT -5 racket said:

Hi

With your current fuel injector you'll be producing a virtually core of pure propane within the flametube because with a multitude of small flametube wall holes their penetration would be limited and fuel/air mixing would be limited , the result is rather poor combustion until further down the flametube where the larger holes produce jets which penetrate the propane core .

You may need to light your propane before feeding the blower air into the comp to spool it up , I always light my start gas before applying the starter , its a common way to do things

Cheers
John

Hi today I made a new injector. Crimped end with 6 x 1/16 size holes drilled radially. I have also taken the regulator off the gas bottle.

I bench tested it and the gas flow was much stronger and more aggressive. It would ignite when in position next to the igniter. But I put the flame tube on and it would not ignite at all.

I also tried to test it assembled into the engine. It would not initiate the burn. So in thought maybe it needed some air. I fed air in from a distance with the leaf blower and still no luck initiating a burn.

The positioning of the injector is covering the primary area of the flame tube.

Could it be that the flame tube primary holes are too small?

I thought I would have a bit more luck today lol 😑😑😑

[racket]

Hi Sebastian

You may need to add a dedicated injection hole for the ignition position .

Don't change your Primary holes .

Most engines need some "tuning??" of the start technique to find what the engine requires.

Cheers
John

[sebsracing86]

Hi. Thanks for your reply.

I did try to locate it so at least one hole was close to the igniter.

I will try again tomorrow and make a dedicated bigger hole closer to the spark.

Is there anything else that you can recommend?

Thanks
Sebastian

[racket]

Hi Sebastian

Ignitors mounted on the end cap can have more problems than if its position in the sidewall where a combustable mix has more chance of being present .

Don't make the dedicated hole bigger , its position is more important , you don't want it spraying directly onto the spark as all you'll get is non combustable pure propane , there needs to be a fuel/air mix at the spark .

Generally just cracking the fuel valve a tad will supply enough fuel to the combustor for ignition to take place before applying the starter.

If all else fails use a propane torch at the exhaust , the first priority is to get the engine to work , we can sort out ignition later on

Cheers
John

[sebsracing86]

Ok great. Thank you John. I will give that a try.

Hopefully it will do more this time. Starting to understand a little more about it.

Thanks

[racket]

One other thing , your 63mm flametube is a tad "skinny" , you may get away with it using very combustable propane , if using liquid fuels like kero its advisable to have 3 times inducer are for the flametube cross sectional area , 40 mm inducer =1256 sq mms X 3 = 3770 sq mms = 69.3 mm diameter flametube ID .