3 inlets

[PyroJoe]

Here is the 3 inlet engine.
little over 4" diameter combustor, 30" in length
It is self starting on propane.
Was able to reduce the tail length by 25% from 40" to the 30" length shown, (the intake length was reduced 25% also)
It retains much of the lower throttle range amplitude.
Fuel air mixing is GREATLY improved, it looks to be a good candidate for liquid fueling.
The total intake to tail area remains at typical 0.88
IMO it is the best engine I have constructed to date, can't wait to try it with a intake augmentor.
If this transfers to the Kraken, it will reduce its length to under 50"
Still have some slight adjustments to test, expanding the tail, and better tuning the intakes.

[PyroJoe]

Kraken

[keith mcconnell]

Very cool! Think you could scale one up to make 100 or 200# thrust?
Keith

[PyroJoe]

Thanks,
My big engine, the Kraken has two (ported) 6.75"dia. CCs pushing a 4.25"dia main tailpipe. With this modification it should have better results with direct liquid fueling. For now I try to avoid the vapor coil/collar systems.
Not sure on the thrust figures, as I haven't been able to feed it enough fuel to reach anywhere near the top end.

[ace_fedde]

Nice, nice, very nice!!
(yes I'm still here sometimes)
Can't wait for numbers...

Fedde

[PyroJoe]

Hi Fedde good to see you here,
Sorry to drag this on for so long, but like most I have to work fulltime to support my pulse jet habits.

[PyroJoe]

Well dang,
The injector position is consistently running deep. This is indicating that I should have reduced the CC length by the same 25% along with the tail and inlet.
It also explains the amplitude at the lower throttle range. By reducing the tail length and intake length, in effect this increased the CC length by default.

I will reduce the CC length this weekend and see how it runs. It appears then that basically this is three engines, blended from the head plate to the tail. The caliber method still withstanding. Ha, I was hoping to cheat, but as is said, there are no free lunches.

So a question presents itself, is it better to run a specific tail diameter via multiple engines blended together, or is it best to run the duct with a full length engine?

I can see how multiple inlets can aid in mixing, but does the drag of multiple inlets reduce the effectiveness of the engine?

[ganuganu]

looks great sir..can i know the main aim of your project..is it to increase the thrust or create a rich air/fuel mixture for the engine..

[PyroJoe]

The short answer is to make it as useful as possible.

I need reasonable efficiency, throttle range, stability and thrust in a package that can fit within most vehicle frame works.

Slicing 25% from the front of the CC placed the injectors in the regular position. It roared to life in a pouring rain this morning with no problems. I do like the mixing three inlets provides and have decided it would be good to apply to the bigger engine.

[ganuganu]

so how much thrust it produced in your first test..

[PyroJoe]

No thrust test yet, will need to add a intake augmenter to make it worth while to bolt to a thrust stand.

[hinote]

Here is the 3 inlet engine.

A word of caution here--might save you some grief later on.

My experience with the (4 inlet) Kentfield was that the "head plate" (my term for the front end of the engine where the intakes are mounted) is prone to bowing outward from the heat and pressure during operation. The bowing can be quite minor--but its effects on the intakes aren't--they tend to splay outward noticeably as a result.

I would recommend some sort of restraint on the intakes to prevent this; it could be as simple as a big "hose clamp" strapped around the 3 tubes, or (my preference) short pieces of metal welded between adjacent tubes.

As a reminder I enclose the attached photo; close observation reveals the splaying effect in progress in the intakes.

Nice work, keep going!

Bill

[PyroJoe]

Thanks for the heads up Bill,
I will add those short pieces in with these types. I did have some splay during re-weld of the head plate. I typically make short weld runs to keep distortion local, but on this one I was running near 3" to 4" runs which made larger distortions. The bottom intakes are slightly splayed away from each other.

[Jutte]

Hi Pryo,
Do you have fuel going into each seperate intake.
That is main fuel line split into three - or do you place the fuel
directely into the combustion chamber?

[Jutte]

Just another question re the following...
"I can see how multiple inlets can aid in mixing, but does the drag of multiple inlets reduce the effectiveness of the engine?"
Is the increased drag only happening in regards to the exhaust phase.
Would multiple intakes effectively contribute more of a 'valving' effect due to the increased drag of the heated exhaust phase?
That is the incoming intake air being cooler passes more freely through the intakes but chokes up on the exhaust phase.
Is this what Kentfield was aiming at?
The reason I ask this is that some of the aircraft instruments I have come across use this aspect of heated air/increased drag
through a narrow pipe to stop damage occurring to delicate internal measuring mechanisms.